Based on Android 4.0. by Lars Vogel. Version 9.8. Copyright 2009, 2010, 2011, 2012 Lars Vogel Home Tutorials Trainings Books Social

Transcription

1 Android Development Tutorial Tutorial 2.6k Based on Android 4.0 Lars Vogel Version 9.8 by Lars Vogel Copyright 2009, 2010, 2011, 2012 Lars Vogel Home Tutorials Trainings Books Social Revision History Revision Created Revision bug fixing and enhancements Development with Android Gingerbread and Eclipse This tutorial describes how to create Android applications with Eclipse. It is based on Eclipse 3.7 (Indigo), Java 1.6 and Android 4.0 (Ice Cream Sandwich). Table of Contents 1. What is Android? 1.1. Android Operation System 1.2. Security and permissions 2. Android components Bomgar.com/Android-Remote-Support Ads by Google 2.1. Activity 1/76

2 2.2. Views and ViewGroups 2.3. Intents 2.4. Services 2.5. ContentProvider 2.6. BroadcastReceiver 2.7. (HomeScreen) Widgets 2.8. Other 3. Android Development Tools 3.1. What are the Android Development Tools? 3.2. Dalvik Virtual Machine 3.3. How to develop Android Applications 4. Android Application Architecture 4.1. AndroidManifest.xml 4.2. R.java and Resources 4.3. Assets 4.4. Reference to resources in XML files 4.5. Activities and Layouts 4.6. Activities and Lifecycle 4.7. Context 5. Installation 5.1. Pre-requisites for using a 64bit Linux 5.2. Eclipse and automatic Android SDK 5.3. Manually install Android SDK 5.4. Install a specific Android version 5.5. Android Source Code 6. Android virtual device - Emulator 6.1. What is the Android Emulator? 6.2. Google vrs. Android AVD 6.3. Emulator Shortcuts 6.4. Performance 6.5. Hardware button 7. Tutorial: Create and run Android Virtual Device 8. Error handling and typical problems 8.1. Clean Project 8.2. Problems with Android Debug Bridge (adb) 8.3. LogCat 8.4. Emulator does not start 8.5. Error message 8.6. Missing Imports 8.7. Eclipse Tips 9. Your first Android project 2/76

3 9.1. Create Project 9.2. Two faces of things 9.3. Create attributes 9.4. Add UI Elements 9.5. Edit UI properties 9.6. Code your application 9.7. Start Project 10. Starting an deployed application 11. Menus and Action Bar Definition of menu entries Action bar tabs Context menus 12. Tutorial: Menus and Action Bar Project Add a menu XML resource 13. Preferences 14. Tutorial: Preferences Using preferences Run 15. Layout Manager and ViewGroups Available Layout Manager LinearLayout RelativeLayout GridLayout 16. ScrollView 17. Fragments Overview When to use Fragments 18. Fragments Tutorial Overview Create project Create layouts for landscape mode Create Fragment classes Create layouts for landscape mode Activities Run 19. DDMS perspective and important views DDMS - Dalvik Debug Monitor Server LogCat View 3/76

4 20. Shell File explorer Android Debugging Bridge - Shell Uninstall an application via adb Emulator Console via telnet 21. Deploy your application on a real device 22. Thank you 23. Questions and Discussion 24. Links and Literature Source Code Android Resources vogella Resources 1. What is Android? 1.1. Android Operation System Android is an operating system based on Linux with a Java programming interface. The Android Software Development Kit (Android SDK) provides all necessary tools to develop Android applications. This includes a compiler, debugger and a device emulator, as well as its own virtual machine to run Android programs. Android is currently primary developed by Google. Android allows background processing, provides a rich user interface library, supports 2-D and 3-D graphics using the OpenGL libraries, access to the file system and provides an embedded SQLite database. Android applications consists out of different components and can re-use components of other applications if these applications declare their components as available. This leads to the concept of a task in Android, an application can re-use other Android components to archive a task. For example you can write an Application which integrates the a map component and a camera component to archive a certain task Security and permissions 4/76

5 During deployment on an Android device, the Android system will create a unique user and group ID for every Android application. Each application file is private to this generated user, e.g. other applications cannot access these files. In addition each Android application will be started in its own process. Therefore by means of the underlying Linux operating system, every Android application is isolated from other running applications. A misbehaving application cannot easily harm other Android applications. If data should be shared the application must do this explicitly, e.g. via a Serviceor a ContentProvider. Android also contains a permission system. Android predefines permissions for certain tasks but every application can also define its own permissions. An application must declare in its configuration file (AndroidManifest.xml) that it requires certain permissions. Depending on the details of the defined permission, the Android system will during installation either automatically grant the permission, reject it or ask the user if he grants these permissions to the application. If for example the application declares that is requires Internet access then the user need to confirm this during installation. This is called "user driven security". The user decides to grant a permission or to deny it. If the user does not want to give all permissions required by the application, this application cannot be installed. The check of the permission is only performed during installation, permissions cannot be denied or granted after the installation. Typically not all users check the permissions in detail but some users do and if there is something strange with them, they will write bad reviews on the corresponding Android markets. 2. Android components The followings gives a short overview of important Android components Activity Activityrepresents the presentation layer of an Android application. A simplified (and slightly incorrect) description is that an Activityis a a screen. This is slightly incorrect as Activitiescan be displayed as 5/76

6 dialogs or transparent. An Android application can have several Activities Views and ViewGroups Viewsare user interface widgets, e.g. buttons or text fields. The base class for all Viewsis android.view.view. Viewsoften have attributes which can be used to change their appearance and behavior. A ViewGroupis responsible for arranging other Viewse.g. they are layout manager. The base class for a layout manager is android.view.viewgroups. ViewGroupalso extends View. ViewGroupscan be nestled to create complex layouts. You should not nestle ViewGroupstoo deeply as this has a negative impact on performance Intents Intentsare asynchronous messages which allow the application to request functionality from other components of the Android systen, e.g. from Servicesor Activities. An application can call a component directly (explicit intent) or ask the Android system to evaluate registered components for a certain Intents(implicit intents). For example the application could implement sharing of data via an Intentand all components which allow sharing of data would be available for the user to select. Applications register themselves to an intent via an IntentFilter. Intentsallow to combine loosely coupled components to perform certain tasks Services Servicesperform background tasks without providing an UI. They can notify the user via the notification framework in Android ContentProvider ContentProviderprovides an structured interface to data. Via a ContentProvideryour application can share data with other applications. Android contains an SQLite database which is frequently used in conjunction with a ContentProviderto persists the data of the ContentProvider BroadcastReceiver BroadcastReceivercan be registered to receives system messages and Intents. BroadcastReceiver 6/76

7 will get notified by the Android system if the specified situation happens. For example a BroadcastReceiver could get called once the system completed its boot process or if a phone call is received (HomeScreen) Widgets Widgetsare interactive components which are primary used on the Android homescreen. They typically display some kind of data and allow the user to perform actions via them. For example a Widget could display a short summary of new s and if the user select a it could start the application with the selected Other Android provide much more components but the list above describes the most important ones. Other Android components are "Live Folders" and "Live Wallpapers". Live Folders display data on the homescreen without launching the corresponding application. 3. Android Development Tools 3.1. What are the Android Development Tools? Google provides the Android Development Tools (ADT) to develop Android applications with Eclipse. ADT is a set of plug-in which extended the Eclipse IDE with Android development capabilities. ADT contains all required functionality to create, compile, debug and deploy Android applications from the Eclipse IDE and from the command line. Other IDE's, e.g. IntellJ, are also reusing components of ADT. ADT also provides an Android device emulator, so that Android applications can be tested without a real Android phone Dalvik Virtual Machine The Android system uses a special virtual machine, i.e. the Dalvik Virtual Machine to run Java based applications. Dalvik uses special bytecode which is different from Java bytecode. Therefore you cannot run standard Java bytecode on Android How to develop Android Applications 7/76

8 Android applications are primary written in the Java programming language. The Java source files are converted to Java class files by the Java compiler. Android provides a tool dxwhich converts Java class files into a dex(dalvik Executable) file. All class files of one application are placed in one compressed.dex file. During this conversion process redundant information in the class files are optimized in the.dex file. For example if the same String in different class file is found, the.dex file is stored only once and reference this String in the corresponding classes..dex files are therefore much smaller in size then the corresponding class files. The.dex file and the resources of an Android project, e.g. the images and XML files are packed into an.apk (Android Package) file. The program aapt(android Asset Packaging Tool) perform this packaging. The resulting.apk file contains all necessary data to run the Android application and can be deployed to an Android device via the "adb" tool. The Android Development Tools (ADT) allows that all these steps are performed transparent to the user; either within Eclipse or via the command line. If you use the ADT tooling you press a button or run a script and the whole Android application (.apk file) will be created and deployed. 4. Android Application Architecture 4.1. AndroidManifest.xml An Android application is described in the file AndroidManifest.xml. This file must declare all components, e.g. Activitiesand Servicesof the application. It must also contain the required permissions for the application. For example if the application requires network access it must be specified here. <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android=" package="de.vogella.android.temperature" android:versioncode="1" android:versionname="1.0"> <application android:icon="@drawable/icon" android:label="@string/app_name"> 8/76

9 <activity android:name=".convert" <intent-filter> <action android:name="android.intent.action.main" /> <category android:name="android.intent.category.launcher" /> </intent-filter> </activity> </application> <uses-sdk android:minsdkversion="9" /> </manifest> The packageattribute defines the base package for the following Java elements. The Android Marketplace requires that very application uses its own unique package. Therefore it is a good habit to use as package name your reverse domain name. This will avoid collisions with other developers. android:versionnameand android:versioncodespecify the version of your application. versionname is what the user sees and can be any string. versioncodemust be an integer. The Android Market determine based on versioncodeif an update of an Android applications on devices is required. You typically start with "1" and increase this value by one, if you roll-out a new version of your application. The tag <activity> defines an Activity, in this example pointing to the de.vogella.android.temperature.convertclass. An intent filter is registered for this class which defines that this Activityis started once the application starts (action android:name="android.intent.action.main" ). The category definition category android:name="android.intent.category.launcher"defines that this application is added to the application directory on the Android device. value refer to resource files which contain the actual values. This makes it easy to provide different resources, e.g. strings, colors, icons, for different devices and makes it easy to translate applications. The "uses-sdk" part of the "AndroidManifest.xml" file defines the minimal SDK version for which your application is valid. This will prevent your application being installed on devices with older SDK versions R.java and Resources 9/76

10 The " gen" directory in an Android project contains generated values. R.javais a generated class which contains references to certain resources of the the project. These resources must be defined in the resdirectory and can be XML files, icons or pictures. Via XML files you can for example define values, menus, layouts or animations. If you create a new resource, the corresponding reference is automatically created in R.java. These references are static int values and define ID's for the resources. The Android system provides methods to access the corresponding resource via these ID's. For example to access a String with the reference id R.string.yourStringuse the method getstring(r.string.yourstring));. R.java is automatically created by the Eclipse development environment, manual changes are not necessary Assets While the directory resis contains structured values which are known to the Android platform the directory assets can be used to store any kind of data. In Java you can access this data via the AssetsManagerand the getassets()method Reference to resources in XML files In your XML files, e.g. your layout files, you can refer to other resources via For example if you want to refer to a color you defined as resources you can refer to it or if you have defined a "hello" string as resource you can access it 4.5. Activities and Layouts The user interface for Activities is defined via layouts. The layout defines the include Views(widgets) and their properties. A layout can be defined via Java code or via XML. You typically uses Java code to generate the layout if you don't know the content until runtime; for example if your layout depends on content which you read from the Internet. XML based layouts are defined via a resource file in the folder /res/layout. This file specifies the 10/76

11 ViewGroups, Views, their relationship and their attributes for a specific layout. If a UI element needs to be accessed via Java code you have to give the UI element an unique id via the android:idattribute. To assign a new id to an UI element By conversion this will create and assign a new id yourvalueto the corresponding UI element. In your Java code you can later access these UI elements via the method findviewbyid(r.id.yourvalue). Defining layouts via XML is usually the preferred way as this separates the programming logic from the layout definition. It also allows the definition of different layouts for different devices. You can also mix both approaches Activities and Lifecycle The operating system controls the life cycle of your application. At any time the Android system may stop or destroy your application, e.g. because of an incoming call. The Android system defines a life cycle for activities via predefined methods. The most important methods are: onsaveinstancestate()- called if the activity is stopped. Used to save data so that the activity can restore its states if re-started onpause()- always called if the Activity ends, can be used to release resource or save data onresume()- called if the Activity is re-started, can be used to initialize fields The activity will also be restarted if a so called "configuration change" happens. A configuration change for example happens if the user changes the orientation of the device (vertical or horizontal). The activity is in this case restarted to enable the Android platform to load different resources for these configuration, e.g. layouts for vertical or horizontal mode. In the emulator you can simulate the change of the orientation via CNTR+F11. You can avoid a restart of your application for certain configuration changes via the configchanges attribute on your activity definition in your AndroidManifest.xml. The following activity will not be restarted in case of orientation changes or position of the physical keyboard (hidden / visible). <activity android:name=".progresstestactivity" android:label="@string/app_name" android:configchanges="orientation keyboardhidden keyboard"> </activity> 11/76

12 4.7. Context The class android.content.contextprovides the connections to the Android system. It is the interface to global information about the application environment. Context also provides access to Android Services, e.g. thelocation Service. As Activities and Services extend the class Contextyou can directly access the context via this. 5. Installation The following assume that you have already Eclipse installed. For details please see Eclipse Tutorial 5.1. Pre-requisites for using a 64bit Linux The Android SDK is 32bit, therefore on an 64bit Linux system you need to have the package ia32-libsinstalled. For Ubuntu you can do this via the following command. apt-get install ia32-libs Please check your distribution documentation if you are using a different flavor of Linux Eclipse and automatic Android SDK Use the Eclipse update manager to install all available components for the Android Development Tools (ADT) from the URL If you are not familiar with the Eclipse update manager the usage is described in Eclipse update manager. After the new Android development components are installed you will be prompted to install the Android SDK. You can use the following wizard or go to the next section to learn how to do it manually. 12/76

13 13/76

14 14/76

15 5.3. Manually install Android SDK The previous step downloads the Android SDK automatically for you. You can also download the Android SDK from the Android SDK download page. The download contains a zip file which you can extract to any place in your file system, e.g. I placed it under "c:\android-sdk-windows". Avoid using spaces in the path name otherwise you may experience problems later. You also have to define the location of the Android SDK in the Eclipse Preferences. In Eclipse open the Preferences dialog via Windows Preferences. Select Android and enter the installation path of the Android SDK. 15/76

16 5.4. Install a specific Android version The Android SDK Manager allows you to install specific versions of Android. Select Window Android SDK Manager from the Eclipse menu. 16/76

17 The dialog allows you to install new packages and also allows you to delete them. Select "Available packages" and open the "Third Party Add-ons". Select the Google API 14 (Android 4.0) version of the SDK and press "Install". 17/76

18 Press the "Install" button and confirm the license for all packages. After the installation completes, restart Eclipse Android Source Code The following step is optional As of Android 4.0 During Android development it is very useful to have the Android source code available as Android uses a lot of defaults. As of Android 4.0 the Android development tools provides also the source code. You can download it via the Android SDK Manager by selecting the "Sources for Android SDK". 18/76

19 The sources are downloaded to the source directory located in "path_to_android_sdk/sources/android-xx". xx is the api level number (15 for 4.0.3). In the Eclipse Package Explorer, right click on your android.jar and select Properties Java Source Attachment. Type in the source directory name and press OK. Afterwards you can browse through the source code Prior to Android 4.0 For earlier versions Haris Peco maintains plugins, which provide the Android Source code code. Use the Eclipse update manager to install the Android Source plugin from the following update site: " More details can be found on the project website. 6. Android virtual device - Emulator 6.1. What is the Android Emulator? The Android Development Tools (ADT) include an emulator to run an Android system. The emulator behaves like a real Android device (in most cases) and allows you to test your application without having a real device. You can configure the version of the Android system you would like to run, the size of the SD card, the screen resolution and other relevant settings. You can define several devices with different configurations. Via the emulator you select which device should be started, you can also start several in parallel. These devices are called "Android Virtual Device" (AVD). The ADT allow to deploy and run your Android program on the AVD Google vrs. Android AVD During the creation of an AVD you decide if you want an Android device or an Google device. An AVD created for Android will contain the programs from the Android Open Source Project. An AVD created for the Google API's will also contain several Google applications, most notable the Google Maps application. If you want to use functionality which is only provided via the Google API's, e.g. Cloud2DeviceMessaging or Google 19/76

20 Maps you must run this application on an AVD with Google API's Emulator Shortcuts Obviously you can use the emulator via the keyboard on the right side of the emulator. But there are also some nice shortcuts which are useful. Alt+Enter Maximizes the emulator. Nice for demos. Ctrl+F11 changes the orientation of the emulator. F8 Turns network on / off Performance Try to use a smaller resolution for your emulator as for example HVGA. The emulator gets slower the more pixels its needs to render as it is using software rendering. Also if you have sufficient memory on your computer, add at least 1 GB of memory to your emulator. This is the value "Device ram size" during the creation of the AVD. Also set the flag "Enabled" for Snapshots. This will save the state of the emulator and let it start much faster Hardware button Android 4.0 introduced that devices do not have to have hardware button anymore. If you want to create such an AVD, add the "Hardware Back/Home keys" property to the device configuration and set it to "false". 20/76

21 7. Tutorial: Create and run Android Virtual Device To define an Android Virtual Device (ADV) open the "AVD Manager" via Windows AVD Manager and press "New". 21/76

22 Enter the following. 22/76

23 We can also select the box "Enabled" for Snapshots. This will make the second start of the virtual device much faster. At the end press the button "Create AVD". This will create the AVD configuration and display it under the "Virtual devices". To test if your setup is correct, select your device and press "Start". 23/76

24 After (a long time) your AVD starts. You are able to use it via the mouse and via the virtual keyboard of the emulator. 8. Error handling and typical problems Things are not always working as they should. This section gives an overview over typical problems and how to solve them Clean Project Several users report that get the following errors: 1. Project... is missing required source folder: 'gen' 2. The project could not be built until build path errors are resolved. 3. Unable to open class file R.java. To solve any of these errors, go to the project menu and select Project Clean Problems with Android Debug Bridge (adb) The communication with the emulator or your Android device might have problems. This communication is handled by the Android Debug Bridge (adb). Eclipse allows to reset the adb in case this causes problems. Select therefore the DDMS perspective via Window Open Perspective Other DDMS To restart the adb, select the "Reset adb" in the Device View. 24/76

25 8.3. LogCat The "LogCat" Viewshows you the log messages of your Android device and help you analyze problems. For example Java exceptions in your program would be shown here. To open this view, select Window Show View Other Android LogCat Emulator does not start If your emulator does not start, make sure that the android-sdk version is in a path without any spaces in the path name Error message annotation was introduced in Java 1.6. If you receive an error message change the Java compiler level to Java 1.6. To do this right-click on the project, select Properties Java Compiler Compiler compliance level and select "1.6" in the drop-down box Missing Imports Java requires that classes which are not part of the standard Java Language be either fully qualified or declared via imports. If you see error message with "XX cannot be resolved to a variable", right-click in your Editorand select Source 25/76

26 Organize Imports to important required packages Eclipse Tips To work more efficiently with Eclipse, select Window Preferences Java Editor Save Actions and select that the source code should be formatted and that the imports should be organized at every save. 1. Conventions for the tutorials Table of Contents 1. API version, package and application name 2. Warnings Messages for Strings 1. API version, package and application name The tutorials of this document have been developed and tested with Android 4.0.3, API Level 15. Please use this version for all tutorials in this book. Higher version usually should also work. Lower version of the Android API might also work, but if you face issues, try the recommended version. The base package for the projects is always the same as the project name, e.g. if you are asked to create a project "de.vogella.android.example.test" then the corresponding package name is "de.vogella.android.example.test". The Application name, which must be entered on the Android project generation wizard, will not be predefined. Choose a name you like. 2. Warnings Messages for Strings The Android development tools are show warnings if you use hard-coded strings, for example in layout files. While for real application its best practice to use string resource files we use use Strings directly to simplify the creation of the examples. 9. Your first Android project 9.1. Create Project This app is also available on the Android Marketplace. Search for "vogella" for find this example. 26/76

27 Select File New Other Android Android Project and create the Android project "de.vogella.android.temperature". Enter the following. 27/76

28 28/76

29 Press "Finish". This should create the following directory structure. 29/76

30 While "res" contains structured values which are known to the Android platform the directory "assets" can be used to store any kind of data. In Java you can access this data via the AssetsManager and the method getassets() Two faces of things The Android SDK allows the developer to define certain artifacts, e.g. strings and UI's, in two ways: via a rich editor, and directly via XML. The following description tries to use the rich UI but for validation the resulting XML is also displayed. You can switch between both things by clicking on the tab on the lower part of the screen. For example in the Package Explorer select "res/layout/main.xml". 30/76

31 9.3. Create attributes Android allows you to create attributes for resources, e.g. for strings or colors. These attributes can be used in your UI definition via XML or in your Java source code. Select the file "res/values/string.xml" and press "Add". Select "Color" and enter "mycolor" as the name and "#3399CC" as the value. 31/76

32 Add also the following "String" attributes. String attributes allow the developer to translate the application at a later point. Table 1. String Attributes Name celsius fahrenheit calc Value to Celsius to Fahrenheit Calculate Switch to the XML representation and validate the values. <?xml version="1.0" encoding="utf-8"?> <resources> <string name="hello">hello World, Convert!</string> 32/76

33 <string name="app_name">temperature Converter</string> <color name="mycolor">#3399cc</color> <string name="myclickhandler">myclickhandler</string> <string name="celsius">to Celsius</string> <string name="fahrenheit">to Fahrenheit</string> <string name="calc">calculate</string> </resources> 9.4. Add UI Elements Select "res/layout/main.xml" and open the Android editor via a double-click. This editor allows you to create the UI via drag and drop or via the XML source code. You can switch between both representations via the tabs at the bottom of the editor. For changing the position and grouping elements you can use the outline view. The following shows a screenshot of the Palette view from which you can drag and drop new UI elements into your layout. Please note that the "Palette" view changes frequently so your view might be a bit different. Right-click on the text object Hello World, Hello! in the layout. Select Delete on the popup menu to remove the text 33/76

34 object. Then, from the Palette view, select Text Fields and locate Plain Text. Drag this onto the layout to create a text input field. All object types in the section "Text Fields derive from the class "EditText", they just specify via an additional attribute which text type can be used. Now select the Palette section Form Widgets and drag a RadioGroup object onto the layout. The number of radio buttons added to the radio button group depends on your version of Eclipse. Make sure there are two radio buttons by deleting or adding radio buttons to the group. From the Palette section Form Widgets, drag a Button object onto the layout. The result should look like the following. Switch to "main.xml" and verify that your XML looks like the following. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <EditText android:layout_height="wrap_content" android:id="@+id/edittext1" android:layout_width="match_parent" android:text="edittext"></edittext> 34/76

35 <RadioGroup android:layout_height="wrap_content" android:layout_width="match_parent"> <RadioButton android:text="radiobutton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:checked="true"></radiobutton> <RadioButton android:text="radiobutton" android:layout_width="wrap_content" android:layout_height="wrap_content"></radiobutton> </RadioGroup> <Button android:text="button" android:layout_width="wrap_content" android:layout_height="wrap_content"></button> </LinearLayout> 9.5. Edit UI properties If you select a UI element you can change its properties via the properties view. Most of the properties can be changed via the right mouse menu. You can also edit properties of fields directy in XML. Typically you change properties directly in the XML file as this is much faster. But the right mouse functionality is nice if you are searching for a certain property. Open your file "main.xml" We will delete the initial text for the EditText field in XML. Switch to the XML tab called "main.xml" and delete the android:text="edittext"property from the EditText part. Switch back to the "Graphical Layout" tab and check that the text is removed. Use the right mouse click on the first radio button to assign the "celsius" string attribute to its "text" property. Assign the and "fahrenheit" string attribute to the second radio button. 35/76

36 36/76

37 From now on I assume you are able to use the properties menu on the UI elements. You can either edit the XML file or modify the properties via right mouse click. Set the property "Checked" to true for the first RadioButton. Assign "calc" to the text property of your button and assign "myclickhandler" to the "onclick" property. Set the "Input type" property to "numbersigned" and "numberdecimal" on your EditText. All your other UI controls are contained in a LinearLayout. We want to assign a background color to this LinearLayout. Right-click on an empty space in Graphical Layout mode, then select Other Properties All by Name Background. Select Color and then mycolor in the list. 37/76

38 Switch to the "main.xml" tab and verify that the XML is correctly maintained. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:inputtype="numberdecimal numbersigned" ></EditText> <RadioGroup android:layout_height="wrap_content" android:layout_width="match_parent"> <RadioButton android:layout_width="wrap_content" android:layout_height="wrap_content" android:checked="true"></radiobutton> <RadioButton android:layout_width="wrap_content" android:layout_height="wrap_content" </RadioGroup> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:onclick="myclickhandler"></button> </LinearLayout> 9.6. Code your application During the generation of your new Android project you specified that an Activitycalled ConvertActivity should get created. The project wizard also created the corresponding Java classs. 38/76

39 Change your code in ConvertActivity.javato the following. Note that the myclickhandlerwill be called based on the OnClickproperty of your button. package de.vogella.android.temperature; import android.app.activity; import android.os.bundle; import android.view.view; import android.widget.edittext; import android.widget.radiobutton; import android.widget.toast; public class ConvertActivity extends Activity { private EditText public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); text = (EditText) findviewbyid(r.id.edittext1); // This method is called at button click because we assigned the name to the // "On Click property" of the button public void myclickhandler(view view) { switch (view.getid()) { case R.id.button1: RadioButton celsiusbutton = (RadioButton) findviewbyid(r.id.radio0); RadioButton fahrenheitbutton = (RadioButton) findviewbyid(r.id.radio1); if (text.gettext().length() == 0) { Toast.makeText(this, "Please enter a valid number", Toast.LENGTH_LONG).show(); return; float inputvalue = Float.parseFloat(text.getText().toString()); if (celsiusbutton.ischecked()) { text.settext(string.valueof(convertfahrenheittocelsius(inputvalue))); celsiusbutton.setchecked(false); fahrenheitbutton.setchecked(true); else { text.settext(string.valueof(convertcelsiustofahrenheit(inputvalue))); fahrenheitbutton.setchecked(false); celsiusbutton.setchecked(true); break; 39/76

40 // Converts to celsius private float convertfahrenheittocelsius(float fahrenheit) { return ((fahrenheit - 32) * 5 / 9); // Converts to fahrenheit private float convertcelsiustofahrenheit(float celsius) { return ((celsius * 9) / 5) + 32; 9.7. Start Project To start the Android Application, select your project, right click on it, and select Run-As Android Application. Be patient, the emulator starts up very slowly. You should get the following result. 40/76

41 Type in a number, select your conversion and press the button. The result should be displayed and the other option should get selected. 10. Starting an deployed application After you run your application on the virtual device you can start it again on the device. If you press the Home button you can also select your application. 41/76

42 42/76

43 Java Accelerate App Performance & Development. Free Download. InterSystem s.com /Cache Android Remote Support Remote Software For Businesses. Support Your Android Users Remotely gar.com /Free-Trial Embedded Jobs For the best Embedded, Embedded C, Software jobs, contact IC Software Menus and Action Bar Definition of menu entries Android provides two possible ways to display global actions which the user can select. The first one is the usage of the Action Bar in the application. The Action Bar is a window feature at the top of the activity that may display the activity title, navigation modes, and other interactive items. 43/76

44 The second option is that the app can open a menu which shows additional actions via a popup menu. Typically you define your menu entries in a way that they are added to the action bar if sufficient space is available in the action bar and if not, remaining menu items are displayed in the popup menu. The option menu and the action bar of your activity is filled by the method oncreateoptionsmenu() of your activity. The ActionBaralso shows an icon of your application. You can also add an action to this icon. If you select this icon the onoptionsitemselected()method will be called with the value android.r.id.home. The recommendation is to return to the main Activityin your program. // If home icon is clicked return to main Activity case android.r.id.home: Intent intent = new Intent(this, OverviewActivity.class); intent.addflags(intent.flag_activity_clear_top); startactivity(intent); break; In this method you can create the menu programmatically or you can use a pre-defined XML resources which you inflate via the MenuInflatorclass. Each Activityhas already an instance of the class available and this instance can get accessed via the getmenuinflator()method. The oncreateoptionsmenu()method is only called once. If you want to influence the menu later you have to use the onprepareoptionsmenu()method Action bar tabs It is also possible to add tabs to an action bar Context menus You can also assign a context menu to an UI widget (view). A context menu is activated if the user "long presses" the view. A context menu for a view is registered via the registerforcontextmenu(view)method. The oncreatecontextmenu()method is called every time a context menu is activated as the context menu is discarded after its usage. The Android platform may also add options to your View, e.g. EditTextprovides context options to select text, etc. 44/76

45 12. Tutorial: Menus and Action Bar Project This chapter will demonstrate how to create and evaluate a option menu which is displayed in the action bar if sufficient space is available. This example will be extended in the chapter about preferences. Create a project called "de.vogella.android.socialapp" with the Activitycalled "OverviewActivity". Change the "main.xml" layout file in the diretory "/res/layout/" to the following: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <Button android:id="@+id/button01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="show Preferences" > </Button> <Button android:id="@+id/button02" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="change Preferences" > </Button> </LinearLayout> Add a menu XML resource Select your project, right click on it and select New Other Android Android XML File to create a new XML resource. Select the option "Menu", enter as File "mainmenu.xml" and press the button "Finish". 45/76

46 This will create a new file "mainmenu.xml" in the folder "res/menu" of your project. Android provides a nice editor to edit this file, unfortunately this editor is not always automatically used due to bugs in the ADT. If that happens, you can open this editor manually. Right-click on your menu file and select Open with Android Menu Editor. Switch if necessary to the "Layout" tab of the editor. Press Add and select "Item". Maintain the following value. This defines the entries in your menu. We will also define that the menu entry is displayed in the action bar if there is sufficient space available. 46/76

47 Change your Activity class "OverviewActivity" to the following. The OnCreateOptionsMenu method is used to create the menu. The behavior in "onoptionsitemselected" is currently hard-coded to show a Toast and will soon call the preference settings. In case you want to disable or hide menu items you can use the method "onprepareoptionsmenu" which is called every time the menu is called. 47/76

48 package de.vogella.android.socialapp; import android.app.activity; import android.os.bundle; import android.view.menu; import android.view.menuinflater; import android.view.menuitem; import android.widget.toast; public class OverviewActivity extends Activity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); public boolean oncreateoptionsmenu(menu menu) { MenuInflater inflater = getmenuinflater(); inflater.inflate(r.menu.mainmenu, menu); return public boolean onoptionsitemselected(menuitem item) { Toast.makeText(this, "Just a test", Toast.LENGTH_SHORT).show(); return true; Run your application. As there is enough space in the action bar your item will be displayed there. If there would be more items you could press "Menu" on the emulator to see them. If you select the menu item you should see a small info message. 48/76

49 The two "Preference" buttons are not yet active. We will use them in the next chapter. 13. Preferences Android supports the usage of Preferences to allow you to save data for your application. Preferences are stored as key values. The definition of Preferences can also be done via an XML resource. Android provides the class "PreferenceActivity" which extends the class Activity. PreferenceActivity supports the simple handling of preferences. This activity can load a preference definition resources via the method addpreferencesfromresource(). To communicate between different components Android uses Intents. Typically the PreferenceActivity is started from another activity via an Intent. 49/76

50 In your application you can access the preference manager via the following: SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this); Values can get access via the key of the preference setting. String username = preferences.getstring("username", "n/a"); To create or change preferences you have to call the edit() methods. Once you have changed the value you have to call commit() to apply your changes. Editor edit = preferences.edit(); edit.putstring("username", "new_value_for_user"); edit.commit(); 14. Tutorial: Preferences Using preferences We will continue using the example project "de.vogella.android.social". Create an Android XML resource "preferences.xml" of type "PreferenceScreen". 50/76

51 Open the file via right-mouse click and Open-with Android XML Resource Editor. Press Add, add a "PreferenceCategory" and add two preferences "EditTextPreferences" to this category : "User" and "Password". 51/76

52 You can also enter values for other properties of EditTextField, e.g. the inputmethod. Add the following attribute to the XML definition of your password field to make the input quoted with *. 52/76

53 android:inputtype="textpassword" Create the class MyPreferencesActivitywhich extends PreferenceActivity. This Activitywill load the "preference.xml" file and will allow the user to change the values. package de.vogella.android.socialapp; import android.os.bundle; import android.preference.preferenceactivity; public class MyPreferencesActivity extends PreferenceActivity public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); addpreferencesfromresource(r.xml.preferences); To make this class available as an activity for Android you need to register it in your "AndroidManifest.xml" file. Select "AndroidManifest.xml" and the tab "Application". Scroll to the botton of the view and add your new activity via the "Add" button. To make use of our new preference activity and the preference values we adjust the "OverviewActivity". The first button will show the current values of the preferences via a Toast and the second button will revert the maintained user name to demonstrate how you could change the preferences via code. package de.vogella.android.socialapp; 53/76

54 import android.app.activity; import android.content.sharedpreferences; import android.content.sharedpreferences.editor; import android.os.bundle; import android.preference.preferencemanager; import android.view.menu; import android.view.menuinflater; import android.view.menuitem; import android.view.view; import android.view.view.onclicklistener; import android.widget.button; import android.widget.toast; public class OverviewActivity extends Activity { SharedPreferences public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); Button button = (Button) findviewbyid(r.id.button01); // Initialize preferences preferences = PreferenceManager.getDefaultSharedPreferences(this); button.setonclicklistener(new OnClickListener() { public void onclick(view v) { String username = preferences.getstring("username", "n/a"); String password = preferences.getstring("password", "n/a"); showprefs(username, password); ); Button buttonchangepreferences = (Button) findviewbyid(r.id.button02); buttonchangepreferences.setonclicklistener(new OnClickListener() { public void onclick(view v) { ); updatepreferencevalue(); private void showprefs(string username, String password){ Toast.makeText( OverviewActivity.this, "Input: " + username + " and password: " + password, Toast.LENGTH_LONG).show(); private void updatepreferencevalue(){ Editor edit = preferences.edit(); String username = preferences.getstring("username", "n/a"); 54/76

55 // We will just revert the current user name and save again StringBuffer buffer = new StringBuffer(); for (int i = username.length() - 1; i >= 0; i--) { buffer.append(username.charat(i)); edit.putstring("username", buffer.tostring()); edit.commit(); // A toast is a view containing a quick little message for the // user. We give a little feedback Toast.makeText(OverviewActivity.this, "Reverted string sequence of user name.", Toast.LENGTH_LONG).show(); To open the new preference Activitywe will use the onoptionsitemselected()method. Even though we currently have only one option in our menu we use a switch to be ready for several new menu entries. To see the current values of the preferences we define a button and use the class PreferenceManagerto get the public boolean oncreateoptionsmenu(menu menu) { MenuInflater inflater = getmenuinflater(); inflater.inflate(r.menu.mainmenu, menu); return true; // This method is called once the menu is public boolean onoptionsitemselected(menuitem item) { switch (item.getitemid()) { // We have only one menu option case R.id.preferences: // Launch Preference activity Intent i = new Intent(OverviewActivity.this, MyPreferencesActivity.class); startactivity(i); // Some feedback to the user Toast.makeText(OverviewActivity.this, "Enter your user credentials.", Toast.LENGTH_LONG).show(); break; return true; 55/76

56 14.2. Run Run your application. Press the "menu" hardware button and then select your menu item "Preferences". You should be able to enter your user settings then press the back hardware button to return to your main activity. The saved values should be displayed in a small message windows (Toast) if you press your first button. If you press the second button the username should be reversed. 15. Layout Manager and ViewGroups Available Layout Manager A layout manager is a subclass of ViewGroupand is responsible for the layout of itself and its child Views. Android supports different default layout managers. 56/76

57 As of Android 4.0 the most relevant layout manager are LinearLayout, FrameLayout, RelativeLayoutand GridLayout. All layouts allow the developer to define attributes. Children can also define attributes which may be evaluated by their parent layout. AbsoluteLayoutLayoutis deprecated and TableLayoutcan be implemented more effectively via GridLayout LinearLayout LinearLayoutputs all its child elements into a single column or row depending on the android:orientation attribute. Possible values for this attribute are horizontaland vertical, horizontalis the default value. LinearLayoutcan be nested to achieve more complex layouts RelativeLayout RelativeLayoutallow to position the widget relative to each other. This allows for complex layouts. A simple usage for RelativeLayoutis if you want to center a single component. Just add one component to the RelativeLayoutand set the android:layout_centerinparentattribute to true. <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android=" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <ProgressBar android:id="@+id/progressbar1" style="?android:attr/progressbarstylelarge" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerinparent="true" /> </RelativeLayout> GridLayout 57/76

58 Overview GridLayoutwas introduced with Android 4.0. This layout allows you to organize a view into a Grid. GridLayout separates its drawing area into: rows, columns, and cells. You can specify how many columns you want for define for each Viewin which row and column it should be placed and how many columns and rows it should use. If not specified GridLayoutuses defaults, e.g. one column, one row and the position of a Viewdepends on the order of the declaration of the Views Tutorial GridLayout Create the project "de.vogella.android.layout.gridlayout" with the Activitycalled "DemoGridLayout". Change "main.xml" to the following. <?xml version="1.0" encoding="utf-8"?> <GridLayout xmlns:android=" android:id="@+id/gridlayout1" android:layout_width="fill_parent" android:layout_height="fill_parent" android:columncount="4" android:usedefaultmargins="true" > <TextView android:layout_column="0" android:layout_columnspan="3" android:layout_gravity="center_horizontal" android:layout_margintop="40dp" android:layout_row="0" android:text="user Credentials" android:textsize="32dip" /> <TextView android:layout_column="0" android:layout_gravity="right" android:layout_row="1" android:text="user Name: " > </TextView> <EditText android:id="@+id/input1" android:layout_column="1" android:layout_columnspan="2" android:layout_row="1" android:ems="10" /> 58/76

59 <TextView android:layout_column="0" android:layout_gravity="right" android:layout_row="2" android:text="password: " > </TextView> <EditText android:layout_column="1" android:layout_columnspan="2" android:layout_row="2" android:ems="8" /> <Button android:layout_column="2" android:layout_row="3" android:text="login" /> </GridLayout> Run your example. You should see a nice arranged layout. This is a layout example wherefore we have not connected any functionality to it. To extend this example you could now connect the Buttonwith a method in the Activityvia its android:onclick. 16. ScrollView ScrollViews can be used to contain one view that might be to big to fit on one screen. If the view is to big the ScrollView will display a scroll bar to scroll the context. Of course this view can be a layout which can then contain other elements. Create an android project "de.vogella.android.scrollview" with the activity "ScrollView". Create the following layout and class. 59/76

60 <?xml version="1.0" encoding="utf-8"?> <ScrollView xmlns:android=" android:layout_width="fill_parent" android:layout_height="fill_parent" android:fillviewport="true" android:orientation="vertical" > <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="vertical" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:paddingleft="8dip" android:paddingright="8dip" android:paddingtop="8dip" android:text="this is a header" android:textappearance="?android:attr/textappearancelarge" > </TextView> <TextView android:id="@+id/textview02" android:layout_width="wrap_content" android:layout_height="fill_parent" android:layout_weight="1.0" android:text="@+id/textview02" > </TextView> <LinearLayout android:id="@+id/linearlayout02" android:layout_width="wrap_content" android:layout_height="wrap_content" > <Button android:id="@+id/button01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1.0" android:text="submit" > </Button> <Button android:id="@+id/button02" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1.0" android:text="cancel" > 60/76

61 </Button> </LinearLayout> </LinearLayout> </ScrollView> package de.vogella.android.scrollview; import android.app.activity; import android.os.bundle; import android.view.view; import android.widget.textview; public class ScrollView extends Activity { /** Called when the activity is first created. public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); TextView view = (TextView) findviewbyid(r.id.textview02); String s=""; for (int i=0; i < 100; i++) { s += "vogella.de "; view.settext(s); The attribute "android:fillviewport="true"" ensures that the scrollview is set to the full screen even if the elements are smaller then one screen and the "layout_weight" tell the android system that these elements should be extended. 61/76

62 17. Fragments Overview Fragmentcomponents allow you to organize your application code so that it is easier to support different sized devices. Fragmentsare components with their own lifecycle and their own user interface. They can be defined via layout files or via coding. Fragmentsalways run in the context of an Activity. If an Activityis stopped its Fragmentswill also be stopped; if an Activityis destroyed its Fragmentswill also get destroyed. 62/76

63 If a Fragmentcomponent is defined in an XML layout file, the android:nameattribute points to the Fragments class. The base class for Fragmentsis android.app.fragment. For special purposes you can also use more special classes, like ListFragmentor DialogFragment. The oncreateview() method is called by Android once the Fragmentshould create its user interface. Here you can inflate an layout. The onstart() method is called once the Fragment gets visible. Fragmentscan be dynamically added and removed from an Activityvia Fragmenttransactions. This will add the action to the history stack of the Activity, i.e. this will allow to revert the Fragmentchanges in the Activityvia the back button When to use Fragments Fragmentsmake it easy to re-use components in different layouts, e.g. you can build single-pane layouts for handsets (phones) and multi-pane layouts for tablets. This is not limited to tablets; for example you can use Fragmentsalso to support different layout for landscape and portrait orientation. But as tablets offer significantly more space you typically include more views into the layout and Fragmentsmakes that easier. The typical example is a list of items in an activity. On a tablet you see the details immediately on the same screen on the right hand side if you click on item. On a handset you jump to a new detail screen. The following discussion will assume that you have two Fragments(main and detail) but you can also have more. We will also have one main activity and one detailed activity. On a tablet the main activity contains both Fragmentsin its layout, on a handheld it only contains the main fragment. To check for an fragment you can use the FragmentManager. DetailFragment fragment = (DetailFragment) getfragmentmanager(). findfragmentbyid(r.id.detail_frag); if (fragment==null! fragment.isinlayout()) { // start new Activity else { fragment.update(...); 63/76

64 To create different layouts with Fragmentsyou can: Use one activity, which displays two Fragmentsfor tablets and only one on handsets devices. In this case you would switch the Fragmentsin the activity whenever necessary. This requires that the fragment is not declared in the layout file as such Fragmentscannot be removed during runtime. It also requires an update of the action bar if the action bar status depends on the fragment. Use separate activities to host each fragment on a handset. For example, when the tablet UI uses two Fragmentsin an activity, use the same activity for handsets, but supply an alternative layout that includes just one fragment. When you need to switch Fragments, start another activity that hosts the other fragment. The second approach is the most flexible and in general preferable way of using Fragments. In this case the main activity checks if the detail fragment is available in the layout. If the detailed fragment is there, the main activity tells the fragment that is should update itself. If the detail fragment is not available the main activity starts the detailed activity. It is good practice that Fragmentsdo not manipulate each other. For this purpose a Fragmenttypically implements an interface to get new data from its host Activity. 18. Fragments Tutorial Overview The following tutorial demonstrates how to use Fragments. The entry Activity(called MainActivityof our application ) will use different layouts for portrait and for landscape mode. In portrait mode MainActivitywill show one Fragment with a list of names. If the user touches an item in the list, a second Activitycalled DetailActivitywill start and show the selected text. In landscape mode MainActivitywill show two Fragments. The first is again the Fragmentswhich shows the list of names. The second Fragmentshows the text of the current selected item. This is similar to the portrait mode, but the whole information will be shown on one screen Create project 64/76

65 Create a new project de.vogella.android.fragmentswith an Activitycalled MainActivity Create layouts for landscape mode Create or change the following layout files in the "res/layout/" folder. First create the following file called "details.xml". This layout will be used by the DetailFragment. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/detailstext" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_gravity="center_horizontal center_vertical" android:layout_margintop="20dip" android:text="large Text" android:textappearance="?android:attr/textappearancelarge" android:textsize="30dip" /> </LinearLayout> Change the existing "main.xml" file. This layout will be used by MainActivityin landscape mode and shows two Fragments. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="horizontal" > <fragment android:id="@+id/listfragment" android:layout_width="150dip" android:layout_height="match_parent" android:layout_margintop="?android:attr/actionbarsize" class="de.vogella.android.fragments.listfragment" ></fragment> <fragment android:id="@+id/detailfragment" 65/76

66 android:layout_width="match_parent" android:layout_height="match_parent" class="de.vogella.android.fragments.detailfragment" > <!-- Preview: --> </fragment> </LinearLayout> Create Fragment classes Create now the Fragmentclasses. Create the ListFragmentclass. package de.vogella.android.fragments; import android.content.intent; import android.os.bundle; import android.view.view; import android.widget.arrayadapter; import android.widget.listview; public class ListFragment extends android.app.listfragment public void oncreate(bundle savedinstancestate) { public void onactivitycreated(bundle savedinstancestate) { super.onactivitycreated(savedinstancestate); String[] values = new String[] { "Android", "iphone", "WindowsMobile", "Blackberry", "WebOS", "Ubuntu", "Windows7", "Max OS X", "Linux", "OS/2" ; ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(), android.r.layout.simple_list_item_1, values); public void onlistitemclick(listview l, View v, int position, long id) { String item = (String) getlistadapter().getitem(position); DetailFragment fragment = (DetailFragment) getfragmentmanager().findfragmentbyid(r.id.detailfragment); if (fragment!= null && fragment.isinlayout()) { fragment.settext(item); else { Intent intent = new Intent(getActivity().getApplicationContext(), DetailActivity.class); 66/76

67 intent.putextra("value", item); startactivity(intent); Create the DetailFragmentclass. package de.vogella.android.fragments; import android.app.fragment; import android.os.bundle; import android.util.log; import android.view.layoutinflater; import android.view.view; import android.view.viewgroup; import android.widget.textview; public class DetailFragment extends Fragment public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); Log.e("Test", public void onactivitycreated(bundle savedinstancestate) { public View oncreateview(layoutinflater inflater, ViewGroup container, Bundle savedinstancestate) { View view = inflater.inflate(r.layout.details, container, false); return view; public void settext(string item) { TextView view = (TextView) getview().findviewbyid(r.id.detailstext); view.settext(item); 67/76

68 18.5. Create layouts for landscape mode We want that Android uses a different main.xml file in portrait model then in landscape mode. For this reason create the "res/layout-port" folder. In portrait mode Android will check the "layout-port" folder for fitting layout files. Only if we would not have a "main.xml" file in "layout-port", Android would check the "layout" folder. Therefore create the following "main.mxl" layout file in "res/layout-port". <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="horizontal" > <fragment android:id="@+id/listfragment" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_margintop="?android:attr/actionbarsize" class="de.vogella.android.fragments.listfragment" /> </LinearLayout> Also create the "details_activity_layout.xml" layout file. This layout will be used in the DetailActivitywhich is only used in portrait mode. Please note that we could have create this file also in the "layout" folder, but as it is only used in portrait mode it is best practise to place it into this folder. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <fragment android:id="@+id/detailfragment" android:layout_width="match_parent" android:layout_height="match_parent" class="de.vogella.android.fragments.detailfragment" /> </LinearLayout> 68/76

69 18.6. Activities Create a new Activitycalled DetailActivitywith the following class. package de.vogella.android.fragments; import android.app.activity; import android.os.bundle; import android.widget.textview; public class DetailActivity extends Activity protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.details_activity_layout); Bundle extras = getintent().getextras(); if (extras!= null) { String s = extras.getstring("value"); TextView view = (TextView) findviewbyid(r.id.detailstext); view.settext(s); MainActivitywill remain unmodified. package de.vogella.android.fragments; import android.app.activity; import android.os.bundle; public class MainActivity extends Activity { /** Called when the activity is first created. public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); 69/76

70 18.7. Run Run your example. If you run the application in portrait mode you should see only one Fragment. Use Ctrl+F11 to switch the orientation. In horizontal mode you should see two Fragments. If you select an item in portrait mode a new Activityshould get started with the selected item. In horizontal mode your second Fragmentshould display the select item. 19. DDMS perspective and important views DDMS - Dalvik Debug Monitor Server Eclipse provides a perspective for interacting with your Android (virtual) device and your Android application program. Select Window Open Perspective Other DDMS to open this perspective. It includes several Viewswhich can also be used independently and allows for example the application to place calls and send SMS to the device. It also allows the application to set the current geo position and allows you to perform a performance trace of your application LogCat View You can see the log (including System.out.print() statements) via the LogCat view. 70/76

71 19.3. File explorer The file explorer allows to see the files on the Android simulator. 71/76

72 20. Shell Android Debugging Bridge - Shell You can access your Android emulator also via the console. Open a shell, switch to your "android-sdk" installation directory into the folder "tools". Start the shell via the following command "adb shell". adb shell You can also copy a file from and to your device via the following commands. // Assume the gesture file exists on your Android device adb pull /sdcard/gestures ~/test // Now copy it back adb push ~/test/gesture /sdcard/gestures2 72/76

73 This will connect you to your device and give you Linux command line access to the underlying file system, e.g. ls, rm, mkdir, etc. The application data is stored in the directory "/data/data/package_of_your_app". If you have several devices running you can issue commands to one individual device. # Lists all devices adb devices #Result List of devices attached emulator-5554 attached emulator-5555 attached # Issue a command to a specific device adb -s emulator-5554 shell Uninstall an application via adb You can uninstall an android application via the shell. Switch the data/app directory (cd /data/app) and simply delete your android application. You can also uninstall an app via adb with the package name. adb uninstall <packagename> Emulator Console via telnet Alternatively to adb you can also use telnet to connect to the device. This allows you to simulate certain things, e.g. incoming call, change the network "stability", set your current geocodes, etc. Use "telnet localhost 5554" to connect to your simulated device. To exit the console session, use the command "quit" or "exit". For example to change the power settings of your phone, to receive an sms and to get an incoming call make the following. # connects to device telnet localhost 5554 # set the power level power status full 73/76

74 power status charging # make a call to the device gsm call # send a sms to the device sms send Will be home soon # set the geo location geo fix For more information on the emulator console please see Emulator Console manual 21. Deploy your application on a real device Turn on "USB Debugging" on your device in the settings. Select in the settings Applications > Development, then enable USB debugging. You also need to install the driver for your mobile phone. For details please see Developing on a Device. Please note that the Android version you are developing for must be the installed version on your phone. To select your phone, select the "Run Configurations", select "Manual" selection and select your device. 74/76