Building Mobile Applications With The.NET Compact Framework

Transcription

1 .NET Mobile Application Development 1 Building Mobile Applications With The.NET Compact Framework Objectives The aim of this tutorial is to provide a practical introduction to the use of the.net Compact Framework and how Visual Studio.NET can be used to build Compact Framework applications which target mobile devices. Prerequisites It is assumed that you have previously used Visual Studio to develop.net applications and that you are familiar with the operation of the Visual Studio debugger.. Lab Setup You should ensure that you have Visual Studio.NET 2003 and the SmartPhone 2003 SDK installed before commencing this tutorial. For More Information The best book on the.net Compact Framework is Microsoft.NET Compact Framework Core Reference, Andy Wigley, Stephen Wheelwright, Microsoft Press, 2003, ISBN The Visual Studio help files and.net Compact Framework SDK also contain a large amount of information and code samples on for the compact framework and its API s.

2 2 Building Mobile Applications With The.NET Compact Framework Characteristics of Mobile Devices and Applications One of the most important features of any application designed to run on a mobile device is the look and feel of the user interface. When designing user interfaces for mobile applications one has to be aware that mobile devices are radically different from desktop PC s. The primary differences are the smaller size of the screen and the way in which the user inputs information. Keyboards are not normally provided on mobile devices and users generally use some sort of stylus or mini-keypad to provide input. Interfaces which require the user to enter large amounts of data are therefore not suited to mobile device applications. In addition to the characteristics mentioned above, mobile devices are also limited in the processing power and resources which they have available. When developing applications for these devices it is important to release the resources held by applications as soon as possible, particularly if the resources are scarce. This includes memory, which is often at a premium on mobile devices. Although mobile devices are limited in their computational power and resources, users still expect their applications to deliver a responsive, interactive experience. As a result developers often find themselves facing a tension between resource/memory usage and application performance when developing applications that are both efficient and meet the user s expectations. Creating a Smart Device Application with Visual Studio 2003 Visual Studio 2003 provides developers with the ability to target an application at the.net Compact Framework on a range of devices. Essentially all a developer needs to do to create a Compact Framework application is to create a Smart Device Application project within Visual Studio. Although the environment used to create both desktop and mobile device applications is the same, the developer must be aware that there are differences. The code within a Smart Device Application project is compiled against the.net Compact Framework. Consequently, only classes from the.net Compact Framework libraries are available and these differ from those of the full.net Framework. COM Interop is also not supported. The.NET Compact Framework does not support the full range of.net languages; all managed code must be written in C# or Visual Basic.NET. When debugging an application, a device must be selected on which that application will be run/debugged. The selected device may be a real mobile device or the device emulator supplied with Visual Studio. Additional tools are supplied for connecting to and debugging a remote device.

3 Building Mobile Applications With The.NET Compact Framework 3 Exercise 1: Creating a SmartDevice Project Visual Studio refers to mobile devices (e.g. PDA s, mobile phones, etc) as smart devices and provides Smart Device Application projects to support mobile application development using the.net Compact Framework. In this exercise you will create a Visual Studio Smart Device Application project to support the development of a simple mobile application for a Pocket PC device. The aim of this exercise is simply to get you used to the process of creating Compact Framework projects Start Visual Studio and select New Project from the File menu. From the New Project dialog (Figure 1), select Visual C# Projects in the left-hand pane and Smart Device Application in the right-hand pane. Give your project a sensible name and, if necessary, change the location where Visual Studio will create the project. Once you have entered the basic information about the project, Visual Studio presents you the Smart Device Application wizard (Figure 2). Using this dialog you should choose the type of device (Pocket PC or Windows CE) that you are targeting and the type of application to be built. In this case we wish to build a Windows Application for the Pocket PC. The wizard will create the project files for us and apply the appropriate default settings. In addition it will also create an empty default form design for the application (Figure 3). Notice that the third toolbar from the top of the Visual Studio window has a drop-down box containing the text Pocket PC 2002 Emulator (Default). This box controls the target device for which the project will be compiled. Normally is set to compile for the device emulator provided with Visual Studio but if you have a real device which you want to target, you can select it from this box. Figure 1 : New Project Dialog

4 4 Building Mobile Applications With The.NET Compact Framework Figure 2 : Smart Device Application Wizard Figure 3 : Default state of a Smart Device Application solution Exercise 2: Creating a Simple Application Once you have created a Smart Device Application project, applications that target mobile devices are developed using Visual Studio in much the same way as any other.net application. You can use the Solution Explorer window to work with and manage your solution e.g. open and edit files, add new files, classes or projects, add references to required libraries and to set project and solution properties. User interfaces can be created graphically by dragging and dropping controls from the Visual Studio toolbox on to a form

5 Building Mobile Applications With The.NET Compact Framework 5 and the IntelliSense feature will assist you in using types and methods from the.net Framework API s. There are some differences between developing a.net application for a desktop Windows platform, and developing a Compact Framework application that targets a mobile device. The Compact Framework provides a much more restricted set of Windows Forms controls for use in user interfaces and not all of the types/methods available in the full.net Framework are available in the Compact Framework. However Visual Studio is clever enough to know when you are building an application that targets the Compact Framework. The toolbox will only show you Windows Forms controls that are relevant to the device you are currently targeting 1 and the IntelliSense feature will offer specific information on using types from the Compact Framework API s. If it is not already open, use the Solution Explorer window to open the main form of the application you created in Exercise 1 by double clicking on the file which contains the form. This will open the form in Design View. You can toggle between the Design (visual) and Code views of the form by using the F7/Shift+F7 key combinations. Open the Toolbox and use the Windows forms controls to add a button and a label to your form. Use the Properties window to set the Text property of the Label to an empty string and the Text property of the button to the string Click Me!. You may also wish to give the label and button more meaningful names than the defaults provided by Visual Studio. In the design view of the form, double click the on your button. This opens an editor window showing the code view of the form and adds a method which will operate as the event handler for Click events on the button. Every time the user clicks the button, this method will be executed. Use the Text property of your label to add some code into this method which will change the text displayed by the label when the button is clicked. Try building your application and check that it compiles correctly without error. If there are any compilation errors, check the Task List and Output Windows in Visual Studio to help you identify and resolve the source of these errors. Targetting a Device or Emulator Visual Studio comes equipped with a number of emulators for a range of Pocket PC and SmartPhone based devices. The emulators faithfully reproduce the form factor, user interface mechanisms, behaviour and features of the real devices on a desktop machine. You may wonder why an emulator is required for development work when real mobile devices are easily obtained, but the 1 Not all devices capable of running Compact Framework applications use the same set of Windows Forms controls. For example, not all of the forms controls available on a Pocket PC device are available on a SmartPhone device. However there are many controls that are common to all platforms, but even these have a different appearance and behaviour depending upon which device you are targeting (e.g. the Menu control on the SmartPhone appears and behaves differently to the Pocket PC Menu control).

6 6 Building Mobile Applications With The.NET Compact Framework emulator is an extremely valuable development tool. In most cases it is significantly quicker to run and debug your code in the emulator than it is to load it into, and debug it on, a real device. The best way of working when developing mobile applications is to do the majority of your debugging and testing using the emulator(s) and only test on the real device when you are confident that the application is working as desired and that most of the functionality bugs have been ironed out. Although it would be possible to develop a mobile application using the emulator alone, this may not be advisable as the emulators provided by the current version of Visual Studio do not emulate the different CPU s and other hardware features used by mobile devices. Consequently, when you come to run your application on a real device, you may find that there are subtle differences in the timing and performance of your application as compared to the emulator. Hence it is often best to perform final performance testing on a real device if one is available. The next version Visual Studio (Visual Studio 2005, in alpha testing at the time of writing) will address the issue of processor emulation by providing a complete processor level emulation of the ARM processor used in the majority of mobile devices. When you create a Smart Device Application project, Visual Studio automatically deploys the application to the default emulator for the software platform you chose in the Smart Device Application Wizard (Figure 2). However you may wish to deploy the application to a different emulator or to a real device. A deployment target configuration drop-down box is displayed on the Visual Studio toolbar when working with a Smart Device Application project (Figure 4). This box may appear in a different place on your Visual Studio toolbar, depending upon how it has been set up or you have chosen to arrange the toolbars. However it is easily recognized as it contains a list of deployment targets including at least one emulator and a real device for the software platform you have chosen for your project. If there are several emulators available then these will also appear in this list. You can change the deployment target at any time, except when your application is running, and you choose which device or emulator to target by simply selecting the desired option from this list. Figure 4 : Selecting a deployment target for the application If you choose to target a real device then you must have ActiveSync 2 installed on your development machine and you must establish an ActiveSync 2 It is advisable to ensure that you always have the latest version of ActiveSync installed on your development machine as some devices will not work with older versions of ActiveSync. At the time of writing, the current version is ActiveSync 3.7.1

7 Building Mobile Applications With The.NET Compact Framework 7 connection 3 with the device before you try running or debugging your code. Each time you start the application, Visual Studio will download the application code to the device and start it running. If any additional code is required but is not present on the device (e.g. the Compact Framework, or SQL Server CE) then this will also be downloaded and automatically installed. Build Configurations and Debugging Visual Studio supports the notion of multiple, customizable build configurations for each solution or project that you create. Every solution is created with two default build configurations, Debug and Release. Debug is the default build configuration but there is a build configuration dropdown box that id displayed on the Visual Studio toolbar (Figure 5) and you can choose which configuration you want to build by selecting the appropriate entry from this list. The list will invariably contain Debug and Release entries, but other entries may be present if you have created your own custom build configurations. Again, the build configuration list box may appear in a different place on your Visual Studio toolbar, depending upon how it has been set up or you have chosen to arrange the toolbars. Figure 5 : Selecting a build configuration for the application When you compile and start your application the behaviour of Visual Studio varies depending upon which build configuration is active. If the Debug configuration is active, extra debugging information is compiled into your application code and a set of debugging symbols is produced. When you start the application, it start running under the control of the debugger and you can set breakpoints, watch values and all the normal things you can do with the debugger to inspect and monitor the execution of your code. When you debug a mobile device application, either on a real device or in an emulator, the Visual Studio debugger operates in remote debugging mode. Your application actually executes on the device or in the emulator; the Visual Studio debugger interacts with your application via the (emulated) ActiveSync connection and allows you to monitor and control the operation of your code. If you set breakpoints in your source code, the application running in the device or emulator will pause when those breakpoints are reached and will not continue until you instruct it to do so using the commands in the debugger IDE. If the Release configuration is active when you compile and start your code, no extra debugging information is compiled in to your application and any breakpoints, watchpoints, etc set in the source code are ignored. If an unhandled exception occurs whilst your application is running, in the emulator 3 It is not necessary to establish a partnership with the device, a guest connection will suffice for debugging and testing

8 8 Building Mobile Applications With The.NET Compact Framework or on a device, the system will catch the exception and give you the chance to inspect the code in the debugger. Often this isn t very useful as the code was not compiled with debugging support and it can be difficult to determine whereabouts in the source the exception has occurred. Generally it is best to undertake all the development and testing of your application using the Debug configuration. The only exception to this is if you wish to make performance measurements on your application, and in these circumstances it is best to perform such testing with the Release configuration as this eliminates any overhead caused by the debugger and the its instrumentation code. The finished version of your application should normally be built using the Release configuration. Exercise 3: Running and Debugging the Application using the Emulator Once you are satisfied that your code compiles correctly, you can start running and debugging it in the emulator. Ensure that the deployment target is set to Pocket PC Emulator and that the Debug configuration is active. Start your application running by pressing F5 or selecting Start from the Debug menu. The Pocket PC emulator will appear on screen and your application will be loaded into it. After a short delay your application will begin running in the emulator. You can use the mouse of your development machine to control the emulator in the same way as you would use a stylus and in this way you can interact with your application. Click the button on your application and make sure that the text of the label changes. Now try setting a breakpoint on the first line of code inside the OnClick() method which handles the Click events generated by the button. When you click the button in the emulator you should find that your application freezes and that the Visual Studio displays the line of code at which execution has paused. You can now use the debugger facilities to inspect the contents of variables in your program, view the call stack, view the contents of emulator memory addresses, call stacks, etc of the emulator and control the execution of your application using the Step Into, Step Over, Step Out and Continue commands of the debugger. Optional Exercise: Running and Debugging Applications using a Device If you have a real PDA device running the Pocket PC available to you (e.g. HP ipaq, Casio Cassiopeia, Dell Axim, etc) then you may wish to try deploying your sample application to this device. To do this you must change the deployment target to Pocket PC Device and establish a connection between the device and your development machine using ActiveSync. When you start your application running, Visual Studio will rebuild your code and download the application and any other required software to the device where it will start running. Occasionally there will be errors in deploying the application to the device. If this happens, try

9 Building Mobile Applications With The.NET Compact Framework 9 starting the application again as a subsequent download will often work. If this does not solve the problem, try re-establishing the ActiveSync connection, resetting the device and/or the development machine. Creating SmartPhone Applications Building an application for the SmartPhone platform is fundamentally the same as building an application for the Pocket PC. You start by creating a new Smart Device Application project but instead of choosing Pocket PC as the target platform in the Smart Device Wizard (), you select SmartPhone as the target platform. Note that if the SmartPhone 2003 SDK has not been installed on your development machine, SmartPhone will not appear as a platform type in the Smart Device Wizard. Note too that it is only possible to.net Compact Framework applications for the SmartPhone using the SmartPhone 2003 SDK. The SmartPhone 2002 SDK does not support the development of.net applications. Two SmartPhone emulators are supplied with the SmartPhone 2003 SDK, and this can be used for testing your code during development. The possible target emulators are SmartPhone 2003 Emulator (Virtual Radio) This is the default emulator and it fully emulates a SmartPhone device. It uses the network connections present on the development machine to emulate network connectivity using GPRS and also emulates the telephony (GSM) features of the device in software. SmartPhone 2003 Emulator (Radio Required) This emulator fully models a SmartPhone device but does not attempt to emulate any of the radio features of a SmartPhone device (i.e. GPRS or GSM). An appropriate radio card must be installed in the development machine if you intend to use this emulator to test applications that rely on SmartPhone radio features (e.g. GPRS network connectivity). The emulator will use the radio card in the development machine as if it were the real radio in a real SmartPhone device. You may also target your application at a real SmartPhone device, connected to the development machine via ActiveSync, by selecting SmartPhone Device as the deployment target. Exercise 4: Building a Simple SmartPhone Application We will conclude this tutorial by building and testing a simple calculator application for a Windows powered SmartPhone device which will read in two integer values and perform one of four simple arithmetic operations upon them. Using Visual Studio.NET 2003, create a new Smart Device Application project which targets the SmartPhone platform. Ensure that the deployment target is SmartPhone Emulator (Virtual Radio). After Visual Studio creates your project, you will be presented with the design view of a main form for your application. Using the Forms components from the Visual Studio toolbox, add two textboxes to the

10 10 Building Mobile Applications With The.NET Compact Framework form to receive the values the user wishes to operate on and add some labels to give guidance to the user. The initial text value held in these textboxes should be set to an empty string. Add a third textbox, and another label, below the previous ones to display the result of the calculation. Set this textbox to be read only using the Properties window. Add an Operation menu to your application and add four items under this menu Add, Subtract, Multiply and Divide. Your form should look something similar to that shown in Figure 6. Figure 6 : User interface for simple SmartPhone calculator Add a new class to your Visual Studio project using the Solution Explorer. This class should be called Calculator and should have four public static methods Add(), Subtract(), Multiply(), Divide(). Each of these methods should accept two integer parameters and return an integer result. Return to the design view of your main form. Double click each menu item under the Operation menu in turn to create an OnClick() event handler for each of the menu items. Add some code to each of these menu handlers which will convert the values from the two textboxes into integers call the relevant static method of the Calculator class, passing in the two integer values that have just been created display the value returned in the third textbox Build your code and test it by deploying it to the SmartPhone emulator. Enter some known values into the textboxes and test each arithmetic operation in turn to make sure that they behave as expected. What happens if you enter non-numeric values in the textboxes or the arithmetic operation produces an error (e.g. divide by zero)? Can you improve your application so that it deals successfully with these kind of errors and does not cause the application to crash?

11 Building Mobile Applications With The.NET Compact Framework 11 Summary In this tutorial we have seen how to create Pocket PC and SmartPhone applications using Visual Studio.NET You should now be able to create a Visual Studio project to build a mobile application for a particular software platform, deploy the application to a specified emulator or device and run or debug that application on the chosen emulator or device.