Android on Intel Course App Development - Advanced

Transcription

1 Android on Intel Course App Development - Advanced Paul Guermonprez paul.guermonprez@intel.com Intel Software

2 Persistence

3 Preferences Shared preference can be used to remember basic information (string, integer, boolean, etc). It is easy to use. To save data, you need to retrieve the SharedPreference object editor.

4 Preferences Here is how to save data. And here is how to load data.

5 Instance State When your application is put onpause, the method onsaveinstancestate is called. If you don't want to loose data, you can save them.

6 SQLite SQLite is a light database that you can use to persist your application's data You can use SQLite in Java and the library is already integrated in Android framework.

7 JSON JSON is an open standard that can be used to send/receive information. Google-gson is a free library that allows to serialize/deserialize java objects Download google gson on

8 JSON Unzip the file anywhere you want but put the jar file in the libs folder of your Android* project Add the jar file to your classpath Here is a snippet of Java code

9 JSON And the result is a JSON string. You can use this string in a HTTP request for example. In most of the applications, using the shared preference system is enough and you don't need to use a SQL database.

10 Background process

11 AsyncTask You can't block the UI thread more than few seconds or the application will crash But you sometimes need more than few seconds to process your data You can create a thread but... you can't refresh UI from the non UI thread

12 AsyncTask AsyncTask can process data on a different thread than the UI thread. They can also refresh the UI (ProgressBar for example)

13 AsyncTask Create an inner class that inherits from AsyncTask

14 AsyncTask In Android* you can also use the Java threads but remember that if you want to update the UI during your background process, the AsyncTask offers an elegant solution.

15 Sensors

16 Sensors To retrieve a sensor, you need to use the SensorManager Then you can get the sensor You also need to implement a SensorEventListener

17 Sensors Then you must register your sensor. A good location is in the OnResume function. Don't forget to unregister your listener in the OnPause function.

18 Sensors full code Using the sensors is simple with Android*. The Sensor interface allows to manipulate any kind of sensor.

19 NFC When your phone detect a NFC Tag, Android* tries to launch an application that can read it. You can declare specific intent-filter in the manifest to inform Android that your application can read NDEF tags In this example, our application will be launched when the tag contains a http link.

20 NFC Here is the Java implementation

21 NFC In the Java side, you can check that your application can really handle the intent. Then you can retrieve the TAG We saw how to use NFC with Android* Intents but it is also possible to read NFC tags in a running application.

22 Good to know

23 Resources It is often a good practice to separate implementations details like text strings or graphical element sizes from the code or user interface definitions. To do so, use resources. From the code : Resources res = getresources(); CharSequence resmsg = res.gettext(r.string.message); It is also possible to reference resources from other resources, or access system resources.

24 Localization It's easy to make your app multilingual if you start using resources from the beginning. You already have a res/values/strings.xml file. All you need to do is create res/values-xx/strings.xml files where XX is the language-region code.

25 Note : Logs Using the Android* log system is really important when you develop your application. You can configure Eclipse* to display only a subset of the logs. First, you need to display the Logcat (Windows Show View Other...) In the search tool, type logcat.

26 Note : Logs Then you can add a new channel Tag name used to filter your logs

27 Note : Logs In your java code And here is the result You can select the log priority Log.d: For debug messages Log.e: For error messages Log.i: For information messages Log.v: For verbose messages Log.w: For warning messages

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