Singleton, Lifecycles and the Application class

Start by creating a basic app:

F:\work> mvn archetype:generate -DarchetypeCatalog=http://kallisti.eoti.org:8081/content/repositories/snapshots/archetype-catalog.xml

Choose the galatea-archetype plugin

groupId: org.eoti.android
artifactId: ApplicationTest
version: 1.0-SNAPSHOT
package: org.eoti.android

Make sure you have your emulator running and:

F:\work> cd ApplicationTest
F:\work\ApplicationTest> mvn clean install

Create a new class in the same package as your activity... In my case, I created src\main\java\org\eoti\android\MyMainApplication.java

public class MyMainApplication extends Application
{
    private static String TAG = "MyMainApplication";
    private static MyMainApplication singleton;
    public static MyMainApplication getInstance(){return singleton;}
    private int count = 0;

    @Override
    public void onCreate() {
        super.onCreate();
        singleton = this;
        Log.i(TAG, "Singleton created");
    }

    public int count(){return count++;}
}

In your AndroidManifest.xml, replace this line:

    <application android:icon="@drawable/icon" android:label="@string/app_name"> 

with this line:

    <application android:icon="@drawable/icon" android:label="@string/app_name" android:name="MyMainApplication">

Open your activity (src\main\java\org\eoti\android\ApplicationTestActivity in my case)
Add this to the end of your onCreate method:

        Log.i(TAG, "Created instance#" + MyMainApplication.getInstance().count());

Redeploy (mvn clean install) and watch the logs (adb logcat) as you launch the app.

• You'll see that the singleton is created and the counter is reported.
• Hit the back button and relaunch the app a few times.  
• You'll see that the counter increments each time.
• Hit the home button. 
• Now, hold down the home button and reselect your app.  
• You'll notice it is started again, but NOT created again (no counter reported).