android.app.Application クラスを拡張する

Manifest の <application に、android:name で、android.app.Application の拡張クラスを定義

Manifest.xml

    <application android:name=".MyApplication" android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".MainActivity">
        …
    </application>

MyApplication.java

public class MyApplication extends android.app.Application {

	private int myField;

	public void setMyField(int field){
		this.myField = field;
	}
	public int getMyField(){
		return this.myField;
	}

}

使う時はこんな感じで使う。

MainActivity.java

public class MainActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // set my activithy to Application context
        MyApplication app = (MyApplication)getApplication();
        app.setMyField(1);
        …
    }
}