public class MainApp extends Application {

      private static ArrayList<WeakReference<Activity>> activitys;

      public volatile static MainApp instance;

     @Override

     public void onCreate() {

         // TODO Auto-generated method stub

         super.onCreate();

      }

     public MainApp() {

         // TODO Auto-generated constructor stub

     }

     public static MainApp getInstance(){

         if(instance==null){

             synchronized (MainApp.class) {

                 if(instance==null){

                     instance=new MainApp();

                 }

             }

         }

         return instance;

     }

         public static void addActivity(Activity context) {

             if(activitys==null){

                 activitys=new ArrayList<WeakReference<Activity>>();

             }

             activitys.add(new WeakReference<Activity>(context));

         }

         public static void removeActivity(Activity activity) {

             if(activity!=null){

                 activitys.remove(new WeakReference<Activity>(activity));

                 activity.finish();

                 activity=null;

             }

         }

         public static void finishAllActivity() {

             Activity activity;

             for (int i = activitys.size() - 1; i >= 0; i--) {

                 activity = activitys.get(i).get();

                 if (activity != null && !activity.isFinishing()) {

                     activity.finish();

                 }

             }

             activitys.clear();

         }