Ytukyg

I hope to define whether a activity is foreground in Android, and bring it to background when it is foreground. How can I do it?

You know the <uses-permission android:name="android.permission.GET_TASKS"/> is Deprecated!

Sample Code

private boolean isTopActivity(String activityName){

    ActivityManager manager = (ActivityManager) mContext.getSystemService(ACTIVITY_SERVICE);

    List<ActivityManager.RunningTaskInfo> runningTaskInfos = manager.getRunningTasks(1);

    String cmpNameTemp = null;

    if(runningTaskInfos != null){

        cmpNameTemp = runningTaskInfos.get(0).topActivity.toString();

    }

    if(cmpNameTemp == null){

        return false;

    }

    return cmpNameTemp.equals(activityName);

}

this is supported natively by the Activity lifecycle which is onResume, which will be called after the activity comes in the foreground.

public void onResume() {

    // do here what you need

}

Put below code in a file in your application

    public class Foreground implements Application.ActivityLifecycleCallbacks {



public static final long CHECK_DELAY = 500;

public static final String TAG = Foreground.class.getName();



public interface Listener {



    public void onBecameForeground();



    public void onBecameBackground();



}



private static Foreground instance;



private boolean foreground = false, paused = true;

private Handler handler = new Handler();

private List<Listener> listeners = new CopyOnWriteArrayList<Listener>();

private Runnable check;



/**

 * Its not strictly necessary to use this method - _usually_ invoking

 * get with a Context gives us a path to retrieve the Application and

 * initialise, but sometimes (e.g. in test harness) the ApplicationContext

 * is != the Application, and the docs make no guarantees.

 *

 * @param application

 * @return an initialised Foreground instance

 */

public static Foreground init(Application application) {

    if (instance == null) {

        instance = new Foreground();

        application.registerActivityLifecycleCallbacks(instance);

    }

    return instance;

}



public static Foreground get(Application application) {

    if (instance == null) {

        init(application);

    }

    return instance;

}



public static Foreground get(Context ctx) {

    if (instance == null) {

        Context appCtx = ctx.getApplicationContext();

        if (appCtx instanceof Application) {

            init((Application) appCtx);

        }

        throw new IllegalStateException(

                "Foreground is not initialised and " +

                        "cannot obtain the Application object");

    }

    return instance;

}



public static Foreground get() {

    if (instance == null) {

        throw new IllegalStateException(

                "Foreground is not initialised - invoke " +

                        "at least once with parameterised init/get");

    }

    return instance;

}



public boolean isForeground() {

    return foreground;

}



public boolean isBackground() {

    return !foreground;

}



public void addListener(Listener listener) {

    listeners.add(listener);

}



public void removeListener(Listener listener) {

    listeners.remove(listener);

}



@Override

public void onActivityResumed(Activity activity) {

    paused = false;

    boolean wasBackground = !foreground;

    foreground = true;



    if (check != null)

        handler.removeCallbacks(check);



    if (wasBackground) {

        Log.i(TAG, "went foreground");

        for (Listener l : listeners) {

            try {

                l.onBecameForeground();

            } catch (Exception exc) {

                Log.e(TAG, "Listener threw exception!", exc);

            }

        }

    } else {

        Log.i(TAG, "still foreground");

    }

}



@Override

public void onActivityPaused(Activity activity) {

    paused = true;



    if (check != null)

        handler.removeCallbacks(check);



    handler.postDelayed(check = new Runnable() {

        @Override

        public void run() {

            if (foreground && paused) {

                foreground = false;

                Log.i(TAG, "went background");

                for (Listener l : listeners) {

                    try {

                        l.onBecameBackground();

                        Intent intent = getPackageManager().getLaunchIntentForPackage("com.package.name");

                        if (intent != null) {

                            // We found the activity now start the activity

                            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

                            startActivity(intent);

                        } else {

                            // Bring user to the market or let them choose an app?

                            intent = new Intent(Intent.ACTION_VIEW);

                            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

                            intent.setData(Uri.parse("market://details?id=" + "com.package.name"));

                            startActivity(intent);

                        }

                    } catch (Exception exc) {

                        Log.e(TAG, "Listener threw exception!", exc);

                    }

                }

            } else {

                Log.i(TAG, "still foreground");

            }

        }

    }, CHECK_DELAY);

}



@Override

public void onActivityCreated(Activity activity, Bundle savedInstanceState) {

}



@Override

public void onActivityStarted(Activity activity) {

}



@Override

public void onActivityStopped(Activity activity) {

}



@Override

public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

}



@Override

public void onActivityDestroyed(Activity activity) {

}

Now in onCreate method of Application.class put the code:

 @Override

public void onCreate() {

    super.onCreate();

    Foreground.init(this);

}

You can now use Foreground.isBackground() to get application is in background or not.

You can even perform specific task in one of the overridden lifecycle methods (onActivityPaused, onActivityStopped etc)