Android：从最近使用的应用程序按钮关闭应用程序时未调用OnDestroy

Question

When we press this button

We see the apps which we didn't close, like this

But when we want to close an app from this screen (below image), the method onDestroy() isn't called, however the app is closed. I need to call onDestroy() when the app is closed in this way. How can I do this?

Answer 1

As specified in the Android documentation, it is not guaranteed that onDestroy() will be called when exiting your application.

"There are situations where the system will simply kill the activity's hosting process without calling this method"

https://developer.android.com/reference/android/app/Activity.html#onDestroy%28%29

Instead, you can create a service which will be notified when the Task your activities are running inside is destroyed.

Create the service class:

public class ClosingService extends Service {

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onTaskRemoved(Intent rootIntent) {
        super.onTaskRemoved(rootIntent);

        // Handle application closing
        fireClosingNotification();

        // Destroy the service
        stopSelf();
    }
}

Declare / register your service in the manifest (within the application tag, but outside any activity tags):

<service android:name=".services.ClosingService"
             android:stopWithTask="false"/>

Specifying stopWithTask="false" will cause the onTaskRemoved() method to be triggered in your service when the task is removed from the Process.

Here you can run your closing application logic, before calling stopSelf() to destroy the Service.

Answer 2

You should read some info about Activity lifecycle. There is one thing about onDestroy method, it doesn't get called all time. You mustn't rely on it.

Specify please what are you trying to achive and I'll try to offer better solution.

Suggestion

So, if I understood you right, I can suggest one thing. Start a Service that will fire LocalBroadcast every N seconds (it's not really heavy to system). Register and BroadcastReceiver for this broadcast in Activities . This way you'll get true or false depending on if there is any BroadcastReceiver that can catch your LocalBroadcast . And if no receivers than check for some SharedPreferences value that indicates if Button was pressed.

Answer 3

More promising approach than using a bound service would be using activity lifecycle callbacks in the Application . Though the approach shown in the accepted answer would work but the service would be running in the background until the activity is terminated which is expensive. Instead, I would suggest the use of your implementation of Application .

1) Make a class extending Application, then use it by providing its name in the name attribute of Application tag in Manifest file

class MusicPlayerApplication: Application() {
    private val TAG = MusicPlayerApplication::class.java.simpleName

    override fun onCreate() {
        super.onCreate()

        registerActivityLifecycleCallbacks(object: ActivityLifecycleCallbacks {
            override fun onActivityPaused(activity: Activity?) {

            }

            override fun onActivityResumed(activity: Activity?) {
            }

            override fun onActivityStarted(activity: Activity?) {
            }

            override fun onActivityDestroyed(activity: Activity?) {
                Log.d(TAG, "onActivityDestroyed: ")
                val activityName = activity!!.localClassName
            }

            override fun onActivitySaveInstanceState(activity: Activity?, outState: Bundle?) {
            }

            override fun onActivityStopped(activity: Activity?) {
            }

            override fun onActivityCreated(activity: Activity?, savedInstanceState: Bundle?) {
            }
        })
    }
}

AndroidManifest.xml

<application
            android:name=".MusicPlayerApplication"
....

I have tested this approach using logcat, my onDestory is not getting called but onActivityDestroyed in the callback is getting called every time I kill the activity from RAM but this doc says that onActivityDestroyed would be called when onDestory of an activity is called but that doesn't seem to happen. However, I find this approach better than using services .

Answer 4

Your problem is that onDestroy is only called in a Service . In an Activity the called method is onPause() Put simply in your Activity the field:

@Override
public void onPause()
{
//Put your Code here
}