why “onPause” is not called in following situation?

Question

By the document, "onPause" is called, when:

when the system is about to start resuming a previous activity.

Compared to "onStop", the difference is:

Called when the activity is no longer visible to the user, because another activity has been resumed and is covering this one.

But when I long-press HW-Home key and the "recent apps" shows up, the "onPause" is not called.

At this moment, I can no long able to interact with the original activity, but it is still visible.

I am confused by this situation. Please help to explain.

Thank you very much. BR, Henry

Answer 1

This actually happens because when the Home key is long pressed, there is no activity being launched. The onPause/onStop will only be called if you select one of the apps present in the "Recent Apps" list.

The docs of onPause() are pretty clear:

Called as part of the activity lifecycle when an activity is going into the background, but has not (yet) been killed.

Answer 2

public class MainActivity extends Activity
{
    String tag="my result";

    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Log.v(tag,"I am in oncreate");
    }

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        Log.v(tag,"I am in onDestroy");
    }

    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        Log.v(tag,"I am in onpause");
    }

    @Override
    protected void onRestart() {
        // TODO Auto-generated method stub
        super.onRestart();
        Log.v(tag,"I am in onRestart");
    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        Log.v(tag,"I am in onresume");
    }

    @Override
    protected void onStart() {
        // TODO Auto-generated method stub
        super.onStart();
        Log.v(tag,"I am in onstart");
    }

    @Override
    protected void onStop() {
        // TODO Auto-generated method stub
        super.onStop();
        Log.v(tag,"I am in onstop");
    }
}

Run it and check logcat.press back button and then check.after again start application and

Press call button then check logcat now press Back button and again check logcat. you can easily understand life cycle of Activity.

Answer 3

In a lot of modern phones, the recent apps list is an activity, and does trigger onPause. I've tested this on a couple of Samsung and LG phones, and the packages are com.android.systemui and com.lge.launcher2 respectively.

That said, it seems like you can't rely on recieving an onPause when you open the recent applications screen. I'm curious to see how many device don't give you the onPause...

Answer 4

@Henry please Try yourself by testing the flow of app. Create an Activity in which Override all the methods and print log under all the methods. The flow is onCreate>>onStart/restart>>onResume and when you press home button or starts any new activity then it called onPause>>onStop and if you finish your app then your app is destroy/finish so where is confusion.

Answer 5

This is what the official documents says about onPause()

Called as part of the activity lifecycle when an activity is going into the background, but has not (yet) been killed. The counterpart to onResume().

When activity B is launched in front of activity A, this callback will be invoked on A. B will not be created until A's onPause() returns, so be sure to not do anything lengthy here.

For detail please see this.