Why onDestroy inActivity A not being called after a call to finish() in ActivityB

Question

The next process is simple to understand and to reproduce but leads to a bug:

• activityA starts an activityB in its onCreate() method
• activityB is created and I call finish() in its onResume() method
• activityB onDestroy() is called
• activityA onResume() is called
• and here in activityA, I click a menu button to call finish() - or press the back key.
• activityA is removed but onDestroy() is NOT called and A is still living ( adb shell dumpsys 'myPackageName' indicates too many living Activities )

Code

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="gleroy.com.algo">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">
        <activity
            android:name=".activity.MainActivity"
            android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>


        <activity
            android:name="gleroy.com.algo.activity.FakeA"
            android:label="@string/app_name"></activity>

        <activity
            android:name="gleroy.com.algo.activity.FakeB"
            android:label="@string/app_name"></activity>
    </application>
</manifest>

Activity A :

public class FakeA extends Activity {

    private final static String TAG = FakeA.class.getCanonicalName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.d(TAG, "onCreate, taskId :" + getTaskId());
        super.onCreate(savedInstanceState);

        Intent intent = new Intent(FakeA.this, FakeB.class);
        startActivity(intent);
    }

    @Override
    protected void onResume() {
        Log.d(TAG, "onResume");
        super.onResume();
    }


    @Override
    protected void onDestroy() {
        Log.d(TAG, "onDestroy");
        super.onDestroy();
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        super.onCreateOptionsMenu(menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()) {
            case R.id.stop_session_menu_item:
                /* stop and quit */
                finish();
                return false;
        }

        return super.onOptionsItemSelected(item);
    }
}

Activity B :

public class FakeB extends Activity {

    private final static String TAG = FakeB.class.getCanonicalName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.d(TAG, "onCreate, taskId :"+getTaskId());
        super.onCreate(savedInstanceState);
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG, "onResume, isFinishing :" + isFinishing());
        finish();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy");
    }
}

Activity A is started from MainActivity which contains a simple button :

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, FakeA.class);
            startActivity(intent);
        }
    });

So I know that we can't be sure that onDestroy() is gonna be called but here my ActivityA is clearly leaking.

Also I observed that if I use a Timer and TimerTask to delay startActivity in ActivityA or finish() in ActivityB then I don't have this bug anymore.

Here are the events :

• FakeA onCreate, taskId :154
• FakeA onResume
• FakeA onPause, isFinishing : false
• FakeB onCreate, taskId :154
• FakeB onResume, isFinishing :false
• FakeA onResume
• FakeB onDestroy
• call finish or press back key : FakeA onPause, isFinishing : true

Answer 1

In place of finish() try finishAffinity() . As far as i know: finish() just destroys the current live Activity while, finishAffinity() destroys all active Activities .

Answer 2

最好的解决方案是检测启动Activity FakeB是否有用。