Notification opens activity, press back button, prevent opening back stack activity?

Question

This looks very similar to my previous question because it's some sort of follow up. I was not very happy with the only solution given; also, the solution was for a problem slightly different from this one. So let me try to explain the problem again...

1. A notification is created at boot (with a BroadcastReceiver).
2. My app main activity is opened and the home button is pressed (the activity will be sent to the back stack).
3. I pull down the status bar and press on the notification previously created at boot.
4. That will start some activity, different from the main one.
5. I press the back button and the main activity is displayed.

This is not very different from my previous question... The thing is, "main activity" was just an example. I could have opened the app main activity and then opened the about activity through a menu option and pressed the home button. The back stack would now be MainActivity » AboutActivity. Which means that when the back button is pressed while in "some activity" (started by pressing the notification), we would be brought to the top of the back stack, that is, the about activity.

What basically want is to prevent any other activity to be opened when I press the back button while in "some activity" (again, started by pressing the notification). I want to be brought exactly where I was, that could be the desktop or some other app's activity, but not my app's MainActivity nor AboutAcitivity cause that's not where I was, those were in the back stack, "sleeping" in the background.

I have come up with a solution, but I don't think it's very elegant and I was looking for something more, well, elegant... If you have any other suggestion, please, let me know.

Anyway, this is my proposed solution:

// I use this class for public static (or public static final) members and
// methods

public final class AppHelper {
    public static final String KEY_RESUME_FROM_NOTIFICATION = "resumeFromNotification";

    private static boolean sResumeFromNotification = false;

    public static boolean getResumeFromNotification() {
        return sResumeFromNotification;
    }

    public static void setResumeFromNotification(boolean resumeFromNotification) {
        sResumeFromNotification = resumeFromNotification;
    }
}

public class MainActivity extends ListActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        (...)
    }

    @Override
    protected void onResume() {
        super.onResume();

        if(AppHelper.getResumeFromNotification()) {
            AppHelper.setResumeFromNotification(false);
            moveTaskToBack(true);
        }
    }

}

public class AboutActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        (...)
    }

    @Override
    protected void onResume() {
        super.onResume();

        if(AppHelper.getResumeFromNotification()) {
            AppHelper.setResumeFromNotification(false);
            moveTaskToBack(true);
        }
    }

}

public class SomeActivity extends Activity {

    // This will be called when the notification is pressed and the activity is
    // not opened yet

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        (...)

        extractIntentExtras(intent);
    }

    // This will be called if the activity is already opened and the
    // notification is pressed

    @Override
    protected void onNewIntent(Intent intent) {
        extractIntentExtras(intent);
        super.onNewIntent(intent);
    }

    private void extractIntentExtras(Intent intent) {
        Bundle bundleExtras = intent.getExtras();

        if(bundleExtras != null) {
            // These intent extras are set on the Intent that starts this activity
            // when the notification is pressed

            AppHelper.setResumeFromNotification(bundleExtras.getBoolean(
                AppHelper.KEY_RESUME_FROM_NOTIFICATION));

            mRowId = bundleExtras.getLong(AgendaNotesAdapter.KEY_ROW_ID);
            populateNoteUpdateFields();
        }
    }

}

I don't know, but this solution doesn't look very elegant to me (but it works as I expect it) and I'm looking for alternatives or for strong opinions on my proposed solution as an acceptable and good solution. Thoughts?

Answer 1

After doing some more reading perhaps this is the combination of flags you need:

Intent intent = new Intent(mContext, SomeActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_MULTIPLE_TASK);
startActivity(intent);

I think that should force your SomeActivity class to be launched in a completely new task.

Answer 2

When launching the Activity from the notification, you can control how the Activity you are about to open is put on the back stack, and what task it's associated with with Intent flags. You can try something like:

Intent intent = new Intent(mContext, SomeActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);

If that doesn't work, try setting a few of the other flags until you get the desired behavior.

Answer 3

Do you ever want your MainActivity to stay in history? If not then my simple, crude solution is to finish the MainActivity when it is paused. (Call this in your MainActivity)

@Override
public void onPause() {
    finish();
}

This will ensure that your MainActivity is removed from history when you navigate away from it, and will never appear when the back button is pressed. This could be used for AboutActivity as well.