Question

I really don’t understand how all this flags working since I do exactly what the doc said, and it didn’t solved my problem. My activity is launching like this : (first) Activity A -> Activity B -> (second) Activity A. If I press button back, it goes back to Activity B -> Activity A -> Exit application. Now I want from second Activity A stated from Activity B, when press back, it will skip Activity B and first Activity A, and Exit application right away. Here’s the code:

From A to B:

TabActivityGroupAbs parentActivity = (TabActivityGroupAbs) ((Activity) ctx).getParent();
detailIntent = new Intent(parentActivity, B.class);
parentActivity.startChildActivity("BFromA", detailIntent);

From B to A:

TabActivityGroupAbs parentActivity = (TabActivityGroupAbs) ((Activity) ctx).getParent();
detailIntent = new Intent(parentActivity, A.class);
detailIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
detailIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
parentActivity.startChildActivity("AFromB", detailIntent);

From B to A, I add the flags FLAG_ACTIVITY_CLEAR_TOP. But it didn’t clear anything. When I pressed back, it still went to Activity B, and then A again. What did I do wrong?

And it seems like none of the flags are working at all. From A to B, I put:

detailIntent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);

It supposed to prevent B be put to activity stack. But it’s not. From the second activity A, it still go back to B when press back.

Now what should I do to exit application and not go back to B from the second activity A.

EDIT: I forgot to mention. From B to A, if I called finish() to kill activity B, then from second activity A, when press back, it go back to first activity A. Why activity A have 2 instance here though I set FLAG_ACTIVITY_CLEAR_TOP? Really strange.

Answer 1

You can use the following methods to start and close child activity

public ArrayList<String> mIdList;
/**
 * Starts an Activity as a child Activity to this.
 * 
 * @param Id
 *            Unique identifier of the activity to be started.
 * @param intent
 *            The Intent describing the activity to be started.
 * @throws android.content.ActivityNotFoundException.
 */
public void startChildActivity(String Id, Intent intent) {
    Window window = getLocalActivityManager().startActivity(Id,
    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
    if (window != null) {
        mIdList.add(Id);
        setContentView(window.getDecorView());
    }
}

/**
 * This is called when a child activity of this one calls its finish method.
 * This implementation calls {@link LocalActivityManager#destroyActivity} on
 * the child activity and starts the previous activity. If the last child
 * activity just called finish(),this activity (the parent), calls finish to
 * finish the entire group.
 */
@Override
public void finishFromChild(Activity child) {
    LocalActivityManager manager = getLocalActivityManager();
    int index = mIdList.size() - 1;

    if (index < 1) {
        finish();
        return;
    }

    manager.destroyActivity(mIdList.get(index), true);
    mIdList.remove(index);
    index--;
    String lastId = mIdList.get(index);
    Intent lastIntent = manager.getActivity(lastId).getIntent();
    Window newWindow = manager.startActivity(lastId, lastIntent);
    setContentView(newWindow.getDecorView());
}

Example:

startChildActivity("Merchants", new Intent(this,MerchantScreen.class));