CODEWITHSUNDEEP
androidandroid-fragments
boeserwolf91
boeserwolf91

Reputation: 176

BackButton for Fragments doesn’t call onPause() or onStop()

In our app we have an Activity with a FrameLayout. This layout shows several Fragments. To change between the Fragments we use the following method:

public static void replaceFragment(FragmentManager manager, Fragment fragment, boolean addToBackStack)
{
    FragmentTransaction transaction = manager.beginTransaction();

    Fragment currentFragment = manager.findFragmentById(R.id.container);
    if (currentFragment != null)
    {
        transaction.remove(currentFragment);

        if (addToBackStack)
        {
            transaction.addToBackStack(currentFragment.getClass().getName());
        }
    }

    transaction.add(R.id.container, fragment);
    transaction.commit();
}

If the fragment is changed with that method everything will work fine. Unfortunately the problem is that the back button seems to be broken.If we push it at one of these Fragments the FrameLayout will be updated correctly. But the Fragment won’t be destroyed. Android doesn’t call the onPause(), the onStop() and the OnDestroyView() methods. Therefore the action bar isn’t updated correctly. It’s still showing the menu items from that fragment. The disturbing thing about this is, that this behavior is just from one special fragment. Every other fragment works fine.

One interesting thing happens after pressing the standby button because after this interaction all missed onPause() and onStop() commands from the fragment are called at once.

EDIT:

I’ll explain the structure of the project. Maybe that helps. There’s an android.support.v7.app.ActionBarActivity with a DrawerLayout containing the FrameLayout and a NavigationDrawerFragment. The FrameLayout is used to show the Fragment related to this app. With a click at a navigation drawer item the fragment which is shown in the FrameLayout changes. With a click at the back button the HomeFragment which is the start fragment is called from the back stack (just this fragment is added to the back stack). It workes from every fragment with the exception of our quiz. The quiz contains several states. The navigation drawer item quiz links to a selector fragment which reads the current state of the quiz and forwards to the quiz fragment which shall be shown (related to the state). just when I click the back button from that fragment the HomeFragment is shown correctly but the fragment isn’t removed. It’s still in the resumed state. Did someone know how to solve this problem?

EDIT 2:

I build a minimal app to test the behaviors. I did it step by step to find my mistake. To test it I added logs for every important method. My results are below.

Szenario 1: add forwarder fragment to back stack

The log means that everything will work fine if the forwarder is added to the back stack!

Szenario 2: don't add forwarder fragment to backstack

The error will occur!

result

The logs told me that the error just happens when the forwarder fragment isn't added to back stack. Does somebody know why there is this difference in the lifecycle?

I think I've to manipulate the back stack in the test fragment. I could pop it so that the forwarder isn't at the top of the back stack anymore. I'll give it a try.

Upvotes: 1

Views: 2009

Answers (1)

Sush
Sush

Reputation: 3874

The behavior is perfectly fine. Life cycle of fragments is completely tied to life of activity. onStart, onPause ,onStop all the methods will be called based on activity lifecycle similar methods. You won't get any call back for fragment 'onPause' until activity 'onPause' method is been called. Please read android fragments documentation.

Fragment is not activity, its just like any other view or widget but its has some callback methods from activity, which makes it different than view.

fragments life cycle

read this check this

Upvotes: 2

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