Nested fragments disappear during transition animation

Question

Here\'s the scenario: Activity contains fragment A, which in turn uses getChildFragmentManager() to add fragments A1 and A2

Answer 1

I was having the same issue with map fragment. It kept disappearing during the exit animation of its containing fragment. The workaround is to add animation for the child map fragment which will keep it visible during the exit animation of the parent fragment. The animation of the child fragment is keeping its alpha at 100% during its duration period.

Animation: res/animator/keep_child_fragment.xml

<?xml version="1.0" encoding="utf-8"?>    
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <objectAnimator
        android:propertyName="alpha"
        android:valueFrom="1.0"
        android:valueTo="1.0"
        android:duration="@integer/keep_child_fragment_animation_duration" />
</set>

The animation is then applied when the map fragment is added to the parent fragment.

Parent fragment

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.map_parent_fragment, container, false);

    MapFragment mapFragment =  MapFragment.newInstance();

    getChildFragmentManager().beginTransaction()
            .setCustomAnimations(R.animator.keep_child_fragment, 0, 0, 0)
            .add(R.id.map, mapFragment)
            .commit();

    return view;
}

Finally, the duration of the child fragment animation is set in a resource file.

values/integers.xml

<resources>
  <integer name="keep_child_fragment_animation_duration">500</integer>
</resources>

Answer 2

Old thread, but in case someone stumbles in here:

All of the approaches above feel very unappealing for me, the bitmap solution is very dirty and non performant; the other ones require the child fragments to know about the duration of the transition used in the transaction used to create the child fragment in question. A better solution in my eyes i something like the following:

val currentFragment = supportFragmentManager.findFragmentByTag(TAG)
val transaction = supportFragmentManager
    .beginTransaction()
    .setCustomAnimations(anim1, anim2, anim1, anim2)
    .add(R.id.fragmentHolder, FragmentB(), TAG)
if (currentFragment != null) {
    transaction.hide(currentFragment).commit()
    Handler().postDelayed({
        supportFragmentManager.beginTransaction().remove(currentFragment).commit()
    }, DURATION_OF_ANIM)
} else {
    transaction.commit()
}

We just hide the current fragment and add the new fragment, when the animation has finished we remove the old fragment. This way it is handled in one place and no bitmap is created.

Answer 3

In order to avoid the user seeing the nested fragments disappearing when the parent fragment is removed/replaced in a transaction you could "simulate" those fragments still being present by providing an image of them, as they appeared on the screen. This image will be used as a background for the nested fragments container so even if the views of the nested fragment go away the image will simulate their presence. Also, I don't see loosing the interactivity with the nested fragment's views as a problem because I don't think you would want the user to act on them when they are just in the process of being removed(probably as a user action as well).

I've made a little example with setting up the background image(something basic).

Answer 4

A simple way to fix this problem is use the Fragment class from this library instead of the standard library fragment class:

https://github.com/marksalpeter/contract-fragment

As a side note, the package also contains a useful delegate pattern called ContractFragment that you might find useful for building your apps leveraging the parent-child fragment relationship.

Answer 5

Im posting my solution for clarity. The solution is quite simple. If you are trying to mimic the parent's fragment transaction animation just simply add a custom animation to the child fragment transaction with same duration. Oh and make sure you set the custom animation before add().

getChildFragmentManager().beginTransaction()
        .setCustomAnimations(R.anim.none, R.anim.none, R.anim.none, R.anim.none)
        .add(R.id.container, nestedFragment)
        .commit();

The xml for R.anim.none (My parents enter/exit animation time is 250ms)

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate android:fromXDelta="0" android:toXDelta="0" android:duration="250" />
</set>

Answer 6

@@@@@@@@@@@@@@@@@@@@@@@@@@@@

EDIT: I ended up unimplementing this solution as there were other problems that this has. Square recently came out with 2 libraries that replace fragments. I'd say this might actually be a better alternative than trying to hack fragments into doing something google doesn't want them doing.

http://corner.squareup.com/2014/01/mortar-and-flow.html

@@@@@@@@@@@@@@@@@@@@@@@@@@@@

I figured I'd put up this solution to help people who have this problem in the future. If you trace through the original posters conversation with other people, and look at the code he posted, you'll see the original poster eventually comes to the conclusion of using a no-op animation on the child fragments while animating the parent fragment. This solution isn't ideal as it forces you to keep track of all the child fragments, which can be cumbersome when using a ViewPager with FragmentPagerAdapter.

Since I use Child Fragments all over the place I came up with this solution that is efficient, and modular (so it can be easily removed) in case they ever fix it and this no-op animation is no longer needed.

There are lots of ways you can implement this. I chose to use a singleton, and I call it ChildFragmentAnimationManager. It basically will keep track of a child fragment for me based on its parent and will apply a no-op animation to the children when asked.

public class ChildFragmentAnimationManager {

private static ChildFragmentAnimationManager instance = null;

private Map<Fragment, List<Fragment>> fragmentMap;

private ChildFragmentAnimationManager() {
    fragmentMap = new HashMap<Fragment, List<Fragment>>();
}

public static ChildFragmentAnimationManager instance() {
    if (instance == null) {
        instance = new ChildFragmentAnimationManager();
    }
    return instance;
}

public FragmentTransaction animate(FragmentTransaction ft, Fragment parent) {
    List<Fragment> children = getChildren(parent);

    ft.setCustomAnimations(R.anim.no_anim, R.anim.no_anim, R.anim.no_anim, R.anim.no_anim);
    for (Fragment child : children) {
        ft.remove(child);
    }

    return ft;
}

public void putChild(Fragment parent, Fragment child) {
    List<Fragment> children = getChildren(parent);
    children.add(child);
}

public void removeChild(Fragment parent, Fragment child) {
    List<Fragment> children = getChildren(parent);
    children.remove(child);
}

private List<Fragment> getChildren(Fragment parent) {
    List<Fragment> children;

    if ( fragmentMap.containsKey(parent) ) {
        children = fragmentMap.get(parent);
    } else {
        children = new ArrayList<Fragment>(3);
        fragmentMap.put(parent, children);
    }

    return children;
}

}

Next you need to have a class that extends Fragment that all your Fragments extend (at least your Child Fragments). I already had this class, and I call it BaseFragment. When a fragments view is created, we add it to the ChildFragmentAnimationManager, and remove it when it's destroyed. You could do this onAttach/Detach, or other matching methods in the sequence. My logic for choosing Create/Destroy View was because if a Fragment doesn't have a View, I don't care about animating it to continue to be seen. This approach should also work better with ViewPagers that use Fragments as you won't be keeping track of every single Fragment that a FragmentPagerAdapter is holding, but rather only 3.

public abstract class BaseFragment extends Fragment {

@Override
public  View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    Fragment parent = getParentFragment();
    if (parent != null) {
        ChildFragmentAnimationManager.instance().putChild(parent, this);
    }

    return super.onCreateView(inflater, container, savedInstanceState);
}

@Override
public void onDestroyView() {
    Fragment parent = getParentFragment();
    if (parent != null) {
        ChildFragmentAnimationManager.instance().removeChild(parent, this);
    }

    super.onDestroyView();
}

}

Now that all your Fragments are stored in memory by the parent fragment, you can call animate on them like this, and your child fragments won't disappear.

FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();
ChildFragmentAnimationManager.instance().animate(ft, ReaderFragment.this)
                    .setCustomAnimations(R.anim.up_in, R.anim.up_out, R.anim.down_in, R.anim.down_out)
                    .replace(R.id.container, f)
                    .addToBackStack(null)
                    .commit();

Also, just so you have it, here is the no_anim.xml file that goes in your res/anim folder:

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" android:interpolator="@android:anim/linear_interpolator">
    <translate android:fromXDelta="0" android:toXDelta="0"
        android:duration="1000" />
</set>

Again, I don't think this solution is perfect, but it's much better than for every instance you have a Child Fragment, implementing custom code in the parent fragment to keep track of each child. I've been there, and it's no fun.