从上至下对片段进行动画处理

Question

I'd like to animate in a new fragment from the bottom up, over top of the previous fragment.

Unfortunately, my current implementation pushes the previous fragment up, as the new fragment is animating in, like this:

https://i.imgur.com/IgMUamp.png

What I would like it to do is have the new fragment animate over top the previous fragment, like so:

https://i.imgur.com/DTrEfcm.png

Here is what my code looks like now:

    private void pushFragment(String fragmentTag, Fragment fragment) {
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.setCustomAnimations(R.anim.anim_in_test, R.anim.anim_out_test);
        fragmentTransaction.replace(
                R.id.fragment_container,
                fragment,
                fragmentTag);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commitAllowingStateLoss();
    }

Here is anim_in_test.xml :

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:anim/accelerate_decelerate_interpolator">
    <translate
        android:duration="@android:integer/config_longAnimTime"
        android:fromYDelta="100%p"
        android:toYDelta="0" />
</set>

And here is anim_out_test.xml :

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:duration="@android:integer/config_longAnimTime"
        android:fromYDelta="0%p"
        android:toYDelta="-100%p"
        />
</set>

What do I need to change to get this working right?

Answer 1

 setCustomAnimations(int enter, int exit)

Exit animation should be empty (because you need old fragment stay on screen while new one appears), but if you pass 0 to second param view dissapear without animation. Thats why I add empty alpha animation which changes alpha from 1 to 1.

fragmentTransaction.setCustomAnimations(R.anim.anim_in_test, R.anim.anim_out_test);

anim_out_test.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <alpha
        android:duration="@android:integer/config_longAnimTime"
        android:fromAlpha="1"
        android:toAlpha="1" />
</set>

But at that point it doesnt' work because android draw and animate new fragment BELOW old fragment. You can see it if you make fragment backgrounds transparent.

To resolve this issue I use setZ(z) , setElevation(z) or setTranslationZ(z) methods on root view of fragment. It looks like all of them are working. Z value of new fragment should be more than old fragment Z .

 @Override
 public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.view, container, false);
        view.setZ(value);

Here is result:

It works but I dont know side effects of this solution. On android 4 I think it can be done via custom ViewGroup as fragment container, which draws children in reverse order.

Answer 2

只需使用添加片段而不是替换片段