fragments, android:zAdjustment (z order) and anima

问题:

I'm using the support library. Now, I want to have a fragment shifting in from the bottom, moving OVER the previous one.

For this I use this to keep the previous fragment (the one that is being slided over) visible until the new fragment is in its place:

<alpha xmlns:android="http://schemas.android.com/apk/res/android"
   android:fromAlpha="1.0" android:toAlpha="1.0" 
   android:duration="2500"
   android:zAdjustment="bottom" />

this is animation used for the new fragment to slide in from bottom:

<set xmlns:android="http://schemas.android.com/apk/res/android">
<translate android:fromYDelta="100%p" android:toYDelta="0"
        android:duration="@android:integer/config_mediumAnimTime" 
        android:zAdjustment="top"/>

I've put the z adjustment to bottom and top for both, but still the 'bottom' animation is still on top of the new fragment! I have put the duration to 2500 for testing and it stays on top for the whole time.

Does zAdjustment not work for fragment animations?

回答1:

According to this google group thread Z adjustment only works for window animations.

"The Z adjustment only works for window animations. I thought this was documented, but apparently not." -- Dianne Hackborn (Android framework engineer)

回答2:

I've also got stuck with that problem. So instead of using transaction.replace(containerId, newFragment) I've created two containers for fragments and now my code looks like this one

Add first fragment:

transaction.add(containerId1, firstFragment).commit();

Add second fragment with animation over the first one:

findViewById(containerId2).bringToFront();
transaction.setCustomAnimations(R.anim.slide_in_up,
 R.anim.stay).remove(oldFragment).add(containerId2, newFragment).commit()

回答3:

You can override the onCreateAnimation method and for any animations you can check what animation is currently running and if you need it to be on top, set the Z-axis from there.

override fun onCreateAnimation(transit: Int, enter: Boolean, nextAnim: Int): Animation? {
    if (nextAnim == R.anim.enter_from_right || nextAnim == R.anim.exit_to_right) {
        ViewCompat.setTranslationZ(view, 1f)
    } else {
        ViewCompat.setTranslationZ(view, 0f)
    }

    return super.onCreateAnimation(transit, enter, nextAnim)
}

Recommend implementing this as a base Fragment class for all your fragments.