How to rotate floating action button without rotaing shadow?

问题

I rotate the FAB in such a simple way:

fab.startAnimation(AnimationUtils.loadAnimation(this, R.anim.rotate));

rotate.xml:

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <rotate
        android:fromDegrees="0"
        android:toDegrees="360"
        android:pivotX="50%"
        android:pivotY="50%"
        android:duration="1000"/>
</set>

This works, but together with the FAB its shadow rotates. But I need only the FAB to rotate (or even its src image, if there's any difference).

回答1:

Did you try with the animate method provided by the Compat library? I too had the same problem when using Animation utils

final OvershootInterpolator interpolator = new OvershootInterpolator();
ViewCompat.animate(fab).
           rotation(135f).
           withLayer().
           setDuration(300).
           setInterpolator(interpolator).
           start();

回答2:

public void rotateFabForward() {
    ViewCompat.animate(fab)
            .rotation(135.0F)
            .withLayer()
            .setDuration(300L)
            .setInterpolator(new OvershootInterpolator(10.0F))
            .start();
}

public void rotateFabBackward() {
    ViewCompat.animate(fab)
            .rotation(0.0F)
            .withLayer()
            .setDuration(300L)
            .setInterpolator(new OvershootInterpolator(10.0F))
            .start();
}

回答3:

There's an entirely another approach that works flawlessly for me (the one suggested in the accepted answer produces a clipped shadow on pre-L). Create an XML drawable and wrap your FAB icon into a <rotate> tag like this:

<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android" android:fromDegrees="0" android:toDegrees="45">
    <bitmap android:src="@drawable/ic_add_white_24dp"/>
</rotate>

Set this drawable to your FAB, and animate either its level directly or the imageLevel property of the FAB itself; it goes from 0 to 10000. If you'd like an OvershootInterpolator, then set toDegrees to 90 and animate the level up to the value of 5000 so it doesn't go beyond the bounds.

回答4:

Same can be achieved via object animator:

  moveRight.rotation = -180f

来源：https://stackoverflow.com/questions/31562333/how-to-rotate-floating-action-button-without-rotaing-shadow