FloatingActionButtonImplLollipop.java 文件源码

@Override
void onElevationsChanged(
    final float elevation,
    final float hoveredFocusedTranslationZ,
    final float pressedTranslationZ) {
  if (Build.VERSION.SDK_INT == VERSION_CODES.LOLLIPOP) {
    // Animations produce NPE in version 21. Bluntly set the values instead in
    // #onDrawableStateChanged (matching the logic in the animations below).
    view.refreshDrawableState();
  } else {
    final StateListAnimator stateListAnimator = new StateListAnimator();

    // Animate elevation and translationZ to our values when pressed, focused, and hovered
    stateListAnimator.addState(
        PRESSED_ENABLED_STATE_SET, createElevationAnimator(elevation, pressedTranslationZ));
    stateListAnimator.addState(
        HOVERED_FOCUSED_ENABLED_STATE_SET,
        createElevationAnimator(elevation, hoveredFocusedTranslationZ));
    stateListAnimator.addState(
        FOCUSED_ENABLED_STATE_SET,
        createElevationAnimator(elevation, hoveredFocusedTranslationZ));
    stateListAnimator.addState(
        HOVERED_ENABLED_STATE_SET,
        createElevationAnimator(elevation, hoveredFocusedTranslationZ));

    // Animate translationZ to 0 if not pressed, focused, or hovered
    AnimatorSet set = new AnimatorSet();
    List<Animator> animators = new ArrayList<>();
    animators.add(ObjectAnimator.ofFloat(view, "elevation", elevation).setDuration(0));
    if (Build.VERSION.SDK_INT >= 22 && Build.VERSION.SDK_INT <= 24) {
      // This is a no-op animation which exists here only for introducing the duration
      // because setting the delay (on the next animation) via "setDelay" or "after"
      // can trigger a NPE between android versions 22 and 24 (due to a framework
      // bug). The issue has been fixed in version 25.
      animators.add(
          ObjectAnimator.ofFloat(view, View.TRANSLATION_Z, view.getTranslationZ())
              .setDuration(ELEVATION_ANIM_DELAY));
    }
    animators.add(
        ObjectAnimator.ofFloat(view, View.TRANSLATION_Z, 0f)
            .setDuration(ELEVATION_ANIM_DURATION));
    set.playSequentially(animators.toArray(new Animator[0]));
    set.setInterpolator(ELEVATION_ANIM_INTERPOLATOR);
    stateListAnimator.addState(ENABLED_STATE_SET, set);

    // Animate everything to 0 when disabled
    stateListAnimator.addState(EMPTY_STATE_SET, createElevationAnimator(0f, 0f));

    view.setStateListAnimator(stateListAnimator);
  }

  if (shadowViewDelegate.isCompatPaddingEnabled()) {
    updatePadding();
  }
}