Android自定义FloatingActionButton滑动行为只隐藏不出现的问题小结

public class FabBehavior extends FloatingActionButton.Behavior{
  private static final Interpolator INTERPOLATOR = new FastOutSlowInInterpolator();
  private boolean mIsAnimatingOut = false;
  public FabBehavior(Context context, AttributeSet attrs) {
    super();
  }
  @Override
  public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                    final View directTargetChild, final View target, final int nestedScrollAxes) {
    // Ensure we react to vertical scrolling
    return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL
        || super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
  }
  @Override
  public void onNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                final View target, final int dxConsumed, final int dyConsumed,
                final int dxUnconsumed, final int dyUnconsumed) {
    super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
    if (dyConsumed > 0 && !this.mIsAnimatingOut && child.getVisibility() == View.VISIBLE) {
      // User scrolled down and the FAB is currently visible -> hide the FAB
      animateOut(child);
    } else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
      // User scrolled up and the FAB is currently not visible -> show the FAB
      animateIn(child);
    }
  }
  // Same animation that FloatingActionButton.Behavior uses to hide the FAB when the AppBarLayout exits
  private void animateOut(final FloatingActionButton button) {
    if (Build.VERSION.SDK_INT >= 14) {
      ViewCompat.animate(button).translationY(button.getHeight() + getMarginBottom(button)).setInterpolator(INTERPOLATOR).withLayer()
          .setListener(new ViewPropertyAnimatorListener() {
            public void onAnimationStart(View view) {
              FabBehavior.this.mIsAnimatingOut = true;
            }
            public void onAnimationCancel(View view) {
              FabBehavior.this.mIsAnimatingOut = false;
            }
            public void onAnimationEnd(View view) {
              FabBehavior.this.mIsAnimatingOut = false;
              view.setVisibility(View.GONE);
            }
          }).start();
    } else {
    }
  }
  // Same animation that FloatingActionButton.Behavior uses to show the FAB when the AppBarLayout enters
  private void animateIn(FloatingActionButton button) {
    button.setVisibility(View.VISIBLE);
    if (Build.VERSION.SDK_INT >= 14) {
      ViewCompat.animate(button).translationY(0)
          .setInterpolator(INTERPOLATOR).withLayer().setListener(null)
          .start();
    } else {
    }
  }
  private int getMarginBottom(View v) {
    int marginBottom = 0;
    final ViewGroup.LayoutParams layoutParams = v.getLayoutParams();
    if (layoutParams instanceof ViewGroup.MarginLayoutParams) {
      marginBottom = ((ViewGroup.MarginLayoutParams) layoutParams).bottomMargin;
    }
    return marginBottom;
  }
}

app:layout_behavior="com.normalframe.widgets.view.FabBehavior"