<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 android:layout_width="match_parent"
 android:layout_height="match_parent">

 <android.support.design.widget.AppBarLayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:theme="@style/AppTheme.AppBarOverlay">

  <android.support.v7.widget.Toolbar
   android:id="@+id/toolbar"
   android:layout_width="match_parent"
   android:layout_height="?attr/actionBarSize"
   app:layout_scrollFlags="scroll|enterAlways|snap"
   app:popupTheme="@style/AppTheme.PopupOverlay" />
 </android.support.design.widget.AppBarLayout>

 <android.support.v7.widget.RecyclerView
  android:id="@+id/recyclerView"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  app:layout_behavior="@string/appbar_scrolling_view_behavior" />

 <LinearLayout
  android:id="@+id/tab_layout"
  android:layout_width="match_parent"
  android:layout_height="?actionBarSize"
  android:layout_alignParentBottom="true"
  android:background="@android:color/white"
  app:layout_behavior="@string/bottom_sheet_behavior">

  <Button
   android:layout_width="0dp"
   android:layout_height="match_parent"
   android:layout_weight="1"
   android:text="第一" />

  <Button
   android:layout_width="0dp"
   android:layout_height="match_parent"
   android:layout_weight="1"
   android:text="第二" />

  <Button
   android:layout_width="0dp"
   android:layout_height="match_parent"
   android:layout_weight="1"
   android:text="第三" />

  <Button
   android:layout_width="0dp"
   android:layout_height="match_parent"
   android:layout_weight="1"
   android:text="第四" />
 </LinearLayout>

 <android.support.design.widget.FloatingActionButton
  android:id="@+id/fab"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_gravity="bottom|end"
  android:layout_marginBottom="70dp"
  android:layout_marginEnd="16dp"
  android:layout_marginRight="16dp"
  android:src="@mipmap/ic_action_new"
  app:layout_behavior="@string/scale_down_show_behavior"
  app:layout_scrollFlags="scroll|enterAlways|snap" />
</android.support.design.widget.CoordinatorLayout>

public class ScaleDownShowBehavior extends FloatingActionButton.Behavior {
 public ScaleDownShowBehavior(Context context, AttributeSet attrs) {
  super();
 }
}

@Override
public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, ...) {
 return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;
}

@Override
// 隐藏动画是否正在执行
private boolean isAnimatingOut = false;

public void onNestedScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child,
View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
 if ((dyConsumed > 0 || dyUnconsumed > 0) && !isAnimatingOut
 && child.getVisibility() == View.VISIBLE) {// 手指上滑，隐藏FAB
  AnimatorUtil.scaleHide(child, listener);
 } else if ((dyConsumed < 0 || dyUnconsumed < 0) && child.getVisibility() != View.VISIBLE) {
  AnimatorUtil.scaleShow(child, null);// 手指下滑，显示FAB
 }
}

private ViewPropertyAnimatorListener listener = new ViewPropertyAnimatorListener() {
 @Override
 public void onAnimationStart(View view) {
  isAnimatingOut = true;
 }

 @Override
 public void onAnimationEnd(View view) {
  isAnimatingOut = false;
  view.setVisibility(View.GONE);
 }

 @Override
 public void onAnimationCancel(View arg0) {
  isAnimatingOut = false;
 }
};