Android实现滑动到顶部悬停的效果

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

 <android.support.design.widget.AppBarLayout
 android:layout_width="match_parent"
 android:layout_height="250dp">

 <android.support.design.widget.CollapsingToolbarLayout
  app:layout_scrollFlags="scroll"
  app:contentScrim="#000000"
  android:layout_width="match_parent"
  android:layout_height="220dp">

  <TextView
  android:text="banner区域"
  android:gravity="center"
  android:textColor="#ffffff"
  android:background="#987545"
  android:layout_width="match_parent"
  android:layout_height="220dp"/>

 </android.support.design.widget.CollapsingToolbarLayout>

 <TextView
  android:gravity="center"
  android:layout_width="match_parent"
  android:layout_height="30dp"
  android:text="悬浮的部分"/>

 </android.support.design.widget.AppBarLayout>

 <android.support.v4.widget.NestedScrollView
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  app:layout_behavior="@string/appbar_scrolling_view_behavior">

  <TextView
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_margin="@dimen/text_margin"
  android:text="@string/large_text"/>

 </android.support.v4.widget.NestedScrollView>

</android.support.design.widget.CoordinatorLayout>