Android点击按钮返回顶部实现代码

<LinearLayout 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:background="#ffffff"
  android:orientation="vertical">

  <ScrollView
    android:id="@+id/sv_home"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:fillViewport="true">

    <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:orientation="vertical">
      <ImageView
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:background="@mipmap/eason"/>

      <ImageView
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:background="@mipmap/eason"/>

      <ImageView
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:background="@mipmap/eason"/>
                    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab_top"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right|bottom"
        android:layout_marginRight="10dp"
        android:src="@mipmap/top"
        app:backgroundTint="#ecefef"
        app:elevation="10dp"
        app:pressedTranslationZ="12dp"
        app:rippleColor="@color/colorPrimary" />
    </LinearLayout>
  </ScrollView>
</LinearLayout>

topBtn.setOnClickListener(new OnClickListener() {

     @Override
     public void onClick(View v) {
      sc.post(new Runnable() {

        @Override
        public void run() {
         sc.post(new Runnable() {
           public void run() {
            // 返回顶部
            sc.fullScroll(ScrollView.FOCUS_UP);
           }
         });
        }
      });

     }
   });

 bottomBtn.setOnClickListener(new OnClickListener() {

     @Override
     public void onClick(View v) {
      sc.post(new Runnable() {

        @Override
        public void run() {
         sc.post(new Runnable() {
           public void run() {
            // 滚动到底部
            sc.fullScroll(ScrollView.FOCUS_DOWN);
           }
         });
        }
      });
     }
   });