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);
           }
         });
        }
      });
     }
   });