AndroidScrollView实现向上滑动控件顶部悬浮效果

package com.willen.topFloatDemo; 
 
import android.content.Context; 
import android.os.Handler; 
import android.util.AttributeSet; 
import android.view.MotionEvent; 
import android.widget.ScrollView; 
 
/** 
 * ScrollView并没有实现滚动监听，所以我们必须自行实现对ScrollView的监听， 
 * 我们很自然的想到在onTouchEvent()方法中实现对滚动Y轴进行监听 
 * ScrollView的滚动Y值进行监听 
 */ 
public class MyScrollView extends ScrollView { 
 private OnScrollListener onScrollListener; 
 /** 
 * 主要是用在用户手指离开MyScrollView，MyScrollView还在继续滑动，我们用来保存Y的距离，然后做比较 
 */ 
 private int lastScrollY; 
 
 public MyScrollView(Context context) { 
 super(context, null); 
 } 
 public MyScrollView(Context context, AttributeSet attrs) { 
 super(context, attrs, 0); 
 } 
 public MyScrollView(Context context, AttributeSet attrs, int defStyle) { 
 super(context, attrs, defStyle); 
 } 
 /** 
 * 设置滚动接口 
 * @param onScrollListener 
 */ 
 public void setOnScrollListener(OnScrollListener onScrollListener){ 
 this.OnScrollListener= onScrollListener; 
 } 
 /** 
 * 用于用户手指离开MyScrollView的时候获取MyScrollView滚动的Y距离，然后回调给onScroll方法中 
 */ 
 private Handler handler = new Handler() { 
 
 public void handleMessage(android.os.Message msg) { 
  int scrollY = MyScrollView.this.getScrollY(); 
  
  //此时的距离和记录下的距离不相等，在隔5毫秒给handler发送消息 
  if(lastScrollY != scrollY){ 
  lastScrollY = scrollY; 
  handler.sendMessageDelayed(handler.obtainMessage(), 5); 
  } 
  if(onScrollListener != null){ 
  onScrollListener.onScroll(scrollY); 
  } 
  
 }; 
 
 }; 
 /** 
 * 重写onTouchEvent， 当用户的手在MyScrollView上面的时候， 
 * 直接将MyScrollView滑动的Y方向距离回调给onScroll方法中，当用户抬起手的时候， 
 * MyScrollView可能还在滑动，所以当用户抬起手我们隔5毫秒给handler发送消息，在handler处理 
 * MyScrollView滑动的距离 
 */ 
 @Override 
 public boolean onTouchEvent(MotionEvent ev) { 
 if(onScrollListener != null){ 
  onScrollListener.onScroll(lastScrollY = this.getScrollY()); 
 } 
 switch(ev.getAction()){ 
 case MotionEvent.ACTION_UP: 
  handler.sendMessageDelayed(handler.obtainMessage(), 20); 
  break; 
 } 
 return super.onTouchEvent(ev); 
 } 
 
 /** 
 * 滚动的回调接口 
 */ 
 public interface OnScrollListener{ 
 /** 
  * 回调方法， 返回MyScrollView滑动的Y方向距离 
  */ 
 public void onScroll(int scrollY); 
 } 
} 

package com.willen.topFloatDemo; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.widget.EditText; 
import android.widget.LinearLayout; 
import android.widget.RelativeLayout; 
 
import com.willen.topFloatDemo.MyScrollView.OnScrollListener; 
 
public class MainActivity extends Activity implements OnScrollListener{ 
 private EditText search_edit; 
 private MyScrollView myScrollView; 
 private int searchLayoutTop; 
 
 LinearLayout search01,search02; 
 RelativeLayout rlayout; 
 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 setContentView(R.layout.activity_main); 
 //初始化控件 
 init(); 
 } 
 
 private void init() { 
 search_edit = (EditText)findViewById(R.id.search_edit); 
 myScrollView = (MyScrollView)findViewById(R.id.myScrollView); 
 search01 = (LinearLayout)findViewById(R.id.search01); 
 search02 = (LinearLayout)findViewById(R.id.search02); 
 rlayout = (RelativeLayout)findViewById(R.id.rlayout); 
 myScrollView.setOnScrollListener(this); 
  
 } 
 
 @Override 
 public void onWindowFocusChanged(boolean hasFocus) { 
 super.onWindowFocusChanged(hasFocus); 
 if(hasFocus){ 
  searchLayoutTop = rlayout.getBottom();//获取searchLayout的顶部位置 
 } 
 } 
 
 //监听滚动Y值变化，通过addView和removeView来实现悬停效果 
 @Override 
 public void onScroll(int scrollY) { 
 if(scrollY >= searchLayoutTop){ 
  if (search_edit.getParent()!=search01) { 
  search02.removeView(search_edit); 
  search01.addView(search_edit); 
  } 
 }else{ 
  if (search_edit.getParent()!=search02) { 
  search01.removeView(search_edit); 
  search02.addView(search_edit); 
  } 
 } 
 } 
}