Android仿美团网、大众点评购买框悬浮效果修改版

package com.example.meituandemo; 
 
import android.content.Context; 
import android.util.AttributeSet; 
import android.widget.ScrollView; 
/** 
 * @blog http://blog.csdn.net/xiaanming 
 * 
 * @author xiaanming 
 * 
 */ 
public class MyScrollView extends ScrollView { 
 private OnScrollListener onScrollListener; 
 
 public MyScrollView(Context context) { 
 this(context, null); 
 } 
 
 public MyScrollView(Context context, AttributeSet attrs) { 
 this(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; 
 } 
 
 
 @Override 
 public int computeVerticalScrollRange() { 
 return super.computeVerticalScrollRange(); 
 } 
 
 
 @Override 
 protected void onScrollChanged(int l, int t, int oldl, int oldt) { 
 super.onScrollChanged(l, t, oldl, oldt); 
 if(onScrollListener != null){ 
  onScrollListener.onScroll(t); 
 } 
 } 
 
 
 
 /** 
 * 
 * 滚动的回调接口 
 * 
 * @author xiaanming 
 * 
 */ 
 public interface OnScrollListener{ 
 /** 
  * 回调方法， 返回MyScrollView滑动的Y方向距离 
  * @param scrollY 
  *  、 
  */ 
 public void onScroll(int scrollY); 
 } 
 
 
 
} 

package com.example.meituandemo; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.view.ViewTreeObserver.OnGlobalLayoutListener; 
import android.widget.LinearLayout; 
 
import com.example.meituandemo.MyScrollView.OnScrollListener; 
 
/** 
 * @blog http://blog.csdn.net/xiaanming 
 * 
 * @author xiaanming 
 * 
 */ 
public class MainActivity extends Activity implements OnScrollListener{ 
 /** 
 * 自定义的MyScrollView 
 */ 
 private MyScrollView myScrollView; 
 /** 
 * 在MyScrollView里面的购买布局 
 */ 
 private LinearLayout mBuyLayout; 
 /** 
 * 位于顶部的购买布局 
 */ 
 private LinearLayout mTopBuyLayout; 
 
 
 @SuppressWarnings("deprecation") 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 setContentView(R.layout.activity_main); 
  
 myScrollView = (MyScrollView) findViewById(R.id.scrollView); 
 mBuyLayout = (LinearLayout) findViewById(R.id.buy); 
 mTopBuyLayout = (LinearLayout) findViewById(R.id.top_buy_layout); 
  
 myScrollView.setOnScrollListener(this); 
  
 //当布局的状态或者控件的可见性发生改变回调的接口 
 findViewById(R.id.parent_layout).getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() { 
  
  @Override 
  public void onGlobalLayout() { 
  //这一步很重要，使得上面的购买布局和下面的购买布局重合 
  onScroll(myScrollView.getScrollY()); 
   
  } 
 }); 
 } 
 
 
 
 
 @Override 
 public void onScroll(int scrollY) { 
 int mBuyLayout2ParentTop = Math.max(scrollY, mBuyLayout.getTop()); 
 mTopBuyLayout.layout(0, mBuyLayout2ParentTop, mTopBuyLayout.getWidth(), mBuyLayout2ParentTop + mTopBuyLayout.getHeight()); 
 } 
 
 
 
}