Android自定义控件实现下拉刷新效果

@Override 
 protected void onLayout(boolean changed, int l, int t, int r, int b) { 
  if (pullText.getTop() == 0) { 
   viewHeight = pullText.getMeasuredHeight(); 
   pullText.layout(l, 0, r, b); 
   myList.layout(l, 0, r, b); 
   pullText.offsetTopAndBottom(-viewHeight); 
  } else { 
   pullText.layout(l, pullText.getTop(), r, pullText.getBottom()); 
   myList.layout(l, myList.getTop(), r, myList.getBottom()); 
  } 
 } 

 /** 
  * 这是拖拽效果的主要逻辑 
  */ 
 private class DragHelperCallback extends ViewDragHelper.Callback { 
 
  @Override 
  public void onViewPositionChanged(View changedView, int left, int top, 
    int dx, int dy) { 
   int childIndex = 1; 
   if (changedView == myList) { 
    childIndex = 2; 
   } 
   onViewPosChanged(childIndex, top); 
  } 
 
  @Override 
  public boolean tryCaptureView(View child, int pointerId) { 
   return true; 
  } 
 
  @Override 
  public int getViewVerticalDragRange(View child) { 
   return 1; 
  } 
 
  @Override 
  public void onViewReleased(View releasedChild, float xvel, float yvel) { 
   refreshOrNot(releasedChild, yvel); 
  } 
 
  @Override 
  public int clampViewPositionVertical(View child, int top, int dy) { 
   int finalTop = top; 
   if (child == pullText) { 
    if (top > 0) { 
     finalTop = 0; 
    } 
   } else if (child == myList) { 
    if (top <0) { 
     finalTop = 0; 
    } 
    if(top >= viewHeight){ 
     pullText.setText("松开刷新"); 
    }else{ 
     pullText.setText("下拉刷新"); 
    } 
   } 
   return child.getTop() + (finalTop - child.getTop()) / 2; 
  } 
 }

public interface pulltorefreshNotifier { 
  public void onPull(); 
 } 

public void setpulltorefreshNotifier(pulltorefreshNotifier pullNotifier) { 
  this.pullNotifier = pullNotifier; 
 } 

private void refreshOrNot(View releasedChild, float yvel) { 
  int finalTop = 0; 
  if (releasedChild == pullText) { 
   // 拖动第一个view松手 
   if (yvel <-50) { 
    finalTop = 0; 
   } else { 
    finalTop = viewHeight; 
   } 
  } else { 
   // 拖动第二个view松手 
   if (yvel > viewHeight - 5 || releasedChild.getTop() >= viewHeight) { 
    finalTop = viewHeight; 
    if (null != pullNotifier) { 
     pullNotifier.onPull(); 
    } 
    pullText.setText("正在刷新"); 
   } 
  } 
 
  if (VDH.smoothSlideViewTo(myList, 0, finalTop)) { 
   ViewCompat.postInvalidateOnAnimation(this); 
  } 
 } 

package com.maxi.pulltorefreshtest; 
 
import android.annotation.SuppressLint; 
import android.app.Activity; 
import android.os.Bundle; 
import android.os.Handler; 
import android.os.Message; 
 
import com.maxi.pulltorefreshtest.adapter.ProjectAdapter; 
import com.maxi.pulltorefreshtest.widget.MyListView; 
import com.maxi.pulltorefreshtest.widget.PullToRefreshGroup; 
import com.maxi.pulltorefreshtest.widget.PullToRefreshGroup.pulltorefreshNotifier; 
 
public class MainActivity extends Activity { 
 private PullToRefreshGroup pullListgroup; 
 private boolean isDown = false; 
 private MyListView myList; 
 private ProjectAdapter pa; 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.activity_main); 
  findView(); 
  init(); 
 } 
 
 private void findView() { 
  pullListgroup = (PullToRefreshGroup) findViewById(R.id.pulltorefresh); 
  myList = pullListgroup.returnMylist(); 
 } 
 
 private void init() { 
  pulltorefreshNotifier pullNotifier = new pulltorefreshNotifier() { 
   @Override 
   public void onPull() { 
    // TODO Auto-generated method stub 
    downLoad(); 
   } 
  }; 
  pullListgroup.setpulltorefreshNotifier(pullNotifier); 
  pa = new ProjectAdapter(this); 
  myList.setAdapter(pa); 
  pa.notifyDataSetChanged(); 
 } 
 
 private void downLoad() { 
  if (!isDown) { 
   isDown = true; 
   new Thread(new Runnable() { 
 
    @Override 
    public void run() { 
     // TODO Auto-generated method stub 
     try { 
      Thread.sleep(2000); 
      handler.sendEmptyMessage(1); 
     } catch (InterruptedException e) { 
//      TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
    } 
   }).start(); 
  } 
 } 
 
 @SuppressLint("HandlerLeak") 
 private Handler handler = new Handler() { 
 
  @Override 
  public void handleMessage(Message msg) { 
   // TODO Auto-generated method stub 
   super.handleMessage(msg); 
   switch (msg.what) { 
   case 1: 
    pullListgroup.refreshComplete(); 
    isDown = false; 
    break; 
   default: 
    break; 
   } 
  } 
 
 }; 
} 

public void refreshComplete() { 
 if (VDH.smoothSlideViewTo(myList, 0, 0)) { 
  ViewCompat.postInvalidateOnAnimation(this); 
 } 
} 

package com.maxi.pulltorefreshtest.widget; 
 
import android.content.Context; 
import android.util.AttributeSet; 
import android.view.MotionEvent; 
import android.view.View; 
import android.widget.ListView; 
 
public class MyListView extends ListView { 
 boolean allowDragBottom = true; 
 float downY = 0; 
 boolean needCOnsumeTouch= true; 
 public MyListView(Context context){ 
  super(context); 
 } 
 public MyListView(Context context, AttributeSet attrs) { 
  super(context, attrs); 
  // TODO Auto-generated constructor stub 
 } 
 
 @Override 
 public boolean dispatchTouchEvent(MotionEvent ev) { 
  if (ev.getAction() == MotionEvent.ACTION_DOWN) { 
   downY = ev.getRawY(); 
   needCOnsumeTouch= true; 
   if (getMyScrollY() == 0) { 
    allowDragBottom = true; 
   } else { 
    allowDragBottom = false; 
   } 
  } else if (ev.getAction() == MotionEvent.ACTION_MOVE) { 
   if (!needConsumeTouch) { 
    getParent().requestDisallowInterceptTouchEvent(false); 
    return false; 
   } else if (allowDragBottom) { 
    if (downY - ev.getRawY() <-2) { 
     needCOnsumeTouch= false; 
     getParent().requestDisallowInterceptTouchEvent(false); 
     return false; 
    } 
   } 
  } 
  getParent().requestDisallowInterceptTouchEvent(needConsumeTouch); 
  return super.dispatchTouchEvent(ev); 
 } 
 
 public int getMyScrollY() { 
  View c = getChildAt(0); 
  if (c == null) { 
   return 0; 
  } 
  int firstVisiblePosition = getFirstVisiblePosition(); 
  int top = c.getTop(); 
  return -top + firstVisiblePosition * c.getHeight(); 
 } 
}