public class DragView extends View{
  private int lastX;
  private int lastY;
  public DragView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }
  public boolean onTouchEvent(MotionEvent event) {
    //获取到手指处的横坐标和纵坐标
    int x = (int) event.getX();
    int y = (int) event.getY();
    switch(event.getAction()){
      case MotionEvent.ACTION_DOWN:
        lastX = x;
        lastY = y;
      break;
      case MotionEvent.ACTION_MOVE:
        //计算移动的距离
        int offX = x - lastX;
        int offY = y - lastY;
        //调用layout方法来重新放置它的位置
        layout(getLeft()+offX, getTop()+offY,
          getRight()+offX  , getBottom()+offY);
      break;
    }
    return true;
  }
} 

public boolean onTouchEvent(MotionEvent event) {
    //获取到手指处的横坐标和纵坐标
    int x = (int) event.getX();
    int y = (int) event.getY();
    switch(event.getAction()){
      case MotionEvent.ACTION_DOWN:
        lastX = x;
        lastY = y;
      break;
      case MotionEvent.ACTION_MOVE:
        //计算移动的距离
        int offX = x - lastX;
        int offY = y - lastY;
        offsetLeftAndRight(offX);
        offsetTopAndBottom(offY);
      break;
    }
    return true;
  } 

public boolean onTouchEvent(MotionEvent event) {
    //获取到手指处的横坐标和纵坐标
    int x = (int) event.getX();
    int y = (int) event.getY();
    switch(event.getAction()){
      case MotionEvent.ACTION_DOWN:
        lastX = x;
        lastY = y;
      break;
      case MotionEvent.ACTION_MOVE:
        //计算移动的距离
        int offX = x - lastX;
        int offY = y - lastY;
        ViewGroup.MarginLayoutParams mlp = 
            (MarginLayoutParams) getLayoutParams();
        mlp.leftMargin = getLeft()+offX;
        mlp.topMargin = getTop()+offY;
        setLayoutParams(mlp);
      break;
    }
    return true;
  }

public boolean onTouchEvent(MotionEvent event) {
    //获取到手指处的横坐标和纵坐标
    int x = (int) event.getX();
    int y = (int) event.getY();
    switch(event.getAction()){
      case MotionEvent.ACTION_DOWN:
        lastX = x;
        lastY = y;
      break;
      case MotionEvent.ACTION_MOVE:
        //计算移动的距离
        int offX = x - lastX;
        int offY = y - lastY;
        ((View) getParent()).scrollBy(-offX,- offY);
      break;
    }
    return true;
  } 

public void computeScroll() {
  super.computeScroll();
  if(mScroller.computeScrollOffset()){
    ((View)getParent()).scrollTo(mScroller.getCurrX(),mScroller.getCurrY());
  }
  invalidate();//必须要调用
} 

startScroll(int startX,int startY, int dx,int dy,int duration)
startScroll(int startX,int startY,int dx,int dy)

public class DragView extends View{
  private int lastX;
  private int lastY;
  private Scroller mScroller;
  public DragView(Context context, AttributeSet attrs) {
    super(context, attrs);
    mScroller = new Scroller(context);
  }
  public boolean onTouchEvent(MotionEvent event) {
    //获取到手指处的横坐标和纵坐标
    int x = (int) event.getX();
    int y = (int) event.getY();
    switch(event.getAction()){
      case MotionEvent.ACTION_DOWN:
        lastX = x;
        lastY = y;
      break;
      case MotionEvent.ACTION_MOVE:
        //计算移动的距离
        int offX = x - lastX;
        int offY = y - lastY;
        View viewGroup = (View) getParent();
        ((View) getParent()).scrollBy(-offX,- offY);
      break;
    case MotionEvent.ACTION_UP:
      View viewGroup = (View) getParent();
      //开启滑动,让其回到原点
      mScroller.startScroll(viewGroup.getScrollX(),
          viewGroup.getScrollY(),
          -viewGroup.getScrollX() ,-viewGroup.getScrollY());
      break;
    }
    return true;
  }
  public void computeScroll() {
    super.computeScroll();
    if(mScroller.computeScrollOffset()) {
      ((View)getParent()).scrollTo(mScroller.getCurrX(),
            mScroller.getCurrY());
    } 
    invalidate();//必须要调用
  }
}