能上下拖拉返回的listview-优快云博客

本文介绍了一个自定义的Pull_ListView类，通过触摸事件实现列表的上下滚动功能，包括滑动距离的计算、返回操作的实现及滚动速度的调整。

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public class Pull_ListView extends ListView implements Runnable {
	private float mLastDownY = 0f; 
    private int mDistance = 0; 
    private int mStep = 10; 
    private boolean mPositive = false; 
 

    public Pull_ListView (Context context, AttributeSet attrs) { 
          super(context, attrs); 
    } 
 
    public Pull_ListView (Context context, AttributeSet attrs, int defStyle) { 
          super(context, attrs, defStyle); 
    } 
 
    public Pull_ListView (Context context) { 
          super(context); 
    } 
 
    @Override 
    public boolean onTouchEvent(MotionEvent event) { 
         switch (event.getAction()) { 
              case MotionEvent.ACTION_DOWN: 
                   if (mLastDownY == 0f && mDistance == 0) { 
                         mLastDownY = event.getY(); 
                   return true; 
              } 
              break; 
 
    case MotionEvent.ACTION_CANCEL: 
           break;

    case MotionEvent.ACTION_UP: 
          if (mDistance != 0) { 
           mStep = 1; 
           mPositive = (mDistance >= 0); 
           this.post(this); 
           return true; 
        } 
        mLastDownY = 0f; 
        mDistance = 0; 
        break; 
 
    case MotionEvent.ACTION_MOVE: 
        if (mLastDownY != 0f) { 
              mDistance = (int) (mLastDownY - event.getY()); 
              if ((mDistance < 0 && getFirstVisiblePosition() == 0 && getChildAt(0).getTop() == 0) || (mDistance > 0 && getLastVisiblePosition() == getCount() - 1)) { 
                   mDistance /= 2;
                  Log.i("info_out",mDistance+"滑动距离");
                   scrollTo(0, mDistance); 
                   return true; 
               } 
        } 
        mDistance = 0; 
        break; 
        } 
        return super.onTouchEvent(event); 
    } 
 
    public void run() { 
          mDistance += mDistance > 0 ? -mStep : mStep;
        Log.i("info_out",mDistance+"返回滑动距离");
          scrollTo(0, mDistance); 
          if ((mPositive && mDistance <= 0) || (!mPositive && mDistance >= 0)) { 
                scrollTo(0, 0); 
                mDistance = 0; 
                mLastDownY = 0f; 
                return; 
           } 
          mStep += 1; 
          this.postDelayed(this, 10); 
     } 
}

这里实验了一下，调用scrollTo方法是在手指移动的时候能快速的跟上，造成了手指拖动的现象。而返回的时候是用了反复调用run方法内的线性++的方法来进行返回，直到0退出