iOS 5 中拖动 UIView

我在 iPhone 应用程序中看到状态栏上有一个可以访问通知中心的手势。我如何在我的应用程序中实现这种转换？我认为这是通过滑动手势识别器完成的，但是如何包含从上到下的滑动手势（如何拖动通知中心完成其完整过渡）？有任何示例代码或其他东西可以帮助我做到这一点吗？ 提前致谢

应该很容易做到。假设你有一个UIView (mainView）你想从中触发下拉事件。

1. 放置一个子视图（pulldownView) 在 mainView 顶部可见区域之外。
2. 实施touchesBegan on mainView并检查触摸是否位于前 30 个像素（或点）内。
3. 实施touchesMoved在哪里检查移动方向是否向下并且pulldownView不可见，如果是则拖动pulldownView向下进入主视图的可见区域或检查移动方向是否向上pulldownView可见，如果是，则向上推出可见区域。
4. 实施touchesEnd通过检查拖动或推动的方向来结束拖动或推动移动pulldownView被感动了。

EDIT:

这是一些示例代码。未经测试，可能包含拼写错误，可能无法编译，但应该包含所需的基本部分。

//... inside mainView impl:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
  UITouch *touch = (UITouch *)[touches anyObject];
  start = [touch locationInView:self.superview].y;
  if(start > 30 && pulldownView.center.y < 0)//touch was not in upper area of view AND pulldownView not visible
  {
    start = -1; //start is a CGFloat member of this view
  }
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
  if(start < 0)
  {
    return;
  }
  UITouch *touch = (UITouch *)[touches anyObject];
  CGFloat now = [touch locationInView:self.superview].y;
  CGFloat diff = now - start;
  directionUp = diff < 0;//directionUp is a BOOL member of this view
  float nuCenterY = pulldownView.center.y + diff;
  pulldownView.center = CGPointMake(pulldownView.center.x, nuCenterY);
  start = now;
}


-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
  if (directionUp)
  {
    //animate pulldownView out of visibel area
    [UIView animateWithDuration:.3 animations:^{pulldownView.center = CGPointMake(pulldownView.center.x, -roundf(pulldownView.bounds.size.height/2.));}];
  }
  else if(start>=0)
  {
    //animate pulldownView with top to mainviews top
    [UIView animateWithDuration:.3 animations:^{pulldownView.center = CGPointMake(pulldownView.center.x, roundf(pulldownView.bounds.size.height/2.));}];
  }
}