Question

我目前有一个imageView，我可以使用panGestureRecognizer和以下方法在屏幕上拖动：

- (void)panDetected:(UIPanGestureRecognizer *)panRecognizer {
  CGPoint translation = [panRecognizer translationInView:self.view];
  CGPoint imageViewPosition = self.imageView.center;
  imageViewPosition.x += translation.x;
  imageViewPosition.y += translation.y;

  self.imageView.center = imageViewPosition;
  [panRecognizer setTranslation:CGPointZero inView:self.view];
}

目前可以将图像拖离屏幕以使其仅部分可见，我想知道是否有办法在屏幕边缘停止图像？我知道它应该是可能的，我只是在挣扎于逻辑。

Answer 1

您是否尝试过使用CGRectContainsRect？

您可以将其用作panDetected:内部的支票，只有在返回YES时才允许翻译。

- (void)panDetected:(UIPanGestureRecognizer *)panRecognizer {
    CGPoint translation = [panRecognizer translationInView:self.view];
    CGPoint imageViewPosition = self.imageView.center;
    imageViewPosition.x += translation.x;
    imageViewPosition.y += translation.y;

    CGFloat checkOriginX = self.imageView.frame.origin.x + translation.x; // imageView's origin's x position after translation, if translation is applied
    CGFloat checkOriginY = self.imageView.frame.origin.y + translation.y; // imageView's origin's y position after translation, if translation is applied

    CGRect rectToCheckBounds = CGRectMake(checkOriginX, checkOriginY, self.imageView.frame.size.width, self.imageView.frame.size.height); // frame of imageView if translation is applied

    if (CGRectContainsRect(self.view.frame, rectToCheckBounds)){
        self.imageView.center = imageViewPosition;
        [panRecognizer setTranslation:CGPointZero inView:self.view];
    }
}

Answer 2

您应该检查imageview的帧是否仍然在当前视图的帧中（或屏幕边界）。

   if ( CGRectContains(self.view.frame, self.imageView.frame) ) 
    // is inside
    else 
    //is outside or intersecting

拖动图像时，不要让图像关闭屏幕

2 个答案: