用 CGPoint 追踪长按手势的准确位置

Question

通过使用 CGPoint 位置，它总是将最后一张图像保存在 uiscrollview 中。当我点击其他图像进行保存时。我该怎么做才能保存我点击的确切图像。

UIScrollView *imageScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
imageScrollView.pagingEnabled = YES;

NSInteger numberOfViews = 61;

for (int i = 0; i < numberOfViews; i++) {

    CGFloat xOrigin = i * self.view.frame.size.width;

 NSString *imageName = [NSString stringWithFormat:@"image%d.png", i];

    _image = [UIImage imageNamed:imageName];

    _imageView = [[UIImageView alloc] initWithImage:_image];

    _imageView.frame = CGRectMake(xOrigin, 0, self.view.frame.size.width, self.view.frame.size.height);

 UILongPressGestureRecognizer *gestureRecognizer = [[UILongPressGestureRecognizer alloc]
                                                       initWithTarget:self
                                                       action:@selector(handleLongPress:)];

    imageScrollView.userInteractionEnabled = YES;
    [imageScrollView addGestureRecognizer:gestureRecognizer];
    gestureRecognizer.delegate = self;
    [gestureRecognizer release];

    [imageScrollView addSubview:_imageView];
imageScrollView.contentSize = CGSizeMake(self.view.frame.size.width * numberOfViews, self.view.frame.size.height);

    - (void)handleLongPress:(UILongPressGestureRecognizer*)gestureRecognizer{
if (gestureRecognizer.state == UIGestureRecognizerStateBegan){
    UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:nil delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Save Photo", nil];
    actionSheet.actionSheetStyle = UIActionSheetStyleBlackTranslucent;
    [actionSheet showInView:self.view];
    [actionSheet release];

     }}

 -(void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {

switch (buttonIndex) {
    case 0:
        [self savePhoto];

       break;

    default:
        break;

}

   -(void)savePhoto{

CGPoint location = [gesture locationInView:_imageView];

if  (CGRectContainsPoint(_imageView.bounds, location)){

UIImageWriteToSavedPhotosAlbum(_image, self, @selector(image: didFinishSavingWithError:contextInfo:), nil);
   }}}

任何想法都会受到赞赏。

谢谢

Answer 1

该点将始终出现在触发LongPressGestureRecognizer 的UIScrollView 的范围内。您应该检查滚动视图的contentOffset（水平布局使用contentOffset.x，垂直布局使用contentOffset.y）来检测您应该保存哪个图像。

此外，您可以将触摸点转换为UIImageView 实例的本地坐标系，并查看该点是否位于图像视图的bounds 矩形内。

更新

例如，您可以使用类似的方法来检测该点是否在图像视图的范围内（注意：我没有对此进行了测试，这是假设添加了多个图像视图滚动视图）：

if (CGRectContainsPoint(_imageView.bounds, [self.view convertPoint:location toView:_imageView]))
{
    // do something
}

您还应该考虑在向用户显示 UIActionSheet 之前检测应该先保存哪个图像并存储对该图像的引用，因为这可能会减少您可能遇到的潜在问题的数量并且以后更容易阅读，但这是我的主观意见。