Tracing the exact location of the longpressgesture with CGPoint

问题

By using CGPoint location it is always saving the last image in uiscrollview. When i m tapping on other image to save. What can i do to save the exact image one i tapped.

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);
   }}}

Any ideas will be appreciated.

Thanks

回答1:

The point will always appear within the bounds of the UIScrollView in which the LongPressGestureRecognizer is triggered. You should check your scroll view's contentOffset (use contentOffset.x for horizontal layouts and contentOffset.y for vertical layouts) to detect which image you should save.

Additionally you could convert the touch point to the UIImageView instance's local coordinate system and see if the the point lies within the image view's bounds rect.

UPDATE

For example you could use something like this to detect if the point is within the image view's bounds (note: I have not tested this and this is assuming there is more than one image view added to the scroll view):

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

You should also consider detecting which image should be saved before and storing a reference to that image before displaying the UIActionSheet to the user as it may decrease the number of potential issues you might encounter and will be easier to read later, but this is my subjective opinion.

来源：https://stackoverflow.com/questions/12963004/tracing-the-exact-location-of-the-longpressgesture-with-cgpoint

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iphone

ios6

cgpoint