Transferring touches to copy of UIImageView - ios

Question

I've been a long journey trying to drag and drop UIImageViews from a UITableView to another view.
I have everything working to a point. I subclass UIPanGestureRecognizer and attach this custom recognizer to all the UIImageViews I load into the table view.
I then override the recognizer's touchesMoved method to, among other things, add a temporary view onto the applications key window, then add a copy of the selected UIImageView onto this temporary view, as follows:
UIView *dragAndDropView = [[UIView alloc] initWithFrame: [[UIScreen mainScreen] applicationFrame]];
dragAndDropView.backgroundColor = [UIColor whiteColor];
[[UIApplication sharedApplication].keyWindow addSubview: dragAndDropView];
ElementImageView * sourceImageView = (ElementImageView*)self.view;
ElementImageView *newImageView = [[ElementImageView alloc] initWithImage:sourceImageView.image];
newImageView.userInteractionEnabled = YES;
newImageView.frame = [self.view convertRect:sourceImageView.frame toView:dragAndDropView];
[dragAndDropView addSubview:newImageView];
As a result of this code, I do indeed get a copy of the source image view on top of my dragAndDropView (I can tell because I set the backgroundcolor of the dragAndDropView to white). And if I lift my finger and touch the copied image view again, I can of course drag it around the screen as I wish. But I can't find a way to seamlessly transfer the existing touch to the new object.
Any ideas?

Answer 1

I think you could do the following on your UIPanGestureRecognizer handler:
-(void) handlePan:(UIPanGestureRecognizer *)recognizer {
if (recognizer.state == UIGestureRecognizerStateBegan) {
// the initial position
initialPanPositionX = self.transform.tx;
initialPanPositionY = self.transform.ty;
// create a copy of the imageview
panImage = [[UIImageView alloc] initWithImage:imageView.image];
panImage.frame = imageView.frame;
[self.view addSubview:panImage];
}
else if (recognizer.state == UIGestureRecognizerStateChanged) {
if (!startedMoving) {
startedMoving = YES;
[UIView beginAnimations:nil context:NULL]; {
[UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
[UIView setAnimationDuration:0.2f];
// an effect to increase a copy a little bit when start dragging
CGAffineTransform zt = CGAffineTransformScale(CGAffineTransformIdentity, 1.2, 1.2);
panImage.bounds = CGRectApplyAffineTransform(panImage.bounds, zt);
}
[UIView commitAnimations];
}
// translation
CGPoint point = [recognizer translationInView:self];
panImage.transform = CGAffineTransformMakeTranslation(initialPanPositionX + point.x, initialPanPositionY + point.y);
}
else if (recognizer.state == UIGestureRecognizerStateEnded ) {
startedMoving = NO;
// drop the imageView if it's inside the droppable view
[panImage release], panImage = nil;
}
}
Hope it helps.