iOS：UIgesture用于拖放

Question

In my app I should implement the drag and drop of a imageView; the problem is that my imageView is inside a scrollview; it's my code

- (void) viewDidLoad{
[super viewDidLoad];
UILongPressGestureRecognizer *downwardGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(dragGestureChanged:)];
[scrollViewAlfabeto addGestureRecognizer:downwardGesture];
for (UIGestureRecognizer *gestureRecognizer in myscrollView.gestureRecognizers)
{
    [gestureRecognizer requireGestureRecognizerToFail:downwardGesture];
}
}

- (void) dragGestureChanged:(UIPanGestureRecognizer*)gesture
{
CGPoint point = [gesture locationInView:scrollViewAlfabeto];

if (gesture.state == UIGestureRecognizerStateBegan) 
{

    [imageViewToMove removeFromSuperview];
    [self.view addSubview:imageViewToMove];

    UIView *draggedView = [myscrollView hitTest:point withEvent:nil];
    if ([draggedView isKindOfClass:[UIImageView class]])
    {
        imageViewToMove = (UIImageView*)draggedView;
    }
}
else if (gesture.state == UIGestureRecognizerStateChanged)
{
    imageToMove.center = point;
}
else if (gesture.state == UIGestureRecognizerStateEnded     ||
         gesture.state == UIGestureRecognizerStateCancelled ||
         gesture.state == UIGestureRecognizerStateFailed)
{
    // Determine if dragged view is in an OK drop zone
    // If so, then do the drop action, if not, return it to original location

    NSLog(@"point.x final:%f", point.x);
    NSLog(@"point.y final:%f", point.y);

    if (CGRectContainsPoint(goal.frame, point)){
        imageToMove.frame = CGRectMake(167, 159, 100, 100);
    }

    else{

    [imageToMove removeFromSuperview];
    [myscrollView addSubview:imageToMove];
    [imageToMove setFrame:CGRectMake(12, 38, 100, 100)];
    imageToMove = nil;



    }
}
}

Then with my code I'm able to take an imageView from scrollView with longpress, drag it inside "self.view"; also if I drop this imageView over another imageView in self.view it puts on it. It work fine. But I have two problems:

1- when I drag this imageView and I do

[imageViewToMove removeFromSuperview];
[self.view addSubview:imageViewToMove];

the image view don't appear under my finger but in other position and I want that it remains under my finger

2- This code work only the first time when I launch my viewcontroller, because If I don't drop the imageview over other imageview inside self.view, itr return inside scrollview, but If I want drag it a second time, it don't work.

Can you help me?

Answer 1

I'm not advanced in objc, but...

1. Allow user ineraction [self.view userInteractionEnabled:YES];
2. Try [self.view setMultipleTouchEnabled:YES];

Taken from the documentation of UIView in relation to userInteractionEnabled :

Discussion
When set to NO, user events—such as touch and keyboard—intended for the view are ignored and removed from the event queue. When set to YES, events are delivered to the view normally. The default value of this property is YES.

During an animation, user interactions are temporarily disabled for all views involved in the animation, regardless of the value in this property. You can disable this behavior by specifying the UIViewAnimationOptionAllowUserInteraction option when configuring the animation.

Hope it works