Why does a UIImageView move all crazy when touchesBegan starts at the UIImageView?

Question

So I create an UIImageView programmatically and I place it on an array. In touchesMoved I set the x-position of the UIImageView to the x-position of the touch.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
for (UIImageView *b in _blocks) {
    if ( b.image != wall) {
        movingimage = b;
        movingimage.userInteractionEnabled = YES;

        NSLog(@"touch");
     }
 }
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [[event allTouches]anyObject];
CGPoint location = [touch locationInView:touch.view];
CGPoint xlocation = CGPointMake(location.x, movingimage.center.y);
movingimage.center = xlocation;
}

This code works fine if instead of using a UIImageView created programmatically I use one created in Interface Builder. But when I use code to create the UIImageView and tochesBegan starts at the UIImageView the touch coordinate from touchesMoved goes crazy and the imageView flashes really fast between 2 places.

Thanks for reading.

Answer 1

I guess this is because you are getting the touch point from a view that you are then relocating. So the next event will be "incorrect". I think that the best you could do is to capture the touch location from the superview.

EDIT:

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches]anyObject];
    CGPoint location = [touch locationInView:[movingimage superview]];
    CGPoint xlocation = CGPointMake(location.x, movingimage.center.y);
    movingimage.center = xlocation;
}