How to drag only one image with iPhone SDK - objective-c

Question

I want to create a little app that takes two images and i want to make only the image over draggable.
After research, i found this solution:
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [[ event allTouches] anyObject];
image.alpha = 0.7;
if([touch view] == image){
CGPoint location = [touch locationInView:self.view];
image.center = location;
}
It works but the problem is that the image is draggable from its center and I don't want that.
So I found another solution:
- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
// Retrieve the touch point
CGPoint pt = [[touches anyObject] locationInView:self.view];
startLocation = pt;
[[self view] bringSubviewToFront:self.view];
}
- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
// Move relative to the original touch point
CGPoint pt = [[touches anyObject] locationInView:self.view];
frame = [self.view frame];
frame.origin.x += pt.x - startLocation.x;
frame.origin.y += pt.y - startLocation.y;
[self.view setFrame:frame];
}
It works very well but when I add another image, all the images of the view are draggable at the same time. I'm a beginner with the iPhone development and I have no idea of how I can only make the image over draggable.

Answer 1

You can use if condition in the touchesBegan: method, See this-
-(void)ViewDidLoad
{
//Your First Image View
UIImageView *imageView1 = [UIImageView alloc]initWithFrame:CGRectMake(150.0, 100.0, 30.0, 30.0)];
[imageView1 setImage:[UIImage imageNamed:#"anyImage.png"]];
[imageView1 setUserInteractionEnabled:YES];
[self.view addSubview:imageView1];
//Your Second Image View
UIImageView *imageView2 = [UIImageView alloc]initWithFrame:CGRectMake(150.0, 200.0, 30.0, 30.0)];
[imageView2 setImage:[UIImage imageNamed:#"anyImage.png"]];
[imageView2 setUserInteractionEnabled:YES];
[self.view addSubview:imageView2];
}
//Now Use Touch begin methods with condition like this
- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches]anyObject];
if([touch view] == imageView1)
{
CGPoint pt = [[touches anyObject] locationInView:imageView1];
startLocation = pt;
}
if([touch view] == imageView2)
{
CGPoint pt = [[touches anyObject] locationInView:imageView2];
startLocation = pt;
}
}
//Use same thing with touch move methods...
- (void) touchesMoved:(NSSet *)touches withEvent: (UIEvent *)event
{
UITouch *touch = [[event allTouches]anyObject];
if([touch view] == imageView1)
{
CGPoint pt = [[touches anyObject] previousLocationInView:imageView1];
CGFloat dx = pt.x - startLocation.x;
CGFloat dy = pt.y - startLocation.y;
CGPoint newCenter = CGPointMake(imageView1.center.x + dx, imageView1.center.y + dy);
imageView1.center = newCenter;
}
if([touch view] == imageView2)
{
CGPoint pt = [[touches anyObject] previousLocationInView:imageView2];
CGFloat dx = pt.x - startLocation.x;
CGFloat dy = pt.y - startLocation.y;
CGPoint newCenter = CGPointMake(imageView2.center.x + dx, imageView2.center.y + dy);
imageView2.center = newCenter;
}
}
These two images will move only when you touch on it and move it. I hope my tutorials will help you.

Answer 2

Simply use these two methods
-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches] anyObject];
CGPoint location = [touch locationInView:touch.view];
myImage.center = location;
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
[self touchesBegan:touches withEvent:event];
}

Answer 3

Let's break it down. You should have a main containerView (object of UIView) in your view controller. Within that, you should have DragableImageView objects.
DragableImageView inherits UIImageView and within that, you add your touches code. (Right now you are doing self.frame = position which is wrong - and obviously it will move all images at once - because if I understand correctly, you are adding these touches in your view controller).
Create only DragableImageView first, test it. Then add two DragableImageView instances. test them in different configurations.. you might want to hit test in the containerView to see which DragableImageView should be dragged (e.g. if you have jigsaw pieces, you might want to pick the one that is at the back rather than the front one).