Dragging an Image View - iphone

Question

I am trying to drag an image view. I have got little bit of success in doing so, but it is not behaving as i want. I wish that it should move only if touch inside the image and drag it.
But it is moving even if I am touching and dragging from anywhere on the screen.
I have written code like this:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
//retrieve touch point
CGPoint pt= [[ touches anyObject] locationInView:[self.view.subviews objectAtIndex:0]];
startLocation = pt;
}
- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
CGPoint pt = [[touches anyObject] locationInView: [self.view.subviews objectAtIndex:0]];
CGRect frame = [[self.view.subviews objectAtIndex:0]frame];
frame.origin.x += pt.x - startLocation.x;
frame.origin.y += pt.y - startLocation.y;
[[self.view.subviews objectAtIndex:0] setFrame: frame];
}

Answer 1

The return value of locationInView method is point relative to the view frame. check it is or not in the view frame first.
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGRect targetFrame = [self.view.subviews objectAtIndex:0].frame;
//retrieve touch point
CGPoint pt= [[ touches anyObject] locationInView:[self.view.subviews objectAtIndex:0]];
//check if the point in the view frame
if (pt.x < 0 || pt.x > targetFrame.size.width || pt.y < 0 || pt.y > targetFrame.size.height)
{
isInTargetFrame = NO;
}
else
{
isInTargetFrame = YES;
startLocation = pt;
}
}
- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
if(!isInTargetFrame)
{
return;
}
//move your view here...
}

Answer 2

Try something like this:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
//retrieve touch point
startLocation = [[ touches anyObject] locationInView:self.view];
// Now here check to make sure that start location is within the frame of
// your subview [self.view.subviews objectAtIndex:0]
// if it is you need to have a property like dragging = YES
// Then in touches ended you set dragging = NO
}
- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
CGPoint pt = [[touches anyObject] locationInView: [self.view.subviews objectAtIndex:0]];
CGRect frame = [[self.view.subviews objectAtIndex:0]frame];
frame.origin.x += pt.x - startLocation.x;
frame.origin.y += pt.y - startLocation.y;
[[self.view.subviews objectAtIndex:0] setFrame: frame];