how to make an object draggable? - ios

Question

hey guys i was wondering if there was away to make an object like a UIImageView draggable. I am aware of the UITouch and touches i.e.
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *drag=[[event allTouches] anyObject];
player.center=[drag locationInView:self.view];
}
but in this way it is possible for the user to make the object jump across the screen to where he or she touches the screen but i want the user to have to manually drag the object across the screen.
please explain with code and let me know if i have to be more specific or clear...

Answer 1

You can do this:
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *aTouch = [touches anyObject];
CGPoint location = [aTouch locationInView:self.view];
if(CGRectContainsPoint(self.playerView.frame,location)) {
[UIView beginAnimations:#"Dragging A DraggableView" context:nil];
self.playerView.center = location;
[UIView commitAnimations];
}
}
This should give you a smooth animation.

Answer 2

if you want your user to drag&drop, first you have to check if the touch is inside the imageview rect frame. To improve the user experience, you can detect the touch offset from the imageview center; a good place to do this is inside the touchesBegan:withEvent:. After that, you have to change the position of the imageview, like this:
CGPoint touchOffset; //insert this inside your interface private iVars
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *drag=[[event allTouches] anyObject];
CGPoint touchLocation = [drag locationInView:self.view];
touchOffset = CGPointMake(player.center.x-touchLocation.x,player.center.y-touchLocation.y)
if(CGRectContainsPoint(player.frame,touchLocation)
player.center = CGPointMake(touchLocation.x+touchOffset.x,touchLocation.y+touchOffset.y);
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *drag=[[event allTouches] anyObject];
CGPoint touchLocation = [drag locationInView:self.view];
if(CGRectContainsPoint(player.frame,touchLocation)
player.center = CGPointMake(touchLocation.x+touchOffset.x,touchLocation.y+touchOffset.y);
}
P.S. - Next time try to search similar questions...

Answer 3

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch* aTouch = [touches anyObject];
UIView* aView = [aTouch view];
if (aView != self.view) {
[self.view bringSubviewToFront:aView];
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch* aTouch = [touches anyObject];
UIView* aView = [aTouch view];
if (aView != self.view) {
aView.center = [aTouch locationInView:self.view];
}
}