How to use UIPanGestureRecognizer to move object? iPhone/iPad

Question

There are several examples of the UIPanGestureRecognizer class. For example I have read this and I am still not able to use it...

On the nib file that I am working on I have a UIView (white rectangle on image) that I wish to drag with that class:

and in my .m file I have placed:

- (void)setTranslation:(CGPoint)translation inView:(UIView *)view {     NSLog(@"Test to see if this method gets executed"); } 

and that method does not get executed when I drag the mouse across the UIView. I have also tried placing:

- (void)pan:(UIPanGestureRecognizer *)gesture {     NSLog(@"testing"); } 

And that method does not get executed either. Maybe I am wrong but I think this methods should work like the - (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event method where I just have to place that method and it will get called whenever there are touches.

What am I doing wrong? Maybe do I have to draw a connection to that method? If so how can I do that?

Answer 1

I found the tutorial Working with UIGestureRecognizers, and I think that is what I am looking for. It helped me come up with the following solution:

-(IBAction) someMethod {     UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(move:)];     [panRecognizer setMinimumNumberOfTouches:1];     [panRecognizer setMaximumNumberOfTouches:1];     [ViewMain addGestureRecognizer:panRecognizer];     [panRecognizer release]; }  -(void)move:(UIPanGestureRecognizer*)sender {     [self.view bringSubviewToFront:sender.view];     CGPoint translatedPoint = [sender translationInView:sender.view.superview];      if (sender.state == UIGestureRecognizerStateBegan) {         firstX = sender.view.center.x;         firstY = sender.view.center.y;     }       translatedPoint = CGPointMake(sender.view.center.x+translatedPoint.x, sender.view.center.y+translatedPoint.y);      [sender.view setCenter:translatedPoint];     [sender setTranslation:CGPointZero inView:sender.view];      if (sender.state == UIGestureRecognizerStateEnded) {         CGFloat velocityX = (0.2*[sender velocityInView:self.view].x);         CGFloat velocityY = (0.2*[sender velocityInView:self.view].y);          CGFloat finalX = translatedPoint.x + velocityX;         CGFloat finalY = translatedPoint.y + velocityY;// translatedPoint.y + (.35*[(UIPanGestureRecognizer*)sender velocityInView:self.view].y);          if (finalX < 0) {             finalX = 0;         } else if (finalX > self.view.frame.size.width) {             finalX = self.view.frame.size.width;         }          if (finalY < 50) { // to avoid status bar             finalY = 50;         } else if (finalY > self.view.frame.size.height) {             finalY = self.view.frame.size.height;         }          CGFloat animationDuration = (ABS(velocityX)*.0002)+.2;          NSLog(@"the duration is: %f", animationDuration);          [UIView beginAnimations:nil context:NULL];         [UIView setAnimationDuration:animationDuration];         [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];         [UIView setAnimationDelegate:self];         [UIView setAnimationDidStopSelector:@selector(animationDidFinish)];         [[sender view] setCenter:CGPointMake(finalX, finalY)];         [UIView commitAnimations];     } } 

Answer 2

UIPanGestureRecognizer * pan1 = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(moveObject:)]; pan1.minimumNumberOfTouches = 1; [image1 addGestureRecognizer:pan1];  -(void)moveObject:(UIPanGestureRecognizer *)pan; {  image1.center = [pan locationInView:image1.superview]; }