我想调整PanGestureRecognizer的大小时不会移动

Question

I Have a UIPanGestureRecognizer. It works fine. I made an if statement so when someone touches the picture, it will be alpha 0.7 and it will be 1,5 times bigger. The alpha works fine, but when i type in the CAAffineTransformMakeScale method, my image won't move.

this is my code:

- (IBAction)Bloemen:(UIPanGestureRecognizer *)recognizer {

    CGPoint translation = [recognizer translationInView:self.view];
    recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
                                     recognizer.view.center.y + translation.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];

     if (UIGestureRecognizerStateBegan)
    {
        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationDelay:0.1];
        [UIView setAnimationDuration:0.4];

        bloemen.alpha = 0.7f;
        bloemen.transform = CGAffineTransformMakeScale(1.5,1.5);

        [UIView commitAnimations];
     }
    if (UIGestureRecognizerStateEnded) {
        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationDelay:0.1];
        [UIView setAnimationDuration:0.1];

        bloemen.alpha = 1.0f;
        bloemen.transform = CGAffineTransformIdentity;

       [UIView commitAnimations];
   }
}

Answer 1

The critical issue is that your if statements are not checking the state property. It should be:

if (recognizer.state == UIGestureRecognizerStateBegan)
{
    // began code here
}
else if (recognizer.state == UIGestureRecognizerStateEnded)
{
    // ended code here
}

Also be aware that this gesture recognizer will only work if you have autolayout turned off. If you're using autolayout, you have to change the constraints.

---

If you forgive the stylistic observations, I might also be inclined to suggest:

• use block-based animations;

• not reference non-local variables if not needed (ie reference recognizer.view rather than bloemen ), which makes it easier to reuse this handler for dragging and dropping of various UIView objects you choose to add this gesture to; and

• use standard naming conventions, start method names with lowercase letter and follow the verbNoun convention.

None of this is critical and please use or disregard as you see fit, but this exhibits a few best practices:

- (void)handlePan:(UIPanGestureRecognizer *)recognizer
{    
    CGPoint translation = [recognizer translationInView:self.view];
    recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
                                         recognizer.view.center.y + translation.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];

    if (recognizer.state == UIGestureRecognizerStateBegan)
    {
        [UIView animateWithDuration:0.4
                              delay:0.0  // you had 0.1, but seems worthwhile to give immediate feedback
                            options:0
                         animations:^{
                             recognizer.view.alpha = 0.7f;
                             recognizer.view.transform = CGAffineTransformMakeScale(1.5,1.5);
                         }
                         completion:nil];
    }
    if (recognizer.state == UIGestureRecognizerStateEnded)
    {
        [UIView animateWithDuration:0.1
                              delay:0.0  // you had 0.1, but seems worthwhile to give immediate feedback
                            options:0
                         animations:^{
                             recognizer.view.alpha = 1.0f;
                             recognizer.view.transform = CGAffineTransformIdentity;
                         }
                         completion:nil];
    }
}