Question

I have this code:

[scrollView setMinimumZoomScale:1.00];
[scrollView setMaximumZoomScale:2.00];
scrollView.delegate=self;

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

   NSSet *allTouches = [event allTouches];
    if ([allTouches count] == 2) {

        NSLog(@"multitouch");
        zoomMultiTouch = TRUE;


    }

     else if ([allTouches count] == 1){

        NSLog(@"single touch");
        zoomMultiTouch = FALSE;
    }

     else return;

}


- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {


    if (zoomMultiTouch){
        scrollView.userInteractionEnabled = YES;
        scrollView.scrollEnabled = YES;
        NSLog(@"zoomMultitouch moved");
    }

    else {
        scrollView.userInteractionEnabled = NO;
        scrollView.scrollEnabled = NO;
        NSLog(@"NOzoom moved");
    }

  //some code for coloring an image

}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    scrollView.userInteractionEnabled = NO;
    scrollView.scrollEnabled = NO;
    zoomMultiTouch = FALSE;
}

as you can see, I want to zoom scrollView with an image inside; when I touch scrollView with a finger I color image, instead when I touch with two fingers scrollview, I want to do a zoom on it, and after if I touch with a finger zomm must be disabled.
with my code it don’t happen; it recognize double touch but don’t active zoom, why?

Answer 1

I think the problem is that you are not implementing all required delegate methods for zooming.

The UIScrollView class can have a delegate that must adopt the UIScrollViewDelegate protocol. For zooming and panning to work, the delegate must implement both viewForZoomingInScrollView: and scrollViewDidEndZooming:withView:atScale:; in addition, the maximum (maximumZoomScale) and minimum ( minimumZoomScale) zoom scale must be different.

Hope it helps.

UIScrollView Class Reference