Question

I have a mapView, in my mapView you can zoom with double tap, pinch, UIButton (+ and -) and with an UISlider.
Now… I want recognize the doubletap and the pinch, to refresh the position of UISlider… I use a NSInteger variable called zoomLevel to make this.

I have tried two way, but not working:

1)

    UIGestureRecognizer *recognizer;


// taps
recognizer = [[ UITapGestureRecognizer alloc] initWithTarget:self  action:@selector(handleTap)];
tapGR = (UITapGestureRecognizer *)recognizer;
tapGR.numberOfTapsRequired = 2;
tapGR.cancelsTouchesInView = NO;
[self.view addGestureRecognizer:tapGR]; 
[recognizer release];

2)

- (void)touchesEnded:(NSSet *)touches withEvent: (UIEvent *) event{
    UITouch* touch = [[event allTouches] anyObject];
    NSLog(@"2 taps");
    if(touch.tapCount == 2 ){
        NSLog(@"2 taps");
        [self zoomLevelWithMapView:mappa];
    }

Can someone help me?
Better with pratical example
Thank you.

Answer 1

Recognizing the change of zoom scale with UIGestureRecognizer is a bad idea.

Better use the MKMapView delegate method that is called when the region displayed by the map view is about to change.

- (void)mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated {
    // detect zoom scale and update slider
}

Use the method in this answer to detect the zoom scale.