How should I be scaling this map picture with UIPinchGestureRecognizer?

Question

I'm really close to being able to scale a picture of a map programmatically with UIPinchGestureRecognizer and a scale method. I've tried a scroll view like this: [mapScrollView addGestureRecognizer:pinchRecognizer];, but of course that won't work because that will scale the entire view and the bounds. If I do [mapImageView addGestureRecognizer:pinchRecognizer] nothing will happen.

How do I scale the image inside the scroll view? Even more, how do I set bounds of max and min scaling? Thanks

The code:

- (id)initWithFrame:(CGRect)frame {

    self = [super initWithFrame:frame];
    if (self) {

        mainMenuAppDelegate *del = (mainMenuAppDelegate *)[[UIApplication sharedApplication] delegate];

        map_List = [[NSMutableArray alloc] init];
        [map_List addObject:@"Pacific_Map_8bit.png"];
        [map_List addObject:@"Atlantic_Map_8bit.png"];

        CGRect mapScrollViewFrame = CGRectMake(0, 0, 1024, 768);

        mapScrollView = [[UIScrollView alloc]   initWithFrame:mapScrollViewFrame];

        mapScrollView.contentSize = CGSizeMake(2437, 1536);

        UIImage *mapImage = [UIImage imageNamed:[map_List objectAtIndex:mapNum]];

        mapImageView = [[UIImageView alloc] initWithImage: mapImage];

        mapScrollView.bounces = NO;

        [mapImage release];

        [mapScrollView addSubview:mapImageView];
        [self addSubview:mapScrollView];

        UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scale:)];
        [mapImageView addGestureRecognizer:pinchRecognizer];

        [pinchRecognizer release];

        UIImage *footerMapIMG = [UIImage imageNamed:@"footer_map_alternate.png"];
        UIImageView *footerMapView = [[UIImageView alloc] initWithImage:(UIImage *)footerMapIMG];
        CGRect footerMapFrame = CGRectMake(0, 686, 213, 82);
        footerMapView.frame = footerMapFrame;
        [self addSubview:footerMapView]; 
        footerMapView.image = footerMapIMG; 

        [footerMapView release];

        CGRect backBTNFrame = CGRectMake(20, 714, 140, 52); 
        UIButton *MAP_backButton = [[UIButton alloc] init];
        MAP_backButton.frame = backBTNFrame;
        UIImage *MAP_backButtonIMG = [UIImage imageNamed:@"button_back.png"];
        [MAP_backButton setImage:MAP_backButtonIMG forState:UIControlStateNormal];
        MAP_backButton.backgroundColor = [UIColor clearColor];
        [self addSubview:MAP_backButton];

        [MAP_backButton release];

        [MAP_backButton addTarget:del.switchVC 
                           action:@selector(gotoMapAndListChooser)
                 forControlEvents:UIControlEventTouchUpInside];
    }
    return self;
}

-(void)scale:(id)sender {
    if([(UIPinchGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {

        lastScale = 1.0;
        return;
    }

    CGFloat scale = 1.0 - (lastScale - [(UIPinchGestureRecognizer*)sender scale]);

    /*
    if(scale > 1){
        scale = 1;
    }
    if(scale < .5){
        scale = .5;
    }
    */

    CGAffineTransform currentTransform = [(UIPinchGestureRecognizer*)sender view].transform;
    CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scale, scale);

    [[(UIPinchGestureRecognizer*)sender view] setTransform:newTransform];

    lastScale = [(UIPinchGestureRecognizer*)sender scale];
}

Answer 1

I don't know for sure, and I don't want to test but try to add

mapImageView.userInteractionEnabled = YES;

Gestures don't work on imageviews without this setting.
EDIT: Maybe I've interpreted your question wrong and your scaling method gets called but doesn't work.

---

Btw, have you read about CATiledLayer? There is also a great introduction in the WWDC10 Session Videos (Session 104 - Designing Apps with Scroll Views). You should get to that video through developer.apple.com
You should watch it, because a 2437x1536 image is quite big for the iphone. You will run into performance and/or memory problems sooner or later.