Scrolling with two fingers with a UIScrollView

Question

I have an app where my main view accepts both touchesBegan and touchesMoved, and therefore takes in single finger touches, and drags. I want to im

Answer 1

we managed to implement similar functionality in our iPhone drawing app by subclassing UIScrollView and filtering events depending on number of touches in simple and rude way:

//OCRScroller.h
@interface OCRUIScrollView: UIScrollView
{
    double pass2scroller;
}
@end

//OCRScroller.mm
@implementation OCRUIScrollView
- (id)initWithFrame:(CGRect)aRect {
    pass2scroller = 0;
    UIScrollView* newv = [super initWithFrame:aRect];
    return newv;
}
- (void)setupPassOnEvent:(UIEvent *)event {
    int touch_cnt = [[event allTouches] count];
    if(touch_cnt<=1){
        pass2scroller = 0;
    }else{
        double timems = double(CACurrentMediaTime()*1000);
        pass2scroller = timems+200;
    }
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [self setupPassOnEvent:event];
    [super touchesBegan:touches withEvent:event];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    [self setupPassOnEvent:event];
    [super touchesMoved:touches withEvent:event];   
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    pass2scroller = 0;
    [super touchesEnded:touches withEvent:event];
}


- (BOOL)touchesShouldBegin:(NSSet *)touches withEvent:(UIEvent *)event inContentView:(UIView *)view
{
    return YES;
}

- (BOOL)touchesShouldCancelInContentView:(UIView *)view
{
    double timems = double(CACurrentMediaTime()*1000);
    if (pass2scroller == 0 || timems> pass2scroller){
        return NO;
    }
    return YES;
}
@end

ScrollView setuped as follows:

scroll_view = [[OCRUIScrollView alloc] initWithFrame:rect];
scroll_view.contentSize = img_size;
scroll_view.contentOffset = CGPointMake(0,0);
scroll_view.canCancelContentTouches = YES;
scroll_view.delaysContentTouches = NO;
scroll_view.scrollEnabled = YES;
scroll_view.bounces = NO;
scroll_view.bouncesZoom = YES;
scroll_view.maximumZoomScale = 10.0f;
scroll_view.minimumZoomScale = 0.1f;
scroll_view.delegate = self;
self.view = scroll_view;

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simple tap does nothing (you can handle it in the way you need), tap with two fingers scrolls/zooms view as expected. no GestureRecognizer is used, so works from iOS 3.1