Objective-c – Scrolling with two fingers with a UIScrollView

iphoneobjective cuiscrollview

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 implement a UIScrollView, and I have it working, but it overrides the drags, and therefore my contentView never receives them. I'd like to implement a UIScrollview, where a two finger drag indicates a scroll, and a one finger drag event gets passed to my content view, so it performs normally. Do I need create my own subclass of UIScrollView?

Here's my code from my appDelegate where I implement the UIScrollView.

@implementation MusicGridAppDelegate

@synthesize window;
@synthesize viewController;
@synthesize scrollView;

- (void)applicationDidFinishLaunching:(UIApplication *)application {    

    // Override point for customization after app launch    
    //[application setStatusBarHidden:YES animated:NO];
    //[window addSubview:viewController.view];

    scrollView.contentSize = CGSizeMake(720, 480);
    scrollView.showsHorizontalScrollIndicator = YES;
    scrollView.showsVerticalScrollIndicator = YES;
    scrollView.delegate = self;
    [scrollView addSubview:viewController.view];
    [window makeKeyAndVisible];

- (void)dealloc {
    [viewController release];
    [scrollView release];
    [window release];
    [super dealloc];

Best Answer

In SDK 3.2 the touch handling for UIScrollView is handled using Gesture Recognizers.

If you want to do two-finger panning instead of the default one-finger panning, you can use the following code:

for (UIGestureRecognizer *gestureRecognizer in scrollView.gestureRecognizers) {     
    if ([gestureRecognizer  isKindOfClass:[UIPanGestureRecognizer class]]) {
        UIPanGestureRecognizer *panGR = (UIPanGestureRecognizer *) gestureRecognizer;
        panGR.minimumNumberOfTouches = 2;               
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