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;               
    }
}

Related Solutions

Ios – UIScrollView scroll to bottom programmatically

You can use the UIScrollView's setContentOffset:animated: function to scroll to any part of the content view. Here's some code that would scroll to the bottom, assuming your scrollView is self.scrollView:

Objective-C:

CGPoint bottomOffset = CGPointMake(0, self.scrollView.contentSize.height - self.scrollView.bounds.size.height + self.scrollView.contentInset.bottom);
[self.scrollView setContentOffset:bottomOffset animated:YES];

Swift:

let bottomOffset = CGPoint(x: 0, y: scrollView.contentSize.height - scrollView.bounds.height + scrollView.contentInset.bottom)
scrollView.setContentOffset(bottomOffset, animated: true)

Hope that helps!

R – UINavigationController doesn’t work in a the moreNavigationController of a UITabBarController

Short answer: you cannot nest navigation controllers

Longer answer: you are doing it wrong. A better way to create what you want goes like this:

NSMutableArray *viewControllers = [NSMutableArray array];

[viewControllers addObject:[[[ConverterViewController alloc] init] autorelease]];
[viewControllers addObject:[[[UINavigationController alloc]
                             initWithRootViewController:[[[CurrencyViewController alloc] init] autorelease]] autorelease]];
[viewControllers addObject:[[[UINavigationController alloc]
                             initWithRootViewController:[[[HistoryViewController alloc] init] autorelease]] autorelease]];
[viewControllers addObject:[[[UINavigationController alloc]
                             initWithRootViewController:[[[SetupViewController alloc] init] autorelease]] autorelease]];
[viewControllers addObject:[[[UINavigationController alloc]
                             initWithRootViewController:[[[HelpViewController alloc] init] autorelease]] autorelease]];
[viewControllers addObject:[[[LinksViewController alloc] init] autorelease]];

self.viewControllers = viewControllers;
self.customizableViewControllers = [viewControllers arrayByRemovingFirstObject];


@implementation HelpViewController

#pragma mark -
#pragma mark Initialization

- (id)init
{
    if ((self = [super initWithNibName:@"HelpView" bundle:nil]) != nil) {
        self.title = NSLocalizedString(@"Help", @"Help"); 
        self.tabBarItem.image = [UIImage imageNamed:@"question.png"];
    }

    return self;
}

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