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POHow to setup a subclass of UIScrollView to respond to touch events?
 

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  1. POHow to setup a subclass of UIScrollView to respond to touch events?
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    <p>I recently had a problem regarding not being able to register touches events (<code>touchesMoved</code>, etc) from within a <code>UIScrollView</code>. After talking with lots of people and reading tons of posts, it turns out <code>UIScrollView</code> does't accept touches itself, and instead the touches need to be passed to a <code>UIScrollView</code> subclass.</p> <p>I am very new to objective-c, and am having a terrible time wrapping my head around how subclasses are defined (in separate .h/.m files or somehow in @interface or something), as well as how iOS deals with responder chains. </p> <p>Please let me describe my exact situation, and anyone willing to explain what I need to do in noob-speak will be really appreciated. </p> <p>I have a single page in my app, and I changed it's default <code>UIView</code> to <code>UIScrollView</code>, so if I inspect it in <code>InterfaceBuidler</code> all I see is my <code>SampleViewController</code> and <code>UIScrollView</code>. I linked my <code>UIScrollView</code> to the <code>@Interface</code> of <code>SampleViewControler.h</code> like this:</p> <pre><code>#import &lt;UIKit/UIKit.h&gt; @interface SampleViewController : UIViewController { } @property (strong, nonatomic) IBOutlet UIScrollView *mainScroller; @end </code></pre> <p>And I referenced my <code>UIScrollView</code> in <code>SampleViewController.m</code> like this:</p> <pre><code>#import "SampleViewController.h" @interface SampleViewController () @end @implementation SampleViewController @synthesize mainScroller = _mainScroller; - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"Movement!"); } -(void)viewWillAppear:(BOOL)animated { [_mainScroller setContentOffset:CGPointMake(0,0) animated:YES]; } </code></pre> <p>If I change the class of <code>UIScrollView</code> to <code>UIView</code>, the touches are detected and I fire off a few <code>NSLog</code> messages. However, once <code>UIView</code> is set back to <code>UIScrollView</code>, touches are ignored.</p> <p>From what I understand I need to setup a subclass of <code>UIScrollView</code> with the code:</p> <pre><code>- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"Movement!"); } </code></pre> <p>...and then change my SampleViewController.m to have the code:</p> <pre><code>- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [[self.nextResponder nextResponder] touchesMoved:touches withEvent:event]; } </code></pre> <p>However, I really don't understand 1) how to setup such a subclass, and 2) why this would work, since I don't see why <code>[[self.nextResponder nextResponder] touchesMoved:touches withEvent:event];</code> would ever be called in the first place from within <code>SampleViewController.m</code>, since my similar <code>NSLog(@"Movement!");</code> statement is never executed.</p> <p>I have tried every tutorial I could find, and am turning toward to the expertise of SE! Thanks.</p>
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