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POCancel UITouch Events When View Covered By Modal UIViewController
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  1. POCancel UITouch Events When View Covered By Modal UIViewController
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    copied!<p>I am writing an application where the user has to move some stuff on the screen using his fingers and drop them. To do this, I am using the touchesBegan,touchesEnded... function of each view that has to be moved.</p> <p>The problem is that sometimes the views are covered by a view displayed using the [UIViewController presentModalViewController] function. As soon as that happens, the UIView that I was moving stops receiving the touch events, since it was covered up. But there is no event telling me that it stopped receiving the events, so I can reset the state of the moved view.</p> <p>The following is an example that demonstrates this. The functions are part of a UIView that is being shown in the main window. It listens to touch events and when I drag the finger for some distance, it presents a modal view that covers everything. In the Run Log, it prints what touch events are received.</p> <pre><code>- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"touchesBegan"); touchStart=[[touches anyObject] locationInView:self]; } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { CGPoint touchAt=[[touches anyObject] locationInView:self]; float xx=(touchAt.x-touchStart.x)*(touchAt.x-touchStart.x); float yy=(touchAt.y-touchStart.y)*(touchAt.y-touchStart.y); float rr=xx+yy; NSLog(@"touchesMoved %f",rr); if(rr &gt; 100) { NSLog(@"Show modal"); [viewController presentModalViewController:[UIViewController new] animated:NO]; } } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"touchesEnded"); } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"touchesCancelled"); } </code></pre> <p>But when I test the application and trigger the modal dialog to be displayed, the following is the output in the Run Log.</p> <blockquote> <p>[Session started at 2010-03-27 16:17:14 -0700.] 2010-03-27 16:17:18.831 modelTouchCancel[2594:207] touchesBegan 2010-03-27 16:17:19.485 modelTouchCancel[2594:207] touchesMoved 2.000000 2010-03-27 16:17:19.504 modelTouchCancel[2594:207] touchesMoved 4.000000 2010-03-27 16:17:19.523 modelTouchCancel[2594:207] touchesMoved 16.000000 2010-03-27 16:17:19.538 modelTouchCancel[2594:207] touchesMoved 26.000000 2010-03-27 16:17:19.596 modelTouchCancel[2594:207] touchesMoved 68.000000 2010-03-27 16:17:19.624 modelTouchCancel[2594:207] touchesMoved 85.000000 2010-03-27 16:17:19.640 modelTouchCancel[2594:207] touchesMoved 125.000000 2010-03-27 16:17:19.641 modelTouchCancel[2594:207] Show modal</p> </blockquote> <p>Any suggestions on how to reset the state of a UIView when its touch events are interrupted by a modal view?</p>
 

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