动画时按住按钮时，UIPageViewController崩溃

Question

I have UIPageViewController that animates programatically. The problem is that the view controllers inside it has UIButtons inside them. When I hold down a button and wait until the UIPageViewController animates, the app crashes with the error:

'Failed to determine navigation direction for scroll'

What I think I need to do is to somehow fake that the user releases the button before the UIPageviewController animates.

However, [self.button sendActionsForControlEvents:UIControlEventTouchCancel]; doesn't seem to do the trick. Neither do UIControlEventTouchUpInside .

Is there a better way do to it or am I using sendActionsForControlEvents wrong?

Answer 1

All sendActionsForControlEvents: does is call any methods you've assigned to the control events passed in for the button. It doesn't call any internal methods to programmatically lift up touches or anything like that.

Right before you programmatically animate your page view controller, try using this method to effectively cancel any touches on the pan gesture recognizer of the page view controller's internal scroll view:

- (void)cancelPanGestureTouchesOfPageViewController:(UIPageViewController *)pageVC
{
    // Since UIPageViewController doesn't provide any API to access its scroll view,
    // we have to find it ourselves by manually looping through its view's subviews.
    for (UIScrollView *scrollView in pageVC.view.subviews) {
        if ([scrollView isKindOfClass:[UIScrollView class]]) {

            // We've found the scroll view, so use this little trick to
            // effectively cancel any touches on its pan gesture recognizer
            BOOL enabled = scrollView.panGestureRecognizer.enabled;
            scrollView.panGestureRecognizer.enabled = !enabled;
            scrollView.panGestureRecognizer.enabled = enabled;
        }
    }
}

(Note that this is messing with the internal view hierarchy of UIPageViewController , so this method is kind of ugly and may break in the future. I generally don't recommend doing stuff like this, but I think in this instance it should be okay.)