我有一个UIViewController使用iOS 7中引入的transitioningDelegate模式呈现/解散另一个带有自定义动画的视图控制器。
我在Crashlytics日志文件中注意到这部分代码偶尔会在生产中崩溃，而我无法理清原因。它从未在我的测试中崩溃，看起来只影响了大约10％的用户。 iOS 7和iOS 8以及iPad，iPhone和iPod都会受到影响。
来自Crashlytics的堆栈跟踪：
Crashed: com.apple.main-thread
EXC_BAD_ACCESS KERN_INVALID_ADDRESS at 0x00014000
Thread : Crashed: com.apple.main-thread
0 libobjc.A.dylib 0x303c3f76 objc_msgSend + 21
1 UIKit 0x25ed0ac5 -[UIViewController _customAnimatorForDismissedController:] + 64
2 UIKit 0x25ed0927 -[UIViewController _dismissViewControllerWithTransition:from:completion:] + 538
3 UIKit 0x25e7e4b3 -[UIViewController dismissViewControllerWithTransition:completion:] + 822
4 UIKit 0x25e7e4b3 -[UIViewController dismissViewControllerWithTransition:completion:] + 822
5 UIKit 0x25e7e127 -[UIViewController dismissViewControllerAnimated:completion:] + 222
6 Skin Creator 0x000f38e7 -[SEUSBodySideChooserViewController imageEditViewController:didFinishWithImage:] (SEUSBodySideChooserViewController.m:251)
7 Skin Creator 0x000ae2e9 -[SEUSImageEditViewController sendFinishedDelegateMethod] (SEUSImageEditViewController.m:409)
8 Skin Creator 0x000d585f -[SEUSCloseMenuController circleMenu:didSelectItemAtIndex:] (SEUSCloseMenuController.m:69)
9 Skin Creator 0x000ceb75 -[SEUSCircleMenu menuButtonPressed:] (SEUSCircleMenu.m:203)
10 UIKit 0x25dec427 -[UIApplication sendAction:to:from:forEvent:] + 70
11 UIKit 0x25dec3c9 -[UIControl sendAction:to:forEvent:] + 44
12 UIKit 0x25dd6fcd -[UIControl _sendActionsForEvents:withEvent:] + 584
13 UIKit 0x25debdf9 -[UIControl touchesEnded:withEvent:] + 584
14 UIKit 0x25db0b47 _UIGestureRecognizerUpdate + 10158
15 UIKit 0x25de5afd -[UIWindow _sendGesturesForEvent:] + 784
16 UIKit 0x25de53cd -[UIWindow sendEvent:] + 520
17 UIKit 0x25dbbb5d -[UIApplication sendEvent:] + 196
18 UIKit 0x2602f4e3 _UIApplicationHandleEventFromQueueEvent + 13874
19 UIKit 0x25dba59f _UIApplicationHandleEventQueue + 1294
20 CoreFoundation 0x228dd5e7 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 14
21 CoreFoundation 0x228dc9fb __CFRunLoopDoSources0 + 222
22 CoreFoundation 0x228db079 __CFRunLoopRun + 768
23 CoreFoundation 0x22828981 CFRunLoopRunSpecific + 476
24 CoreFoundation 0x22828793 CFRunLoopRunInMode + 106
25 GraphicsServices 0x29ba9051 GSEventRunModal + 136
26 UIKit 0x25e1a981 UIApplicationMain + 1440
27 Skin Creator 0x000ead6f main (main.m:16)
只是这样你可以理解这一点[SEUSBodySideChooserViewController imageEditViewController：didFinishWithImage：]是一个委托回调，我解雇了视图控制器。
代码我用来呈现视图控制器
_toPixelEditTransitioningDelegate = [[SEUSFadeInTransitioningDelegate alloc] init];
_imageEditViewController.transitioningDelegate = _toPixelEditTransitioningDelegate;
[self presentViewController:_imageEditViewController animated:YES completion:nil];
代码我用来关闭视图控制器
[viewController dismissViewControllerAnimated:YES completion:nil];
我的过渡代表
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source
{
SEUSFadeInTransitioning *transitioning = [[SEUSFadeInTransitioning alloc] init];
return transitioning;
}
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
{
SEUSFadeInTransitioning *transitioning = [[SEUSFadeInTransitioning alloc] init];
transitioning.reverse = YES;
return transitioning;
}
Transition Object，它实现了UIViewControllerAnimatedTransitioning协议
- (instancetype)init
{
if (self = [super init])
{
_reverse = NO;
_duration = 0.25f;
}
return self;
}
- (void)animateToPixelEdit:(id<UIViewControllerContextTransitioning>)transitionContext
{
UIViewController* overviewVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController* pixelVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
[[transitionContext containerView] addSubview:overviewVC.view];
[[transitionContext containerView] addSubview:pixelVC.view];
pixelVC.view.alpha = 0;
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^
{
pixelVC.view.alpha = 1;
}
completion:^(BOOL finished)
{
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
}
- (void)animateToOverview:(id<UIViewControllerContextTransitioning>)transitionContext
{
UIViewController* pixelVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController* overviewVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
[[transitionContext containerView] addSubview:pixelVC.view];
[[transitionContext containerView] addSubview:overviewVC.view];
overviewVC.view.alpha = 0;
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^
{
overviewVC.view.alpha = 1;
}
completion:^(BOOL finished)
{
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
}
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
return _duration;
}
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
if (self.reverse == NO)
{
[self animateToPixelEdit:transitionContext];
}
else
{
[self animateToOverview:transitionContext];
}
}
有人注意到任何可能出错的事吗？由于我无法复制崩溃，因此很难排除故障。
这段代码看起来很花哨。我怀疑用户能够加倍呈现或双重解雇你的模态 - 这是这类事情的常见失败点。
我解决了类似于这个的错误，它最终成为已被解除分配的transitioningDelegate（问题示例中的_toPixelEditTransitioningDelegate）引用。
如果您看到EXC_BAD_ACCESS，则可以启用NSZombies，它将帮助您跟踪错误引用的对象。
希望这证明对别人有用！