Question

我已经看过几次此崩溃报告了。这是非常随机和罕见的，我无法理解。我所做的就是使用以下代码提供模态视图控制器

ComposeController *newcontrol = [[ComposeController alloc]initWithMode:1 withNIB:@"ComposeController"];
newcontrol.delegate = self;

UINavigationController  *holder = [[UINavigationController alloc] initWithRootViewController:newcontrol];
[self presentViewController:holder animated:YES completion:NULL];

不知何故，这完全随机地导致了这一点：

OS Version:      iPhone OS 6.1 (10B143)
Report Version:  104

Exception Type:  SIGSEGV
Exception Codes: SEGV_ACCERR at 0x9
Crashed Thread:  0

Thread 0 Crashed:
0   libobjc.A.dylib                     0x3b25c5d0 objc_msgSend + 16
1   CoreFoundation                      0x334ba73f -[__NSPlaceholderArray initWithObjects:count:] + 271
2   CoreFoundation                      0x334bae09 +[NSArray arrayWithObject:] + 45
3   UIKit                               0x353e80ab -[UIWindow _rotationViewControllers] + 51
4   UIKit                               0x353e7fe3 -[UIViewController viewControllerForRotation] + 91
5   UIKit                               0x353e7f39 -[UIViewController _visibleView] + 97
6   UIKit                               0x3546c05b -[UIWindowController transition:fromViewController:toViewController:target:didEndSelector:] + 2483
7   UIKit                               0x3546afab -[UIViewController presentViewController:withTransition:completion:] + 3399
8   MyApp                               0x00046e97 -[Inbox composeHit] (Inbox.m:207)

Answer 1

我一直都有同样的问题。这似乎是由于我从弹出窗口呈现模态视图控制器这一事实，该控制器没有经过良好测试并触发Apple代码中的错误。问题在于UIKit保留了对我的View Controller的未经授权的引用，该引用已经被解除并被释放，因此稍后会引用该引用。我的解决方法是要么避免从弹出窗口呈现模态VC，要么无限期地保留所有这些VC（在成员变量或某些变量中）。

以下是血腥的细节。

以下是我用来触发问题的代码。

-(void) handlePinchFromCell:(AMPSupportingPhotoCell*) cell
{
    UIViewController * vc = [[UIViewController alloc] init]; // UIViewController #0
    [self presentViewController:vc animated:YES completion:nil];
    [self performSelector:@selector(dismiss:) withObject:vc afterDelay:2];
}

-(void) dismiss:(UIViewController*)vc
{
    [self dismissViewControllerAnimated:YES completion:^(){NSLog(@"-------");}];
}

此代码是UIViewController＃1的一部分，它位于UIPopoverController中，从另一个UIViewController＃2弹出，它本身是从另一个视图UIViewController＃3呈现的。在弹出窗口关闭，控制器＃2 id被解除后发生崩溃。

如果我启用Zombies，我会获得相同的堆栈跟踪，但会显示一条消息：

2013-03-13 20:04:24.681 Mercury[16698:19d03] handlePinchFromCell: a225710
2013-03-13 20:04:27.083 Mercury[16698:19d03] -------
2013-03-13 20:04:31.606 Mercury[16698:19d03] *** -[UIViewController retain]: message sent to deallocated instance 0xa225710

所以，请注意VC＃0在2秒后被分配，呈现，解散，取消分配，但在Apple的代码中仍有一个悬挂引用。当popover关闭并且VC＃2被解雇时，整个事情都会崩溃，试图访问解除分配的VC。我相当肯定这是Apple的错误。我也猜测它与从弹出窗口中呈现VC有关，所以如果你远离它，或者自己保留VC，你应该没问题。

针对同一问题的另一个堆栈跟踪是这样的。如果上面的代码运行两次，就会发生这种情况：

2013-03-13 20:12:53.883 Mercury[16735:19d03] handlePinchFromCell: 16d54da0
2013-03-13 20:12:56.285 Mercury[16735:19d03] -------
2013-03-13 20:13:03.481 Mercury[16735:19d03] handlePinchFromCell: a2565f0
2013-03-13 20:13:03.481 Mercury[16735:19d03] *** -[UIViewController isKindOfClass:]: message sent to deallocated instance 0x16d54da0
(lldb) bt
* thread #1: tid = 0x1f03, 0x017f8a97 CoreFoundation`___forwarding___ + 295, stop reason = EXC_BREAKPOINT (code=EXC_I386_BPT, subcode=0x0)
    frame #0: 0x017f8a97 CoreFoundation`___forwarding___ + 295
    frame #1: 0x017f894e CoreFoundation`_CF_forwarding_prep_0 + 14
    frame #2: 0x00c42f90 UIKit`-[UIWindowController transition:fromViewController:toViewController:target:didEndSelector:] + 907
    frame #3: 0x00a40ee3 UIKit`-[UIViewController presentViewController:withTransition:completion:] + 4521
    frame #4: 0x00a41167 UIKit`-[UIViewController presentViewController:animated:completion:] + 112
    frame #5: 0x0006c32d Mercury`-[AMPSupportingPhotosViewController handlePinchFromCell:](self=0x16d55360, _cmd=0x0007a64a, cell=0x0a22a2a0) + 205 at AMPSupportingPhotosViewController.m:184
    frame #6: 0x015336b0 libobjc.A.dylib`-[NSObject performSelector:withObject:] + 70
    frame #7: 0x0006f317 Mercury`-[AMPSupportingPhotoCell handlePinch:](self=0x0a22a2a0, _cmd=0x00efb0db, sender=0x0a2504a0) + 215 at AMPSupportingPhotoCell.m:53
    frame #8: 0x00c2185a UIKit`_UIGestureRecognizerSendActions + 139

Answer 2

尝试这样做

[holder pushViewController：newcontrol animated：YES completion：NULL];

呈现模态UIViewController时出现奇怪的崩溃

2 个答案: