使用旋转动画分配和解除 UIAlert：有时会崩溃，做错了吗？

Question

我正在创建一个带有旋转图形的警报对话框。

UIAlertView *alert; //(at top of controller)

alert = [[[UIAlertView alloc] initWithTitle:@"Looking for someone to connnect to via WiFi" message:nil delegate:self cancelButtonTitle:nil otherButtonTitles: nil] autorelease];
[alert show];

UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
indicator.center = CGPointMake(alert.bounds.size.width / 2, alert.bounds.size.height - 50);

[indicator startAnimating];
[alert addSubview:indicator];
[indicator release];

然后它后来像这样被驳回：

[alert dismissWithClickedButtonIndex:0 animated:YES];

这偶尔会导致崩溃：

Sun Mar  7 12:01:29 unknown com.apple.SpringBoard[24] <Notice>: CoreAnimation: timed out fence 500
Sun Mar  7 12:01:29 unknown ReportCrash[1615] <Notice>: Formulating crash report for process someApp[1614]

和跟踪：

Exception Type:  EXC_CRASH (SIGABRT)
Exception Codes: 0x00000000, 0x00000000
Crashed Thread:  0

Thread 0 Crashed:
0   libSystem.B.dylib               0x00090b2c __kill + 8
1   libSystem.B.dylib               0x00090b1a kill + 4
2   libSystem.B.dylib               0x00090b0e raise + 10
3   libSystem.B.dylib               0x000a7e34 abort + 36
4   libstdc++.6.dylib               0x00066390 __gnu_cxx::__verbose_terminate_handler() + 588
5   libobjc.A.dylib                 0x00008898 _objc_terminate + 160
6   libstdc++.6.dylib               0x00063a84 __cxxabiv1::__terminate(void (*)()) + 76
7   libstdc++.6.dylib               0x00063afc std::terminate() + 16
8   libstdc++.6.dylib               0x00063c24 __cxa_throw + 100
9   libobjc.A.dylib                 0x00006e54 objc_exception_throw + 104
10  CoreFoundation                  0x00026b2c +[NSException raise:format:arguments:] + 76
11  CoreFoundation                  0x00026acc +[NSException raise:format:] + 24
12  GameKit                         0x00025a50 -[GKPeerPickerViewController _shouldShowConnectTypeView] + 124
13  GameKit                         0x00026200 -[GKPeerPickerViewController loadInitialView] + 76
14  GameKit                         0x000262a4 -[GKPeerPickerViewController loadView] + 108
15  UIKit                           0x00069750 -[UIViewController view] + 44
16  GameKit                         0x000263fc -[GKPeerPickerViewController show] + 204
17  GameKit                         0x00023fbc -[GKPeerPickerController show] + 80
18  someApp                         0x00002a0c -[someAppViewController btnConnect:] (someAppViewController.m:43)
19  CoreFoundation                  0x00059888 -[NSObject performSelector:withObject:withObject:] + 20
20  UIKit                           0x0005b77c -[UIApplication sendAction:to:from:forEvent:] + 128
21  UIKit                           0x0005b6e4 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 32
22  UIKit                           0x0005b6ac -[UIControl sendAction:to:forEvent:] + 44
23  UIKit                           0x0005b304 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 528
24  UIKit                           0x0005bf84 -[UIControl touchesEnded:withEvent:] + 452
25  UIKit                           0x0005a8f8 -[UIWindow _sendTouchesForEvent:] + 520
26  UIKit                           0x00059f8c -[UIWindow sendEvent:] + 108
27  UIKit                           0x00055788 -[UIApplication sendEvent:] + 400
28  UIKit                           0x0005508c _UIApplicationHandleEvent + 4528
29  GraphicsServices                0x000057dc PurpleEventCallback + 1044
30  CoreFoundation                  0x00057524 CFRunLoopRunSpecific + 2296
31  CoreFoundation                  0x00056c18 CFRunLoopRunInMode + 44
32  GraphicsServices                0x000041c0 GSEventRunModal + 188
33  UIKit                           0x00003c28 -[UIApplication _run] + 552
34  UIKit                           0x00002228 UIApplicationMain + 960
35  someApp                         0x0000266e main (main.m:14)
36  someApp                         0x00002604 start + 44

令人好奇的一件事是对来自 GameKit 的 GKPeerPicker 的引用；我没有在任何地方使用它（我正在使用 GameKit 的 GKSession，但我没有使用 GKPeerPicker 组件）。

Answer 1

一个可能的问题是您在 alert 中存储了一个不属于您的引用！

试试这个：

- (void)hideAlert {
    [alert dismissWithClickedButtonIndex:0 animated:YES];
    [alert release];
    alert = nil;
}

- (void)showAlert {
    if (alert)
        return;
    alert = [[UIAlertView alloc] initWithTitle:@"Looking for someone to connnect to via WiFi" message:nil delegate:self cancelButtonTitle:nil otherButtonTitles: nil];
    [alert show];

    UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    indicator.center = CGPointMake(alert.bounds.size.width * 0.5f, alert.bounds.size.height * 0.5f);

    [indicator startAnimating];
    [alert addSubview:indicator];
    [indicator release];
}

- (void)dealloc {
    [alert dismissWithClickedButtonIndex:0 animated:YES];
    [alert release];
    [super dealloc];
}

Answer 2

查看 UIAlertView 的文档后：

alert = ... message:nil ...

该文档没有提及允许的 nil ：

消息
提供比标题更多详细信息的描述性文本。

尽管

cancelButtonTitle
取消按钮的标题，如果没有取消按钮，则为 nil。

所以尝试使用空字符串。