分配和解除UIAlert w /微調器動畫：有時崩潰，做錯了？

Question

我使用微調圖形創建了一個警告對話框。

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]; 

然後它以後駁回這樣的：

[alert dismissWithClickedButtonIndex:0 animated:YES]; 

這偶爾會導致崩潰：

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] 

和跟蹤：

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 

一件事這很引人注目是引用從GameKit轉到GKPeerPicker;我沒有在任何地方使用它（我使用GameKit的GKSession，但我沒有使用GKPeerPicker組件）。

Answer 1

一個可能的問題是，你有一個存儲在alert，你不擁有的參考！

試試這個：

- (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

檢查出UIAlertView中的文檔後：

alert = ... message:nil ... 

文檔隻字未提允許一個nil：

消息
提供比冠軍更多的細節描述性文本。

雖然

cancelButtonTitle
取消按鈕的標題或nil如果沒有取消按鈕。

因此請嘗試一個空字符串。