如何在IOS4中处理UIApplicationWillTerminateNotification？

Question

在 iOS4 中，我注册了以下通知：

[[NSNotificationCenter defaultCenter]   addObserver:self
                                                 selector:@selector(appWillTerminate:)
                                                 name:UIApplicationWillTerminateNotification
                                                 object:[UIApplication sharedApplication]];

-(void)appWillTerminate:(UIApplication *) app {
    NSLog(@"terminate");
}

我知道在所有情况下都不会像以前的 iOS 版本那样调用此通知，但是，只需注册此通知，当应用程序退出时，我就会收到 EXC_BAD_ACCESSS 。不过，我无法删除它，因为我的应用程序支持 iOS3.0+。我该如何处理这个问题？

更新：这是崩溃日志：

Exception Type:  EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x00000011
Crashed Thread:  0

Thread 0 Crashed:
0   libobjc.A.dylib                 0x0000441c objc_msgSend + 20
1   Foundation                      0x00015432 _nsnote_callback + 150
2   CoreFoundation                  0x000271da __CFXNotificationPost_old + 390
3   CoreFoundation                  0x00026e7a _CFXNotificationPostNotification + 122
4   Foundation                      0x00004720 -[NSNotificationCenter postNotificationName:object:userInfo:] + 64
5   Foundation                      0x0000de3a -[NSNotificationCenter postNotificationName:object:] + 14
6   UIKit                           0x000bef10 -[UIApplication _terminateWithStatus:] + 164
7   UIKit                           0x000be1b0 -[UIApplication _handleApplicationSuspend:eventInfo:] + 1980
8   UIKit                           0x0007e4a0 -[UIApplication handleEvent:withNewEvent:] + 3620
9   UIKit                           0x0007d470 -[UIApplication sendEvent:] + 60
10  UIKit                           0x0007ccf8 _UIApplicationHandleEvent + 6804
11  GraphicsServices                0x00005dd8 PurpleEventCallback + 1024
12  CoreFoundation                  0x00035e40 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 22
13  CoreFoundation                  0x00035dfe __CFRunLoopDoSource1 + 158
14  CoreFoundation                  0x0002809e __CFRunLoopRun + 574
15  CoreFoundation                  0x00027d74 CFRunLoopRunSpecific + 220
16  CoreFoundation                  0x00027c82 CFRunLoopRunInMode + 54
17  GraphicsServices                0x00004e84 GSEventRunModal + 188
18  UIKit                           0x00004f8c -[UIApplication _run] + 564
19  UIKit                           0x000024cc UIApplicationMain + 964

Answer 1

确保删除任何正在侦听终止通知的类中的观察者。如果您不删除通知，它会尝试将其发布到已释放的对象，然后您的应用程序将崩溃。您不应该因为监听不存在的通知而崩溃，它只是不会被调用。

//YourClass
-(id)init
{
    if((self = [super init]))
    {
        [[NSNotificationCenter defaultCenter]   addObserver:self
                                             selector:@selector(appWillTerminate:)
                                             name:UIApplicationWillResignActiveNotification
                                             object:[UIApplication sharedApplication]];
    }
    return self;
}

-(void)appWillTerminate:(NSNotification *)note {
    NSLog(@"terminate");
}

-(void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];

    //Other releases
    [super dealloc];
}

Answer 2

您可以做的是检测 iOS 版本，如果是 3.0 版，则使用 appWillTerminate，如果是 4.0 版，则使用 appWillResignActive 或 appDidEnterBackground，例如：

NSString *ver = [[UIDevice currentDevice] systemVersion];
if([ver isEqualToString:@"3.0"]){
    //Device is running 3.0
    [[NSNotificationCenter defaultCenter]   addObserver:self
                                             selector:@selector(appWillTerminate:)
                                             name:UIApplicationWillTerminateNotification
                                             object:[UIApplication sharedApplication]];
}
else if([ver isEqualToString:@"4.0"]){
    //4.0
    [[NSNotificationCenter defaultCenter]   addObserver:self
                                             selector:@selector(appWillTerminate:)
                                             name:UIApplicationWillResignActiveNotification
                                             object:[UIApplication sharedApplication]];
}

Answer 3

传递给您的 appWillTerminate: 方法的第一个参数将是一个 NSNotification 对象，而不是您的 UIApplication。请参阅NSNotificationCenter 类参考