NSNotification不会调用选择器

Question

我在appDelegate中创建NSNotification。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkRegister:) name:@"checkRegister" object:nil]; 

    return YES; 
} 

-(void)checkRegister:(NSNotification *) notification{ 

//Some code 

} 

而且我在其他一些类发布通知：

-(void)connectionDidFinishLoading:(NSURLConnection *)connection 
{ 
    NSLog(@"DONE. Received Bytes: %d", [webData length]); 
    NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding]; 
    NSLog(@"%@",theXML); 
    [theXML release]; 

    NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithData: webData]; 
    [xmlParser setDelegate:self]; 
    [xmlParser setShouldResolveExternalEntities: YES]; 
    [xmlParser parse]; 
    [xmlParser release]; 

    [connection release]; 
    [webData release]; 

    if(strUserName != NULL) 
     [[NSNotificationCenter defaultCenter] postNotificationName:@"checkRegister" object:nil]; 


} 

的问题是，checkRegister不会被调用。
有人可以帮我在这里。
谢谢，
尼蒂什

Answer 1

什么是你@"checkRegister"通知的目的，你有你的if(strUserName != NULL)检查，如果您发布通知之前，但我没有看到你在哪里设置该strUserName所以肯定，尝试NSLog(@"%@", strUserName) 。我很确定它是空的。如果strUserName来自您解析的XML数据，则应在XML解析代码之后发布通知，该代码将位于您实施的NSXMLParser委托方法中。这将是one of these you use.

[xmlParser parse]不会阻塞，所以你

if(strUserName != NULL) 
    [[NSNotificationCenter defaultCenter] postNotificationName:@"checkRegister" object:nil]; 

将被调用，之前xmlParser完成解析，那么，你的strUserName中尚未设定，这就是它是零和的原因，你的postNoticationName:将不会被调用

编辑：

把你

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkRegister:) name:@"checkRegister" object:nil]; 

您 application:didFinishLaunchingWithOptions:的最顶端

，它很可能你张贴在你的主视图通知您注册通知之前，例如

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkRegister:) name:@"checkRegister" object:nil]; 
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease]; 
    // Override point for customization after application launch. 
    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) { 
     self.mainViewController = [[[MainViewController alloc] initWithNibName:@"MainViewController_iPhone" bundle:nil] autorelease]; 
    } else { 
     self.mainViewController = [[[MainViewController alloc] initWithNibName:@"MainViewController_iPad" bundle:nil] autorelease]; 
    } 
    self.window.rootViewController = self.mainViewController; 
    [self.window makeKeyAndVisible]; 
    return YES; 
} 

会的工作，而

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease]; 
    // Override point for customization after application launch. 
    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) { 
     self.mainViewController = [[[MainViewController alloc] initWithNibName:@"MainViewController_iPhone" bundle:nil] autorelease]; 
    } else { 
     self.mainViewController = [[[MainViewController alloc] initWithNibName:@"MainViewController_iPad" bundle:nil] autorelease]; 
    } 
    self.window.rootViewController = self.mainViewController; 
    [self.window makeKeyAndVisible]; 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkRegister:) name:@"checkRegister" object:nil]; 
    return YES; 
} 

如果您的数据加载在MainControllerViewviewDidLoad方法中完成将无法正常工作。