iphone - 主线程上的 NSOperation 和 NSNotificationCenter

Question

我有一个 NSOperation。完成后，我触发 NSNotificationCenter 让程序知道 NSoperation 已完成并更新 gui。

据我了解，NSNotification 的监听器不会在主线程上运行，因为 NSOperation 不在主线程上。

我怎样才能让监听器在我触发事件时在主线程上运行？

[[NSNotificationCenter defaultCenter] postNotificationName:@"myEventName" object:self]; 

Answer 1

更新:调度队列使得在主线程上发布通知变得非常容易。

dispatch_async(dispatch_get_main_queue(),^{
   [[NSNotificationCenter defaultCenter] postNotification...];
});

要等待通知处理程序完成，只需将 dispatch_async 替换为 dispatch_sync。

---

在 notnoop 的回答之后，这里有一些基础设施，您可以使用它来安全地将通知发布到主线程上， 无需等待它们完成。希望有人会发现这有帮助!

NSNotificationCenter+Utils.h:

@interface NSNotificationCenter (Utils)

-(void)postNotificationOnMainThread:(NSNotification *)notification;
-(void)postNotificationNameOnMainThread:(NSString *)aName object:(id)anObject;
-(void)postNotificationNameOnMainThread:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo;

@end

NSNotificationCenter+Utils.m:

@interface NSNotificationCenter (Utils_Impl) {
}

-(void)postNotificationOnMainThreadImpl:(NSNotification*)notification;
-(void)postNotificationNameOnMainThreadImpl:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo;

@end

@implementation NSNotificationCenter (Utils)

-(void)postNotificationOnMainThread:(NSNotification *)notification {
    [notification retain];
    [notification.object retain];
    [self performSelectorOnMainThread:@selector(postNotificationOnMainThreadImpl:) 
                           withObject:notification
                        waitUntilDone:NO];
}

-(void)postNotificationNameOnMainThread:(NSString *)aName object:(id)anObject {
    [self postNotificationNameOnMainThread:aName object:anObject userInfo:nil];
}

-(void)postNotificationNameOnMainThread:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo {
    [aName retain];
    [anObject retain];
    [aUserInfo retain];

    SEL sel = @selector(postNotificationNameOnMainThreadImpl:object:userInfo:);
    NSMethodSignature* sig = [self methodSignatureForSelector:sel];
    NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:sig];
    [invocation setTarget:self];
    [invocation setSelector:sel];
    [invocation setArgument:&aName atIndex:2];
    [invocation setArgument:&anObject atIndex:3];
    [invocation setArgument:&aUserInfo atIndex:4];
    [invocation invokeOnMainThreadWaitUntilDone:NO];
}

@end

@implementation NSNotificationCenter (Utils_Impl)

-(void)postNotificationOnMainThreadImpl:(NSNotification*)notification {
    [self postNotification:notification];
    [notification.object release];
    [notification release];
}

-(void)postNotificationNameOnMainThreadImpl:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo {
    [self postNotificationName:aName object:anObject userInfo:aUserInfo];
    [aName release];
    [anObject release];
    [aUserInfo release];
}

@end

NSInvocation+Utils.h:

@interface NSInvocation (Utils)

-(void)invokeOnMainThreadWaitUntilDone:(BOOL)wait;

@end

NSInvocation+Utils.m:

@implementation NSInvocation (Utils)

-(void)invokeOnMainThreadWaitUntilDone:(BOOL)wait
{
    [self performSelectorOnMainThread:@selector(invoke)
                           withObject:nil
                        waitUntilDone:wait];
}

@end