IOS在子線程中使用定時器，將定時器添加至RunLoop中

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    
    //用NSObject的方法建立一個多線程
    [self performSelectorInBackground:@selector(multiThread) withObject:nil];
    
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}
- (void)multiThread
{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    if (![NSThread isMainThread]) {
        
        // 第1種方式
        //此種方式建立的timer已經添加至runloop中
//        [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(timerAction) userInfo:nil repeats:YES];
        //保持線程爲活動狀態，才能保證定時器執行
//        [[NSRunLoop currentRunLoop] run];//已經將nstimer添加到NSRunloop中了
        
        //第2種方式
        //此種方式建立的timer沒有添加至runloop中
       NSTimer *timer = [NSTimer timerWithTimeInterval:1.0f target:self selector:@selector(timerAction) userInfo:nil repeats:YES];
        //將定時器添加到runloop中
        [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
        [[NSRunLoop currentRunLoop] run];
        NSLog(@"多線程結束");
    }
     [pool release];
}

- (void)timerAction
{
    //定時器也是在子線程中執行的
    if (![NSThread isMainThread]) {
        NSLog(@"定時器");
    }
}