线程中添加定时器NSTimer

参考：https://my.oschina.net/u/936286/blog/159490

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];

    //用NSObject的方法创建一个多线程
    [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种方式
        //此种方式创建的timer已经添加至runloop中
//        [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(timerAction) userInfo:nil repeats:YES];
        //保持线程为活动状态，才能保证定时器执行
//        [[NSRunLoop currentRunLoop] run];//已经将nstimer添加到NSRunloop中了

        //第2种方式
        //此种方式创建的timer没有添加至runloop中
       NSTimer *timer = [NSTimer timerWithTimeInterval:1.0f target:self selector:@selector(timerAction) userInfo:nil repeats:YES];
        //将定时器添加到runloop中
        [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
        [[NSRunLoop currentRunLoop] run];
        NSLog(@"多线程结束");
    }
     [pool release];
}

- (void)timerAction
{
    //定时器也是在子线程中执行的
    if (![NSThread isMainThread]) {
        NSLog(@"定时器");
    }
}