iOS--NSTimer设置定时器的两种方法

//方法一:
    //创建定时器
    NSTimer *timer=[NSTimer timerWithTimeInterval:2.0 target:self selector:@selector(nextCilcked) userInfo:nil repeats:YES];
    //利用消息循环来开启定时器
    //创建消息循环
    NSRunLoop *runLoop =[NSRunLoop currentRunLoop];
    //Mode:1: NSDefaultRunLoopMode;
    //     2: NSRunLoopCommonModes ;
    //将定时器添加到到runLoop
    [runLoop addTimer:timer forMode:NSDefaultRunLoopMode];

    //方法二：
   //创建定时器
    NSTimer *timer1 =[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextCilcked) userInfo:nil repeats:YES];
    //开启定时器
    [timer1 setFireDate:[NSDate distantPast]];
    //暂停定时器
    [timer setFireDate:[NSDate distantFuture]];

    //取消定时器(永久性停止)
    [timer invalidate];
    //释放计时器
    timer = nil;

}
-(void)nextCilcked
{

    NSLog(@"timer执行中......");
}