NStimer
[NStimer timerWithTimeInteraval: target: selector@selector( ) userInfo: repeats: ];
NSRunLoop *runloop = [NSRunLoop currentRunLoop];
[runloop addTimer:timer forMode:NSDefaultRunLoopMode];
[NStimer scheduledTimerWithTimeInteralval: target: selector:@selector( ) userInfo: repeats: ];
//拖拽时候 销毁定时器
//松手时候 重新创建定时器
//线程问题 NSCommentModes解决 加入到NSRunLoop消息循环中、