在开发过程中,对于定时器相信大家都不陌生,在http://www.jianshu.com/p/0194a0866872 这篇文章中,我有谈过各种定时器的优缺点,这里就简单封装一个实用的不依赖于RunLoop运行模式的GCD定时器

• 首先GCD定时器本质也是对象必须有一个强引用应用着,不然就会被释放,由于提供的是类方法,就定义一个全局静态变量字典来保存timer对象

//存放timer对象
static NSMutableDictionary *timerDictionary;
//根据index来存储不同的timer对象
static NSInteger timerIndex = 0;

- 提供了一下两个类方法来初始化定时器,区别在于第一个初始化完成后自动开启定时器,第二个需要自己选择开启与否

//初始化定时器,默认初始化完成后开启

• (void)timerWithTimeInterval:(NSTimeInterval)timeInterval dispatchQueue:(dispatch_queue_t)dispatchQueue withBlock:(void(^)(XHR_dispatch_timer *))block;

//初始化定时器,需要手动开启

• (void)timerWithTimeInterval:(NSTimeInterval)timeInterval dispatchQueue:(dispatch_queue_t)dispatchQueue isOn:(BOOL)isOn withBlock:(void(^)(XHR_dispatch_timer *))block;

- 具体方法的实现如下
  

//初始化定时器

• (void)timerWithTimeInterval:(NSTimeInterval)timeInterval dispatchQueue:(dispatch_queue_t)dispatchQueue withBlock:(void (^)())block
  {
  //默认方法自动开启定时器
  [self timerWithTimeInterval:timeInterval dispatchQueue:dispatchQueue isOn:YES withBlock:block];
  }

• (void)timerWithTimeInterval:(NSTimeInterval)timeInterval dispatchQueue:(dispatch_queue_t)dispatchQueue isOn:(BOOL)isOn withBlock:(void (^)(XHR_dispatch_timer *))block
  {
  XHR_dispatch_timer *timer = [[XHR_dispatch_timer alloc]initWithTimeInterval:timeInterval dispatchQueue:dispatchQueue withBlock:block];

  [self.timerDictionary setObject:timer forKey:[NSString stringWithFormat:@"timerIndex_%ld",timerIndex++]];
  //根据设置是否需要在初始化完成后开启
  if (isOn) {
  timer.timerStatus = XHR_dispatch_timerStatusRuning;
  }
  }

- 那么解释一下这里的XHR_dispatch_timer，它是定义在XHRTimer这个单例内的一个私有类，是用来管理每一个timer对象的，以便在创建不同的timer对象执行不同的任务，并且定义了一个定时器状态枚举来标记运作状态，通过调整运作状态就可以控制定时器的开启、暂停、取消等操作，也避免了多次开启、暂停、取消而引起的bug,具体实现如下

• (instancetype)initWithTimeInterval:(NSTimeInterval)timeInterval dispatchQueue:(dispatch_queue_t)dispatchQueue withBlock:(void(^)(XHR_dispatch_timer *))block
  {
  if (self = [super init]) {
  //timer本质也是对象必须有强应用引用,不然就会被释放
  self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatchQueue);
  //设置开始时间和时间间隔
  dispatch_source_set_timer(self.timer, DISPATCH_TIME_NOW, timeInterval * NSEC_PER_SEC, 0 * NSEC_PER_SEC);
  //设置回调时间
  dispatch_source_set_event_handler(self.timer, ^{
  block(self);
  });
  self.timerStatus = XHR_dispatch_timerStatusSuspend;
  }
  return self;
  }
• (void)setTimerStatus:(XHR_dispatch_timerStatus)timerStatus
  {
  if (!self.timer) return;
  if (timerStatus == XHR_dispatch_timerStatusSuspend && _timerStatus != XHR_dispatch_timerStatusSuspend) {
  dispatch_suspend(self.timer);
  }
  else if (timerStatus == XHR_dispatch_timerStatusRuning && _timerStatus == XHR_dispatch_timerStatusSuspend)
  {
  dispatch_resume(self.timer);
  }
  else if(timerStatus == XHR_dispatch_timerStatusCanceled && _timerStatus != XHR_dispatch_timerStatusCanceled)
  {
  dispatch_cancel(self.timer);
  self.timer = nil;
  }
  _timerStatus = timerStatus;
  }

- 暂停定时器的方法

//暂停定时器

• (void)suspend:(XHR_dispatch_timer *)timer
  {
  if (timer) {
  timer.timerStatus = XHR_dispatch_timerStatusSuspend;
  }
  }
• (void)suspendAllTimer
  {
  [self.timerDictionary enumerateKeysAndObjectsUsingBlock:^(id _Nonnull key, XHR_dispatch_timer *_Nonnull obj, BOOL * _Nonnull stop) {
  obj.timerStatus = XHR_dispatch_timerStatusSuspend;
  }];
  }

- 手动开启/继续 定时器的方法

//手动开启/继续 定时器

• (void)resume:(XHR_dispatch_timer *)timer
  {
  if (timer) {
  timer.timerStatus = XHR_dispatch_timerStatusRuning;
  }
  }
• (void)resumeAllTimer
  {
  [self.timerDictionary enumerateKeysAndObjectsUsingBlock:^(id _Nonnull key, XHR_dispatch_timer *_Nonnull obj, BOOL * _Nonnull stop) {
  obj.timerStatus = XHR_dispatch_timerStatusRuning;
  }];
  }

- 取消定时器

//取消定时器
//取消定时器

• (void)cancel:(XHR_dispatch_timer *)timer
  {
  if (timer) {
  timer.timerStatus = XHR_dispatch_timerStatusCanceled;
  }
  [self.timerDictionary enumerateKeysAndObjectsUsingBlock:^(id _Nonnull key, id _Nonnull obj, BOOL * _Nonnull stop) {
  if ([obj isEqual:timer]) {
  [self.timerDictionary removeObjectForKey:key];
  return;
  }
  }];
  }
• (void)cancelAllTimer
  {
  [self.timerDictionary enumerateKeysAndObjectsUsingBlock:^(id _Nonnull key, XHR_dispatch_timer *_Nonnull obj, BOOL * _Nonnull stop) {
  obj.timerStatus = XHR_dispatch_timerStatusCanceled;
  }];
  [self.timerDictionary removeAllObjects];
  }

注：
- 调用方法和NSTimer类似,使用类方法,需要执行的代码直接写在方法的block中,非常方便.需要注意的是,如果取消了定时器,如果想重新开启就需要重新初始化,不然就会崩溃。
- bolock传出去的参数是为了供外部解决循环应用问题的

作者:胥鸿儒
demo地址:https://github.com/xuhongru/GCDTimer