iOS GCD定时器
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编程学习
iOS学习
前面我们介绍了NSTimer和CADisplayLink两种定时器,而且也介绍了如何去解决这些定时器引起的循环引用的问题,这次来介绍一下GCD定时器,这个也是我们很常用的定时器。
简单的使用
// 创建串行队列
dispatch_queue_t queue = dispatch_queue_create("timer", DISPATCH_QUEUE_SERIAL);
// 创建定时器
dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
// 设置时间
uint64_t start = 1.0; // 1秒后开始执行
uint64_t interval = 1.0; // 每隔1秒执行
dispatch_source_set_timer(timer, dispatch_time(DISPATCH_TIME_NOW, start * NSEC_PER_SEC), interval * NSEC_PER_SEC, 0);
// 设置回调
dispatch_source_set_event_handler(timer, ^{
NSLog(@"1111 - %@", [NSThread currentThread]);
});
// 启动定时器
dispatch_resume(timer);
封装工具
@implementation DCTimer
static NSMutableDictionary *timers_;
dispatch_semaphore_t semaphore_;
// 单例
+ (void)initialize {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
timers_ = [NSMutableDictionary dictionary];
semaphore_ = dispatch_semaphore_create(1);
});
}
+ (NSString *)execTask:(void (^)(void))task start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeats:(BOOL)repeats async:(BOOL)async {
if (!task || start < 0 || (interval <= 0 && repeats)) return nil;
// 创建队列
dispatch_queue_t queue = async ? dispatch_get_global_queue(0, 0) : dispatch_get_main_queue();
// 创建定时器
dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
// 设置时间
dispatch_source_set_timer(timer,
dispatch_time(DISPATCH_TIME_NOW, start * NSEC_PER_SEC),
interval * NSEC_PER_SEC, 0);
/// 信号量控制(类似于加锁)
dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER);
// 定时器的唯一标识
NSString *name = [NSString stringWithFormat:@"%zd", timers_.count];
// 存放到字典中
timers_[name] = timer;
/// 信号量控制
dispatch_semaphore_signal(semaphore_);
// 设置回调
dispatch_source_set_event_handler(timer, ^{
task();
if (!repeats) { // 不重复的任务
[self cancelTask:name];
}
});
// 启动定时器
dispatch_resume(timer);
return name;
}
+ (NSString *)execTask:(id)target selector:(SEL)selector start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeats:(BOOL)repeats async:(BOOL)async {
if (!target || !selector) return nil;
return [self execTask:^{
if ([target respondsToSelector:selector]) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
[target performSelector:selector];
#pragma clang diagnostic pop
}
} start:start interval:interval repeats:repeats async:async];
}
/// 取消任务
+ (void)cancelTask:(NSString *)name {
if (name.length == 0) return;
dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER);
dispatch_source_t timer = timers_[name];
if (timer) {
dispatch_source_cancel(timer);
[timers_ removeObjectForKey:name];
}
dispatch_semaphore_signal(semaphore_);
}
@end