iOS 定时器NSTimer+dispatchTimer.md

一、初始化方法

+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;
+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;

+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo;
+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo;

- (instancetype)initWithFireDate:(NSDate *)date interval:(NSTimeInterval)ti target:(id)t selector:(SEL)s userInfo:(nullable id)ui repeats:(BOOL)rep

1、参数repeats是指定是否循环执行，YES将循环，NO将只执行一次。
2、timerWithTimeInterval这两个类方法创建出来的对象如果不用 addTimer: forMode方法手动加入主循环池中，将不会循环执行。所以需要调用addTimer: forMode方法, 调用就会启动fire.
3、scheduledTimerWithTimeInterval这两个方法自动加入当前runloop中(只是当前的runloop=NSDefaultRunLoopMode, 其他runloop mode未处理), 所以会自动fire.
4、init和timerWithTimeInterval一样, 都需要手动加入runloop，它会在设定的启动时间启动。

二、相关属性/方法

• (void)fire;//点燃，立即触发该定时器
  @property (copy) NSDate *fireDate;//点燃日期，确定触发定时器的日期
  @property (readonly) NSTimeInterval timeInterval;//只读属性，获取定时器调用间隔时间(如果循环的话)
  @property NSTimeInterval tolerance；//设置误差范围, 毕竟NSTimer不完全精确
• (void)invalidate;//将定时器从runloop中移除
  @property (readonly, getter=isValid) BOOL valid;//定时器是否有效
  @property (nullable, readonly, retain) id userInfo;//其他参数信息

//再次开启定时器 
[self.timer setFireDate:[NSDate distantPast]];
或者
[self.timer setFireDate:[NSDate date]];

//关闭定时器：
[self.timer setFireDate:[NSDate distantFuture]];

⚠️
1.App置于后台时, 最好将timer暂停, 否则会消耗资源(比如电量).
2.如果是在ViewController中处理的timer, 可以在其生命周期方法viewWillAppear和viewWillDisappear中将timer暂停或者重启.

三、应用, 对NSTimer的一个封装：(注意循环引用的问题)

.h中
@property (nonatomic, assign)CGFloat timerChangeInterval;///计时器计时间隔
@property (nonatomic, copy) void (^timerHandlerBlock)(CGFloat timerIntervalTime);

- (void)startTimer;

- (void)stopTimer;

- (void)pauseTimer;



.m中
@property (nonatomic, strong)NSTimer *timer;

- (NSTimer *)timer
{
    if (!_timer) {
        YYTextWeakProxy *weakProxy = [YYTextWeakProxy proxyWithTarget:self];
        _timer = [NSTimer timerWithTimeInterval:self.timerChangeInterval target:weakProxy selector:@selector(timeChange) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop] addTimer:_timer forMode:NSDefaultRunLoopMode];
        /**
         scheduledTimerWithTimeInterval和上面两行效果一样.
         _timer = [NSTimer scheduledTimerWithTimeInterval:self.timeChangeInterval target:weakProxy selector:@selector(timeChange) userInfo:nil repeats:YES];
         */

//        //发生滚动事件时也计时
        [[NSRunLoop currentRunLoop] addTimer:_timer forMode:UITrackingRunLoopMode];

        //加入到runloop会自动出发fire. 所以这里先暂停, startFire由业务触发
        [_timer setFireDate:[NSDate distantFuture]];
    }

    return _timer;
}


- (void)stopTimer
{
    if (_timer) {
        [self.timer invalidate];//停止
        if (self.timer) {
            self.timer = nil;
        }
    }
}

- (void)pauseTimer
{
    //暂停
    if (_timer) {
        [_timer setFireDate:[NSDate distantFuture]];
    }
}

- (void)startTimer
{
    [self.timer setFireDate:[NSDate date]];
}

- (void)timeChange
{
    if (_timerHandlerBlock) {
        _timerHandlerBlock(self.timerChangeInterval);
    }
}

四、dispatch定时器

@property (nonatomic)dispatch_source_t dispatchTimer;

////创建定时器
if (!self.dispatchTimer) {
    self.dispatchTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());

    dispatch_source_set_timer(self.dispatchTimer, DISPATCH_TIME_NOW, 1*NSEC_PER_SEC, 0*NSEC_PER_SEC);

    dispatch_source_set_event_handler(self.dispatchTimer, ^{
        //hanlde user action


    });

    dispatch_resume(self.dispatchTimer);
}

//挂起定时器
if (self.dispatchTimer) {
    dispatch_suspend(self.dispatchTimer);
}

//释放定时器
if (self.dispatchTimer) {
    dispatch_source_cancel(self.dispatchTimer);
    self.dispatchTimer = nil;
}