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最近在跟一个新项目...

整个项目只有不到20个接口,而且做的是即时通讯,socket协议有不到20个命令,前端逻辑重的不要不要的...

为了能完成需求文档上关于延时逻辑的任务,我把各种定时器都给用上了...

1. NSTimer;
NSTimer是一种非常省事的定时器,但是好多猿都没躲过它的坑.

一号坑-----重复创建NSTimer;

有时候,我们在写方法的时候需要注意,避免重复创建,在设置属性了以后,多加个判断,像下面一样:

if (self.connectTimer == nil) {
   self.connectTimer = [NSTimer scheduledTimerWithTimeInterval:5 target:self selector:@selector(<##>) userInfo:@{<##>} repeats:YES];
   [self.connectTimer fire];

}

而且建议我们尽量要将fire写在创建定时器方法外面:

- (void)timerFire {

      if ([_connectTimer isValid]) {
         [_connectTimer invalidate];
      }

[self.connectTimer fire];

}

二号坑-----清除NSTimer;

清除和暂停是两回事,一旦再次调用,就会发现定时器会跑不止一遍,正确严谨的销毁NSTimer 的姿势应该是下面这样的:
- (void)shutDownTimer {
    if ([_connectTimer isValid]) {
        [_connectTimer invalidate];
    }
    _connectTimer =nil;
}

这样,我们就可以在任何地方创建,启动,销毁NSTimer了;

2.GCD;

GCD不用多说了吧,验证码倒计时最经典的使用方法了

__block int timeout = 60; //倒计时时间

                    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

                    dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);

                    dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行

                    dispatch_source_set_event_handler(_timer, ^{

                        if(timeout<=0){ //倒计时结束，关闭

                            dispatch_source_cancel(_timer);

                            dispatch_async(dispatch_get_main_queue(), ^{

                                //设置界面的按钮显示根据自己需求设置
                                [weakSelf.verificationCodeBtn setTitle:@"获取验证码" forState:UIControlStateNormal];

                                [weakSelf.verificationCodeBtn setTitleColor:WHITE_COLOR forState:(UIControlStateNormal)];

                                weakSelf.verificationCodeBtn.userInteractionEnabled = YES;

                            });

                        }else{

                            int seconds = timeout % 60;

                            NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];

                            dispatch_async(dispatch_get_main_queue(), ^{

                                [UIView beginAnimations:nil context:nil];

                                [UIView setAnimationDuration:1];

                                [weakSelf.verificationCodeBtn setTitle:[NSString stringWithFormat:@"%@秒后重新发送",strTime] forState:UIControlStateNormal];

                                [UIView commitAnimations];

                                weakSelf.verificationCodeBtn.userInteractionEnabled = NO;

                            });

                            timeout--;

                        }
                    });

                    dispatch_resume(_timer);

3.CADisplayLink

这个方法很有意思,思来想去,写在动画里是最完美的,这里分享一个单波纹的layer动画的定时器写法;

- (void)startAnimation {

CALayer *layer = [[CALayer alloc] init];

layer.cornerRadius = 15;

    layer.frame = CGRectMake(0, 0, SCREEN_WIDTH, 30);

    UIColor *color = BASIC_COLOR;

layer.backgroundColor = color.CGColor;

    [self.aniView.layer addSublayer:layer];

    CAMediaTimingFunction *defaultCurve = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];

    _animaTionGroup = [CAAnimationGroup animation];

_animaTionGroup.delegate = self;

_animaTionGroup.duration = 4;

_animaTionGroup.removedOnCompletion = YES;

    _animaTionGroup.timingFunction = defaultCurve;

    CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale.xy"];

scaleAnimation.fromValue = @0.0;

scaleAnimation.toValue = @1.0;

    scaleAnimation.duration = 4;

    CAKeyframeAnimation *opencityAnimation = [CAKeyframeAnimation animationWithKeyPath:@"opacity"];

opencityAnimation.duration = 4;

opencityAnimation.values = @[@0.8,@0.4,@0];

opencityAnimation.keyTimes = @[@0,@0.5,@1];

    opencityAnimation.removedOnCompletion = YES;

    NSArray *animations = @[scaleAnimation,opencityAnimation];

_animaTionGroup.animations = animations;

    [layer addAnimation:_animaTionGroup forKey:nil];

    [self performSelector:@selector(removeLayer:) withObject:layer afterDelay:3];
}

- (void)removeLayer:(CALayer *)layer {

[layer removeFromSuperlayer];

}

- (void)start {

    _disPlayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(delayAnimation)];

    _disPlayLink.frameInterval = 300;

    [_disPlayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

}

- (void)delayAnimation {

    [self startAnimation];

    [self updateTime];

}

- (void)stop {

    [self.aniView.layer removeAllAnimations];

    [_disPlayLink invalidate];

    _disPlayLink = nil;

    [_disPlayLink removeFromRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];

}

4.performSelector:@selector(<##>) withObject:<##> afterDelay:<##>;

这个更好理解了,在多少秒后实现指定的方法,注意,这个方法苹果是想废弃的,因为确实可能会有内存管理上的问题;

所以,我们可能要用上取消performSelector:方法的方法:

取消指定的延时:

[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(<##>) object:nil];

取消全部延时:

[NSObject cancelPreviousPerformRequestsWithTarget:self];

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