鄭州iOS點 - 點哥講iOS的時間管理

最近在跟一個新專案...

整個專案只有不到20個介面,而且做的是即時通訊,socket協議有不到20個命令,前端邏輯重的不要不要的...

為了能完成需求文件上關於延時邏輯的任務,我把各種定時器都給用上了...

1. NSTimer;
NSTimer是一種非常省事的定時器,但是好多猿都沒躲過它的坑.

一號坑-----重複建立NSTimer;

有時候,我們在寫方法的時候需要注意,避免重複建立,在設定屬性了以後,多加個判斷,像下面一樣:

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

}

而且建議我們儘量要將fire寫在建立定時器方法外面:

- (void)timerFire {

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

[self.connectTimer fire];

}

二號坑-----清除NSTimer;

清除和暫停是兩回事,一旦再次呼叫,就會發現定時器會跑不止一遍,正確嚴謹的銷燬NSTimer 的姿勢應該是下面這樣的:
- (void)shutDownTimer {
    if ([_connectTimer isValid]) {
        [_connectTimer invalidate];
    }
    _connectTimer =nil;
}

這樣,我們就可以在任何地方建立,啟動,銷燬NSTimer了;

2.GCD;

GCD不用多說了吧,驗證碼倒數計時最經典的使用方法了

__block int timeout = 60; //倒數計時時間

                    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); //每秒執行

                    dispatch_source_set_event_handler(_timer, ^{

                        if(timeout<=0){ //倒數計時結束，關閉

                            dispatch_source_cancel(_timer);

                            dispatch_async(dispatch_get_main_queue(), ^{

                                //設定介面的按鈕顯示根據自己需求設定
                                [weakSelf.verificationCodeBtn setTitle:@"獲取驗證碼" 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:@"%@秒後重新傳送",strTime] forState:UIControlStateNormal];

                                [UIView commitAnimations];

                                weakSelf.verificationCodeBtn.userInteractionEnabled = NO;

                            });

                            timeout--;

                        }
                    });

                    dispatch_resume(_timer);

3.CADisplayLink

這個方法很有意思,思來想去,寫在動畫裡是最完美的,這裡分享一個單波紋的layer動畫的定時器寫法;

- (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:<##>;

這個更好理解了,在多少秒後實現指定的方法,注意,這個方法蘋果是想廢棄的,因為確實可能會有記憶體管理上的問題;

所以,我們可能要用上取消performSelector:方法的方法:

取消指定的延時:

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

取消全部延時:

[NSObject cancelPreviousPerformRequestsWithTarget:self];

鄭州iOS點 - 點哥講iOS的時間管理

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