脉冲 UIButton 子类

Question

我正在制作一个简单的 UIButton 子类，它通过使用 UIView 动画更改 alpha 来“脉冲”。我遇到的问题是当用户按下按钮时将 alpha 设置为 1 (100%)。我有代码来暂停和恢复动画，但在调用pauseAnimations之前或之后设置不透明度似乎不起作用。

在 UIView 层上暂停/恢复动画：

-(void)pauseAnimation {
    CFTimeInterval pausedTime = [self convertTime:CACurrentMediaTime()
                                        fromLayer:nil];
    self.speed = 0.0;
    self.timeOffset = pausedTime;
}

-(void)resumeAnimation {
    CFTimeInterval pausedTime = [self timeOffset];
    self.speed = 1.0;
    self.timeOffset = 0.0;
    self.beginTime = 0.0;
    CFTimeInterval timeSincePause = [self convertTime:CACurrentMediaTime() 
                                            fromLayer:nil] - pausedTime;
    self.beginTime = timeSincePause;
}

UIButton 子类的代码：

-(id)initWithAnimationInterval:(NSTimeInterval)interval andMinimumAlpha:
(float)minimumAlpha andMaximumAlpha:(float)maximumAlpha {
    if ((self = [super init])) {
        _animationInterval = interval;
        _minimumAlpha = minimumAlpha;
        _maximumAlpha = maximumAlpha;

        self.alpha = self.minimumAlpha;

        [self addTarget:self action:@selector(buttonDown) 
                forControlEvents:UIControlEventTouchDown];
        [self addTarget:self action:@selector(buttonUp) 
                forControlEvents:UIControlEventTouchUpInside];
        [self addTarget:self action:@selector(buttonUp) 
                forControlEvents:UIControlEventTouchUpOutside];

        [self startAnimating];
    }

    return self;
}

-(void)startAnimating {
    [UIView animateWithDuration:self.animationInterval
                          delay:0
                        options:UIViewAnimationOptionAllowAnimatedContent | 
UIViewAnimationOptionAllowUserInteraction | 
UIViewAnimationOptionAutoreverse | 
UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionRepeat
                     animations:^{
                         self.alpha = self.maximumAlpha;
                     }
                     completion:^(BOOL finished) {

                     }];
}

-(void)buttonDown {
    [self.layer pauseAnimation];

    self.oldAlpha = self.alpha;
    self.alpha = self.maximumAlpha;
}

-(void)buttonUp {
    self.alpha = self.oldAlpha;
    [self.layer resumeAnimation];
}

Answer 1

尝试从动画选项中删除 UIViewAnimationOptionRepeat。如果您在那里使用它，则意味着动画将无限期地重复。所以停止计时器没有帮助，因为动画将继续重复。

你有没有想过使用NSTimer？这似乎是一种更简单的方法。这就是我所做的：

- (void)viewDidLoad
{
    [super viewDidLoad];

    [button addTarget:self action:@selector(buttonDown) forControlEvents:UIControlEventTouchDown];
    [button addTarget:self action:@selector(buttonUp) forControlEvents:UIControlEventTouchUpInside];
    [button addTarget:self action:@selector(buttonUp) forControlEvents:UIControlEventTouchUpOutside];

    [self startTimer];

}

- (void)startTimer {
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.4 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];
}

- (void)stopTimer {
    [timer invalidate];
}

- (void)buttonDown {
    [self stopTimer];
    button.alpha = 1;
}

- (void)buttonUp {
    [self startTimer];
}

- (void)timerFired:(NSTimer *)timer {
    [UIView animateWithDuration:0.4
                          delay:0
                        options:UIViewAnimationOptionAllowAnimatedContent | 
     UIViewAnimationOptionAllowUserInteraction | 
     UIViewAnimationOptionAutoreverse | 
     UIViewAnimationOptionCurveEaseInOut
                     animations:^{
                         button.alpha = MIN_ALPHA;
                     }
                     completion:^(BOOL finished) {
                         button.alpha = 1;
                     }];
}

我没有使用按钮的子类，但您可以轻松地将其移动到那里。

希望有帮助。

Answer 2

除非您使用自定义核心动画层，否则您可能希望暂停和恢复方法如下所示（来自 http://developer.apple.com/library/ios/#qa/qa1673/_index.html):

-(void)pauseLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
    layer.speed = 0.0;
    layer.timeOffset = pausedTime;
}

-(void)resumeLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer timeOffset];
    layer.speed = 1.0;
    layer.timeOffset = 0.0;
    layer.beginTime = 0.0;
    CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
    layer.beginTime = timeSincePause;
}

并传入 button.layer作为CAL层。如果您不想传入图层，请将 self.speed 和 self.timeOffset 等引用更改为 self.layer.speed和 self.layer.timeOffset ，因为这些属性仅适用于图层，而不适用于按钮本身。