iOS在CAAnimationDelegate代理方法animationDidStop中区分是哪个动画

最近在做一个类似iOS最新版QQ提示框的控件，遇到了一些小问题，因为QQ的提示框是在点击的时候就自动弹回去，那么首先就要解决一个UIView的动画如何接收点击事件，但是对于UIView的frame动画来说，只要是改变了frame的动画都不能点击，哪怕你设置了可以点击，UIView的animation方法也设置了可以点击的type，但依然不管用的。

既然没法用UIView的动画，那么就在进一层，用Layer动画，那这样就跟View没有关系了，View自然可以接收点击事件。

那么问题来了，在CAAnimation的代理方法里面，并没有直接区分是哪个动画开始，哪个动画结束的方法，看了看官方文档，也没有在代理方法中给出判断的方法，那么就只能自己研究一下了。。

在NSObject里有一个很有用的方法，叫

- (void)setValue:(nullable id)value forKey:(NSString *)key;

这个方法可以为对象存一个键值对，用来个性化判断。既然找到了方法，那么一切就非常好办了。

例子如下。其中self.animView是一个全局变量，用来改变View位置的。因为Layer动画不会改变view本身的位置，所以需要重新设置。

    UIView * vc = [[UIView alloc] initWithFrame:CGRectMake(0, 0, width, height)];
    vc.layer.frame = CGRectMake(0, -height, width, height);
    vc.backgroundColor = [UIColor redColor];
    [vc addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(stopVCAnimation:)]];
    self.animView = vc;
    [self.view addSubview:vc];

    CABasicAnimation * animation1 = [CABasicAnimation animationWithKeyPath:@"position"];
    animation1.delegate = self;
    animation1.fromValue = [NSValue valueWithCGPoint:CGPointMake(width/2, -height/2)];
    animation1.toValue = [NSValue valueWithCGPoint:CGPointMake(width/2, height/2)];
    animation1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    animation1.autoreverses = NO;
    animation1.removedOnCompletion = NO;
    animation1.fillMode = kCAFillModeForwards;
    animation1.beginTime = CACurrentMediaTime() + 2;
    animation1.duration = 0.25;
    //这里的AnimationKey应该写成一个宏定义，偷个懒。
    [animation1 setValue:@"StartShowAnimation" forKey:@"AnimationKey"];
    [vc.layer addAnimation:animation1 forKey:@"StartShowAnimation"];

    CABasicAnimation * animation2 = [CABasicAnimation animationWithKeyPath:@"position"];
    animation2.delegate = self;
    animation2.fromValue = [NSValue valueWithCGPoint:CGPointMake(width/2, height/2)];
    animation2.toValue = [NSValue valueWithCGPoint:CGPointMake(width/2, -height/2)];
    animation2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    animation2.autoreverses = NO;
    animation2.removedOnCompletion = NO;
    animation2.fillMode = kCAFillModeForwards;
    animation2.beginTime = CACurrentMediaTime() + 4;
    animation2.duration = 0.25;
    //这里的AnimationKey应该写成一个宏定义，偷个懒。
    [animation2 setValue:@"StartHiddenAnimation" forKey:@"AnimationKey"];
    [vc.layer addAnimation:animation2 forKey:@"StartHiddenAnimation"];

这里是点击事件的方法：

- (void)stopVCAnimation:(UITapGestureRecognizer *)sender {
    UIView * v = sender.view;
    [v.layer removeAnimationForKey:@"StartHiddenAnimation"];
    CABasicAnimation * animation2 = [CABasicAnimation animationWithKeyPath:@"position"];
    animation2.fromValue = [NSValue valueWithCGPoint:CGPointMake(v.center.x, v.center.y)];
    animation2.toValue = [NSValue valueWithCGPoint:CGPointMake(v.center.x, -v.center.y)];
    animation2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    animation2.autoreverses = NO;
    animation2.removedOnCompletion = NO;
    animation2.fillMode = kCAFillModeForwards;
    animation2.beginTime = CACurrentMediaTime();
    animation2.duration = 0.25;
    [animation2 setValue:@"StartHiddenAnimation" forKey:@"AnimationKey"];
    [v.layer addAnimation:animation2 forKey:@"StartHiddenAnimation"];
}

代理方法：

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
    if (flag) {
        CABasicAnimation * animation = (CABasicAnimation *)anim;
        if ([[anim valueForKey:@"AnimationKey"] isEqualToString:@"StartShowAnimation"]) {
            NSLog(@"StartShowAnimation End");
            self.animView.center = CGPointMake(self.animView.center.x, 32);
        }else if ([[animation valueForKey:@"AnimationKey"] isEqualToString:@"StartHiddenAnimation"]) {
            NSLog(@"StartHiddenAnimation End");
            self.animView.center = CGPointMake(self.animView.center.x, -32);
        }
    }
}