iOS pop动画之衰减动画的基本使用

衰减动画

- (void)viewDidLoad {

    [super viewDidLoad];

    [self initCircleBtn];

}

- (void)initCircleBtn {

    // 实例化手势，并最终将手势添加到圆形按钮上

　 UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePan:)];

    // 实例化圆形按钮

    UIButton *circleBtn = [[UIButton alloc]init];

    circleBtn.bounds = CGRectMake(0, 0, 100, 100);

    circleBtn.center = self.view.center;

    circleBtn.backgroundColor = [UIColor redColor];

    circleBtn.layer.cornerRadius = CGRectGetWidth(circleBtn.frame) / 2;

    [circleBtn addGestureRecognizer:pan];

    [circleBtn addTarget:self action:@selector(handleDown:) forControlEvents:UIControlEventTouchDown];

    [self.view addSubview:circleBtn];

}

- (void)handlePan:(UIPanGestureRecognizer *)recognizer {

    CGPoint translation = [recognizer translationInView:self.view];

    recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y);

    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view]; // 这句比较重要，因为handlePan:会持续调用，如果不把上一次调用该方法产生的位移清零，按钮会移动得很快

    // 松手时，启动衰减动画

    if (recognizer.state == UIGestureRecognizerStateEnded) {

        CGPoint velocity = [recognizer velocityInView:self.view]; // 获取松手时，手势在控制器view的速度

        POPDecayAnimation *popAnimation = [POPDecayAnimation animationWithPropertyNamed:kPOPLayerPosition]; // 实例化衰减动画，该衰减动画作用于Position

        [popAnimation setVelocity:[NSValue valueWithCGPoint:velocity]]; // 设置衰减动画的初始速度

        [recognizer.view pop_addAnimation:popAnimation forKey:@"suibian"]; // 添加衰减动画到圆形按钮

    }

}