14
  • 在 XCode 中创建一个简单的项目
  • 设置视图以接收多点触控事件
  • 在 touchesBegan 中响应,检测到触摸事件时创建 CALayer
  • 为 CALayer 制作不透明淡出动画
  • 当动画停止时,从父级移除 CALayer

期望:CALayer 正常消失

实际:CALayer 在消失前闪烁(闪烁)

完整源代码:

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    self.view.multipleTouchEnabled = YES;
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    for (UITouch* touch in touches) {
        CGPoint p = [touch locationInView:self.view];

        //NSLog(@"touch=%@ p=%@", touch, NSStringFromCGPoint(p));

        CALayer *layer = [CALayer layer];
        layer.position = p;
        layer.bounds = CGRectMake(0, 0, 70, 70);
        layer.cornerRadius = 30;
        layer.masksToBounds = NO;
        layer.backgroundColor = [UIColor colorWithRed:102.0/255.0 green:156.0/255.0 blue:255.0/255.0 alpha:0.8].CGColor;
        layer.shouldRasterize = YES;

        CABasicAnimation *fadeOutAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];
        fadeOutAnimation.fromValue = [NSNumber numberWithFloat:1.0];
        fadeOutAnimation.toValue = [NSNumber numberWithFloat:0.0];
        fadeOutAnimation.duration = 0.5;
        fadeOutAnimation.delegate = self;
        fadeOutAnimation.removedOnCompletion = NO;
        [fadeOutAnimation setValue:layer forKey:@"parentLayer"];
        [layer addAnimation:fadeOutAnimation forKey:@"opacity"];

        [self.view.layer addSublayer:layer];
    }
}

- (void)animationDidStop:(CAAnimation *)theAnimation finished:(BOOL)flag {
    if(flag) {
        CALayer *layer = [theAnimation valueForKey:@"parentLayer"];
        if(layer) {
            layer.opaque = NO;
            layer.opacity = 0.0;
            //layer.hidden = YES;
            //NSLog(@"The layer object was: %@ (%@)", layer, [layer name]);
            [layer removeFromSuperlayer];
            [layer removeAllAnimations];
        }
    }
}

@end
4

1 回答 1

17

tl; dr:fillMode在将动画kCAFillModeForwards添加到图层之前,将动画设置为或将值更改为最终值。


基本动画只是动画期间的视觉动画,不会改变实际值。当您将动画设置为在完成后不被删除时,这意味着该图层仍将动画对象作为其动画之一进行引用。然而,它已经运行了它的动画。

动画外观(填充模式)的默认行为是kCAFillModeRemoved,这意味着在动画持续时间之后,图层看起来就像动画从未发生过一样。通过将填充模式更改为kCAFillModeForwardskCAFillModeBoth您可以使图层看起来好像图层保持在动画的结束状态。

您可以在动画开始时做同样的事情,kCAFillModeBackwards但它主要适用于您为动画设置开始时间的情况。

因此,要使动画看起来像动画的最终状态,您可以将填充模式设置为...Forwards而不删除动画,或者将图层的实际值更改为您希望它们在添加之前的值动画到视图。这将更改值,然后从旧值动画到新值。

于 2012-05-16T07:59:58.040 回答