如何在ios sdk中使用动画增加和减少图像alpha值？

Question

在这段代码中我使用的是动画.但是我一次也需要更改图像的alpha值.

-(void)animation
{
    CGPoint point = CGPointMake(imgView.frame.origin.x, imgView.frame.origin.y);
    imgView.layer.position = point;
    CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:@"position.x"];
    anim.fromValue  = [NSValue valueWithCGPoint:point];
    anim.toValue    = [NSValue valueWithCGPoint:CGPointMake(point.x + 50, point.y)];
    anim.duration   = 10.0f;
    anim.repeatCount =1;
    anim.removedOnCompletion = YES;

    anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];

    [imgView.layer addAnimation:anim forKey:@"position.x"];
    imgView.layer.position = point;
}

Answer 1

您可以使用opacity键CABasicAnimation来执行此操作:

CABasicAnimation *alphaAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];
alphaAnimation.fromValue = [NSNumber numberWithFloat:1.0];
alphaAnimation.toValue = [NSNumber numberWithFloat:0.0];
[imgView.layer addAnimation:alphaAnimation forKey:@"opacity"];

编辑:

要通过指定值设置动画,您可以使用CAKeyframeAnimation:

CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"opacity"];
    animation.duration = 10.0f;
    animation.repeatCount = 1;
    animation.values  =  [NSArray arrayWithObjects:
                          [NSNumber numberWithFloat:1.0,
                          [NSNumber numberWithFloat:0.5],
                          [NSNumber numberWithFloat:1.0],nil];
    animation.keyTimes = [NSArray arrayWithObjects:
                          [NSNumber numberWithFloat:0.0],
                          [NSNumber numberWithFloat:5.0],
                          [NSNumber numberWithFloat:10.0], nil];
    [imgView.layer addAnimation:animation forKey:@"opacity"];