iOS 在 ImageView 中交叉淡化多个图像

Question

我有 9 张图像需要交叉淡入淡出。我尝试用 imageview 的 animationImages 方法做动画。但不幸的是，它不支持图像之间的交叉淡入淡出效果。谁能告诉我如何实现这一点？

Answer 1

我通常使用Core Animation，特别是CABasicAnimation，

我最近使用了这个，一个 ImageView ，带有几个用于左右滑动的手势识别器。查看我正在使用的淡入淡出动画:

_someImageView = [[UIImageView alloc] initWithFrame:myFrame];
_someImageView.image = [myArrayOfImages objectAtIndex:0];
[self.view addSubview:_someImageView];
[_someImageView release];

_currentImageIndex = 0;

_someImageView.userInteractionEnabled = YES;

UISwipeGestureRecognizer *swipeLeftGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(changeImage:)];
swipeLeftGesture.direction = UISwipeGestureRecognizerDirectionLeft;
[_someImageView addGestureRecognizer:swipeLeftGesture];
[swipeLeftGesture release];

UISwipeGestureRecognizer *swipeRightGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(changeImage:)];
swipeRightGesture.direction = UISwipeGestureRecognizerDirectionRight;
[_someImageView addGestureRecognizer:swipeRightGesture];
[swipeRightGesture release];

然后每次我滑动时都会调用它，或者如果你喜欢做一些基于时间的事情，那么让你的计时器调用它，只要确保你增加一个计数器以便你可以循环图像:

- (void)changeImage:(UISwipeGestureRecognizer *)swipe{

    NSArray *images = [myArrayOfImages images];
    NSInteger nextImageInteger = _currentImageIndex;


    if(swipe.direction == UISwipeGestureRecognizerDirectionLeft)
        nextImageInteger++;
    else
        nextImageInteger--;


    if(nextImageInteger < 0)
        nextImageInteger = images.count -1;
    else if(nextImageInteger > images.count - 1)
        nextImageInteger = 0;

    _currentImageIndex = nextImageInteger;

    UIImage *target = [images objectAtIndex:_currentImageIndex];

    CABasicAnimation *crossFade = [CABasicAnimation animationWithKeyPath:@"contents"];
    crossFade.duration      = 0.5;
    crossFade.fromValue     = _someImageView.image;
    crossFade.toValue       = target;
    [_someImageView.layer addAnimation:crossFade forKey:@"animateContents"];
    _someImageView.image = target;
}