objective-c - CoreAnimation，在 iOS 5 Xcode 4 中移动带有动画阴影的 UIImageView

Question

我正在尝试为图像添加一个(假的)3d 效果(UIImageView 从点 A 移动到 B，在此移动过程中，我希望在点 C=(A+B)/2 处具有最大的阴影大小(或更大的阴影偏移量)，所以看起来它又在上下移动。当我什至尝试更改阴影大小时，它都没有动画。你能帮我如何编辑这段代码吗:

NSValue *pointB = [NSValue valueWithCGPoint:CGPointMake(CGRectGetMinX(imageView.frame)+50, CGRectGetMinY(imageView.frame)+50)];
[self.view bringSubviewToFront:ImageView];    
[UIView beginAnimations:@"UIImage Move" context:NULL];
CGPoint point = [pointB CGPointValue];
CGSize size =imageView.frame.size;
[UIView setAnimationDuration:1.0];
imageView.frame = CGRectMake(point.x, point.y, size.width, size.height);
imageView.layer.shadowOffset = CGSizeMake(0, 4); //actually I want this to happen in mid point and revert to offset 1
[UIView commitAnimations];


//sorry for possible problems with syntax, the code works fine, I had to rewrite and simplify it for understanding

Answer 1

您需要使用 CAAnimation 为图层的 shadowOffset 设置动画。下面是一个关于如何在移动对象时放大 shadowOffset 的示例。此示例使用 UIButton。

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
@interface ViewController : UIViewController 
@property (nonatomic, retain) IBOutlet UIButton *button;
@end

在 M 文件中，我从按钮 IBAction 调用按钮上的动画。

-(IBAction)shadowGrow:(id)sender {
    CABasicAnimation *shadowGrow = [CABasicAnimation animationWithKeyPath:@"shadowRadius" ];
    shadowGrow.delegate = self;
    [shadowGrow setFromValue:[NSNumber numberWithFloat:3.0]];
    [shadowGrow setToValue:[NSNumber numberWithFloat:20.0]];
    [shadowGrow setDuration:1.0f];
    shadowGrow.autoreverses = YES;

    CABasicAnimation *move = [CABasicAnimation animationWithKeyPath:@"transform.translation.x" ];
    move.delegate = self;
    [move setFromValue:[NSNumber numberWithFloat:0]];
    [move setToValue:[NSNumber numberWithFloat:50]];
    [move setDuration:1.0f];
    move.autoreverses = YES;

    //Add animation to a specific element's layer. Must be called after the element is displayed.
    [[button layer] addAnimation:shadowGrow forKey:@"shadowRadius"];
    [[button layer] addAnimation:move forKey:@"transform.translation.x"];
}

使用 CoreAnimation 需要记住的一件事是，当像这样为属性设置动画时，除非您在动画结束后在 CAAnimation 的委托(delegate)方法中设置这些值，否则它们将从一开始就恢复为它们的值。

- (void) animationDidStop:(NSString *)theAnimation finished:(NSNumber *)finished context:(void *)context

这里是一些关于 CALayer 的动画属性的附加信息。

CALayer and CIFilter animatable properties