iphone - CAAnimation 的问题

Question

//卡片类的头文件

#import "OWCardView.h"

@implementation OWCardView;

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        self.layer.contents      = (id) [UIImage imageNamed:@"4.png"].CGImage;
        self.layer.shadowColor   = [UIColor whiteColor].CGColor;
        self.layer.shadowOpacity = 0.3;
    }
    return self;
}


- (void) moveCard:(float)xPoint along:(float)yPoint
{
    CGRect someRect = CGRectMake(xPoint, yPoint, 72, 96);

    [UIView animateWithDuration: 3.5
                          delay: 0.3
                        options: UIViewAnimationCurveEaseOut
                     animations: ^{ self.frame = someRect;}
                     completion: ^(BOOL finished) { }];
}


@end


// part of the Implementation in the view controller's viewDidLoad

[...]
     CGRect myImageRect = CGRectMake(20.0f, 20.0f, 72.0f, 96.0f);

     // myCard is a property of the viewController
     self.myCard = [[OWCardView alloc] initWithFrame:myImageRect];
     [self.view addSubview:self.myCard];
     [self.myCard moveCard: 240 along: 355];     // First call
     [self.myCard moveCard: 50 along: 355];      // Second call
     [self.myCard moveCard: 50 along: 50];       // Third call
[...]

问题:只执行viewController中moveCard的最后一条消息；第一次和第二次调用不执行。代码有什么问题？

当我将第三条消息评论到 moveCard 时，第二个调用被执行而第一个没有。如果我评论第二个和第三个调用，那么第一个调用就会执行。但我希望所有三个动画都出现在卡片上。

Answer 1

当您为 View 设置动画时，您之前应用到该 View 的任何动画都会立即取消，即使任一动画具有非零延迟也是如此。所以如果你想应用顺序动画，你必须在第一个动画结束后添加第二个动画。您可以使用完成 block 来检测第一个动画何时结束。

很容易让 moveCard:along: 维护一个目标矩形队列并按顺序应用动画:

@implementation OWCardView {
    NSMutableArray *pendingRects;
    BOOL isAnimating;
}

- (void)moveCard:(float)xPoint along:(float)yPoint {
    CGRect someRect = CGRectMake(xPoint, yPoint, 72, 96);
    if (!pendingRects) {
        pendingRects = [NSMutableArray array];
    }
    [pendingRects addObject:[NSValue valueWithCGRect:someRect]];
    [self startAnimatingIfNeeded];
}

- (void)startAnimatingIfNeeded {
    if (isAnimating)
        return;
    if (pendingRects.count == 0)
        return;
    CGRect rect = [[pendingRects objectAtIndex:0] CGRectValue];
    [pendingRects removeObjectAtIndex:0];

    isAnimating = YES;
    [UIView animateWithDuration:3.5 delay:0.3 options:UIViewAnimationCurveEaseOut animations:^{
        self.frame = rect;
    } completion:^(BOOL finished) {
        isAnimating = NO;
        [self startAnimatingIfNeeded];
    }];
}