UIImageView animationImages Cannot Be Changed?

I am animating images with UIImageView:

    imageView.animationImages = [NSArray arrayWithArray:imgNameArr];    
    imageView.animationDuration = 2;
    imageView.animationRepeatCount = 0;
    [imageView startAnimating];

At some point later I am trying to change images to some new ones:

    [imageView stopAnimating];
    imageView.animationImages = nil;
    [imageView.animationImages release]; 
    imageView.animationImages = [NSArray arrayWithObjects:  
            [UIImage imageNamed:@"1.png"],
    [UIImage imageNamed:@"2.png"],
    nil];
    [imageView setAnimationDuration:1];
    [imageView startAnimating];

This does NOT work. My app either crashes or images disappear. I've seen a few people have the same problem and they create various workaround. Is something wrong with my code? Can something be done?

In addition I discovered that with this code below the object disappears at end of animation.

    int x = rect.origin.x;
int y = rect.origin.y;
int w = rect.size.width;    
    float _frequency 开发者_StackOverflow= 0;
    CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.duration = speed;
pathAnimation.calculationMode = kCAAnimationPaced;
pathAnimation.fillMode = kCAFillModeForwards;
pathAnimation.removedOnCompletion = NO;

CGMutablePathRef pointPath = CGPathCreateMutable();
CGPathMoveToPoint(pointPath, NULL, rect.origin.x, rect.origin.y);

    do {        
        CGFloat yVal = sin (_frequency * M_PI/180);
        CGPathAddLineToPoint(pointPath, NULL, x, y + yVal * 15);
        _frequency += freq;
        x--;        
    } while (x > w);//does not go outside

pathAnimation.path = pointPath;
CGPathRelease(pointPath);

[imageView.layer addAnimation:pathAnimation forKey:@"pathAnimation"];
[imageView release];

Since animationImages is a property, you don't need to set it to nil, and releasing it AFTER you set it to nil does nothing (it sends release to nil). Releasing it beforehand will cause a crash. Just set it to the new value, or to nil. You shouldn't be releasing another object's properties.

I do not know why your code does not work.

It is my sample. It works fine.

    animationView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];

    NSMutableArray *animationImages = [[NSMutableArray alloc] init];
    for (int i=0;  i < [contents count]; i++) {
        [animationImages addObject: [UIImage imageNamed:[contents objectAtIndex:i]]];
    }

    animationView.animationImages = animationImages;
    animationView.animationDuration = playTime;
    animationView.animationRepeatCount = 0;

    [self.view addSubview:animationView];
    [animationView startAnimating];