iOS：随机模式并非在每个循环中都有效

Question

这就是我的iOS程序的目的。 按下开始按钮后，企鹅的随机图像将从右侧出现，向左移动并消失，然后一次又一次地重复，而无需再次按下开始按钮。 我试图在每个周期中显示一组不同的企鹅。 它确实会循环，但是，每个周期它仍显示相同的企鹅。 当我按下开始按钮，但只想按一次按钮时，它只会更改为其他企鹅，当循环继续进行时，每个循环中都会出现不同的企鹅。 我将随机代码放入循环中，但是我看不到它会随机化每个循环，它只会在每次按下开始按钮时才随机化。 任何想法如何解决？

-(IBAction)start:(id)sender {
[UIView animateKeyframesWithDuration:3 delay:0 options:UIViewKeyframeAnimationOptionRepeat animations:^{
    [UIView addKeyframeWithRelativeStartTime:0 relativeDuration:0.3 animations:^{
    NSArray *imageNameArray = [[NSMutableArray alloc] initWithObjects:@"Right.png", @"Left.png", @"Straight.png", nil];
    Penguin.image = [UIImage imageNamed:[imageNameArray objectAtIndex:arc4random_uniform((uint32_t)[imageNameArray count])]];
    Penguin.center = CGPointMake(294, 373);
    Penguin.alpha = 1;
    Penguin.center = CGPointMake(Penguin.center.x - 40, Penguin.center.y);}];
    [UIView addKeyframeWithRelativeStartTime:0.3 relativeDuration:0.4 animations:^{
    Penguin.center = CGPointMake(Penguin.center.x - 200, Penguin.center.y);}];
    [UIView addKeyframeWithRelativeStartTime:0.7 relativeDuration:0.3 animations:^{
    Penguin.alpha = 0;
    Penguin.center = CGPointMake(Penguin.center.x - 40, Penguin.center.y);}];
    }completion:nil
    ];
    }

Answer 1

我认为重复动画的所有参数都只能设置一次，因此随机图像只能被拾取一次。 无需制作重复的动画，而是从动画的完成块调用start：方法，然后在动画方法之外进行随机选择，

-(IBAction)start:(id)sender {

    NSArray *imageNameArray = [[NSMutableArray alloc] initWithObjects:@"Right.png", @"Left.png", @"Straight.png", nil]; // There's no need to define this every time the method is called. It would be better to make this a property, and define it outside this method
    Penguin.image = [UIImage imageNamed:[imageNameArray objectAtIndex:arc4random_uniform((uint32_t)[imageNameArray count])]];

    [UIView animateKeyframesWithDuration:3 delay:0 options:0 animations:^{
        [UIView addKeyframeWithRelativeStartTime:0 relativeDuration:0.3 animations:^{

            Penguin.center = CGPointMake(294, 373);
            Penguin.alpha = 1;
            Penguin.center = CGPointMake(Penguin.center.x - 40, Penguin.center.y);}];
        [UIView addKeyframeWithRelativeStartTime:0.3 relativeDuration:0.4 animations:^{
            Penguin.center = CGPointMake(Penguin.center.x - 200, Penguin.center.y);}];
        [UIView addKeyframeWithRelativeStartTime:0.7 relativeDuration:0.3 animations:^{
            Penguin.alpha = 0;
            Penguin.center = CGPointMake(Penguin.center.x - 40, Penguin.center.y);}];
    }completion:^(BOOL finished) {
        [self start:nil];
    }
     ];
}