iOS 来回切换多张图片，形成动画效果

在imageView上，设置animationImages，来实现这个效果，项目中喇叭播放的效果就是这么实现的

- (UIImageView *)animationImageView {
    if (!_animationImageView) {
        _animationImageView = [[UIImageView alloc] init];
        _animationImageView.frame = CGRectMake(self.recordButton.x - 42 - 31, (self.height - 31) / 2, 31, 31);
        NSArray *images=[NSArray arrayWithObjects:[UIImage imageNamed:@"spoken_selfaudio_select_1"],[UIImage imageNamed:@"spoken_selfaudio_select_2"], nil];
        _animationImageView.image = [UIImage imageNamed:@"spoken_selfaudio_select_1"];
        //imageView的动画图片是数组images
        _animationImageView.animationImages = images;
        //按照原始比例缩放图片，保持纵横比
        _animationImageView.contentMode = UIViewContentModeScaleAspectFit;
        //切换动作的时间3秒，来控制图像显示的速度有多快，
        _animationImageView.animationDuration = 0.5;
        //动画的重复次数，想让它无限循环就赋成0
        _animationImageView.animationRepeatCount = 0;

    }
    return _animationImageView;
}

开始动画

    [self.animationImageView startAnimating];

结束动画

    [self.animationImageView stopAnimating];