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HTML5 发布时间：2022-04-27 发布网站：大佬教程 code.js-code.com

大佬教程收集整理的这篇文章主要介绍了ios – Animate AVPlayerLayer videoGravity属性，大佬教程大佬觉得挺不错的，现在分享给大家，也给大家做个参考。

我正在尝试复制Apple在视频播放中的行为,允许用户拉伸视频图像以填充边界.

@interface FHVideoPlayerView : UIView
@end
@interface FHVideoPlayerView

+ (Class)layerClass
{
    return [AVPlayerLayer class];
}

- (void)setAspectMode:(FHVideoPlayerAspectModE)aspectMode animated:(BOOL)animated
{
    FHVideoPlayerAspectMode current = [self aspectMode];
    FHVideoPlayerAspectMode final   = aspectMode;

    NSString *fromValue;
    NSString *toValue;

    AVPlayerLayer *layer = (AVPlayerLayer *)[self layer];

    switch (current) {
        case FHVideoPlayerAspectFill:
            fromValue = AVLayerVideoGravityResizeAspectFill;
            break;
        case FHVideoPlayerAspectFit:
            fromValue = AVLayerVideoGravityResizeAspect;
            break;
       default:
           break;
    }

    switch (final) {
        case FHVideoPlayerAspectFill:
            toValue = AVLayerVideoGravityResizeAspectFill;
            break;
        case FHVideoPlayerAspectFit:
            toValue = AVLayerVideoGravityResizeAspect;
            break;
        default:
            break;
    }

    if (toValue != fromvalue) {
        if (animated == YES) {
            // Manually added CABasicAnimation based on the understanding the implicit animations are disabled for CALayers that BACk a UIView
            CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"videoGravity"];
            [layer addAnimation:animation forKey:@"animateVideoGravity"];

            [CAtransaction begin];
            [CAtransaction setAnimationDuration:0.333];
        }

        [layer setVideoGravity:toValue];

        if (animated == YES) {
            [CAtransaction commit];
        }
    }
}

当我尝试为不透明度这样的数字属性设置动画时,这很好用.但是,你会从类引用中注意到,AVPlayerLayer的videoGravity属性是一个NSString.类引用确实指出它是可动画的.

所以我的问题是：如何！？

我相信这可能与CALayer的内容属性以及可能的contentsGravity有某种关系.

解决方法

正如voromax所指出的,这是iOS 5.0中的一个错误.我在iOS 5.1中进行了逆向工程 – [AVPlayerLayer setVideoGravity：]实现,以便了解动画应该如何工作.以下是如何解决这个错误,并在iOS 5.0上有一个很好的动画.

@implementation VideoPlayerView

+ (Class) layerClass
{
    return [AVPlayerLayer class];
}

- (AVPlayerLayer *) playerLayer
{
    return (AVPlayerLayer *)[self layer];
}

- (NSString *) videoGravity
{
    return self.playerLayer.videoGravity;
}

- (void) setVideoGravity:(NSString *)videoGravity
{
    self.playerLayer.videoGravity = videoGravity;

    // Workaround a bug in iOS 5.0
    float avFoundationVersion = [[[NSBundle bundleForClass:[AVPlayerLayer class]] objectForInfoDictionaryKey:(NSString *)kcfBundLeversionKey] floatValue];
    if (avFoundationVersion < 292.24f)
    {
        @try
        {
            NSString *contentLayerKeyPath = [NSString StringWithFormat:@"%1$@%2$@.%3$@%2$@",@"player",[@"layer" capitalizedString],@"content"]; // playerLayer.contentLayer
            CALayer *contentLayer = [self.playerLayer valueForKeyPath:contentLayerKeyPath];
            if ([contentLayer isKindOfClass:[CALayer class]])
                [contentLayer addAnimation:[CABasicAnimation animation] forKey:@"sublayerTransform"];
        }
        @catch (NSException *exception)
        {
        }
        self.bounds = self.bounds;
    }
}

@end