全屏：调整其父视图的大小时不调整 AVPlayerLayer 的大小

Question

我正在使用 MonoTouch 中的 AV Foundation 的 AVPlayer API 开发视频播放器（但 Objective-c 中的解决方案也可能很好）。我正在尝试实现全屏模式。

为了显示视频帧，我有一个 UIView（我们称之为播放视图），我在其中添加了 AVPlayerLayer 作为播放视图层的子视图：

UIView *playbackView = ...
AVPlayerLayer *playerLayer = ...
[playbackView.layer addSublayer:playerLayer];

图层属性设置如下：

playerLayer.needsDisplayOnBoundsChange = YES;
playbackView.layer.needsDisplayOnBoundsChange = YES;

以确保在播放视图大小发生更改时调整它们的大小。最初，播放视图的坐标为 (0, 0, 320, 180)（仅显示在 UI 顶部）。然后，我通过将播放视图帧大小设置为窗口大小来制作全屏动画：

playbackView.frame = playbackView.window.bounds;

它工作正常。播放视图现在填充了所有窗口（设置背景颜色以查看它）。但是我的 AVPlayerLayer 仍然像以前在非全屏模式下一样停留在视图的顶部。

为什么AVPlayer层没有根据播放视图的新大小调整大小？我还需要在 AVPlayerLayer 上制作动画吗？用 setNeedsLayout、layoutSubviews 刷新（它似乎没有改变什么......）？把AVPlayerLayer去掉再重新添加？

Answer 1

不要添加为子图层。只需将playbackView的图层用作AVPlayerLayer，如下所示：

+ (Class)layerClass {
    return [AVPlayerLayer class];
}
- (AVPlayer*)player {
    return [(AVPlayerLayer *)[self layer] player];
}
- (void)setPlayer:(AVPlayer *)player {
    [(AVPlayerLayer *)[self layer] setPlayer:player];
}

参见AV Foundation Programming Guide - 播放器视图

Answer 2

如果您将 AVPlayerLayer 添加为子图层，则需要更新其框架

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    self.avPlayerLayer.frame = self.movieContainerView.bounds;
}

Answer 3

有更好的方法来实现这一点。这是AVPlayerLayer-backed 视图，它试图保持视频纵横比。像往常一样使用 AutoLayout。

PlayerView.h：

@interface PlayerView : UIView

@property (strong, nonatomic) AVPlayerLayer *layer;

@end

PlayerView.m：

@interface PlayerView ()

@property (strong, nonatomic) NSLayoutConstraint *aspectConstraint;

@end

@implementation PlayerView

@dynamic layer;

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

- (instancetype)init {
    self = [super init];
    if (self) {
        self.userInteractionEnabled = NO;

        [self addObserver:self forKeyPath:@"layer.videoRect" options:NSKeyValueObservingOptionInitial|NSKeyValueObservingOptionNew context:nil];
    }
    return self;
}

- (void)dealloc {
    [self removeObserver:self forKeyPath:@"layer.videoRect"];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    if ([keyPath isEqualToString:@"layer.videoRect"]) {
        CGSize size = [change[NSKeyValueChangeNewKey] CGRectValue].size;
        if (change[NSKeyValueChangeNewKey] && size.width && size.height) {
            self.aspectConstraint.active = NO;
            self.aspectConstraint = [self.widthAnchor constraintEqualToAnchor:self.heightAnchor multiplier:size.width / size.height];
            self.aspectConstraint.priority = UILayoutPriorityDefaultHigh;
            self.aspectConstraint.active = YES;
        }
        else {
            self.aspectConstraint.active = NO;
        }
    }
}

@end

Swift 上的解决方案相同：

import UIKit
import AVFoundation

class PlayerView : UIView {

    override var layer: AVPlayerLayer {
        return super.layer as! AVPlayerLayer
    }

    override class var layerClass: AnyClass {
        return AVPlayerLayer.self
    }

    var aspectConstraint: NSLayoutConstraint?

    override init(frame: CGRect) {
        super.init(frame: frame)
        self.isUserInteractionEnabled = false
        self.addObserver(self, forKeyPath:"layer.videoRect", options:[.initial, .new], context:nil)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.isUserInteractionEnabled = false
        self.addObserver(self, forKeyPath:"layer.videoRect", options:[.initial, .new], context:nil)
    }

    deinit {
        self.removeObserver(self, forKeyPath: "layer.videoRect")
    }

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if (keyPath == "layer.videoRect") {
            if let rect = change?[.newKey] as? NSValue {
                let size = rect.cgRectValue.size
                if (size.width > 0 && size.height > 0) {
                    self.aspectConstraint?.isActive = false
                    self.aspectConstraint = self.widthAnchor.constraint(equalTo: self.heightAnchor, multiplier:size.width / size.height)
                    self.aspectConstraint?.priority = UILayoutPriorityDefaultHigh
                    self.aspectConstraint?.isActive = true
                }
                else {
                    self.aspectConstraint?.isActive = false
                }
            }
        }
    }
}