全屏：调整其父视图大小时不调整AVPlayerLayer的大小

Question

I am developing a video player with the AVPlayer API from AV Foundation in MonoTouch (but a solution in objective-c could be nice too). I am trying to implement a fullscreen mode.

To display the video frames, I have a UIView (let's call it playback view) where I added the AVPlayerLayer as subview of the playback view layer:

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

the layer properties are set like that:

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

to be sure that they are resized if the playback view size is changed. Initially, the playback view has the coordinates (0, 0, 320, 180) (only displayed at the top of the UI). Then, I am doing a fullscreen animation by setting the playback view frame size as being the window size:

playbackView.frame = playbackView.window.bounds;

It's works fine. The playback view is now filling all the window (set a background color to see it). But my AVPlayerLayer is still staying at the top of the view like previously in non-fullscreen mode.

Why the AVPlayer layer is not resized according to the playback view new size? Do I need to make an animation on the AVPlayerLayer as well? A refresh with setNeedsLayout, layoutSubviews (it doesn't seems to change something...)? Remove the AVPlayerLayer and add it again?

Answer 1

Don't add as sublayer. Just use playbackView's layer as AVPlayerLayer, like this:

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

See AV Foundation Programming Guide - The Player View

Answer 2

In case you add AVPlayerLayer as sublayer, you need to update its frame

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

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

Answer 3

There is a better way to achieve this. Here is AVPlayerLayer -backed view, that is trying to keep video aspect ratio. Just use AutoLayout as usually.

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

And the same solution on Swift :

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
                }
            }
        }
    }
}