AVFoundation 框架初探究（四）

叨叨两句

动手写这篇总结时候也是二月底过完年回来上班了，又开始新的一年了，今年会是什么样子？这问题可能得年底再回答自己了。在家窝了那么久，上班还是的接着看我们要看的东西，毕竟我们要做的事还真的太多的。

总结第五章的内容，这两天把后面几章的内容大概的翻着看了看，知道了下后面几章的内容大致讲的都是那些内容。这里就先开始总结书本中第五章的内容。前面第四章的内容视频播放我们再前面的确也总过了，就不在这里再去重复总结。

一：AVPlayerViewController

在第五章的最开始讲述的就是AVPlayerViewController，这个控制器在前面也没有好好说过，不过苹果给我们的关于AVPlayerViewController的API也就那么多，我们在这里看看它的头文件，以及它的一些使用。下面就先看看AVPlayerViewController这个类的头文件的方法，我们对它的属性进行一个解释说明：

File: AVPlayerViewController.h

Framework: AVKit

导入库头文件

#import <UIKit/UIKit.h>

#import <AVFoundation/AVFoundation.h>

NS_ASSUME_NONNULL_BEGIN

//AVPlayerViewController有这个代理，这个代理方法就在下面

@protocol AVPlayerViewControllerDelegate;

@class AVPlayerViewController

这个摘要说明了AVPlayerViewController这个控制器的基本特征

@abstract AVPlayerViewController is a subclass of UIViewController that can be used to display the visual content of an AVPlayer object and the standard playback controls.

// 8.0之后有的AVPlayerViewController

API_AVAILABLE(ios(8.0))

@interface AVPlayerViewController : UIViewController

// 简单的播放器AVPlayer属性

@property player

@abstract The player from which to source the media content for the view controller.

@property (nonatomic, strong, nullable) AVPlayer *player;

// 是否展示添加在上面的子控件

@property showsPlaybackControls

@abstract Whether or not the receiver shows playback controls. Default is YES.

@discussion Clients can set this property to NO when they don't want to have any playback controls on top of the visual content (e.g. for a game splash screen).

@property (nonatomic) BOOL showsPlaybackControls;

// 这个属性字面意思是视频重力 其实它是用来确定在承载层的范围内视频可以拉伸或者缩放的程度

// 具体的在下面@discussion部分有讨论，我们再总结一下它三个值分别代表的含义

// AVLayerVideoGravityResizeAspect 会在承载层的范围内缩放视频的大小来保持视频的原始比例宽高，默认值

// AVLayerVideoGravityResizeAspectFill 保留视频的宽高比，并且通过缩放填满整个播放界面

// AVLayerVideoGravityResize 会将视频内容拉伸匹配承载层的范围，一般不常用，因为会把图片扭曲导致变形

@property videoGravity

@abstract A string defining how the video is displayed within an AVPlayerLayer bounds rect.

@discussion Options are AVLayerVideoGravityResizeAspect, AVLayerVideoGravityResizeAspectFill and AVLayerVideoGravityResize. AVLayerVideoGravityResizeAspect is default.

See <AVFoundation/AVAnimation.h> for a description of these options.

@property (nonatomic, copy) NSString *videoGravity;

// 通过这个bool类型的值确定视频是否已经准备好展示

@property readyForDisplay

@abstract Boolean indicating that the first video frame has been made ready for display for the current item of the associated AVPlayer.

@property (nonatomic, readonly, getter = isReadyForDisplay) BOOL readyForDisplay;

// 视频的尺寸

@property videoBounds

@abstract The current size and position of the video image as displayed within the receiver's view's bounds.

@property (nonatomic, readonly) CGRect videoBounds;

// 有自定义的控件可以添加在这里UIView上

@property contentOverlayView

@abstract Use the content overlay view to add additional custom views between the video content and the controls.

@property (nonatomic, readonly, nullable) UIView *contentOverlayView;

// 是否允许使用画中画播放模式，这个画中画播放在下面会写Demo 9.0之后的属性

@property allowsPictureInPicturePlayback

@abstract Whether or not the receiver allows Picture in Picture playback. Default is YES.

@property (nonatomic) BOOL allowsPictureInPicturePlayback API_AVAILABLE(ios(9.0));

// 10.0之后的属性

@property updatesNowPlayingInfoCenter

@abstract Whether or not the now playing info center should be updated. Default is YES.

@property (nonatomic) BOOL updatesNowPlayingInfoCenter API_AVAILABLE(ios(10.0));

// 理解摘要的意思是是否允许点击播放之后自动全屏播放视频 默认值是NO

@property entersFullScreenWhenPlaybackBegins

@abstract Whether or not the receiver automatically enters full screen when the play button is tapped. Default is NO.

@discussion If YES, the receiver will show a user interface tailored to this behavior.

@property (nonatomic) BOOL entersFullScreenWhenPlaybackBegins API_AVAILABLE(ios(11.0));

// 也是理解摘要，是否允许退出全屏播放在播放结束之后

@property exitsFullScreenWhenPlaybackEnds

@abstract Whether or not the receiver automatically exits full screen when playback ends. Default is NO.

@discussion If multiple player items have been enqueued, the receiver exits fullscreen once no more items are remaining in the queue.

@property (nonatomic) BOOL exitsFullScreenWhenPlaybackEnds API_AVAILABLE(ios(11.0));

// AVPlayerViewControllerDelegate代理

@property delegate

@abstract The receiver's delegate.

@property (nonatomic, weak, nullable) id <AVPlayerViewControllerDelegate> delegate API_AVAILABLE(ios(9.0));

@end

// 下面就是AVPlayerViewControllerDelegate代理方法 下面的代理方法都是optional可选的

@protocol AVPlayerViewControllerDelegate

@abstract A protocol for delegates of AVPlayerViewController.

@protocol AVPlayerViewControllerDelegate <NSObject>

@optional

@method playerViewControllerWillStartPictureInPicture: