AVPlayer

    AVPlayerLayer是CALayer的一个子类，由于AVPlayer这个播放器只能安置在AVPlayerLayer 这个图层之上，所以我们需要实例化一个UIView，并且修改它默认生成的图层类型（默认是CALayer，不具备安置AVPlayer的功能）
        
    1.修改UIView自带的CALayer类型
    +(Class)layerClass

    2.媒体对象
    AVPlayerItem
    
    3.通过KVO来观察AVPlayerItem的status属性值的变化，当status的属性值变为AVPlayerItemStatusReadyToPlay的时候，才允许播放

    4.通过以下方法观察播放进度的变化
    - (id)addPeriodicTimeObserverForInterval:(CMTime)interval queue:(dispatch_queue_t)queue usingBlock:(void (^)(CMTime time))block;

    5. 专门用于显示视频时间的一个结构体
    CMTime
    
    ps：CMTimeMake（a,b）创建一个CMTime结构体，a代表当前第几帧，b代表每一秒钟播放多少帧

1. 然后监听playerItem的status和loadedTimeRange属性，status有三种状态 ==>这是原文中的话，但是后面列出的属性却是AVPlayer 的status（应该是作者笔误），其实AVPlayerItem和__AVPlayer__ 都有status 属性的，而且可以使用KVO监听的。
文档中枚举类型如下：

typedef NS_ENUM(NSInteger, AVPlayerItemStatus) {
 AVPlayerItemStatusUnknown,
 AVPlayerItemStatusReadyToPlay,
 AVPlayerItemStatusFailed
};

而AVPlayer 的status 枚举类型如下：

typedef NS_ENUM(NSInteger, AVPlayerStatus) {
 AVPlayerStatusUnknown,
 AVPlayerStatusReadyToPlay,
 AVPlayerStatusFailed
};

看清楚啊！！！看清楚这两个之间的区别，这里我主要想说明：
AVPlayerItemStatus是代表当前播放资源item 的状态（可以理解成这url链接or视频文件。。。可以播放成功/失败）
AVPlayerStatus是代表当前播放器的状态。

我在编程的时候遇到一个问题就是AVPlayer 的status 为
AVPlayerStatusReadyToPlay，但是视频就是播放不成功，后来将KVO的监听换成了AVPlayerItem ，返回了AVPlayerItemStatusFailed。

编程的时候最好使用item 的status，会准确点。
2.addPeriodicTimeObserverForInterval
给AVPlayer 添加time Observer 有利于我们去检测播放进度
但是添加以后一定要记得移除，其实不移除程序不会崩溃，但是这个线程是不会释放的，会占用你大量的内存资源（当时发现这个问题的时候我搞了一上午，说实话当时我根本不知道是哪里出现了问题，自己对AVPlayer 根本不了解）
苹果文档中的注释：

@result
An object conforming to the NSObject protocol. You must retain this returned value as long as you want the time observer to be invoked by the player.
Pass this object to -removeTimeObserver: to cancel time observation.

3.CMTime 结构体
连接的教程里面 给的参数是CMTimeMake(1, 1)，其实就是1s调用一下block，
打个比方CMTimeMake(a, b)就是a/b秒之后调用一下block
介绍一个网站有关这个结构体的:
https://zwo28.wordpress.com/2015/03/06/%E8%A7%86%E9%A2%91%E5%90%88%E6%88%90%E4%B8%ADcmtime%E7%9A%84%E7%90%86%E8%A7%A3%EF%BC%8C%E4%BB%A5%E5%8F%8A%E5%88%A9%E7%94%A8cmtime%E5%AE%9E%E7%8E%B0%E8%BF%87%E6%B8%A1%E6%95%88%E6%9E%9C/

4.拖动slider 播放跳跃播放，要使用AVPlayer 对象的seekToTime:方法,
举个最简单的例子：假如一个video视频有20s，想要跳到10s进行播放(_palyer 为AVPlayer 对象)
[_player seekToTime:CMTimeMake(10,1)];后面的参数写1，前面的参数写将要播放的秒数，我试验得出的结果，不要问我问什么，需要自己理解。
5.播放到结尾怎么回到开头呢？
[_player seekToTime:kCMTimeZero];

下面放上我的写的代码：写的不好请指正，多谢。

AVViewController.h

#import <UIKit/UIKit.h> 
@interface AVViewController : UIViewController 
@end

AVViewController.m

#import "AVViewController.h"
#import "VideoView.h"

@interface AVViewController () <VideoSomeDelegate>

@property (nonatomic ,strong) VideoView *videoView;

@property (nonatomic ,strong) NSMutableArray<NSLayoutConstraint *> *array;

@property (nonatomic ,strong) UISlider *videoSlider;

@property (nonatomic ,strong) NSMutableArray<NSLayoutConstraint *> *sliderArray;

@end

@implementation AVViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.view setBackgroundColor:[UIColor whiteColor]];
    [self initVideoView];

}

- (void)initVideoView {

    //NSString *path = [[NSBundle mainBundle] pathForResource:@"some" ofType:@"mp4"];//这个时播放本地的，播放本地的时候还需要改VideoView.m中的代码
    NSString *path = @"http://static.tripbe.com/videofiles/20121214/9533522808.f4v.mp4";
    _videoView = [[VideoView alloc] initWithUrl:path delegate:self];
    _videoView.someDelegate = self;
    [_videoView setTranslatesAutoresizingMaskIntoConstraints:NO];
    [self.view addSubview:_videoView];
    [self initVideoSlider];

    if (self.traitCollection.verticalSizeClass == UIUserInterfaceSizeClassCompact) {
        [self installLandspace];
    } else {
        [self installVertical];
    }
}
- (void)installVertical {
    if (_array != nil) {
        [self.view removeConstraints:_array];
        [_array removeAllObjects];
        [self.view removeConstraints:_sliderArray];
        [_sliderArray removeAllObjects];
    } else {
        _array = [NSMutableArray array];
        _sliderArray = [NSMutableArray array];
    }
    id topGuide = self.topLayoutGuide;
    NSDictionary *dic = @{@"top":@100,@"height":@180,@"edge":@20,@"space":@80};
    [_array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[_videoView]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_videoView)]];
    [_array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(edge)-[_videoSlider]-(edge)-|" options:0 metrics:dic views:NSDictionaryOfVariableBindings(_videoSlider)]];
    [_array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[topGuide]-(top)-[_videoView(==height)]-(space)-[_videoSlider]" options:0 metrics:dic views:NSDictionaryOfVariableBindings(_videoView,topGuide,_videoSlider)]];
    [self.view addConstraints:_array];



}
- (void)installLandspace {
    if (_array != nil) {

        [self.view removeConstraints:_array];
        [_array removeAllObjects];

        [self.view removeConstraints:_sliderArray];
        [_sliderArray removeAllObjects];
    } else {

        _array = [NSMutableArray array];
        _sliderArray = [NSMutableArray array];
    }

    id topGuide = self.topLayoutGuide;
    NSDictionary *dic = @{@"edge":@20,@"space":@30};

    [_array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[_videoView]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_videoView)]];
    [_array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[topGuide][_videoView]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_videoView,topGuide)]];
    [self.view addConstraints:_array];

    [_sliderArray addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(edge)-[_videoSlider]-(edge)-|" options:0 metrics:dic views:NSDictionaryOfVariableBindings(_videoSlider)]];
    [_sliderArray addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[_videoSlider]-(space)-|" options:0 metrics:dic views:NSDictionaryOfVariableBindings(_videoSlider)]];
    [self.view addConstraints:_sliderArray];
}
- (void)initVideoSlider {

    _videoSlider = [[UISlider alloc] init];
    [_videoSlider setTranslatesAutoresizingMaskIntoConstraints:NO];
    [_videoSlider setThumbImage:[UIImage imageNamed:@"sliderButton"] forState:UIControlStateNormal];
    [self.view addSubview:_videoSlider];

}
- (void)willTransitionToTraitCollection:(UITraitCollection *)newCollection withTransitionCoordinator:(id <UIViewControllerTransitionCoordinator>)coordinator {

    [super willTransitionToTraitCollection:newCollection withTransitionCoordinator:coordinator];
    [coordinator animateAlongsideTransition:^(id <UIViewControllerTransitionCoordinatorContext> context) {

        if (newCollection.verticalSizeClass == UIUserInterfaceSizeClassCompact) {
            [self installLandspace];
        } else {
            [self installVertical];
        }
        [self.view setNeedsLayout];
    } completion:nil];

}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}
#pragma mark -
- (void)flushCurrentTime:(NSString *)timeString sliderValue:(float)sliderValue {
    _videoSlider.value = http://www.mamicode.com/sliderValue;"hljs-comment">/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end

VideoView.h

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>

@protocol VideoSomeDelegate <NSObject>

@required

- (void)flushCurrentTime:(NSString *)timeString sliderValue:(float)sliderValue;

//- (void)flushVideoLength:(float)videoLength;




@end

@interface VideoView : UIView

@property (nonatomic ,strong) NSString *playerUrl;


@property (nonatomic ,readonly) AVPlayerItem *item;

@property (nonatomic ,readonly) AVPlayerLayer *playerLayer;

@property (nonatomic ,readonly) AVPlayer *player;

@property (nonatomic ,weak) id <VideoSomeDelegate> someDelegate;

- (id)initWithUrl:(NSString *)path delegate:(id<VideoSomeDelegate>)delegate;


@end

@interface VideoView  (Guester)

- (void)addSwipeView;

@end

VideoView.m

#import "VideoView.h"
#import <AVFoundation/AVFoundation.h>
#import <MediaPlayer/MPVolumeView.h>    
typedef enum  {
    ChangeNone,
    ChangeVoice,
    ChangeLigth,
    ChangeCMTime
}Change;


@interface VideoView ()

@property (nonatomic ,readwrite) AVPlayerItem *item;

@property (nonatomic ,readwrite) AVPlayerLayer *playerLayer;

@property (nonatomic ,readwrite) AVPlayer *player;

@property (nonatomic ,strong)  id timeObser;

@property (nonatomic ,assign) float videoLength;

@property (nonatomic ,assign) Change changeKind;

@property (nonatomic ,assign) CGPoint lastPoint;

//Gesture
@property (nonatomic ,strong) UIPanGestureRecognizer *panGesture;
@property (nonatomic ,strong) MPVolumeView *volumeView;
@property (nonatomic ,weak) UISlider *volumeSlider;
@property (nonatomic ,strong) UIView *darkView;
@end

@implementation VideoView

- (id)initWithUrl:(NSString *)path delegate:(id<VideoSomeDelegate>)delegate {
    if (self = [super init]) {
        _playerUrl = path;
        _someDelegate = delegate;
        [self setBackgroundColor:[UIColor blackColor]];
        [self setUpPlayer];
        [self addSwipeView];

    }
    return self;
}
- (void)setUpPlayer {
    //本地视频
    //NSURL *rul = [NSURL fileURLWithPath:_playerUrl];

     NSURL *url = [NSURL URLWithString:_playerUrl];
     NSLog(@"%@",url);

    _item = [[AVPlayerItem alloc] initWithURL:url];
    _player = [AVPlayer playerWithPlayerItem:_item];
    _playerLayer = [AVPlayerLayer playerLayerWithPlayer:_player];
    _playerLayer.videoGravity = AVLayerVideoGravityResizeAspect;
    [self.layer addSublayer:_playerLayer];

    [self addVideoKVO];
    [self addVideoTimerObserver];
    [self addVideoNotic];
}


#pragma mark - KVO
- (void)addVideoKVO
{
    //KVO
    [_item addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:nil];
    [_item addObserver:self forKeyPath:@"loadedTimeRanges" options:NSKeyValueObservingOptionNew context:nil];
    [_item addObserver:self forKeyPath:@"playbackBufferEmpty" options:NSKeyValueObservingOptionNew context:nil];
}
- (void)removeVideoKVO {
    [_item removeObserver:self forKeyPath:@"status"];
    [_item removeObserver:self forKeyPath:@"loadedTimeRanges"];
    [_item removeObserver:self forKeyPath:@"playbackBufferEmpty"];
}
- (void)observeValueForKeyPath:(nullable NSString *)keyPath ofObject:(nullable id)object change:(nullable NSDictionary<NSString*, id> *)change context:(nullable void *)context {

    if ([keyPath isEqualToString:@"status"]) {
        AVPlayerItemStatus status = _item.status;
        switch (status) {
            case AVPlayerItemStatusReadyToPlay:
            {
                NSLog(@"AVPlayerItemStatusReadyToPlay");
                [_player play];
                _videoLength = floor(_item.asset.duration.value * 1.0/ _item.asset.duration.timescale);
            }
                break;
            case AVPlayerItemStatusUnknown:
            {
                NSLog(@"AVPlayerItemStatusUnknown");
            }
                break;
            case AVPlayerItemStatusFailed:
            {
                NSLog(@"AVPlayerItemStatusFailed");
                NSLog(@"%@",_item.error);
            }
                break;

            default:
                break;
        }
    } else if ([keyPath isEqualToString:@"loadedTimeRanges"]) {

    } else if ([keyPath isEqualToString:@"playbackBufferEmpty"]) {

    }
}
#pragma mark - Notic
- (void)addVideoNotic {

    //Notification
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieToEnd:) name:AVPlayerItemDidPlayToEndTimeNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieJumped:) name:AVPlayerItemTimeJumpedNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieStalle:) name:AVPlayerItemPlaybackStalledNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(backGroundPauseMoive) name:UIApplicationDidEnterBackgroundNotification object:nil];

}
- (void)removeVideoNotic {
    //
    [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemDidPlayToEndTimeNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemPlaybackStalledNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:AVPlayerItemTimeJumpedNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)movieToEnd:(NSNotification *)notic {
    NSLog(@"%@",NSStringFromSelector(_cmd));
}
- (void)movieJumped:(NSNotification *)notic {
    NSLog(@"%@",NSStringFromSelector(_cmd));
}
- (void)movieStalle:(NSNotification *)notic {
    NSLog(@"%@",NSStringFromSelector(_cmd));
}
- (void)backGroundPauseMoive {
    NSLog(@"%@",NSStringFromSelector(_cmd));
}

#pragma mark - TimerObserver
- (void)addVideoTimerObserver {
    __weak typeof (self)self_ = self;
    _timeObser = [_player addPeriodicTimeObserverForInterval:CMTimeMake(1, 1) queue:NULL usingBlock:^(CMTime time) {
        float currentTimeValue = http://www.mamicode.com/time.value*1.0/time.timescale/self_.videoLength;"no response");
        }
        NSLog(@"%@",self_.someDelegate);
    }];
}
- (void)removeVideoTimerObserver {
    NSLog(@"%@",NSStringFromSelector(_cmd));
    [_player removeTimeObserver:_timeObser];
}


#pragma mark - Utils
- (NSString *)getStringFromCMTime:(CMTime)time
{
    float currentTimeValue = http://www.mamicode.com/(CGFloat)time.value/time.timescale;//得到当前的播放时"%ld:%ld:%ld",components.hour,components.minute,components.second];
    }
    else
    {
        return [NSString stringWithFormat:@"%ld:%ld",components.minute,components.second];
    }
}

- (NSString *)getVideoLengthFromTimeLength:(float)timeLength
{
    NSDate * date = [NSDate dateWithTimeIntervalSince1970:timeLength];
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    NSInteger unitFlags = NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond ;
    NSDateComponents *components = [calendar components:unitFlags fromDate:date];

    if (timeLength >= 3600 )
    {
        return [NSString stringWithFormat:@"%ld:%ld:%ld",components.hour,components.minute,components.second];
    }
    else
    {
        return [NSString stringWithFormat:@"%ld:%ld",components.minute,components.second];
    }
}

- (void)layoutSubviews {
    [super layoutSubviews];
    _playerLayer.frame = self.bounds;
}

#pragma mark - release 
- (void)dealloc {
    NSLog(@"%@",NSStringFromSelector(_cmd));
    [self removeVideoTimerObserver];
    [self removeVideoNotic];
    [self removeVideoKVO];
}

@end

#pragma mark - VideoView (Guester)

@implementation VideoView (Guester)

- (void)addSwipeView {
    _panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(swipeAction:)];
    [self addGestureRecognizer:_panGesture];
    [self setUpDarkView];
}
- (void)setUpDarkView {
    _darkView = [[UIView alloc] init];
    [_darkView setTranslatesAutoresizingMaskIntoConstraints:NO];
    [_darkView setBackgroundColor:[UIColor blackColor]];
    _darkView.alpha = 0.0;
    [self addSubview:_darkView];

    NSMutableArray *darkArray = [NSMutableArray array];
    [darkArray addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[_darkView]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_darkView)]];
    [darkArray addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[_darkView]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(_darkView)]];
    [self addConstraints:darkArray];
}

- (void)swipeAction:(UISwipeGestureRecognizer *)gesture {

    switch (gesture.state) {
        case UIGestureRecognizerStateBegan:
        {
            _changeKind = ChangeNone;
            _lastPoint = [gesture locationInView:self];
        }
            break;
        case  UIGestureRecognizerStateChanged:
        {
            [self getChangeKindValue:[gesture locationInView:self]];

        }
            break;
        case UIGestureRecognizerStateEnded:
        {
            if (_changeKind == ChangeCMTime) {
                [self changeEndForCMTime:[gesture locationInView:self]];
            }
            _changeKind = ChangeNone;
            _lastPoint = CGPointZero;
        }
        default:
            break;
    }

}
- (void)getChangeKindValue:(CGPoint)pointNow {

    switch (_changeKind) {

        case ChangeNone:
        {
            [self changeForNone:pointNow];
        }
            break;
        case ChangeCMTime:
        {
            [self changeForCMTime:pointNow];
        }
            break;
        case ChangeLigth:
        {
            [self changeForLigth:pointNow];
        }
            break;
        case ChangeVoice:
        {
            [self changeForVoice:pointNow];
        }
            break;

        default:
            break;
    }
}
- (void)changeForNone:(CGPoint) pointNow {
    if (fabs(pointNow.x - _lastPoint.x) > fabs(pointNow.y - _lastPoint.y)) {
        _changeKind = ChangeCMTime;
    } else {
        float halfWight = self.bounds.size.width / 2;
        if (_lastPoint.x < halfWight) {
            _changeKind =  ChangeLigth;
        } else {
            _changeKind =   ChangeVoice;
        }
        _lastPoint = pointNow;
    }
}
- (void)changeForCMTime:(CGPoint) pointNow {
    float number = fabs(pointNow.x - _lastPoint.x);
    if (pointNow.x > _lastPoint.x && number > 10) {
        float currentTime = _player.currentTime.value / _player.currentTime.timescale;
        float tobeTime = currentTime + number*0.5;
        NSLog(@"forwart to  changeTo  time:%f",tobeTime);
    } else if (pointNow.x < _lastPoint.x && number > 10) {
        float currentTime = _player.currentTime.value / _player.currentTime.timescale;
        float tobeTime = currentTime - number*0.5;
        NSLog(@"back to  time:%f",tobeTime);
    }
}
- (void)changeForLigth:(CGPoint) pointNow {
    float number = fabs(pointNow.y - _lastPoint.y);
    if (pointNow.y > _lastPoint.y && number > 10) {
        _lastPoint = pointNow;
        [self minLigth];

    } else if (pointNow.y < _lastPoint.y && number > 10) {
        _lastPoint = pointNow;
        [self upperLigth];
    }
}
- (void)changeForVoice:(CGPoint)pointNow {
    float number = fabs(pointNow.y - _lastPoint.y);
    if (pointNow.y > _lastPoint.y && number > 10) {
        _lastPoint = pointNow;
        [self minVolume];
    } else if (pointNow.y < _lastPoint.y && number > 10) {
        _lastPoint = pointNow;
        [self upperVolume];
    }
}
- (void)changeEndForCMTime:(CGPoint)pointNow {
    if (pointNow.x > _lastPoint.x ) {
        NSLog(@"end for CMTime Upper");
        float length = fabs(pointNow.x - _lastPoint.x);
        [self upperCMTime:length];
    } else {
        NSLog(@"end for CMTime min");
        float length = fabs(pointNow.x - _lastPoint.x);
        [self mineCMTime:length];
    }
}
- (void)upperLigth {

    if (_darkView.alpha >= 0.1) {
        _darkView.alpha =  _darkView.alpha - 0.1;
    }

}
- (void)minLigth {
    if (_darkView.alpha <= 1.0) {
        _darkView.alpha =  _darkView.alpha + 0.1;
    }
}

- (void)upperVolume {
    if (self.volumeSlider.value <= 1.0) {
        self.volumeSlider.value =  http://www.mamicode.com/self.volumeSlider.value + 0.1 ;"%@",[self.volumeView subviews]);
        for (UIView  *subView in [self.volumeView subviews]) {
            if ([subView.class.description isEqualToString:@"MPVolumeSlider"]) {
                _volumeSlider = (UISlider*)subView;
                break;
            }
        }
    }
    return _volumeSlider;
}

@end

AVPlayer