滚动滚动时，Avplayer项目在uitableview上进行缓冲

Question

我已经创建了一个使用自定义的ViewCells的UitableView。 UitaiteView由通过Internet加载的图像和视频组成。当用户滚动时，在一个uitaiteviewcell中滚动时，我加载了avplayer来播放HLS视频。我以HLS格式将URL设置为Avplayer项目以播放该项目。

self.playerController = [[AVPlayerViewController alloc] init];
NSURL *videoURL = @"https://playeritemvideourl";
self.player = [AVPlayer playerWithURL:url];
self.playerController.player = self.player;
[self.player play];

视频播放，但从[self.player play]触发的时刻延迟约3到5秒。如何将视频放在avplayer的CurrentItem上，因此当我滚动到特定的uitableviewcell时，视频开始播放？我查看了avplayeritem上的 preferredforwardbufferduration 属性，但似乎没有任何区别。任何帮助或建议都感谢！

Answer 1

avplayer在实例化时开始流M3U8。 （我通过监视Xcode的调试导航器中的网络图来注意到这一点。我在不调用的情况下实例化了Avplayer，而网络正在加载。）而不是加载avplayer < /code>一旦单元格变得可见，实例化 avplayer play content < em>当它变为可见时。

可以通过首先让一些数据结构保存avplayer项目来实现这一点。我会推荐一个nsmutabledictionary，因为我们可以设置您想要的视频URL的键，并且该对象可以是已加载带有URL的avplayer。有两种填充结构的方法。您可以在-viewDidload之类的方法中立即加载所有内容，也可以在-scrollviewDidsCroll中动态加载项目：确定我们是否靠近带有视频的单元格。如果没有很多内容，我会使用前者，并且用户几乎可以保证观看所有视频。如果我们有很多内容可以加载，或者用户可能无法观看所有视频，我将使用后者。这是一个带有uitaiteViewController的示例。

mytableViewController.h

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

@interface MyTableViewController : UITableViewController
{
    NSMutableDictionary *mediaPlayers; // stores the media players, key = NSString with URL, value = AVPlayer
    // you don't need mediaKeyIndexPaths or mediaKeyURLs if you are taking the load-all-at-once approach
    NSMutableSet *mediaKeyIndexPaths; // set that stores the key NSIndexPaths that trigger loading a media player
    NSDictionary *mediaKeyURLs; // dictionary that maps a key NSIndexPath to a URL (NSString), key = NSIndexPath, value = NSString
}

@property (strong, nonatomic) AVPlayerViewController *playerController;

@end

mytableViewController.m

#import "MyTableViewController.h"

@implementation MyTableViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // if you want to load all items at once, you can forget mediaKeyIndexPaths and mediaKeyURLs
    // and instead just load all of your media here
    mediaPlayers = [[NSMutableDictionary alloc] init];
    
    // if taking the load-all-at-once approach, load mediaPlayers like this
//  NSString *videoURLString = @"https://playeritemvideourl";
//  AVPlayer *player = [AVPlayer playerWithURL:videoURLString];
//  [mediaPlayers setObject:player forKey:@"https://playeritemvideourl"];

    // lets say that the cell with the media in it is defined here
    NSIndexPath *dummyMediaIndexPath = [NSIndexPath indexPathForRow:40 inSection:0];
    // calculate an index path that, when visible, will trigger loading the media at dummyMediaIndexPath
    NSIndexPath *dummyKeyIndexPath = [NSIndexPath indexPathForRow:dummyMediaIndexPath.row-10
                                                  inSection:dummyMediaIndexPath.section];
    
    // add the key index path to the set of key index paths
    mediaKeyIndexPaths = [[NSMutableSet alloc] initWithObjects:dummyKeyIndexPath, nil];
    // define mediaKeyURLs mapping the key dummyKeyIndexPath to the value of the URL string we want
    mediaKeyURLs = [[NSDictionary alloc] initWithObjectsAndKeys:
                    @"https://playeritemvideourl", dummyKeyIndexPath,
                    nil];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return 100;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"TextCell" forIndexPath:indexPath];
    
    // this is the row of dummyMediaIndexPath defined in -viewDidLoad
    if (indexPath.row == 40)
    {
        self.playerController = [[AVPlayerViewController alloc] init];
        NSString *videoURLString = @"https://playeritemvideourl";
        AVPlayer *player = [mediaPlayers objectForKey:videoURLString]; // load player with URL
        if (!player)
        {
            player = [AVPlayer playerWithURL:[NSURL URLWithString:videoURLString]];
            NSLog(@"Video with URL: %@ was not preloaded. Loading now.", videoURLString);
        }
        self.playerController.player = player;
//      [player play];
// present your playerController here
        [cell setText:@"Player cell"];
    }
    else
    {
        [cell setText:[NSString stringWithFormat:@"Cell #%li", (long)indexPath.row]];
    }
    
    return cell;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    // get visible rows
    NSArray *visibleRows = [self.tableView indexPathsForVisibleRows];
    // traverse through rows
    for (NSIndexPath *i in visibleRows)
    {
        // we use an NSSet to quickly determine if i is contained in mediaKeyIndexPaths
        if ([mediaKeyIndexPaths containsObject:i])
        {
            [mediaKeyIndexPaths removeObject:i]; // we only need to load a player once
            NSString *videoURLString = [mediaKeyURLs objectForKey:i];
            NSLog(@"Preloading URL: %@", videoURLString); // for information purposes only
            AVPlayer *player = [AVPlayer playerWithURL:[NSURL URLWithString:videoURLString]];
            [mediaPlayers setObject:player forKey:videoURLString];
        }
    }
}

@end

这与您提供的代码和信息的数量一样具体。希望这有帮助！