在UITableView上滾動時，Avplayer專案預緩沖

我創建了一個帶有自定義 UITableViewCells 的 UITableView。UITableView 由通過互聯網加載的影像和視頻組成。當用戶在其中一個 UITableViewCell 中滾動時，我加載 AVPlayer 來播放 hls 視頻。我將 hls 格式的 URL 設定為 avplayer 專案以播放該專案。

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

視頻播放，但從[self.player play]觸發的那一刻起大約有 3 到 5 秒的延遲。如何將視頻預緩沖到 avplayer 的當前項，以便當我滾動到特定的 UITableViewCell 時，視頻會立即開始播放？我查看preferredForwardBufferDuration了 AVPlayerItem 上的屬性，但似乎沒有任何區別。任何幫助或建議表示贊賞！

uj5u.com熱心網友回復：

AVPlayer實體化時開始流式傳輸 m3u8。（我通過在 Xcode 的除錯導航器中監視網路圖注意到了這一點。我在沒有呼叫的情況下實體化了一個 AVPlayer，-[play]并且網路處于負載狀態。）AVPlayer一旦單元變得可見，就不要加載，而是在單元可見之前實體化并播放內容可見時。AVPlayer

這可以通過首先讓一些資料結構保存AVPlayer專案來實作。我會推薦一個NSMutableDictionary，因為我們可以將密鑰設定為我們想要的視頻 URL，并且物件可以是AVPlayer已經加載了 URL 的物件。有兩種填充結構的方法。您可以使用類似的方法一次性加載所有內容，也可以-viewDidLoad動態加載專案-scrollViewDidScroll:以確定我們是否靠近帶有視頻的單元格。如果內容不多并且幾乎可以保證用戶觀看所有視頻，我會使用前者。如果我們要加載很多內容或者用戶可能不會觀看所有視頻，我會使用前者。這是一個帶有UITableViewController.

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

這與您提供的代碼和資訊的數量一樣具體。希望這可以幫助！

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