AVplayer 2-3 次后未在 ScrollView 中显示

Question

我在滚动视图中添加多个 AVPlayer 对象。这是第一次正常工作，但是当我回到以前的视图并再次返回时，我无法在 scrollView 中看到 AVPlayer 对象。

我需要作为多个 AVPlayer 的矩阵来显示我的视频的缩略图。

请尽快帮助我

提前致谢。

Answer 1

我遇到了类似的问题，经过大量搜索发现是 AVPLayerItem 对象导致了这个问题。

基本上，当 AVPlayer 项目离开屏幕时，您需要确保所有内容都已正确发布，然后在它们返回屏幕时重新创建所有内容。

作为发布过程的一部分，包括以下行：

[AVPlayer replaceCurrentItemWithPlayerItem:nil];

这对我来说是一个非常相似的问题。

Answer 2

[AVPlayer replaceCurrentItemWithPlayerItem:nil];

也解决了我无法立即释放当前玩家物品的问题。 （不能手动这样做，因为它被类保留了..）

Answer 3

以下是如何让 10 个 AVPlayer 在同一个 scrollView 中同时播放，每次滚动时：

//
//  ViewController.m
//  VideoWall
//
//  Created by James Alan Bush on 6/13/16.
//  Copyright © 2016 James Alan Bush. All rights reserved.
//

#import "ViewController.h"
#import "AppDelegate.h"

static NSString *kCellIdentifier = @"Cell Identifier";

@interface ViewController () {
    dispatch_queue_t dispatchQueueLocal;
}

@end

@implementation ViewController

- (id)initWithCollectionViewLayout:(UICollectionViewFlowLayout *)layout
{
    if (self = [super initWithCollectionViewLayout:layout])
    {
        [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:kCellIdentifier];
        dispatchQueueLocal = dispatch_queue_create( "local session queue", DISPATCH_QUEUE_CONCURRENT );
    }
    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    [self.collectionView setDataSource:self];
    [self.collectionView setContentSize:CGSizeMake(AppDelegate.sharedAppDelegate.width, AppDelegate.sharedAppDelegate.height)];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

- (void)dealloc {
    [super dealloc];
}

#pragma mark <UICollectionViewDataSource>

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}

#pragma mark - UICollectionViewDataSource

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return AppDelegate.sharedAppDelegate.assetsFetchResults.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

    UICollectionViewCell *cell = (UICollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:kCellIdentifier forIndexPath:indexPath];
    [CATransaction begin];
    [CATransaction setCompletionBlock:^{
        cell.contentView.layer.sublayers = nil;
        dispatch_release(dispatchQueueLocal);
    }];
    dispatch_retain(dispatchQueueLocal);
    dispatch_async( dispatchQueueLocal, ^{
        [self drawPlayerLayerForCell:cell atIndexPath:indexPath];
    });
    [CATransaction commit];

    return cell;
}

- (void)drawPlayerLayerForCell:(UICollectionViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
    void (^drawPlayerLayer)(UICollectionViewCell*, NSIndexPath*) = ^(UICollectionViewCell* cell, NSIndexPath* indexPath) {
        [AppDelegate.sharedAppDelegate.imageManager requestPlayerItemForVideo:AppDelegate.sharedAppDelegate.assetsFetchResults[indexPath.item] options:nil resultHandler:^(AVPlayerItem * _Nullable playerItem, NSDictionary * _Nullable info) {
            dispatch_async(dispatch_get_main_queue(), ^{
                if(![[info objectForKey:PHImageResultIsInCloudKey] boolValue]) {
                    AVPlayerLayer *playerLayer = [AVPlayerLayer playerLayerWithPlayer:[AVPlayer playerWithPlayerItem:playerItem]];
                    [playerLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
                    [playerLayer setBorderColor:[UIColor whiteColor].CGColor];
                    [playerLayer setBorderWidth:1.0f];
                    [playerLayer setFrame:cell.contentView.bounds];

                    [cell.contentView.layer addSublayer:playerLayer];
                    [(AVPlayer *)playerLayer.player play];

                } else {
                    [AppDelegate.sharedAppDelegate.imageManager requestImageForAsset:AppDelegate.sharedAppDelegate.assetsFetchResults[indexPath.item]
                                                                          targetSize:CGSizeMake(AppDelegate.sharedAppDelegate.flowLayout.itemSize.width, AppDelegate.sharedAppDelegate.flowLayout.itemSize.height)
                                                                         contentMode:PHImageContentModeAspectFill
                                                                             options:nil
                                                                       resultHandler:^(UIImage *result, NSDictionary *info) {
                                                                           dispatch_async(dispatch_get_main_queue(), ^{
                                                                               cell.contentView.layer.contents = (__bridge id)result.CGImage;
                                                                           });
                                                                       }];
                }
            });
        }];
    };
    drawPlayerLayer(cell, indexPath);
}

@end

这是 AppDelegate 实现文件：

//
//  AppDelegate.m
//  VideoWall
//
//  Created by James Alan Bush on 6/13/16.
//  Copyright © 2016 James Alan Bush. All rights reserved.
//

#import "AppDelegate.h"
#import "ViewController.h"

@implementation AppDelegate

+ (AppDelegate *)sharedAppDelegate
{
    return (AppDelegate *)[[UIApplication sharedApplication] delegate];
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch

    self.width = [[UIScreen mainScreen] bounds].size.width / 2.0;
    self.height = [[UIScreen mainScreen] bounds].size.height / 4.0;

    self.window                    = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.rootViewController = [self viewController];
    self.window.rootViewController.view = self.viewController.view;


    [self.window makeKeyAndVisible];

    return YES;
}

- (ViewController *)viewController {
    ViewController *c = self->_viewController;
    if (!c) {
        c = [[ViewController alloc] initWithCollectionViewLayout:[self flowLayout]];
        [c.view setFrame:[[UIScreen mainScreen] bounds]];
        self->_viewController = c;
    }
    return c;
}

- (UICollectionViewFlowLayout *)flowLayout {
    UICollectionViewFlowLayout *v = self->_flowLayout;
    if (!v) {
        v = [UICollectionViewFlowLayout new];
        [v setItemSize:CGSizeMake(AppDelegate.sharedAppDelegate.width, AppDelegate.sharedAppDelegate.height)];
        [v setSectionInset:UIEdgeInsetsMake(0.0, 0.0, 0.0, 0.0)];
        [v setMinimumLineSpacing:0.0];
        [v setMinimumInteritemSpacing:0.0];
        [v setEstimatedItemSize:CGSizeMake(AppDelegate.sharedAppDelegate.width, AppDelegate.sharedAppDelegate.height)];
        self->_flowLayout = v;
    }
    return v;
}

- (PHCachingImageManager *)imageManager {
    PHCachingImageManager *i = self->_imageManager;
    if (!i) {
        i = [[PHCachingImageManager alloc] init];
        self->_imageManager = i;
    }
    return i;
}

- (PHFetchResult *)assetsFetchResults {
    PHFetchResult *i = self->_assetsFetchResults;
    if (!i) {
        PHFetchResult *smartAlbums = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:PHAssetCollectionSubtypeSmartAlbumVideos options:nil];
        PHAssetCollection *collection = smartAlbums.firstObject;
        if (![collection isKindOfClass:[PHAssetCollection class]])
            return nil;
        PHFetchOptions *allPhotosOptions = [[PHFetchOptions alloc] init];
        allPhotosOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
        i = [PHAsset fetchAssetsInAssetCollection:collection options:allPhotosOptions];
        self->_assetsFetchResults = i;
    }
    return i;
}

- (void)applicationWillResignActive:(UIApplication *)application {
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

- (void)applicationWillTerminate:(UIApplication *)application {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

@end

这是您唯一需要的两个文件；没有NIB/XIB。