每个AVPlayer对应一个AVPlayer与多个AVPlayerLayer

Question

我正在尝试创建像Vine这样的应用程序。我有一个集合视图，其中每个项目都包含一个带有AVPlayerLayer和AVPlayer实例的视图，相应地，avplayer已附加到层。

一切都很好。

但是我想知道，如果我对集合视图中包含的每个AVPlayerLayer只使用一个AVPlayer实例，可能会更好。如果我想显示下一个项目，我将从当前项目的层中删除AVPlayer实例，并将其移动到下一个项目的层中。毕竟我给[videoPlayer replaceCurrentItemWithPlayerItem:newItem];打电话

也许有人知道更好的解决方案来获得像Vine应用程序一样的性能。

Answer 1

下面是我在一个集合视图中是如何做到的：

//
//  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

AppDelegate实现文件如下所示：

//
//  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。