對於每個AVPlayerLayer，一個AVPlayer與多個AVPlayer

Question

我正在嘗試創建類似Vine的應用程序。我有一個收集視圖，其中每個項目包含一個視圖，其中AVPlayerLayer和AVPlayer實例，並且相應avplayer已被附加到圖層。

Everythings work fine。

但是我想知道，如果我只爲集合視圖中包含的每個AVPlayerLayer使用一個AVPlayer實例，情況會好一些。如果我想顯示下一個項目，我將從當前項目的圖層中移除AVPlayer實例並將其移至下一個項目的圖層。畢竟我打電話[videoPlayer replaceCurrentItemWithPlayerItem:newItem];

也許有人知道更好的解決方案，以獲得像藤應用相同的性能。

Answer 1

以下是我收集視圖中做到了：

// 
// 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 

的AppDelegate中實現文件看起來是這樣的：

// 
// 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 

這是你唯一需要的兩個文件;沒有NIB/XIB。