如何将视频从 ALAsset 显示到 UICollectionview Cell

Posted 2023-02-23

【中文标题】如何将视频从 ALAsset 显示到 UICollectionview Cell

【英文标题】：How to display video from ALAsset to UICollectionview Cell

【发布时间】：2014-09-02 12:06:31

【问题描述】：

我尝试使用此代码将所有 ALAsset 创建的视频添加到我的应用程序中，然后播放它，但视频没有显示在 UICollectionView 中，所以这是可能的。 感谢高级。

我在 View Did Load 中编写了这段代码。

_collectionView.dataSource=self;
_collectionView.delegate=self;
[self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cellIdentifier"];

_allVideos = [[NSMutableArray alloc] init];
ALAssetsLibrary *assetLibrary = [[ALAssetsLibrary alloc] init];

[assetLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop)
 
     if (group)
     
         [group setAssetsFilter:[ALAssetsFilter allVideos]];
         [group enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop)
          
              if (asset)
              
                  _dic = [[NSMutableDictionary alloc] init];
                  ALAssetRepresentation *defaultRepresentation = [asset defaultRepresentation];
                  NSString *uti = [defaultRepresentation UTI];
                  NSURL  *videoURL = [[asset valueForProperty:ALAssetPropertyURLs] valueForKey:uti];
                  NSString *title = [NSString stringWithFormat:@"video %d", arc4random()%100];
                  UIImage *image = [self imageFromVideoURL:videoURL];
                  [_dic setValue:image forKey:@"image"];
                  [_dic setValue:title forKey:@"name"];
                  [_dic setValue:videoURL forKey:@"url"];
                  //[_allVideos addObject:_dic];
                  [_allVideos addObject:asset];
                  [_collectionView reloadData];
              
          ];
     
 
                          failureBlock:^(NSError *error)

    NSLog(@"error enumerating AssetLibrary groups %@\n", error);
];

一种方法是

 - (UIImage *)imageFromVideoURL:(NSURL*)videoURL

// result
UIImage *image = nil;

// AVAssetImageGenerator
AVAsset *asset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];;
AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
imageGenerator.appliesPreferredTrackTransform = YES;

// calc midpoint time of video
Float64 durationSeconds = CMTimeGetSeconds([asset duration]);
CMTime midpoint = CMTimeMakeWithSeconds(durationSeconds/2.0, 600);

// get the image from
NSError *error = nil;
CMTime actualTime;
CGImageRef halfWayImage = [imageGenerator copyCGImageAtTime:midpoint actualTime:&actualTime error:&error];

if (halfWayImage != NULL)

    // CGImage to UIImage
    image = [[UIImage alloc] initWithCGImage:halfWayImage];
    [_dic setValue:image forKey:@"name"];
    NSLog(@"Values of dictionary==>%@", _dic);
    NSLog(@"Videos Are:%@",videoURL);
    CGImageRelease(halfWayImage);

return image;

我在 UICollectionView 中写了这个

 - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section

return _allVideos.count;


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

UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cellIdentifier" forIndexPath:indexPath];

NSLog(@"allvideo %@", _allVideos);
ALAsset *alasset = [_allVideos objectAtIndex:indexPath.row];
UIImageView *imageview=[[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 80, 80)];
imageview.image = [UIImage imageWithCGImage:alasset.thumbnail];
[cell.contentView addSubview:imageview];

return cell;

【参考方案1】：

在 ViewDidLoad 中编写代码

assets = [[NSMutableArray alloc] init];
_library = [[ALAssetsLibrary alloc] init];

UIImage *viewImage;

[_library writeImageToSavedPhotosAlbum:[viewImage CGImage] orientation:(ALAssetOrientation)[viewImage imageOrientation] completionBlock:^(NSURL *assetURL, NSError *error)
    if (error) 
        NSLog(@"error");
     else 
        NSLog(@"url %@", assetURL);


    
];
[_library enumerateGroupsWithTypes:ALAssetsGroupAll  usingBlock:^(ALAssetsGroup *group, BOOL *stop)

    if (group != NULL) 

        [group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop)


            if ([[result valueForProperty:ALAssetsGroupPropertyName] isEqual:@"VideoMaker"])  
                NSLog(@"asset: %@", result);
                [assets addObject:result];
            

        ];
    

    [self.collectionView reloadData];
    //[self.activity stopAnimating];
    //[self.activity setHidden:YES];


                     failureBlock:^(NSError *error)

                         NSLog(@"failure"); ];` `

在这个 assets 中是 NSMutableArray 而 library 是 ALAssetLibrary。

在 UIcollectionviewcell 单元格中的 rowAtIndexpath 方法

-(VideoCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath

    VideoCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"CELL" forIndexPath:indexPath];
    ALAsset *asset = [assets objectAtIndex:indexPath.row];
    [cell.videoImageView setImage:[UIImage imageWithCGImage:[asset thumbnail]]];
    return cell;