11

在 Objective-C 中，有一个照片框架又名 PhotoKit，它使 iOS 开发人员能够访问 iPhone 和 iPad 上的照片库，并检索图片/视频及其元数据。

Mac 开发人员将如何执行类似的任务？看来 PhotoKit 仅在 iOS 8.0 中可用。是否有相当于 Mac OS X 的照片框架？

4

3 回答 3

11

媒体库框架是去的地方。

用法：

@import MediaLibrary;

- (void) awakeFromNib
{
  NSDictionary *options = @{
     MLMediaLoadSourceTypesKey: @(MLMediaSourceTypeImage),
     MLMediaLoadIncludeSourcesKey: @[MLMediaSourcePhotosIdentifier]
  };

  MLMediaLibrary *mediaLibrary = [[MLMediaLibrary alloc] initWithOptions:options];
  self.mediaLibrary = mediaLibrary;

  [mediaLibrary addObserver:self
                 forKeyPath:@"mediaSources"
                    options:0
                    context:(__bridge void *)@"mediaLibraryLoaded"];

  [mediaLibrary mediaSources]; // returns nil and starts asynchronous loading
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object 
                        change:(NSDictionary *)change context:(void *)context
{
   if (context == (__bridge void *)@"mediaLibraryLoaded") {
      // Media Library is loaded now, we can access mediaSources
      MLMediaSource *mediaSource = [self.mediaLibrary.mediaSources objectForKey:@"com.apple.Photos"];
   }
}

该库背后的概念是您必须请求它读取对象的属性，该属性返回一个空引用。然后，您使用 key-value-observer 订阅此属性，并等待它加载。然后你可以用同样的原理检索下一个孩子等等......

于 2015-05-10T19:40:43.857 回答
4

基于 Pierre F 的回答，我扩展了用于显示所有照片的 url 的代码：

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {

    NSDictionary *options = @{
                              MLMediaLoadSourceTypesKey: @(MLMediaSourceTypeImage),
                              MLMediaLoadIncludeSourcesKey: @[MLMediaSourcePhotosIdentifier]
                              };

    self.mediaLibrary = [[MLMediaLibrary alloc] initWithOptions:options];

    [self.mediaLibrary addObserver:self
                        forKeyPath:@"mediaSources"
                           options:0
                           context:(__bridge void *)@"mediaLibraryLoaded"];

    [self.mediaLibrary.mediaSources objectForKey:MLMediaSourcePhotosIdentifier];
}


- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
                        change:(NSDictionary *)change context:(void *)context
{
     MLMediaSource *mediaSource = [self.mediaLibrary.mediaSources objectForKey:MLMediaSourcePhotosIdentifier];

    if (context == (__bridge void *)@"mediaLibraryLoaded")
    {
        [mediaSource addObserver:self
                            forKeyPath:@"rootMediaGroup"
                               options:0
                               context:(__bridge void *)@"rootMediaGroupLoaded"];

        [mediaSource rootMediaGroup];
    }
    else if (context == (__bridge void *)@"rootMediaGroupLoaded")
    {
        MLMediaGroup *albums = [mediaSource mediaGroupForIdentifier:@"TopLevelAlbums"];

        for (MLMediaGroup *album in albums.childGroups)
        {
            NSString *albumIdentifier = [album.attributes objectForKey:@"identifier"];

            if ([albumIdentifier isEqualTo:@"allPhotosAlbum"])
            {
                self.allPhotosAlbum = album;

                [album addObserver:self
                        forKeyPath:@"mediaObjects"
                           options:0
                           context:@"mediaObjects"];

                [album mediaObjects];

                break;
            }
        }
    }
    else if (context == (__bridge void *)@"mediaObjects")
    {
        NSArray * mediaObjects = self.allPhotosAlbum.mediaObjects;

        for(MLMediaObject * mediaObject in mediaObjects)
        {
            NSURL * url  = mediaObject.URL;

            NSLog(url.path);
        }
    }
}
于 2016-01-21T16:47:49.817 回答
1

虽然这不是一个正式记录的API，但 w0lfschild发布了Apple macOS 的 PhotoKit 框架的标头。该 API 看起来与 iOS 非常相似，所以也许您可以仅使用 iOS 文档来弄清楚。除了 MediaLibrary 框架之外，您还可以对库进行更改。

于 2019-01-22T09:39:29.850 回答