如何从 Android 中的 Facebook Graph API 检索图像

Question

我已从请求 GET 的 facebook graph api 检索到 json 数据

https://graph.facebook.com/YOUR_PAGE_ID/albums?fields=name,photos{picture}&access_token=YOUR_ACCESS_TOKEN/

Json数据如下：

{
  "data": [
    {
      "name": "School Kids",
      "photos": {
        "data": [
          {
            "picture": "https://scontent.xx.fbcdn.net/v/t1.0-0/s130x130/15267641_1789056354665765_6384898034258459703_n.jpg?oh=44daa7be0ac1878e769bc16df444bd0a&oe=58B29329",
            "id": "1789056354665765"
          },
          {
            "picture": "https://scontent.xx.fbcdn.net/v/t1.0-0/s130x130/15356660_1789056361332431_834718824553815513_n.jpg?oh=69b3f1b1697808b87eed1e3053a67aaf&oe=58B735FB",
            "id": "1789056361332431"
          },
          {
            "picture": "https://scontent.xx.fbcdn.net/v/t1.0-0/s130x130/15356635_1789056401332427_1231396155404307815_n.jpg?oh=3de32d320ac6762adc0dbf8b1ef64e0e&oe=58F69648",
            "id": "1789056401332427"
          },
          {
            "picture": "https://scontent.xx.fbcdn.net/v/t1.0-0/s130x130/15380574_1789337074637693_1697389498501034556_n.jpg?oh=ddd57d119882b47172af689abde20cfb&oe=58F15477",
            "id": "1789337074637693"
          }
        ],
        "paging": {
          "cursors": {
            "before": "MTc4OTA1NjM1NDY2NTc2NQZDZD",
            "after": "MTc4OTMzNzA3NDYzNzY5MwZDZD"
          }
        }
      },
      "id": "1789056284665772"
    },
    {
      "name": "Cover Photos",
      "photos": {
        "data": [
          {
            "picture": "https://scontent.xx.fbcdn.net/v/t1.0-0/s130x130/14519945_1762073987364002_4539899568406717011_n.jpg?oh=fc8c02e9ced0839eea22d08859b964d0&oe=58BC80D4",
            "id": "1762073987364002"
          }
        ],
        "paging": {
          "cursors": {
            "before": "MTc2MjA3Mzk4NzM2NDAwMgZDZD",
            "after": "MTc2MjA3Mzk4NzM2NDAwMgZDZD"
          }
        }
      },
      "id": "1762074137363987"
    },
    {
      "name": "Profile Pictures",
      "photos": {
        "data": [
          {
            "picture": "https://scontent.xx.fbcdn.net/v/t1.0-0/p130x130/14495327_1762072887364112_1611299743258720903_n.jpg?oh=ae87944069fd154e817468a38d9cb4a1&oe=58AE8D02",
            "id": "1762072887364112"
          }
        ],
        "paging": {
          "cursors": {
            "before": "MTc2MjA3Mjg4NzM2NDExMgZDZD",
            "after": "MTc2MjA3Mjg4NzM2NDExMgZDZD"
          }
        }
      },
      "id": "1762072884030779"
    }
  ],
  "paging": {
    "cursors": {
      "before": "MTc4OTA1NjI4NDY2NTc3MgZDZD",
      "after": "MTc2MjA3Mjg4NDAzMDc3OQZDZD"
    }
  }
}

我想要从这些数据中获取图像和专辑名称并在 android 的 GridView 中显示。

我尝试解析这些数据是来自此方法的 json 对象

public async void downloadJsonFeedAsync(string url) {
  var httpClient = new HttpClient();
  Task < string > contentsTask = httpClient.GetStringAsync(url);

  // await! control returns to the caller and the task continues to run on another thread
  string content = await contentsTask;
  Console.Out.WriteLine("Response Body: \r\n {0}", content);

  //Convert string to JSON object
  mObject = Newtonsoft.Json.JsonConvert.DeserializeObject < ImageGridItemRootObject > (content);

  //Update listview
  Activity.RunOnUiThread(() => {
    mGridView.Adapter = new PhotoGalleryGridViewAdapter(this.Activity, Resource.Layout.PhotoGalleryGridItemView, mObject.data);
    mProgressBar.Visibility = ViewStates.Gone;
  });
}

// 根对象

public class ImageGridItemRootObject
    {
        public string name { get; set; }
        public string photos { get; set; }
        public List<ImageGridItem> data { get; set; }

    }

//ImageGridItem

public class ImageGridItem
    {
        private string picture;
        private string id;

        public ImageGridItem():base()
        {

        }
        public string Picture
        {
            get { return picture; }
            set { picture = value; }
        }

        public string Id
        {
            get { return id; }
            set { id = value; }
        }
    }

问题是我得到了 Picture Null。我想知道哪个是 jSon Object，哪个是 jSon Array，以便我可以格式化 rootObject 以检索 jSon Array。

提前谢谢你。

Answer 1

如果您获取返回的 JSON 并使用 Edit > Paste Special > Paste JSON as 作为 Visual Studio 中的类，您将获得以下类：

public class Rootobject
{
    public Datum[] data { get; set; }
    public Paging paging { get; set; }
}

public class Paging
{
    public Cursors cursors { get; set; }
}

public class Cursors
{
    public string before { get; set; }
    public string after { get; set; }
}

public class Datum
{
    public string name { get; set; }
    public Photos photos { get; set; }
    public string id { get; set; }
}

public class Photos
{
    public Datum1[] data { get; set; }
    public Paging1 paging { get; set; }
}

public class Paging1
{
    public Cursors1 cursors { get; set; }
}

public class Cursors1
{
    public string before { get; set; }
    public string after { get; set; }
}

public class Datum1
{
    public string picture { get; set; }
    public string id { get; set; }
}

看起来您的类与 JSON 不匹配，这意味着反序列化器不知道如何处理您的合同中不匹配的键/值。

调整你的类以更好地匹配上面的类，它会使用图像 url 反序列化。