android - 使用 GSON 读取 JSON 数据

Question

在过去的 4 个小时里，我查看了各种答案和其他资源，但我根本无法理解 JSON 解析。我需要一些帮助。

这是 JSON 字符串:

{
  "success": true,
  "categories": [
    {
      "category_id": "20",
      "parent_id": "0",
      "name": "Desktops",
      "image": "***",
      "href": "***",
      "categories": null
    },
    {
      "category_id": "25",
      "parent_id": "0",
      "name": "Components",
      "image": "***",
      "href": "***",
      "categories": null
    },
    {
      "category_id": "34",
      "parent_id": "0",
      "name": "MP3 Players",
      "image": "***",
      "href": "***",
      "categories": null
    }
  ]
}

这是我的数据类:

public class Data
{
    String success;
    List<Category> categories;

    // Various get/set functions and a toString override

    public class Category
    {
        String category_id;
        String name;
        String image;

        // Various get/set functions
    }
}

这是我试图阅读的地方:

private class GetJson extends AsyncTask<String, Void, String>
    {
        @Override
        protected String doInBackground(String... params)
        {
            String results = "Fail";
            URL url = null;
            try
            {
                url = new URL("***");
            }

            catch (MalformedURLException e)
            {
                e.printStackTrace();
            }

            URLConnection ucon = null;

            try
            {
                ucon = url.openConnection();
                InputStream is = ucon.getInputStream();
                BufferedReader bufferedReader = new BufferedReader( new InputStreamReader(is));
                String line = "";
                String result = "";
                while((line = bufferedReader.readLine()) != null)
                {
                    result += line;
                }

                Data data = new Gson().fromJson(result, Data.class);

                result = data.toString();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }

            return results;
        }

        protected void onPostExecute(String result)
        {
            Toast.makeText(con, result, Toast.LENGTH_SHORT);
        }
    }

我在堆栈跟踪中根本没有得到任何信息。我检查了亚行几次。一切似乎都正常，但我没有收到 Toast 或错误消息。

我做错了什么？

Answer 1

你忘了展示你的Toast

试试这个

Toast.makeText(con, result, Toast.LENGTH_SHORT).show();

哈哈

进一步

    Data data = new Gson().fromJson(result, Data.class);

    result = data.toString();
    return result; // need return this

否则总是得到"Fail"