Gson - 从Json转换为List<> [英] Gson - Convert from Json to List<>

问题描述

我的json结果如下所示：

我的json结果如下所示：

b
$ b

  {
返回：0，
列表：[
 {
Code ：524288，
Label：TEST
}，
 {
Code：524289，
Label：TEST1
}，
 {
Code：524290，
Label：TEST2
} 
] 
} 
  

我的代码：

  protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.activity_main）; 
列表<问题> qstlist = new ArrayList< Questionaire>（）; 
 try {
 result = new RequestTask（）。execute（http：/dd.com/categories/current？owner = ccc）。get（）; 
 json = new JSONObject（result）; 
 
} catch（InterruptedException e）{
 // TODO自动生成的catch块
 e.printStackTrace（）; 
} catch（ExecutionException e）{
 // TODO自动生成的catch块
 e.printStackTrace（）; 
} catch（JSONException e）{
 // TODO自动生成的catch块
 e.printStackTrace（）; 
} 
 GsonBuilder gsonb = new GsonBuilder（）; 
 Gson gson = gsonb.create（）; 
 Type listType = new TypeToken< List< Questionaire>>（）{}。getType（）; 
 qstlist =（List< Questionaire>）gson.fromJson（result，listType）; 
问卷qst = null; 
 qst = gson.fromJson（result，Questionaire.class）; 
 
 Toast.makeText（MainActivity.this，Result+ qstlist.size（），Toast.LENGTH_SHORT）.show（）; 
 
 $ b $ class RequestTask extends AsyncTask< String，String，String> {
 
 @Override 
 protected String doInBackground（String ... uri）{ 
 HttpClient httpclient = new DefaultHttpClient（）; 
 HttpResponse响应; 
 String responseString = null; 
尝试{
 response = httpclient.execute（new HttpGet（uri [0]））; 
 StatusLine statusLine = response.getStatusLine（）; 
 if（statusLine.getStatusCode（）== HttpStatus.SC_OK）{
 ByteArrayOutputStream out = new ByteArrayOutputStream（）; 
 response.getEntity（）。writeTo（out）; 
 responseString = out.toString（）; 
 out.close（）; 
} else {
 //关闭连接。 
 response.getEntity（）。getContent（）。close（）; 
抛出新的IOException（statusLine.getReasonPhrase（））; 
} 
} catch（ClientProtocolException e）{
 // TODO Handle problems .. 
} catch（IOException e）{
 // TODO Handle problems .. 
} 
 return responseString; 
} 
 
 @Override 
 protected void onPostExecute（String result）{
 super.onPostExecute（result）; 
} 
} 
  

我的调查问卷类：



  public class Questionaire {
 String code; 
字符串标签; 
 public String getCode（）{
 return Code; 
} 
 public void setCode（String Code）{
 this.Code = Code; 
} 
 public String getLabel（）{
 return Label; 
} 
 public void setLabel（String Label）{
 this.Label = Label; 
 
 
  

以下是我无法看到的问题在这个JSON中，你得到了一个{Code，Label}对象的列表，但是在 List 一个对象的属性。

首先需要将这个列表封装在另一个对象中。
如：

  public class QuestionaireList {
 public List< Questionaire>清单; 
} 
 
 List< Questionaire> qsts = gson.fromJson（result，QuestionaireList.class）.List; 
  

i'm having an issue converting Json to List<>, I have tried different solutions but no clue

My json result looks like :

{  
   "Return":0,
   "List":[  
      {  
         "Code":524288,
         "Label":"TEST"
      },
      {  
         "Code":524289,
         "Label":"TEST1"
      },
      {  
         "Code":524290,
         "Label":"TEST2"
      }
   ]
}

My code :

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    List<Questionaire> qstlist = new ArrayList<Questionaire>();
    try {
        result = new RequestTask().execute("http:/dd.com/categories/current?owner=ccc").get();
        json = new JSONObject(result);

    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    GsonBuilder gsonb = new GsonBuilder();
    Gson gson = gsonb.create();
    Type listType = new TypeToken<List<Questionaire>>(){}.getType();
    qstlist = (List<Questionaire>) gson.fromJson(result, listType);
    Questionaire qst = null;
    qst = gson.fromJson(result,  Questionaire.class);

    Toast.makeText(MainActivity.this, "Result "+qstlist.size(), Toast.LENGTH_SHORT).show(); 
}

class RequestTask extends AsyncTask<String, String, String>{

    @Override
    protected String doInBackground(String... uri) {
        HttpClient httpclient = new DefaultHttpClient();
        HttpResponse response;
        String responseString = null;
        try {
            response = httpclient.execute(new HttpGet(uri[0]));
            StatusLine statusLine = response.getStatusLine();
            if(statusLine.getStatusCode() == HttpStatus.SC_OK){
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                response.getEntity().writeTo(out);
                responseString = out.toString();
                out.close();
            } else{
                //Closes the connection.
                response.getEntity().getContent().close();
                throw new IOException(statusLine.getReasonPhrase());
            }
        } catch (ClientProtocolException e) {
            //TODO Handle problems..
        } catch (IOException e) {
            //TODO Handle problems..
        }
        return responseString;
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
    }
}

My questionnaire class :

public class Questionaire {
    String Code;
    String Label;
    public String getCode() {
        return Code;
    }
    public void setCode(String Code) {
        this.Code = Code;
    }
    public String getLabel() {
        return Label;
    }
    public void setLabel(String Label) {
        this.Label = Label;
    }
}

Here is everything I can't see what's wrong about that

解决方案

In this JSON, you get a list of {Code, Label} objects, but in the List property of an object.

You first need to encapsulate this list in an other object. As in:

public class QuestionaireList {
  public List<Questionaire> List;
}

List<Questionaire> qsts = gson.fromJson(result,  QuestionaireList.class).List;

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