Question

我已经为另一个项目完成了这个任务并且它给了JSON值但是当我使用extends Fragment时这个代码显示空值。
以下是Fragment扩展类代码：

注意：我使用与之前项目相同的ServiceHandler课程

public class NewsActivity extends Fragment {

private NewsActivity activity;

//  url to get JSON
private static String url = "http://vikashparajuli.orgfree.com/zz/get_all_products.php";

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_news, container, false);
    activity = this;

    //TODO: if Internet is connected
    if(AutoLifeUtils.isConnectedToInternet(getActivity())){
        new Get_postlist().execute();       
    }else{

    }
    return rootView;
}

public  class Get_postlist extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
          }

        @Override
        protected Void doInBackground(Void... params) {
            // Creating service handler class instance
            ServiceHandler sh = new ServiceHandler();

            // Making a request to API url and getting response
            String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);

            Log.d("Response: ", "> " + jsonStr);
            return null;
        }

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

        }

}

}

这是ServiceHandler类

public class ServiceHandler {

static String response = null;
public final static int GET = 1;
public final static int POST = 2;

/**
 * Making service call
 * @url - url to make request
 * @method - http request method
 * */

public String makeServiceCall(String url, int method){

    return this.makeServiceCall(url, method, null);

}

 /**
 * Making service call
 * @url - url to make request
 * @method - http request method
 * @params - http request params
 * */

private String makeServiceCall(String url, int method, List<NameValuePair> params) {
    // TODO Auto-generated method stub
    try{
        // http client
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpEntity httpEntity = null;
        HttpResponse httpResponse = null;

        // Checking http request method type
        if (method == POST) {
            HttpPost httpPost = new HttpPost(url);
            // adding post params
            if (params != null) {
                httpPost.setEntity(new UrlEncodedFormEntity(params));  // UrlEncodedFormEntity() is useful to send HTTP POST request
            }

            httpResponse = httpClient.execute(httpPost);

        } else if (method == GET) {
            // appending params to url
            if (params != null) {
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
            }
            HttpGet httpGet = new HttpGet(url);

            httpResponse = httpClient.execute(httpGet);

        }
        httpEntity = httpResponse.getEntity();
        response = EntityUtils.toString(httpEntity);


    }catch(UnsupportedEncodingException e){
        e.printStackTrace();
    }catch(ClientProtocolException ex){
        ex.printStackTrace();
    }catch(IOException exc){
        exc.printStackTrace();
    }
    return null;
}

}

Answer 1

在makeServiceCall结束时，你有返回null;

将其更改为返回响应; ，如下所示。

private String makeServiceCall(String url, int method, List<NameValuePair> params) {

     ....
    //return null;
      return response; //this should fix your problem. 
}

从JSON返回的空数据

1 个答案: