Question

我正在学习Json Parsing我想从url中显示listview中的数据为此，我做了一些代码，但listview中的数据没有显示哪个来自url，请告诉我我在代码中犯了什么错误。

MainActivity Code

public class MainActivity extends ListActivity {

private ProgressDialog pDialog;

// URL to get Cities JSON
private static String url = "http://14.140.200.186/Hospital/get_city.php";

// JSON Node names
private static final String TAG_CITIES = "Cities";
//private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";


// Cities JSONArray
JSONArray Cities = null;

// Hashmap for ListView
ArrayList<HashMap<String, String>> citylist;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    citylist = new ArrayList<HashMap<String, String>>();



    // Calling async task to get json
    new GetCities().execute();
}

/**
 * Async task class to get json by making HTTP call
 * */
private class GetCities extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Showing progress dialog
        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Please wait...");
        pDialog.setCancelable(false);
        pDialog.show();

    }

    @Override
    protected Void doInBackground(Void... arg0) {
        // Creating service handler class instance
        ServiceHandler sh = new ServiceHandler();

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

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

        if (jsonStr != null) {
            try {
                JSONObject jsonObj = new JSONObject(jsonStr);

                // Getting JSON Array node
                Cities = jsonObj.getJSONArray(TAG_CITIES);

                // looping through All Cities
                for (int i = 0; i < Cities.length(); i++) {
                    JSONObject c = Cities.getJSONObject(i);

                    //String id = c.getString(TAG_ID);
                    String name = c.getString(TAG_NAME);


                    HashMap<String, String> Cities = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    //Cities.put(TAG_ID, id);
                    Cities.put(TAG_NAME, name);

                    // adding contact to Cities list
                    citylist.add(Cities);

                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        } else {
            Log.e("ServiceHandler", "Couldn't get any data from the url");
        }

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
        // Dismiss the progress dialog
        if (pDialog.isShowing())
            pDialog.dismiss();
        /**
         * Updating parsed JSON data into ListView
         * */
        ListAdapter adapter = new SimpleAdapter(MainActivity.this, citylist, R.layout.list_item, new String[] { TAG_NAME}, new int[] { R.id.name,});
        setListAdapter(adapter);
    }

}

第二类代码是

public class ServiceHandler {

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

public ServiceHandler() {

}

/*
 * 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
 * */
public String makeServiceCall(String url, int method,
        List<NameValuePair> params) {
    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));
            }

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

    return response;}

在activity_main中我只是在LinearLayout中有一个列表视图我还有另一个布局文件list_item，其中包含单个texview，用于显示结果..

现在请解决我的问题

Thanku

Answer 1

更改自：

     private static final String TAG_NAME = "name";

到

   private static final String TAG_NAME = "city_name";

现在有用了请检查您正在使用的服务。

Answer 2

更改自：

 private static final String TAG_NAME = "name";

要

 private static final String TAG_NAME = "city_name";

Answer 3

你可以这样做：

这

ArrayList<HashMap<String, String>> citylist;

到

ArrayList<String> citylist;

您的循环应如下所示：

for (int i = 0; i < Cities.length(); i++) {
       JSONObject c = Cities.getJSONObject(i);

        //String id = c.getString(TAG_ID);
        String name = c.getString(TAG_NAME);

         // adding contact to Cities list
         citylist.add(name);

 }

仅将ArrayList传递给适配器。

编辑2 ：

这

ListAdapter adapter = new SimpleAdapter(MainActivity.this, citylist, R.layout.list_item, new String[] { TAG_NAME}, new int[] { R.id.name,});

要

ArrayAdapter adapter = new ArrayAdapter<String>(MainActivity.this, R.layout.list_item, citylist);

希望这会对你有所帮助。

Answer 4

有几个地方可能出现问题。

首先：

} else if (method == GET) {

检查是否满足上述条件。您可能希望将GET替换为ServiceHandler.GET。

第二：

setListAdapter(adapter);

您需要编写代码才能使列表适配器可见。

Answer 5

 protected void onPostExecute(Void result) {
    super.onPostExecute(result);
    // Dismiss the progress dialog
    if (pDialog.isShowing())
        pDialog.dismiss();
    /**`enter code here`
     * Updating parsed JSON data into ListView
     * */
    ListAdapter adapter = new SimpleAdapter(MainActivity.this, citylist, R.layout.list_item, new String[] { TAG_NAME}, new int[] { R.id.name,});
    list.setAdapter(adapter);
}

希望它会对你有所帮助。

Json Data未在listview中显示

5 个答案: