Simple parse JSON from URL on Android and display in listview

Question

I'm trying to parse a JSON result fetched from a URL in my Android app...

I have tried a few examples on the Internet, but can't get it to work. The JSON data looks like this:

[
    {
        "city_id": "1",
        "city_name": "Noida"
    },
    {
        "city_id": "2",
        "city_name": "Delhi"
    },
    {
        "city_id": "3",
        "city_name": "Gaziyabad"
    },
    {
        "city_id": "4",
        "city_name": "Gurgaon"
    },
    {
        "city_id": "5",
        "city_name": "Gr. Noida"
    }
]

What's the simplest way to fetch the URL and parse the JSON data show it in the listview

Answer 1

You could use AsyncTask , you'll have to customize to fit your needs, but something like the following

---

Async task has three primary methods:

1. onPreExecute() - most commonly used for setting up and starting a progress dialog

2. doInBackground() - Makes connections and receives responses from the server (Do NOT try to assign response values to GUI elements, this is a common mistake, that cannot be done in a background thread).

3. onPostExecute() - Here we are out of the background thread, so we can do user interface manipulation with the response data, or simply assign the response to specific variable types.

---

First we will start the class, initialize a String to hold the results outside of the methods but inside the class, then run the onPreExecute() method setting up a simple progress dialog.

class MyAsyncTask extends AsyncTask<String, String, Void> {

    private ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
    InputStream inputStream = null;
    String result = ""; 

    protected void onPreExecute() {
        progressDialog.setMessage("Downloading your data...");
        progressDialog.show();
        progressDialog.setOnCancelListener(new OnCancelListener() {
            public void onCancel(DialogInterface arg0) {
                MyAsyncTask.this.cancel(true);
            }
        });
    }

Then we need to set up the connection and how we want to handle the response:

    @Override
    protected Void doInBackground(String... params) {

        String url_select = "http://yoururlhere.com";

        ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();

        try {
            // Set up HTTP post

            // HttpClient is more then less deprecated. Need to change to URLConnection
            HttpClient httpClient = new DefaultHttpClient();

            HttpPost httpPost = new HttpPost(url_select);
            httpPost.setEntity(new UrlEncodedFormEntity(param));
            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();

            // Read content & Log
            inputStream = httpEntity.getContent();
        } catch (UnsupportedEncodingException e1) {
            Log.e("UnsupportedEncodingException", e1.toString());
            e1.printStackTrace();
        } catch (ClientProtocolException e2) {
            Log.e("ClientProtocolException", e2.toString());
            e2.printStackTrace();
        } catch (IllegalStateException e3) {
            Log.e("IllegalStateException", e3.toString());
            e3.printStackTrace();
        } catch (IOException e4) {
            Log.e("IOException", e4.toString());
            e4.printStackTrace();
        }
        // Convert response to string using String Builder
        try {
            BufferedReader bReader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"), 8);
            StringBuilder sBuilder = new StringBuilder();

            String line = null;
            while ((line = bReader.readLine()) != null) {
                sBuilder.append(line + "\n");
            }

            inputStream.close();
            result = sBuilder.toString();

        } catch (Exception e) {
            Log.e("StringBuilding & BufferedReader", "Error converting result " + e.toString());
        }
    } // protected Void doInBackground(String... params)

Lastly, here we will parse the return, in this example it was a JSON Array and then dismiss the dialog:

    protected void onPostExecute(Void v) {
        //parse JSON data
        try {
            JSONArray jArray = new JSONArray(result);    
            for(i=0; i < jArray.length(); i++) {

                JSONObject jObject = jArray.getJSONObject(i);

                String name = jObject.getString("name");
                String tab1_text = jObject.getString("tab1_text");
                int active = jObject.getInt("active");

            } // End Loop
            this.progressDialog.dismiss();
        } catch (JSONException e) {
            Log.e("JSONException", "Error: " + e.toString());
        } // catch (JSONException e)
    } // protected void onPostExecute(Void v)
} //class MyAsyncTask extends AsyncTask<String, String, Void>

Answer 2

I would suggest using the JSONParser class. It's very easy to use.

public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

// function get json from url
// by making HTTP POST or GET method
public JSONObject makeHttpRequest(String url, String method,
        List<NameValuePair> params) throws IOException {

    // Making HTTP request
    try {

        // check for request method
        if(method == "POST"){
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);

            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        }else if(method == "GET"){
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient(httpParameters);
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }           


    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (Exception ex) {
        Log.d("Networking", ex.getLocalizedMessage());
        throw new IOException("Error connecting");
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}

Then in your application, create an instance of this class. You may want to pass the constructor 'GET' or 'POST' if desired.

public JSONParser jsonParser = new JSONParser();

try {

    // Building Parameters ( you can pass as many parameters as you want)
    List<NameValuePair> params = new ArrayList<NameValuePair>();

    params.add(new BasicNameValuePair("name", name));
    params.add(new BasicNameValuePair("age", 25));

    // Getting JSON Object
    JSONObject json = jsonParser.makeHttpRequest(YOUR_URL, "POST", params);
} catch (JSONException e) {
    e.printStackTrace();
}

Answer 3

JSONObject(html).getString("name");

如何获取html字符串： 使用android发出HTTP请求

Answer 4

Since HttpClient is deprecated, here 'sa good example of how to do it using URLConnection :

Create one class the class name like HttpHandler.java . In below I have include the HttpHandler.java file.

 import android.util.Log; import java.io.BufferedInputStream; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.ProtocolException; import java.net.URL; public class HttpHandler { private static final String TAG = HttpHandler.class.getSimpleName(); public HttpHandler() { } public String makeServiceCall(String reqUrl) { String response = null; try { URL url = new URL(reqUrl); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); // read the response InputStream in = new BufferedInputStream(conn.getInputStream()); response = convertStreamToString(in); } catch (MalformedURLException e) { Log.e(TAG, "MalformedURLException: " + e.getMessage()); } catch (ProtocolException e) { Log.e(TAG, "ProtocolException: " + e.getMessage()); } catch (IOException e) { Log.e(TAG, "IOException: " + e.getMessage()); } catch (Exception e) { Log.e(TAG, "Exception: " + e.getMessage()); } return response; } private String convertStreamToString(InputStream is) { BufferedReader reader = new BufferedReader(new InputStreamReader(is)); StringBuilder sb = new StringBuilder(); String line; try { while ((line = reader.readLine()) != null) { sb.append(line).append('\\n'); } } catch (IOException e) { e.printStackTrace(); } finally { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } return sb.toString(); } } 

Now, you have to open activity.main.xml make the list of JSON parsing data's. The activity_main.xml code like,

  <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="in.vetbossel.androidjsonparse.MainActivity"> <ListView android:id="@+id/list" android:layout_width="fill_parent" android:layout_height="wrap_content" /> </RelativeLayout> Hereafter create one xml file, the name is `list_item.xml` used for list the all values from *JSON*. The code is, <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="vertical" android:padding="@dimen/activity_horizontal_margin"> <TextView android:id="@+id/name" android:layout_width="fill_parent" android:layout_height="wrap_content" android:paddingBottom="2dip" android:paddingTop="6dip" android:textColor="#3498db" android:textSize="16sp" android:textStyle="bold" /> <TextView android:id="@+id/email" android:layout_width="fill_parent" android:layout_height="wrap_content" android:paddingBottom="2dip" android:textColor="#16a085" android:textStyle="bold" /> <TextView android:id="@+id/mobile" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#e74c3c" android:textStyle="bold" /> </LinearLayout> 

Parsing JSON in MainActivity

Get the value of JSON , to make the Http call for fetch the JSON value. There are many library file will be there in fetch the JSON values like, volley library & retrofit library etc. The volley library and retrofit library commonly used for parse the JSON value. Finally, the MainActivity.java code like,

 import android.app.ProgressDialog; import android.os.AsyncTask; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.util.Log; import android.widget.ListAdapter; import android.widget.ListView; import android.widget.SimpleAdapter; import android.widget.Toast; import org.json.JSONArray; import org.json.JSONException; import org.json.JSONObject; import java.util.ArrayList; import java.util.HashMap; public class MainActivity extends AppCompatActivity { private String TAG = MainActivity.class.getSimpleName(); private ProgressDialog pDialog; private ListView lv; // URL to get contacts JSON private static String url = "http://demos.vetbossel.in/ajson/sample"; ArrayList<HashMap<String, String>> contactList; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); contactList = new ArrayList<>(); lv = (ListView) findViewById(R.id.list); new GetContacts().execute(); } /** * Async task class to get json by making HTTP call */ private class GetContacts 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) { HttpHandler sh = new HttpHandler(); // Making a request to url and getting response String jsonStr = sh.makeServiceCall(url); Log.e(TAG, "Response from url: " + jsonStr); if (jsonStr != null) { try { JSONObject jsonObj = new JSONObject(jsonStr); // Getting JSON Array node JSONArray contacts = jsonObj.getJSONArray("contacts"); // looping through All Contacts for (int i = 0; i < contacts.length(); i++) { JSONObject c = contacts.getJSONObject(i); String id = c.getString("id"); String name = c.getString("name"); String email = c.getString("email"); String address = c.getString("address"); String gender = c.getString("gender"); // Phone node is JSON Object JSONObject phone = c.getJSONObject("phone"); String mobile = phone.getString("mobile"); String home = phone.getString("home"); String office = phone.getString("office"); // tmp hash map for single contact HashMap<String, String> contact = new HashMap<>(); // adding each child node to HashMap key => value contact.put("id", id); contact.put("name", name); contact.put("email", email); contact.put("mobile", mobile); // adding contact to contact list contactList.add(contact); } } catch (final JSONException e) { Log.e(TAG, "Json parsing error: " + e.getMessage()); runOnUiThread(new Runnable() { @Override public void run() { Toast.makeText(getApplicationContext(), "Json parsing error: " + e.getMessage(), Toast.LENGTH_LONG) .show(); } }); } } else { Log.e(TAG, "Couldn't get json from server."); runOnUiThread(new Runnable() { @Override public void run() { Toast.makeText(getApplicationContext(), "Couldn't get json from server. Check LogCat for possible errors!", Toast.LENGTH_LONG) .show(); } }); } 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, contactList, R.layout.list_item, new String[]{"name", "email", "mobile"}, new int[]{R.id.name, R.id.email, R.id.mobile}); lv.setAdapter(adapter); } } } 

And dont forget to add internet permission to your manifest file:

<uses-permission android:name="android.permission.INTERNET" />

Answer 5

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;

public class GetJsonFromUrl {
    String url = null;

    public GetJsonFromUrl(String url) {
        this.url = url;
    }

    public String GetJsonData() {
        try {
            URL Url = new URL(url);
            HttpURLConnection connection = (HttpURLConnection) Url.openConnection();
            InputStream is = connection.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(is));
            StringBuilder sb = new StringBuilder();
            String line;
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
            line = sb.toString();
            connection.disconnect();
            is.close();
            sb.delete(0, sb.length());
            return line;
        } catch (Exception e) {
            return null;
        }
    }
} 

and this class use for post data

import android.util.Log;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

import javax.net.ssl.HttpsURLConnection;

/**
 * Created by user on 11/2/16.
 */
public class sendDataToServer {
   public String postdata(String requestURL,HashMap<String,String> postDataParams){
        try {
            String response = "";
            URL url = new URL(requestURL);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(15000);
            conn.setConnectTimeout(15000);
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);
            OutputStream os = conn.getOutputStream();
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(os, "UTF-8"));
            writer.write(getPostDataString(postDataParams));

            writer.flush();
            writer.close();
            os.close();
            String line;
            BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream()));
            while ((line=br.readLine()) != null) {
                response+=line;
            }
            Log.d("test", response);
            return response;
        }catch (Exception e){
            return e.toString();
        }
    }

    public String postjson(String url,String json){
        try {

            URL obj = new URL(url);
            HttpURLConnection con= (HttpURLConnection) obj.openConnection();

            //add reuqest header
            con.setRequestMethod("POST");
            con.setRequestProperty("Accept", "application/json");
            String urlParameters = ""+json;

            // Send post request
            con.setDoOutput(true);
            con.setDoInput(true);
            con.setRequestProperty("Content-Type", "application/json");
            OutputStreamWriter wr = new OutputStreamWriter(con.getOutputStream());
            wr.write(urlParameters);
            wr.flush();
            wr.close();

            int responseCode = con.getResponseCode();
            System.out.println("\nSending 'POST' request to URL : " + url);
            System.out.println("Post parameters : " + urlParameters);
            System.out.println("Response Code : " + responseCode);

            BufferedReader in = new BufferedReader(
                    new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();

            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();

            //print result
            System.out.println(response.toString());
            return response.toString();
        }catch(Exception e){

            return e.toString();
        }
    }

    private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException {
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for(Map.Entry<String, String> entry : params.entrySet()){
            if (first)
                first = false;
            else
                result.append("&");

            result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
        }
        return result.toString();
    }

   /* public String postdata(String url) {
    }*/
}

Answer 6

try as:

 // your get json request to server.. 
 HttpResponse response = httpClient.execute(httpPost);
 HttpEntity entity = response.getEntity();

 if(entity != null){
    JSONObject respObject = new JSONObject(EntityUtils.toString(entity));
    String active = respObject.getString("active");   
    String name = respObject.getString("name");  
    String tab1_text = respObject.getString("tab1_text");  
    //.... 
  }
else{
       //Do something here...
    }

see this example for Getting and parsing json response from server :

http://adblogcat.com/parse-json-data-from-a-web-server-and-display-on-listview/

Answer 7

HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet();
request.setURI(new URI(url));
HttpResponse response = client.execute(request);
BufferedReader in = new BufferedReader(new InputStreamReader(response
        .getEntity().getContent()));
String line = "";

while ((line = in.readLine()) != null) {

    JSONObject jObject = new JSONObject(line);

    if (jObject.has("name")) {

        String temp = jObject.getString("name");
        Log.e("name",temp);

    }

}