Simple parse JSON from URL on Android and display in listview
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
You could use AsyncTask, you'll have to customize to fit your needs, but something like the following
Async task has three primary methods:
onPreExecute()- most commonly used for setting up and starting a progress dialogdoInBackground()- 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).-
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>
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();
}
JSONObject(html).getString("name");
How to get the html String:
Make an HTTP request with android
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) {
}*/
}