Tuesday, July 23, 2013

[android help] Android: I have the error of parsing a JSON object to String in Android


Android: I have the error of parsing a JSON object to String in Android



I wanted to learn about Android in connection with php and I found a code in this web: demo web So, the code works perfectly fine, but when I want to do the select it says that there is an error when parsing the JSON Object into String. I will give you the 3 parts of the code. You can see all the code in the website from abobe.


Here you have the two codes:



public class JSONParser {

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

// constructor
public JSONParser() {

}


public JSONObject getJSONFromUrl(final String url) {

// Making HTTP request
try {
// Construct the client and the HTTP request.
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);

// Execute the POST request and store the response locally.
HttpResponse httpResponse = httpClient.execute(httpPost);
// Extract data from the response.
HttpEntity httpEntity = httpResponse.getEntity();
// Open an inputStream with the data content.
is = httpEntity.getContent();

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

try {
// Create a BufferedReader to parse through the inputStream.
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
// Declare a string builder to help with the parsing.
StringBuilder sb = new StringBuilder();
// Declare a string to store the JSON object data in string form.
String line = null;

// Build the string until null.
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}

// Close the input stream.
is.close();
// Convert the string builder data to an actual string.
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}

// Try to 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 the JSON Object.
return jObj;

}


// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
List params) {

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

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;

}
}


The other class:



package com.example.mysqltest;

import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;

public class ReadComments extends ListActivity {

// Progress Dialog
private ProgressDialog pDialog;

// php read comments script

// localhost :
// testing on your device
// put your local ip instead, on windows, run CMD > ipconfig
// or in mac's terminal type ifconfig and look for the ip under en0 or en1
// private static final String READ_COMMENTS_URL =
// "http://xxx.xxx.x.x:1234/webservice/comments.php";

// testing on Emulator:
private static final String READ_COMMENTS_URL = "http://10.0.2.2/webservice/comments.php";

// testing from a real server:
// private static final String READ_COMMENTS_URL =
// "http://www.mybringback.com/webservice/comments.php";

// JSON IDS:
private static final String TAG_SUCCESS = "success";
private static final String TAG_TITLE = "title";
private static final String TAG_POSTS = "posts";
private static final String TAG_POST_ID = "post_id";
private static final String TAG_USERNAME = "username";
private static final String TAG_MESSAGE = "message";
// it's important to note that the message is both in the parent branch of
// our JSON tree that displays a "Post Available" or a "No Post Available"
// message,
// and there is also a message for each individual post, listed under the
// "posts"
// category, that displays what the user typed as their message.

// An array of all of our comments
private JSONArray mComments = null;
// manages all of our comments in a list.
private ArrayList> mCommentList;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// note that use read_comments.xml instead of our single_post.xml
setContentView(R.layout.read_comments);
}

@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
// loading the comments via AsyncTask
new LoadComments().execute();
}

public void addComment(View v) {
Intent i = new Intent(ReadComments.this, AddComment.class);
startActivity(i);
}

/**
* Retrieves recent post data from the server.
*/
public void updateJSONdata() {

// Instantiate the arraylist to contain all the JSON data.
// we are going to use a bunch of key-value pairs, referring
// to the json element name, and the content, for example,
// message it the tag, and "I'm awesome" as the content..

mCommentList = new ArrayList>();

// Bro, it's time to power up the J parser
JSONParser jParser = new JSONParser();
// Feed the beast our comments url, and it spits us
// back a JSON object. Boo-yeah Jerome.
JSONObject json = jParser.getJSONFromUrl(READ_COMMENTS_URL);

// when parsing JSON stuff, we should probably
// try to catch any exceptions:
try {

// I know I said we would check if "Posts were Avail." (success==1)
// before we tried to read the individual posts, but I lied...
// mComments will tell us how many "posts" or comments are
// available
mComments = json.getJSONArray(TAG_POSTS);

// looping through all posts according to the json object returned
for (int i = 0; i < mComments.length(); i++) {
JSONObject c = mComments.getJSONObject(i);

// gets the content of each tag
String title = c.getString(TAG_TITLE);
String content = c.getString(TAG_MESSAGE);
String username = c.getString(TAG_USERNAME);

// creating new HashMap
HashMap map = new HashMap();

map.put(TAG_TITLE, title);
map.put(TAG_MESSAGE, content);
map.put(TAG_USERNAME, username);

// adding HashList to ArrayList
mCommentList.add(map);

// annndddd, our JSON data is up to date same with our array
// list
}

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

/**
* Inserts the parsed data into the listview.
*/
private void updateList() {
// For a ListActivity we need to set the List Adapter, and in order to do
//that, we need to create a ListAdapter. This SimpleAdapter,
//will utilize our updated Hashmapped ArrayList,
//use our single_post xml template for each item in our list,
//and place the appropriate info from the list to the
//correct GUI id. Order is important here.
ListAdapter adapter = new SimpleAdapter(this, mCommentList,
R.layout.single_post, new String[] { TAG_TITLE, TAG_MESSAGE,
TAG_USERNAME }, new int[] { R.id.title, R.id.message,
R.id.username });

// I shouldn't have to comment on this one:
setListAdapter(adapter);

// Optional: when the user clicks a list item we
//could do something. However, we will choose
//to do nothing...
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener() {

@Override
public void onItemClick(AdapterView parent, View view,
int position, long id) {

// This method is triggered if an item is click within our
// list. For our example we won't be using this, but
// it is useful to know in real life applications.

}
});
}

public class LoadComments extends AsyncTask {

@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(ReadComments.this);
pDialog.setMessage("Loading Comments...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}

@Override
protected Boolean doInBackground(Void... arg0) {
updateJSONdata();
return null;

}

@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
pDialog.dismiss();
updateList();
}
}
}


Here you have the php code:



*/
require("config.inc.php");


$query = "Select post_id,username,title,message FROM comments";


try {
$stmt = $db->prepare($query);
$result = $stmt->execute($query_params);

}
catch (PDOException $ex) {
$response["success"] = 0;
$response["message"] = "Database Error!";
die(json_encode($response));
}


$rows = $stmt->fetchAll();


if ($rows) {
$response["success"] = 1;
$response["message"] = "Post Available!";
json_encode($response)
$response["posts"] = array();


foreach ($rows as $row) {
$post = array();
$post["post_id"] = $row["post_id"];
$post["username"] = $row["username"];
$post["title"] = $row["title"];
$post["message"] = $row["message"];


//update our repsonse JSON data
array_push($response["posts"], $post);
}

// echoing JSON response
echo json_encode($response);


} else {
$response["success"] = 0;
$response["message"] = "No Post Available!";
die(json_encode($response));
}


I hope you can help me, because I am loving Android, but this code is for an advance person I think. I am still learning all about JSON. Thank you a lot.



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