Develop Reference

How to parse unnamed JSON Array in Android app

I have a JSON array sent from my SQL server via PHP in the following format which I am finding difficult to parse without encountering errors.
[
{
"placename": "place1",
"latitude": "50",
"longitude": "-0.5",
"question": "place1 existed when?",
"answer1": "1800",
"answer2": "1900",
"answer3": "1950",
"answer4": "2000",
"correctanswer": "1900"
},
{
"placename": "place2",
"latitude": "51",
"longitude": "-0.5",
"question": "place2 existed when?",
"answer1": "800",
"answer2": "1000",
"answer3": "1200",
"answer4": "1400",
"correctanswer": "800"
},
{
"placename": "place3",
"latitude": "52",
"longitude": "-1",
"question": "place 3 was established when?",
"answer1": "2001",
"answer2": "2005",
"answer3": "2007",
"answer4": "2009",
"correctanswer": "2009"
}
]
I have verified my JSON at JSONLint and it comes up as valid. I have also used log code to print out my JSON in the Eclipse app debugger after my HTTP client has processed it and that also works fine (it shows the JSON as above so I know it has downloaded correctly).
I'm trying to fit the JSON Parser into the following activity but all my attempts thus far have either contained too many errors to run or have simply returned no results because of JSON parsing errors.
Here is the code of the main activity. The code for this activity is adapted from NewThinkTank.com (Android Development 15) and I'm trying to tweak it for my needs but the structure of the JSON used in the example is very different to mine.
I was hoping someone could suggest some code, or give me some pointers, as to how I could go about parsing this JSON array properly. I am fairly new to Android programming so this is a fairly steep task to figure out on my own.
Thanks for your time.
public class MainActivity extends Activity {
// The JSON REST Service I will pull from
static String dlquiz = "http://exampleserver.php";
// Will hold the values I pull from the JSON
static String placename = "";
static String latitude = "";
static String longitude = "";
static String question = "";
static String answer1 = "";
static String answer2 = "";
static String answer3 = "";
static String answer4 = "";
static String correctanswer = "";
#Override
public void onCreate(Bundle savedInstanceState) {
// Get any saved data
super.onCreate(savedInstanceState);
// Point to the name for the layout xml file used
setContentView(R.layout.main);
// Call for doInBackground() in MyAsyncTask to be executed
new MyAsyncTask().execute();
}
// Use AsyncTask if you need to perform background tasks, but also need
// to change components on the GUI. Put the background operations in
// doInBackground. Put the GUI manipulation code in onPostExecute
private class MyAsyncTask extends AsyncTask<String, String, String> {
protected String doInBackground(String... arg0) {
// HTTP Client that supports streaming uploads and downloads
DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams());
// Define that I want to use the POST method to grab data from
// the provided URL
HttpPost httppost = new HttpPost(dlquiz);
// Web service used is defined
httppost.setHeader("Content-type", "application/json");
// Used to read data from the URL
InputStream inputStream = null;
// Will hold the whole all the data gathered from the URL
String result = null;
try {
// Get a response if any from the web service
HttpResponse response = httpclient.execute(httppost);
// The content from the requested URL along with headers, etc.
HttpEntity entity = response.getEntity();
// Get the main content from the URL
inputStream = entity.getContent();
// JSON is UTF-8 by default
// BufferedReader reads data from the InputStream until the Buffer is full
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
// Will store the data
StringBuilder theStringBuilder = new StringBuilder();
String line = null;
// Read in the data from the Buffer untilnothing is left
while ((line = reader.readLine()) != null)
{
// Add data from the buffer to the StringBuilder
theStringBuilder.append(line + "\n");
}
// Store the complete data in result
result = theStringBuilder.toString();
} catch (Exception e) {
e.printStackTrace();
}
finally {
// Close the InputStream when you're done with it
try{if(inputStream != null)inputStream.close();}
catch(Exception e){}
}
//this allowed me to verify the JSON download in the debugger
Log.v("JSONParser RESULT ", result);
// JSON parsing needs to happen here...
return result;
}
protected void onPostExecute(String result){
// Gain access so I can change the TextViews
TextView line1 = (TextView)findViewById(R.id.line1);
TextView line2 = (TextView)findViewById(R.id.line2);
TextView line3 = (TextView)findViewById(R.id.line3);
// Change the values for all the TextViews
line1.setText("Place Name: " + placename);
line2.setText("Question: " + question);
line3.setText("Correct Answer: " + correctanswer);
}
}
}

Check this answer out: How to parse JSON in Android
You'll be using:
JSONArray array = new JSONArray(result);
From there, you'll loop through and get each JSONObject:
for(int i = 0; i < array.length(); i++)
{
JSONObject obj = array.getJSONObject(i);
//now, get whatever value you need from the object:
placename = obj.getString("placename");
//or if on the MainUI thread you can set your TextView from here:
yourTextView.setText(obj.getString("placename"));
}
Good luck!

android HttpGet incomplete response BufferedReader

Im doing a simple http get,
I see on my result an incomplete response,
what Im doing wrong?
here the code:
class GetDocuments extends AsyncTask<URL, Void, Void> {
#Override
protected Void doInBackground(URL... urls) {
Log.d("mensa", "bajando");
//place proper url
connect(urls);
return null;
}
public static void connect(URL[] urls)
{
HttpClient httpclient = new DefaultHttpClient();
// Prepare a request object
HttpGet httpget = new HttpGet("http://tiks.document.dev.chocolatecoded.com.au/documents/api/get?type=tree");
// Execute the request
HttpResponse response;
try {
response = httpclient.execute(httpget);
// Examine the response status
Log.d("mensa",response.getStatusLine().toString());
// Get hold of the response entity
HttpEntity entity = response.getEntity();
// If the response does not enclose an entity, there is no need
// to worry about connection release
if (entity != null) {
// A Simple JSON Response Read
InputStream instream = entity.getContent();
String result= convertStreamToString(instream);
// now you have the string representation of the HTML request
Log.d("mensa", "estratagema :: "+result);
JSONObject jObject = new JSONObject(result);
Log.d("mensa", "resposta jObject::"+jObject);
Log.d("mensa", "alive 1");
JSONArray contacts = null;
contacts = jObject.getJSONArray("success");
Log.d("mensa", "resposta jObject::"+contacts);
Log.d("mensa", "alive");
//instream.close();
}
} catch (Exception e) {}
}
private static String convertStreamToString(InputStream is) {
/*
* To convert the InputStream to String we use the BufferedReader.readLine()
* method. We iterate until the BufferedReader return null which means
* there's no more data to read. Each line will appended to a StringBuilder
* and returned as String.
*/
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
try {
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
Log.d("mensa", "linea ::"+line);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
}
i call it with:
GetDocuments get = new GetDocuments();
URL url = null;
try {
url = new URL("ftp://mirror.csclub.uwaterloo.ca/index.html");
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//URL url = new URL("http://www.google.es");
get.execute(url);
edit 1
I refer to incomplete as the response that gets truncated?
please notice in below image of response how string gets truncated,
is this because of the log size?,
but the other problem is that it doesn't parse?
thanks!

I don't know if this is going to resolve your problem but you can get rid of your method and use simply:
String responseString = EntityUtils.toString(response.getEntity());

I've had exactly the same issue for the last couple of days. I found that my code worked over WiFi but not 3G. In other words I eliminated all the usual threading candidates. I also found that when I ran the code in the debugger and just waited for (say) 10 seconds after client.execute(...) it worked.
My guess is that
response = httpclient.execute(httpget);
is an asynchronous call in itself and when it's slow returns a partial result... hence JSON deserialization goes wrong.
Instead I tried this version of execute with a callback...
try {
BasicResponseHandler responseHandler = new BasicResponseHandler();
String json = httpclient.execute(httpget, responseHandler);
} finally {
httpclient.close();
}
And suddenly it all works. If you don't want a string, or want your own code then have a look at the ResponseHandler interface. Hope that helps.

I have confirmed that this is because size limit of java string. I have checked this by adding the string "abcd" with the ressponse and printed the response string in logcat. But the result is the truncated respose without added string "abcd".
That is
try {
BasicResponseHandler responseHandler = new BasicResponseHandler();
String json = httpclient.execute(httpget, responseHandler);
json= json+"abcd";
Log.d("Json ResponseString", json);
} finally {
httpclient.close();
}
So I put an arrayString to collect the response. To make array, I splitted My json format response by using "}"
The code is given below(This is a work around only)
BasicResponseHandler responseHandler = new BasicResponseHandler();
String[] array=client.execute(request, responseHandler).split("}");
Then you can parse each objects in to a json object and json array with your custom classes.
If you get any other good method to store response, pls share because i am creating custom method for every different json responses );.
Thank you
Arshad

Hi Now I am using Gson library to handle the responses.
http://www.javacodegeeks.com/2011/01/android-json-parsing-gson-tutorial.html
Thanks
Arshad

I cant' comment directly due to reputation, but in response to https://stackoverflow.com/a/23247290/4830567 I felt I should point out that the size limit of a Java String is about 2GB (Integer.MAX_VALUE) so this wasn't the cause of the truncation here.
According to https://groups.google.com/d/msg/android-developers/g4YkmrFST6A/z8K3vSdgwEkJ it is logcat that has a size limit, which is why appending "abcd" and printing in logcat didn't work. The String itself would have had the appended characters. The previously linked discussion also mentioned that size limits with the HTTP protocol itself can occasionally be a factor, but that most servers and clients handle this constraint internally so as to not expose it to the user.

Trouble sending JSON Post Android

It has been a while since I programmed for Android and I have lost all my previous work which had the code in it I am having problems with. I am developing an app for both Android and iPhone which connect to the same server to download data. All is well in the iPhone version but on Android when I hit the server with the post data containing the method name I would like to to run on the server it seems that the data is not added to the request.
Why is the POST not working in this request for Android but does for the iPhone version of the app?
Here is the code I am using:
public static void makeRequest() throws Exception {
Thread t = new Thread() {
public void run() {
Looper.prepare(); //For Preparing Message Pool for the child Thread
HttpClient client = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(client.getParams(), 10000);
HttpResponse response;
HttpEntity entity;
JSONObject json = new JSONObject();
try {
HttpPost post = new HttpPost("http://divisi.co.uk/rest/requesthandler.php");
json.put("method", "getEventListData");
StringEntity se = new StringEntity(json.toString());
se.setContentType(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
post.setEntity(se);
response = client.execute(post);
entity = response.getEntity();
String retSrc = EntityUtils.toString(entity);
JSONObject result = new JSONObject(retSrc); //Convert String to JSON Object
if(result.getString("SC") == "200"){
JSONArray data = result.getJSONArray("data");
}
else{
}
} catch(Exception e) {
e.printStackTrace();
}
Looper.loop(); //Loop in the message queue
}
};
t.start();
}
The response I get mack from the server is:
{"data":{"scalar":""},"SC":405,"timestamp":1363788265}
Meaning the method name was not found, i.e. not posted in my request to the server.

heres an example of how i do things like this:
HttpClient httpClient = new DefaultHttpClient();
HttpPost postRequest = new HttpPost("http://divisi.co.uk/rest/requesthandler.php");
MultipartEntity reqEntity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
reqEntity.addPart(new FormBodyPart("method", new StringBody("getEventListData")));
reqEntity.addPart(new FormBodyPart("NEED_A_KEY_HERE", new StringBody("" + json.toString())));
postRequest.setEntity(reqEntity);
HttpResponse response = httpClient.execute(postRequest);
JSONObject responseDict = new JSONObject(EntityUtils.toString(response.getEntity()));

allow this is your "http://divisi.co.uk/rest/requesthandler.php" page code, then in android you can use this... you don't allow post in your URL,

use fiddler on your sever side. see if the http message is correct. it seems your sever side problem, can you show us your sever side code which receive and parse json.

If the server can't read your request try to remove:
se.setContentType(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
It will use the mime type defaults HTTP.PLAIN_TEXT_TYPE i.e. "text/plain".
I don't see any other possibility, if your code is the one you posted and not a more complicated input JSON object.

Your code to set the POST body may be just fine. I think the problem may be with your web service. Try using something like Rested or curl to manually make the call to your server. I made exactly the same request you are making, including with and without the POST body, and I got the same response from your server:
{"data":{"scalar":""},"SC":405,"timestamp":1365704082}
Some things that may be tripping you up:
JSONObject result = new JSONObject(retSrc); //Convert String to JSON Object
if(result.getString("SC") == "200"){
JSONArray data = result.getJSONArray("data");
}
Here, you are comparing the string "405" to "200" using ==, when you should first do a null check and then use .equals("200") instead. Or, use result.getInt("SC") == 200 since this is an integer type in your response JSON.
Also, the "data" entity from your server response is not actually coming back as a JSON array. You should use getJSONObject("data") instead.
Additionally, it's always a good idea to externalize your strings.
Here's how the code should look:
public static final String JSON_KEY_SC = "SC";
public static final String JSON_KEY_DATA = "data";
...
JSONObject result = new JSONObject(retSrc); //Convert String to JSON Object
String sc = result.getString(JSON_KEY_SC);
if (sc != null && sc.equals("200")) {
JSONObject data = result.getJSONObject(JSON_KEY_DATA);
}
else {
...
}

Error Android - received HTML instead of JSON

I'm working on a Android application and I'm trying to get a JSON response from a server which is configured to return a json object (".../current_user.json") when receives a GET message, but the answer I get is in HTML format and not in JSON format as expected.
I don't understand why is this happening because I did the same requests on the browser and with the program RESTClient and got the right answer in JSON format.
Here is the code I'm using.
JSONObject json = new JSONObject();
HttpParams params = new BasicHttpParams();
HttpConnectionParams.setSoTimeout(params, 10000);
HttpClient httpClient = new DefaultHttpClient(params);
HttpGet get = new HttpGet(url_getiduser);
HttpResponse response = httpClient.execute(get);
String sresponse = "error";
Log.d("url get", url_getiduser);
Log.d("pedido get", get.getMethod());
if(response != null)
{
InputStream in = response.getEntity().getContent();
sresponse = convertStreamToString(in);
Log.d("resposta http", sresponse);
if(!sresponse.equals("error"))
{
JSONObject object = new JSONObject(sresponse);
id_user = (String) object.get("id");
json = object;
Log.d("objecto json", object.toString());
}
else Log.d("Error on json parser", sresponse);

There are few cases where you get HTML text
You might have called a wrong function which gives a 404 page.
Might be a database error on server side where you will get database error message
Server might be sending a styled data which has HTML tags
But you better Log the response and paste it here.

How do I prevent my app from crashing unexpectedly, "force close", when using JSON data, and handle the exception instead?

In my application, I have a food activity in which the user enters his/her food, and the app requests the food, by the name entered by the user, from a MYSQL database. In the case that the entered food not exist, the string returned by the database should be null.
Currently, when this happens, an exception to occurs since the null value cannot be parsed to a JSON array. My question is: "Is there a way to prevent my app from force closing? Can I handle the exception and display a toast notifying the user that the requested food was not found?" I would like to prevent the app from crashing, and, rather, fail gracefully.
Please help me.
I've shown the relevant code in my application..
private class LoadData extends AsyncTask<Void, Void, String>
{
private JSONArray jArray;
private String result = null;
private InputStream is = null;
private String entered_food_name=choice.getText().toString().trim();
protected void onPreExecute()
{
}
#Override
protected String doInBackground(Void... params)
{
try {
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://10.0.2.2/food.php");
nameValuePairs.add(new BasicNameValuePair("Name",entered_food_name));
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs,"UTF-8"));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
//convert response to string
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"utf-8"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line);
}
is.close();
result =sb.toString();
result = result.replace('\"', '\'').trim();
}
catch(Exception e){
Log.e("log_tag", " connection" + e.toString());
}
return result;
}
#Override
protected void onPostExecute(String result)
{
try{
String foodName="";
int Description=0;
jArray = new JSONArray(result); // here if the result is null an exeption will occur
JSONObject json_data = null;
for (int i = 0; i < jArray.length(); i++) {
json_data = jArray.getJSONObject(i);
foodName=json_data.getString("Name");
.
.
.
.
.
}
catch(JSONException e){
**// what i can do here to prevent my app from crash and
// make toast " the entered food isnot available " ????**
Log.e("log_tag", "parssing error " + e.toString());
}
}
}

This will fix your code:
jArray = (result == null) ? new JSONArray() : new JSONArray(result);
Now that you have an empty JSONArray, you will be able to test for null JSONObjects later in your program. Many of the JSON methods return a JSONObject if one is found, of null if none exists.
You might also want to initialize your JSONObject with the no-argument JSON constructor, rather than simply setting it to null. It will avoid problems when passing it to other JSON methods (such as using it in a constructor to a JSONArray():
JSONObject json_data = new JSONObject();
Finally, if you're still getting JSONExceptions, it's because you're not actually passing a valid JSON string to the constructor. You can print out the value of result to the log:
Log.d("JSON Data", result);
You may see some SQL error text or if you retrieve from a web server, then an HTTP error code (404 is common if you don't have your url correct).
If your result does look like JSON, then you can verify whether it's actually valid JSON or not using the JSONLint validator. It will help you catch any errors you may have, especially if you're formatting the JSON yourself.

Are you looking to capture the Exception and log it (remotely) to aid in crash reporting and debugging? I've used this package to remotely capture Exceptions and it works pretty good:
http://code.google.com/p/android-remote-stacktrace/