Develop Reference

Parse Json data into a Json object

I have a problem with parsing a tag inside a Json object.
My json code is structured like that:
{"giocatori":[{"nome":"Giovanni","cognome":"Muchacha","numero":"1","ruolo":"F-G"},
{"nome":"Giorgio","cognome":"Rossi","numero":"2","ruolo":"AG"},
{"nome":"Andrea","cognome":"Suagoloso","numero":"3","ruolo":"P"},
{"nome":"Salvatore","cognome":"Aranzulla","numero":"4","ruolo":"G"},
{"nome":"Giulio","cognome":"Muchacha","numero":"5","ruolo":"F"}]}
I got the code that let me get the Json file from here: Get JSON Data from URL Using Android? and I'm trying to parse a tag (for example the "nome" tag) into a Json object.
This is the code I got:
public class MainActivity extends AppCompatActivity {
Button btnHit;
TextView txtJson;
ProgressDialog pd;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnHit = (Button) findViewById(R.id.btnHit);
txtJson = (TextView) findViewById(R.id.tvJsonItem);
btnHit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
new JsonTask().execute("https://api.myjson.com/bins/177dpo");
}
});
}
private class JsonTask extends AsyncTask<String, String, String> {
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(MainActivity.this);
pd.setMessage("Please wait");
pd.setCancelable(false);
pd.show();
}
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line+"\n");
Log.d("Response: ", "> " + line);
}
return buffer.toString();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
if (pd.isShowing()){
pd.dismiss();
}
txtJson.setText(result);
}
}
}
I've never worked with this type of file so I'll really appreciate your help!

You can use something like this:
try {
String servResponse = response.toString();
JSONObject parentObj = new JSONObject(servResponse);
JSONArray parentArray = parentObj.getJSONArray("giocatori");
if (parentArray.length() == 0) {
//if it's empty, do something (or not)
} else {
//Here, finalObj will have your jsonObject
JSONObject finalObj = parentArray.getJSONObject(0);
//if you decide to store some value of the object, you can do like this (i've created a nomeGiocatori for example)
nomeGiocatori = finalObj.getString("nome");
}
} catch (Exception e) {
Log.d("Exception: ", "UnknownException");
}
I use this kind of code all the time, works like a charm.

How to parse data from multiple URLs using asyncTask

The main problem is I'm unable to return two value help. i have tried lot of time but no success. And guys I'm new to this so please write your answer with respect to my code thanks in advance.
Here's my code
public class calculate extends AsyncTask<String, String, String> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
try {
uss = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22INRUSD%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject usjObj;
usjObj = new JSONObject(uss);
usResult = usjObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
eurr = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22INREUR%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject eurjObj;
eurjObj = new JSONObject(eurr);
eurResult = eurjObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return eurResult + usResult;
////PROBLEM IS HERE ACTUALLY I DON'T KNOW HOW TO RETURN TWO OR MORE VALUE/////"
}
#Override
protected void onPostExecute(String usResult) {
valueus = Double.parseDouble(usResult);
inputus = lengthvalue * valueus;
us.setText("" + inputus);
valueeur = Double.parseDouble(eurResult);
inputeur = lengthvalue * valueeur;
eur.setText("" + inputeur);
}
}
public String getJson(String url) throws ClientProtocolException, IOException {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return build.toString();
}
}

You should not try to cram everything into a String. There are better data structures to hold multiple values: array, Vector, List, etc. Declare your AsyntTask as:
public class calculate extends AsyncTask<String, String, String[]>
and then your doInBackgorund method would be something like this:
#Override
protected String doInBackground(String... params) {
String[] result = new String[numResults];
...
result[0] = usjObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
...
result[1] = usjObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
...
return result;
}
And finally your onPostExecute would be
#Override
protected void onPostExecute(String[] usResult) {
...
}

Asynctask android return contents "doinBackground

I would like to retrieve the contents of my variable "$content" in my activity.
But I don't know how to use the return value of my doinbackground.
Can you help me ?
thank you in advance
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String restURL = "https://proxyepn-test.epnbn.net/wsapi/epn";
RestOperation test = new RestOperation();
test.execute(restURL);
}
private class RestOperation extends AsyncTask<String, Void, String> {
//final HttpClient httpClient = new DefaultHttpClient();
String content;
String error;
ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
String data = "";
TextView serverDataReceived = (TextView)findViewById(R.id.serverDataReceived);
TextView showParsedJSON = (TextView) findViewById(R.id.showParsedJSON);
// EditText userinput = (EditText) findViewById(R.id.userinput);
#Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog.setTitle("Please wait ...");
progressDialog.show();
}
#Override
protected String doInBackground(String... params) {
BufferedReader br = null;
URL url;
try {
url = new URL(params[0]);
URLConnection connection = url.openConnection();
connection.setDoOutput(true);
OutputStreamWriter outputStreamWr = new OutputStreamWriter(connection.getOutputStream());
outputStreamWr.write(data);
outputStreamWr.flush();
br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
StringBuilder sb = new StringBuilder();
String line = null;
while((line = br.readLine())!=null) {
sb.append(line);
sb.append(System.getProperty("line.separator"));
}
content = sb.toString();
} catch (MalformedURLException e) {
error = e.getMessage();
e.printStackTrace();
} catch (IOException e) {
error = e.getMessage();
e.printStackTrace();
} finally {
try {
br.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return content;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
progressDialog.dismiss();
if(error!=null) {
serverDataReceived.setText("Error " + error);
} else {
serverDataReceived.setText(content);
String output = "";
JSONObject jsonResponse;
try {
jsonResponse = new JSONObject(content);
JSONArray jsonArray = jsonResponse.names();
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject child = jsonArray.getJSONObject(i);
String name = child.getString("name");
String number = child.getString("number");
String time = child.getString("date_added");
output = "Name = " + name + System.getProperty("line.separator") + number + System.getProperty("line.separator") + time;
output += System.getProperty("line.separator");
Log.i("content",content);
}
showParsedJSON.setVisibility(View.INVISIBLE);
showParsedJSON.setText(output);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}

You can directly call to the method which exist in activity, from onPostExecute method of asynctask by passing "content" value.
#Override
protected void onPostExecute(String content) {
Activity.yourMethod(content);
}
If you want to return the value from asynctask you can use
content = test.execute(url).get();
but it is not a good practice of asynctask, because it is working as serial execution. So it is not fulfill the use of asynctask for palatalization.Because get() will block the UI thread.

Android Studio OnCreate Never used warning

This is an rssfeed and everything compiles and I don't think i am missing anything but my app wont launch and there is a warning about my OnCreate never being used. I am unsure if this is related to the problem.
public class MainActivity extends AppCompatActivity {
private TextView src;
private Button btn;
protected void OnCreate(Bundle SavedInstanceState) {
super.onCreate(SavedInstanceState);
setContentView(R.layout.activity_main);
src = (TextView) findViewById(R.id.text);
btn = (Button)findViewById(R.id.Fetch);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
fetch();
}
});
}
public void fetch() {
Downloader d = new Downloader();
d.execute("https://en.wikipedia.org/wiki/Main_Page");
try {
src.setText(d.get());
} catch (Exception e) {
Log.e("Error to thread", e.toString());
}
}
class Downloader extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
String result = null;
try {
URL url = new URL(urls[0]);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
InputStream in = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line = null;
while ((line = reader.readLine()) != null) {
result = result + line;
}
conn.disconnect();
reader.close();
} catch (Exception e) {
Log.e("error to fetching", e.toString());
}
return result;
}
}

The correct writing is onCreate, not OnCreate. Try to change that.

OnCreate --> onCreate and use #Override

HTTP Client on android app returning blank screen

I wrote a simple method to get some string data using the apache HTTPClient, however it returns a blank screen when I run it on my phone; I'm trying to display the data in a textarea. The manifest has the internet permission. Can anybody point out what I could be doing wrong?
public String getInternetData() throws Exception
{
BufferedReader in = null;
String data = null;
try
{
HttpClient client = new DefaultHttpClient();
URI website = new URI("http://www.yahoo.com");
HttpGet request = new HttpGet();
request.setURI(website);
HttpResponse response = client.execute(request);
in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
StringBuffer sb = new StringBuffer("");
String l = "";
String nl = System.getProperty("line.separator");
while((l=in.readLine())!=null){
sb.append(l+nl);
}
in.close();
data = sb.toString();
return data;
}finally{
if(in !=null){
try{
in.close();
return data;
}catch (Exception e){
e.printStackTrace();
}
}
}
}
for completeness, I am adding the code I use to see the data.
public class MainActivity extends Activity {
TextView httpStuff;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
httpStuff = (TextView) findViewById(R.id.tvHttp);
GetMethodEx test = new GetMethodEx();
String returned;
try {
returned = test.getInternetData();
httpStuff.setText(returned);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

You are probably getting Network on UI thread error, and because it is in a try catch, the app isnt crashing
you are supposed to invoke network operations only in background threads, or AsyncTasks which are great for that
there is nothing wrong with your HTTP client and request data, the problem indeed lies in your onCreate method
try rewriting it this way
public class MainActivity extends Activity {
TextView httpStuff;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
httpStuff = (TextView) findViewById(R.id.tvHttp);
AsyncTask<Void,Void,String>getDataTask = new AsyncTask<Void,Void,String>(){
#Override
protected String doInBackground(Void... params){
GetMethodEx test = new GetMethodEx();
String returned = test.getInternalData();
return returned;
}
#Override
protected void onPostExecute(String returned){
httpStuff.setText(returned);
}
}
}
getDataTask.execute();
}