We Keep Coding

Wait for the server response using callback java

I am creating a Quiz app on android studio and the questions will be called from an URL containing a JSONObject, and since these API calls happen asynchronously,
i have to make sure that my app is waiting for the server to respond with a callback, below is the parsing method i created following some internet tutorials, it would be nice if you could help me understand which changes should i apply
private void jsonParse(){
final Question[] quest =new Question[10];
String url="https://opentdb.com/api.php?amount=10";
JsonObjectRequest request =new JsonObjectRequest(Request.Method.GET, url, null,
new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject response) {
try {
JSONArray ja=response.getJSONArray("results");
for(int i=0;i<3;i++){
JSONObject temp_quest=ja.getJSONObject(i);
String question =temp_quest.getString("question");
String correctanswer=temp_quest.getString("correct_answer");
String incorrectanswer_1=(String)temp_quest.getJSONArray("incorrect_answers").getString(0);
String incorrectanswer_2=(String)temp_quest.getJSONArray("incorrect_answers").getString(1);
String incorrectanswer_3=(String)temp_quest.getJSONArray("incorrect_answers").getString(2);
String[] temp=new String[3];
temp[0]=incorrectanswer_1;
temp[1]=incorrectanswer_2;
temp[2]=incorrectanswer_3;
quest[i]=new Question(question,correctanswer,temp);
mTextViewResult.append(quest[i].getQuestion()+" \n"+ quest[i].getCorrectAnswer()+"\n "+
quest[i].getAnswer(1)+"\n "+quest[i].getAnswer(2)+"\n "+
quest[i].getAnswer(3)+"\n" +quest[i].getAnswer(4)+"\n\n");
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
error.printStackTrace();
}
});
mQueue.add(request);
}
}

I consider that you are not using the correct form to call a service.
You can use a async task
package principal.concrete.concrete;
import android.os.AsyncTask;
import android.util.Log;
import java.io.IOException;
import java.net.URL;
import java.net.HttpURLConnection;
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Post extends AsyncTask<String, Void, String> {
private InputStreamReader inputStreamReader;
private BufferedReader bufferedReader;
#Override
protected String doInBackground(String... params){
try {
URL obj = new URL(params[0]);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("GET");
con.setRequestProperty("User-Agent", " ");
con.connect();
inputStreamReader=new InputStreamReader(con.getInputStream());
bufferedReader = new BufferedReader(inputStreamReader);
return bufferedReader.readLine();
}catch(Exception e){
Log.d("Url doInBackground", e.toString());
return null;
} finally {
try {
closeConnection();
} catch(Exception e){
}
}
}
private void closeConnection() {
try {
if(bufferedReader!=null){
bufferedReader.close();
}
if(inputStreamReader!=null){
inputStreamReader.close();
}
}catch(IOException ex){
Log.d("Url disconnect", ex.toString());
}
}
#Override
protected void onPostExecute(String result){
super.onPostExecute(result);
}
}
You can use a retrofit to call a service
link the implementation
https://programacionymas.com/blog/consumir-una-api-usando-retrofit
I have a code to call service
asyn task

Writing/Updating JSON to URL (www.myjson.com)

I'm using www.myjson.com as a storage for my json file which will be accessed/updated frequently.
I currently have this as my json file online:
https://api.myjson.com/bins/f5fr0
I'm planning to update it frequently using android studio, but I have no idea on how to do it. How can I write/update it so that I can change the values of my json using android/java code?

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();
}
}
public class MainActivity extends AppCompatActivity {
private String TAG = MainActivity.class.getSimpleName();
ArrayList<HashMap<String, String>> contactList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new GetJSON().execute();
}
private class GetJSON extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
Toast.makeText(MainActivity.this,"Json Data is
downloading",Toast.LENGTH_LONG).show();
}
#Override
protected Void doInBackground(Void... arg0) {
HttpHandler sh = new HttpHandler();
// Making a request to url and getting response
String url = "https://api.myjson.com/bins/f5fr0";
String jsonStr = sh.makeServiceCall(url);
Log.e(TAG, "Response from url: " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON OBJECT node
JSONArray jsonObjInner = jsonObj.getJSONObject("channel");
String id = jsonObjInner.getString("id");
String name = jsonObjInner.getString("name");
String description = jsonObjInner.getString("description");
}
} 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);
}
}
}

java.io.IOException: bt socket closed, read return: -1

As i am working on OBD Reader Demo .Through my app i am trying to connect obd reader device and my app is installed in Nexus 7.OBD Reader device is connecting to other apps which is available on google play but if i am connecting with my app it is getting error java.io.IOException: bt socket closed, read return: -1 after connection establish .Any suggestions...
=========================================================
**MainActivity:-**
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Set;
import java.util.UUID;
import android.annotation.SuppressLint;
import android.app.AlertDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import com.virgosys.demo.commands.SpeedObdCommand;
import com.virgosys.demo.commands.engine.EngineRPMObdCommand;
import com.virgosys.demo.commands.fuel.FindFuelTypeObdCommand;
public class MainActivity extends Bluetooth {
#SuppressWarnings("unused")
private Button On, Off, Visible, list;
private BluetoothAdapter BA;
private Set<BluetoothDevice> pairedDevices;
#SuppressWarnings("unused")
private ListView lv;
private BluetoothDevice device;
// private UUID uuid;
// private BluetoothSocketWrapper bluetoothSocket;
private BluetoothSocket socket;
private String deviceAddress;
String RPM, Speed, FuelType;
private TextView uuidTextView, deviceTextView, showRpm, showSpeed,
showFuelType, tv_connection_e, tv_connection_f;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
showRpm = ((TextView) findViewById(R.id.show_rpm));
showSpeed = ((TextView) findViewById(R.id.txt_speed));
showFuelType = ((TextView) findViewById(R.id.txt_fueltype));
uuidTextView = ((TextView) findViewById(R.id.txt_uuid));
deviceTextView = ((TextView) findViewById(R.id.txt_device));
// tv_connection_e = ((TextView) findViewById(R.id.txt_device));
// tv_connection_f = ((TextView) findViewById(R.id.show_error));
On = (Button) findViewById(R.id.button1);
Off = (Button) findViewById(R.id.button2);
Visible = (Button) findViewById(R.id.button3);
list = (Button) findViewById(R.id.button4);
lv = (ListView) findViewById(R.id.listView1);
BA = BluetoothAdapter.getDefaultAdapter();
try {
Process process = Runtime.getRuntime().exec("logcat -d");
BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(process.getInputStream()));
StringBuilder log = new StringBuilder();
String line = "";
while ((line = bufferedReader.readLine()) != null) {
log.append(line);
}
TextView tv_connection_e = (TextView) findViewById(R.id.show_error);
tv_connection_e.setText(log.toString());
} catch (IOException e) {
}
}
public void on(View view) {
if (!BA.isEnabled()) {
Intent turnOn = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(turnOn, 0);
Toast.makeText(getApplicationContext(), "Turned on",
Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), "Already on",
Toast.LENGTH_LONG).show();
}
}
#SuppressWarnings("unchecked")
public void list(View view) {
ArrayList deviceStrs = new ArrayList();
final ArrayList devices = new ArrayList();
BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();
pairedDevices = btAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
for (BluetoothDevice device : pairedDevices) {
deviceStrs.add(device.getName() + "\n" + device.getAddress());
devices.add(device.getAddress());
}
}
// show list
final AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);
ArrayAdapter adapter = new ArrayAdapter(this,
android.R.layout.select_dialog_singlechoice,
deviceStrs.toArray(new String[deviceStrs.size()]));
alertDialog.setSingleChoiceItems(adapter, -1,
new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
int position = ((AlertDialog) dialog).getListView()
.getCheckedItemPosition();
deviceAddress = (String) devices.get(position);
System.out.println("Device Address-->" + deviceAddress);
/*
* Intent i = new Intent(MainActivity.this,
* SecondActivity.class); i.putExtra("uuid",
* "00001101-0000-1000-8000-00805F9B34FB");
* i.putExtra("deviceAddress", deviceAddress);
* i.putExtra("RPM", RPM); i.putExtra("Speed", Speed);
* startActivity(i);
*/
try {
dothings();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// save deviceAddress
}
});
alertDialog.setTitle("Choose Bluetooth device");
alertDialog.show();
}
#SuppressLint("NewApi")
protected void dothings() throws InterruptedException {
System.out.println("Inside Do things");
System.out.println("Device address in Do things -->" + deviceAddress);
device = BA.getRemoteDevice(deviceAddress);
// UUID SERIAL_UUID = device.getUuids()[0].getUuid();
// uuid = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
System.out.println("Device Name-->" + device.getName());
System.out.println("Device Address-->" + device.getAddress());
System.out.println("Device Bond State-->" + device.getBondState());
System.out.println("Device Type-->" + device.getType());
System.out.println("Device UUIDS-->" + device.getUuids());
ConnectThread t = new ConnectThread(device);
t.start();
showRpm.setText(RPM);
showSpeed.setText(Speed);
showFuelType.setText(FuelType);
uuidTextView.setText("00001101-0000-1000-8000-00805F9B34FB");
deviceTextView.setText(deviceAddress);
}
public void off(View view) {
BA.disable();
Toast.makeText(getApplicationContext(), "Turned off", Toast.LENGTH_LONG)
.show();
}
public void visible(View view) {
Intent getVisible = new Intent(
BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
startActivityForResult(getVisible, 0);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
private class ConnectThread extends Thread {
private final BluetoothSocket mmSocket;
private final UUID WELL_KNOWN_UUID = UUID
.fromString("00001101-0000-1000-8000-00805f9b34fb");
private Object e;
public ConnectThread(BluetoothDevice device) {
// Use a temporary object that is later assigned to mmSocket,because
// mmSocket is final
BluetoothSocket tmp = null;
// Get a BluetoothSocket to connect with the given BluetoothDevice
try {
tmp = device.createRfcommSocketToServiceRecord(WELL_KNOWN_UUID);
// This is the trick
Method m = device.getClass().getMethod("createRfcommSocket",
new Class[] { int.class });
tmp = (BluetoothSocket) m.invoke(device, 1);
} catch (Exception e) {
e.printStackTrace();
}
mmSocket = tmp;
}
public void run() {
System.out.println("Trying to connect...");
// Cancel discovery because it will slow down the connection
BA.cancelDiscovery();
try {
// Connect the device through the socket. This will block
// until it succeeds or throws an exception
mmSocket.connect();
System.out.println("Connection established");
// tv_connection_e.setText(e.print.stacktrace);
ConnectedThread tc = new ConnectedThread(mmSocket);
tc.start();
} catch (IOException connectException) {
// Unable to connect; close the socket and get out
System.out.println("Fail to connect!");
try {
mmSocket.close();
} catch (IOException closeException) {
System.out.println("Fail to close connection");
}
return;
}
}
/** Will cancel an in-progress connection, and close the socket */
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
}
}
}
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket) {
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) {
}
System.out.println("Inside the thread");
mmInStream = tmpIn;
mmOutStream = tmpOut;
try {
EngineRPMObdCommand engineRpmCommand = new EngineRPMObdCommand();
SpeedObdCommand speedCommand = new SpeedObdCommand();
FindFuelTypeObdCommand fueltypeCommand = new FindFuelTypeObdCommand();
System.out.println("Inside the try block");
while (!Thread.currentThread().isInterrupted()) {
System.out.println("Inside while");
// TODO handle commands result
Log.d("Poonam",
"RPM: " + engineRpmCommand.getFormattedResult());
Log.d("Poonam",
"Speed: " + speedCommand.getFormattedResult());
Log.d("Poonam",
"FuelType: " + fueltypeCommand.getFormattedResult());
RPM = engineRpmCommand.getFormattedResult();
Speed = speedCommand.getFormattedResult();
FuelType = fueltypeCommand.getFormattedResult();
try {
engineRpmCommand.run(mmInStream, mmOutStream);
speedCommand.run(mmInStream, mmOutStream);
fueltypeCommand.run(mmInStream, mmOutStream);
System.out.println("Commands Processed");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("outside try catch");
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("inside catch before while");
}
// Get the input and output streams, using temp objects because
// member streams are final
}
public void run() {
byte[] buffer = new byte[1024]; // buffer store for the stream
int bytes; // bytes returned from read()
// Keep listening to the InputStream until an exception occurs
while (true) {
}
}
/* Call this from the main activity to send data to the remote device */
public void write(byte[] bytes) {
try {
mmOutStream.write(bytes);
} catch (IOException e) {
}
}
/* Call this from the main activity to shutdown the connection */
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
}
}
}
}
**Bluetooth.java**
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.util.Log;
public class Bluetooth extends Activity{
private BluetoothSocketWrapper bluetoothSocket;
private BluetoothDevice device;
private boolean secure;
private BluetoothAdapter adapter;
private List<UUID> uuidCandidates;
private int candidate;
/**
* #param device the device
* #param secure if connection should be done via a secure socket
* #param adapter the Android BT adapter
* #param uuidCandidates a list of UUIDs. if null or empty, the Serial PP id is used
* #return
*/
public void BluetoothConnector(BluetoothDevice device, boolean secure, BluetoothAdapter adapter,
List<UUID> uuidCandidates) {
this.device = device;
this.secure = secure;
this.adapter = adapter;
this.uuidCandidates = uuidCandidates;
if (this.uuidCandidates == null || this.uuidCandidates.isEmpty()) {
this.uuidCandidates = new ArrayList<UUID>();
this.uuidCandidates.add(UUID.fromString("00001101-0000-1000-8000-00805f9b34fb"));
}
}
public BluetoothSocketWrapper connect() throws IOException {
boolean success = false;
while (selectSocket()) {
adapter.cancelDiscovery();
try {
bluetoothSocket.connect();
success = true;
break;
} catch (IOException e) {
//try the fallback
try {
bluetoothSocket = new FallbackBluetoothSocket(bluetoothSocket.getUnderlyingSocket());
Thread.sleep(500);
bluetoothSocket.connect();
success = true;
break;
} catch (FallbackException e1) {
Log.w("BT", "Could not initialize FallbackBluetoothSocket classes.", e);
} catch (InterruptedException e1) {
Log.w("BT", e1.getMessage(), e1);
} catch (IOException e1) {
Log.w("BT", "Fallback failed. Cancelling.", e1);
}
}
}
if (!success) {
throw new IOException("Could not connect to device: "+ device.getAddress());
}
return bluetoothSocket;
}
private boolean selectSocket() throws IOException {
if (candidate >= uuidCandidates.size()) {
return false;
}
BluetoothSocket tmp = null;
UUID uuid = uuidCandidates.get(candidate++);
Log.i("BT", "Attempting to connect to Protocol: "+ uuid);
if (secure) {
Method m = null;
try {
m = device.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
tmp = (BluetoothSocket) m.invoke(device, 1);
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else {
tmp = device.createInsecureRfcommSocketToServiceRecord(uuid);
}
bluetoothSocket = new NativeBluetoothSocket(tmp);
return true;
}
public static interface BluetoothSocketWrapper {
InputStream getInputStream() throws IOException;
OutputStream getOutputStream() throws IOException;
String getRemoteDeviceName();
void connect() throws IOException;
String getRemoteDeviceAddress();
void close() throws IOException;
BluetoothSocket getUnderlyingSocket();
}
public static class NativeBluetoothSocket implements BluetoothSocketWrapper {
private BluetoothSocket socket;
public NativeBluetoothSocket(BluetoothSocket tmp) {
this.socket = tmp;
}
#Override
public InputStream getInputStream() throws IOException {
return socket.getInputStream();
}
#Override
public OutputStream getOutputStream() throws IOException {
return socket.getOutputStream();
}
#Override
public String getRemoteDeviceName() {
return socket.getRemoteDevice().getName();
}
#Override
public void connect() throws IOException {
socket.connect();
}
#Override
public String getRemoteDeviceAddress() {
return socket.getRemoteDevice().getAddress();
}
#Override
public void close() throws IOException {
socket.close();
}
#Override
public BluetoothSocket getUnderlyingSocket() {
return socket;
}
}
public class FallbackBluetoothSocket extends NativeBluetoothSocket {
private BluetoothSocket fallbackSocket;
public FallbackBluetoothSocket(BluetoothSocket tmp) throws FallbackException {
super(tmp);
try
{
Class<?> clazz = tmp.getRemoteDevice().getClass();
Class<?>[] paramTypes = new Class<?>[] {Integer.TYPE};
Method m = clazz.getMethod("createRfcommSocket", paramTypes);
Object[] params = new Object[] {Integer.valueOf(1)};
fallbackSocket = (BluetoothSocket) m.invoke(tmp.getRemoteDevice(), params);
}
catch (Exception e)
{
throw new FallbackException(e);
}
}
#Override
public InputStream getInputStream() throws IOException {
return fallbackSocket.getInputStream();
}
#Override
public OutputStream getOutputStream() throws IOException {
return fallbackSocket.getOutputStream();
}
#Override
public void connect() throws IOException {
fallbackSocket.connect();
}
#Override
public void close() throws IOException {
fallbackSocket.close();
}
}
public static class FallbackException extends Exception {
/**
*
*/
private static final long serialVersionUID = 1L;
public FallbackException(Exception e) {
super(e);
}
}
}
(MainActivity.java:367)
try {
engineRpmCommand.run(mmInStream, mmOutStream);
speedCommand.run(mmInStream, mmOutStream);
fueltypeCommand.run(mmInStream, mmOutStream);
System.out.println("Commands Processed");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
367--> e.printStackTrace();
}
System.out.println("outside try catch");
}
(ObdCommand.java:164)
protected void readRawData(InputStream in) throws IOException {
byte b = 0;
StringBuilder res = new StringBuilder();
// read until '>' arrives
164--> while ((char) (b = (byte) in.read()) != '>')
res.append((char) b);

Have you checked if your string builder / buffer contains anything at the time the exception is thrown?
I've had this trouble with Bluetooth on a Nexus 7 2012 and the only thing I can suggest is that you Thread.sleep() while waiting for data and use .available() from the stream to make sure you don't read more than what is available.
You could sleep loop while .available() is zero and not equal to the amount as the last loop, and then assume you have all the data when it stabilizes. Alternatively you can simply catch the exception and assume you have received all the data at that point.

I think its a bug in read() method. From #Keilaron's answer.. I tried this and this works:
while (inputStream.available() == 0);
val available = inputStream.available()
val bytes = ByteArray(available)
inputStream.read(bytes, 0, available)
val text = String(bytes)

Android read json from restful service

I am trying to get a response from a service (the response comes in json).
I made my checks if the device is connected and now I need to make the http request to the service. I found out on other questions that I have to use a background thread but I am not sure I got a working sample.
So I need to find out how I can make a connection to a given uri and read the response.
My service needs to get a content header application/json in orderto return a json, so before the request I need to set this header as well.
Thank you in advance
UPDATE
package com.example.restfulapp;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.provider.Settings;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.concurrent.ExecutionException;
public class MainActivity extends Activity {
private int code = 0;
private String value = "";
private ProgressDialog mDialog;
private Context mContext;
private String mUrl ="http://192.168.1.13/myservice/upfields/";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (!isOnline())
{
displayNetworkOption ("MyApp", "Application needs network connectivity. Connect now?");
}
try {
JSONObject s = getJSON(mUrl);
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
public class Get extends AsyncTask<Void, Void, String> {
#Override
protected String doInBackground(Void... arg) {
String linha = "";
String retorno = "";
mDialog = ProgressDialog.show(mContext, "Please wait", "Loading...", true);
HttpClient client = new DefaultHttpClient();
HttpGet get = new HttpGet(mUrl);
try {
HttpResponse response = client.execute(get);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) { // Ok
BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
while ((linha = rd.readLine()) != null) {
retorno += linha;
}
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return retorno;
}
#Override
protected void onPostExecute(String result) {
mDialog.dismiss();
}
}
public JSONObject getJSON(String url) throws InterruptedException, ExecutionException {
setUrl(url);
Get g = new Get();
return createJSONObj(g.get());
}
private void displayNetworkOption(String title, String message){
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder
.setTitle(title)
.setMessage(message)
.setPositiveButton("Wifi", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
startActivity(new Intent(Settings.ACTION_WIFI_SETTINGS));
}
})
.setNeutralButton("Data", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
startActivity(new Intent(Settings.ACTION_DATA_ROAMING_SETTINGS));
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
return;
}
})
.show();
}
private boolean isOnline() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnectedOrConnecting()) {
return true;
}
return false;
}
}
This throws errors:
Gradle: cannot find symbol method setUrl(java.lang.String)
Gradle: cannot find symbol method createJSONObj(java.lang.String)

After derogatory responses from EvZ who think that he was born knowing everything, I ended up with a subclass MyTask that I call like this inside the onCreate of my Activity.
new MyTask().execute(wserviceURL);
private class MyTask extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
URL myurl = null;
try {
myurl = new URL(urls[0]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
URLConnection connection = null;
try {
connection = myurl.openConnection();
} catch (IOException e) {
e.printStackTrace();
}
connection.setConnectTimeout(R.string.TIMEOUT_CONNECTION);
connection.setReadTimeout(R.string.TIMEOUT_CONNECTION);
HttpURLConnection httpConnection = (HttpURLConnection) connection;
httpConnection.setRequestProperty("Content-Type", getString(R.string.JSON_CONTENT_TYPE));
int responseCode = -1;
try {
responseCode = httpConnection.getResponseCode();
} catch (SocketTimeoutException ste) {
ste.printStackTrace();
}
catch (Exception e1) {
e1.printStackTrace();
}
if (responseCode == HttpURLConnection.HTTP_OK) {
StringBuilder answer = new StringBuilder(100000);
BufferedReader in = null;
try {
in = new BufferedReader(new InputStreamReader(httpConnection.getInputStream()));
} catch (IOException e) {
e.printStackTrace();
}
String inputLine;
try {
while ((inputLine = in.readLine()) != null) {
answer.append(inputLine);
answer.append("\n");
}
} catch (IOException e) {
e.printStackTrace();
}
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
httpConnection.disconnect();
return answer.toString();
}
else
{
//connection is not OK
httpConnection.disconnect();
return null;
}
}
#Override
protected void onPostExecute(String result) {
String userid = null;
String username = null;
String nickname = null;
if (result!=null)
{
try {
//do read the JSON here
} catch (JSONException e) {
e.printStackTrace();
}
}
//stop loader dialog
mDialog.dismiss();
}
}
lory105's answer guided me to somewhere near the answer, thanx.

here is an example of how to process the HTTP response and convert to JSONObject:
/**
* convert the HttpResponse into a JSONArray
* #return JSONObject
* #param response
* #throws IOException
* #throws IllegalStateException
* #throws UnsupportedEncodingException
* #throws Throwable
*/
public static JSONObject processHttpResponse(HttpResponse response) throws UnsupportedEncodingException, IllegalStateException, IOException {
JSONObject top = null;
StringBuilder builder = new StringBuilder();
try {
BufferedReader reader = new BufferedReader(
new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
for (String line = null; (line = reader.readLine()) != null;) {
builder.append(line).append("\n");
}
String decoded = new String(builder.toString().getBytes(), "UTF-8");
Log.d(TAG, "decoded http response: " + decoded);
JSONTokener tokener = new JSONTokener(Uri.decode(builder.toString()));
top = new JSONObject(tokener);
} catch (JSONException t) {
Log.w(TAG, "<processHttpResponse> caught: " + t + ", handling as string...");
} catch (IOException e) {
Log.e(TAG, "caught: " + e, e);
} catch (Throwable t) {
Log.e(TAG, "caught: " + t, t);
}
return top;
}

From Android 3+, the http connections must be done within a separate thread. Android offers a Class named AsyncTask that help you do it.
Here you can find a good example of an AsyncTask that performs an http request and receives a JSON response.
Remember that in the doInBackgroud(..) method you CAN'T modify the UI such as to launch a Toast, to change activity or others. You have to use the onPreExecute() or onPostExecute() methods to do this.
ADD
For the mDialog and mContext variables, add the code below, and when you create the JSONTask write new JSONTask(YOUR_ACTIVITY)
public abstract class JSONTask extends AsyncTask<String, Void, String> {
private Context context = null;
ProgressDialog mDialog = new ProgressDialog();
public JSONTask(Context _context){ context=_context; }
..

Start Activity from Class in new Thread

Basically the idea is I check to see if the web session is still valid, if not I start the main activity which logs the user in automatically.
I have this working, not sure if it's the best way to do it. If anyone has a better way please let me know.
Thanks
Useage:
#Override
public void onResume() {
super.onResume();
new LoginCheck(this,new Intent(this,MyActivity.class));
}
The Class
public class LoginCheck extends Application {
Intent home;
Activity activity;
public LoginCheck(Activity activity, Intent home) {
this.activity = activity;
this.home = home;
new Check().execute();
}
public class Check extends AsyncTask {
#Override
protected Object doInBackground(Object... objects) {
try {
InputStream is = null;
String result = "";
JSONObject jArray = null;
PersistentCookieStore myCookieStore = new PersistentCookieStore(MyApp.getAppContext());
//http post
DefaultHttpClient mClient = AppSettings.getClient();
try {
HttpPost request = new HttpPost(MyApp.getServiceUrl() + "/Api/Login/AmILoggedIn");
mClient.setCookieStore(myCookieStore);
HttpResponse response = mClient.execute(request);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
//convert response to string
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();
result = sb.toString();
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
final String r = result;
final Intent i = home;
activity.runOnUiThread(new Runnable() {
#Override
public void run() {
try {
JSONObject j = new JSONObject(r);
if (!j.getBoolean("Success")) {
try {
activity.startActivity(i);
} catch (Exception e) {
Log.e("log_tag", e.getMessage());
}
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
}
});
return true;
} catch (Exception e) {
}
return null;
}
}
}

Here is the cleaned up version
Use:
new LoginCheck() {
#Override
public void LoggedIn() {
//To change body of implemented methods use File | Settings | File Templates.
}
#Override
public void LoggedOut() {
//To change body of implemented methods use File | Settings | File Templates.
}
};
Class
public abstract class LoginCheck {
public LoginCheck(){
new Check().execute(true);
}
public class Check extends AsyncTask<Boolean,Boolean,Boolean>{
#Override
protected Boolean doInBackground(Boolean... objects) {
JSONStringer jsonSend = null;
try {
jsonSend = new JSONStringer()
.object()
.endObject();
} catch (JSONException e) {
Log.e("log_tag", "Error creating Json " + e.toString());
}
JSONObject result = JsonPost.postJSONtoURL(MyApp.getServiceUrl() + "/Api/Login/AmILoggedIn", jsonSend);
try {
if (result.getBoolean("Success")) {
return true;
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
try {
if (!result.getBoolean("Success")) {
return false;
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
return false;
}
#Override
protected void onPostExecute(Boolean result){
if(result)
LoggedIn();
if(!result)
LoggedOut();
}
}
public abstract void LoggedIn();
public abstract void LoggedOut();
}