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Android SeekBar NullPointerException

I have a probleme with my code. When I lunch my program i have a crash.
On the Android monitor i can see :
04-04 20:21:10.369 2042-2042/com.led.led E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.led.led, PID: 2042
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.led.led/com.led.led.ledControlSeekBar}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.SeekBar.setOnSeekBarChangeListener(android.widget.SeekBar$OnSeekBarChangeListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2358)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2420)
at android.app.ActivityThread.access$900(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5294)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.SeekBar.setOnSeekBarChangeListener(android.widget.SeekBar$OnSeekBarChangeListener)' on a null object reference
at com.led.led.ledControlSeekBar.onCreate(ledControlSeekBar.java:76)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2311)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2420) 
at android.app.ActivityThread.access$900(ActivityThread.java:154) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5294) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699) 
And there is my class :
package com.led.led;
import android.bluetooth.BluetoothDevice;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.Switch;
import android.widget.SeekBar;
import android.app.ProgressDialog;
import android.bluetooth.BluetoothAdapter;
import android.os.AsyncTask;
import android.widget.TextView;
import android.widget.Toast;
import android.view.View.OnClickListener;
import java.io.IOException;
import java.util.UUID;
import java.lang.String;
public class ledControlSeekBar extends AppCompatActivity {
Button btnDis;
SeekBar seek_r, seek_g, seek_b;
String address = null;
private ProgressDialog progress;
BluetoothAdapter myBluetooth = null;
BluetoothSocket btSocket = null;
private boolean isBtConnected = false;
static final UUID myUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
ConnectBT bt = new ConnectBT();
String phraseAEnvoyer = "000000000";
String phraseTemp;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//receive the address of the bluetooth device
Intent newint = getIntent();
address = newint.getStringExtra(DeviceList.EXTRA_ADDRESS);
bt.execute();
//view of the ledControl layout
setContentView(R.layout.activity_led_control);
//call the widgtes
btnDis = (Button)findViewById(R.id.button_disconnect);
seek_r = (SeekBar)findViewById(R.id.seekBar_r);
seek_g = (SeekBar)findViewById(R.id.seekBar_g);
seek_b = (SeekBar)findViewById(R.id.seekBar_b);
seek_r.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
int progressChanged = 0;
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
progressChanged = progress;
}
public void onStartTrackingTouch(SeekBar seekBar) {
}
public void onStopTrackingTouch(SeekBar seekBar) {
msg("Rouge : " + progressChanged);
phraseTemp = phraseAEnvoyer.substring(3, 9);
phraseAEnvoyer = progressChanged + phraseTemp;
envoyerPhrase(phraseAEnvoyer);
}
});
seek_g.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
int progressChanged = 0;
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
progressChanged = progress;
}
public void onStartTrackingTouch(SeekBar seekBar) {
}
public void onStopTrackingTouch(SeekBar seekBar) {
msg("Vert : " + progressChanged);
phraseTemp = phraseAEnvoyer.substring(6, 9);
phraseAEnvoyer = phraseAEnvoyer.substring(0, 3);
phraseAEnvoyer = phraseAEnvoyer + progressChanged + phraseTemp;
envoyerPhrase(phraseAEnvoyer);
}
});
seek_b.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
int progressChanged = 0;
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
progressChanged = progress;
}
public void onStartTrackingTouch(SeekBar seekBar) {
}
public void onStopTrackingTouch(SeekBar seekBar) {
msg("Bleu : " + progressChanged);
phraseTemp = phraseAEnvoyer.substring(0, 6);
phraseAEnvoyer = phraseTemp + progressChanged;
envoyerPhrase(phraseAEnvoyer);
}
});
btnDis.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
Disconnect(); //close connection
}
});
}
private void Disconnect()
{
if (btSocket!=null) //If the btSocket is busy
{
try
{
btSocket.close(); //close connection
}
catch (IOException e)
{ msg("Error");}
}
finish(); //return to the first layout
}
private void envoyerPhrase(String phrase)
{
if (btSocket!=null)
{
try
{
btSocket.getOutputStream().write(phraseAEnvoyer.getBytes());
msg(phraseAEnvoyer);
}
catch (IOException e)
{
msg("Error");
}
}
}
private void msg(String s)
{
Toast.makeText(getApplicationContext(),s,Toast.LENGTH_LONG).show();
}
private class ConnectBT extends AsyncTask<Void, Void, Void> // UI thread
{
private boolean ConnectSuccess = true; //if it's here, it's almost connected
#Override
protected void onPreExecute()
{
progress = ProgressDialog.show(ledControlSeekBar.this, "Connecting...", "Please wait!"); //show a progress dialog
}
#Override
protected Void doInBackground(Void... devices) //while the progress dialog is shown, the connection is done in background
{
try
{
if (btSocket == null || !isBtConnected)
{
myBluetooth = BluetoothAdapter.getDefaultAdapter();//get the mobile bluetooth device
BluetoothDevice dispositivo = myBluetooth.getRemoteDevice(address);//connects to the device's address and checks if it's available
btSocket = dispositivo.createInsecureRfcommSocketToServiceRecord(myUUID);//create a RFCOMM (SPP) connection
BluetoothAdapter.getDefaultAdapter().cancelDiscovery();
btSocket.connect();//start connection
}
}
catch (IOException e)
{
ConnectSuccess = false;//if the try failed, you can check the exception here
}
return null;
}
#Override
protected void onPostExecute(Void result) //after the doInBackground, it checks if everything went fine
{
super.onPostExecute(result);
if (!ConnectSuccess)
{
msg("Connection Failed. Is it a SPP Bluetooth? Try again.");
finish();
}
else
{
msg("Connected.");
isBtConnected = true;
}
progress.dismiss();
}
}
}
I don't finish and some lines are useful sorry.
If someone can help me I will happy.
Thank you.

I have also the same error . I resolved this error by defining a function outside the onCreate() method. Inside that function you need to call the different seek bar findViewByid method . Like this
private void initializeVariables() {
// Showing progress dialog
pDialog = new ProgressDialog(Search.this);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
seekBar = (SeekBar) findViewById(R.id.seekBarprice);
seekBarKilometer = (SeekBar) findViewById(R.id.seekBarDis);
}
Declare pDialog first private ProgressDialog pDialog;
call the initializeVariables() method inside the oncreate method , here i mention my seekbar names replace these names with your code .
`

error in android application ArrayList

Hello how are you? I'm creating an android app news and is working very well, the only problem is when I'm doing the reading of the text and minimize the app to do something else and then return the app presents this error.
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: FATAL EXCEPTION: main
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at java.util.ArrayList.get(ArrayList.java:304)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at com.brfgd.ActivityDetailStory.setAdapterToListview(ActivityDetailStory.java:179)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at com.brfgd.ActivityDetailStory$MyTask.onPostExecute(ActivityDetailStory.java:171)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at com.brfgd.ActivityDetailStory$MyTask.onPostExecute(ActivityDetailStory.java:119)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at android.os.AsyncTask.finish(AsyncTask.java:631)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at android.os.AsyncTask.access$600(AsyncTask.java:177)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:99)
03-21 16:49:03.279 10567-10567/? E/AndroidRuntime: at android.os.Looper.loop(Looper.java:153)
part of the error
import android.content.Context;
import android.content.Intent;
import android.content.res.Resources;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.ads.AdListener;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.InterstitialAd;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
public class ActivityDetailStory extends AppCompatActivity {
int position;
String str_cid, str_cat_id, str_cat_image, str_cat_name, str_title, str_image, str_desc, str_date;
TextView news_title, news_date;
WebView news_desc;
ImageView img_news, img_fav;
DatabaseHandler db;
List<ItemStoryList> arrayOfRingcatItem;
ItemStoryList objAllBean;
final Context context = this;
ProgressBar progressBar;
LinearLayout content;
private AdView mAdView;
private InterstitialAd interstitial;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail_story);
final Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
final android.support.v7.app.ActionBar actionBar = getSupportActionBar();
if (actionBar != null) {
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setTitle(Constant.CATEGORY_TITLE);
}
//show admob banner ad
mAdView = (AdView) findViewById(R.id.adView);
mAdView.loadAd(new AdRequest.Builder().build());
mAdView.setAdListener(new AdListener() {
#Override
public void onAdClosed() {
}
#Override
public void onAdFailedToLoad(int error) {
mAdView.setVisibility(View.GONE);
}
#Override
public void onAdLeftApplication() {
}
#Override
public void onAdOpened() {
}
#Override
public void onAdLoaded() {
mAdView.setVisibility(View.VISIBLE);
}
});
content = (LinearLayout) findViewById(R.id.content);
progressBar = (ProgressBar) findViewById(R.id.progressBar);
img_fav = (FloatingActionButton) findViewById(R.id.img_fav);
img_news = (ImageView) findViewById(R.id.image);
news_title = (TextView) findViewById(R.id.title);
news_date = (TextView) findViewById(R.id.subtitle);
news_desc = (WebView) findViewById(R.id.desc);
db = new DatabaseHandler(ActivityDetailStory.this);
arrayOfRingcatItem = new ArrayList<ItemStoryList>();
//imageLoader = new ImageLoader(ActivityDetailStory.this);
if (JsonUtils.isNetworkAvailable(ActivityDetailStory.this)) {
new MyTask().execute(Constant.SERVER_URL + "/api.php?nid=" + Constant.NEWS_ITEMID);
MyApplication.getInstance().trackScreenView("Lendo de cara : " + (Constant.CATEGORY_TITLE));
}
else {
Toast.makeText(getApplicationContext(), "Problema com sua Rede de Internet", Toast.LENGTH_SHORT).show();
}
}
private class MyTask extends AsyncTask<String, Void, String> {
#Override
protected void onPreExecute() {
super.onPreExecute();
progressBar.setVisibility(View.VISIBLE);
}
#Override
protected String doInBackground(String... params) {
return JsonUtils.getJSONString(params[0]);
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
progressBar.setVisibility(View.GONE);
content.setVisibility(View.VISIBLE);
if (null == result || result.length() == 0) {
Toast.makeText(getApplicationContext(), "Problema com sua Rede de Internet!", Toast.LENGTH_SHORT).show();
} else {
try {
JSONObject mainJson = new JSONObject(result);
JSONArray jsonArray = mainJson.getJSONArray(Constant.CATEGORY_ARRAY_NAME);
JSONObject objJson = null;
for (int i = 0; i < jsonArray.length(); i++) {
objJson = jsonArray.getJSONObject(i);
ItemStoryList objItem = new ItemStoryList();
objItem.setCId(objJson.getString(Constant.CATEGORY_ITEM_CID));
objItem.setCategoryName(objJson.getString(Constant.CATEGORY_ITEM_NAME));
objItem.setCategoryImage(objJson.getString(Constant.CATEGORY_ITEM_IMAGE));
objItem.setCatId(objJson.getString(Constant.CATEGORY_ITEM_CAT_ID));
objItem.setNewsImage(objJson.getString(Constant.CATEGORY_ITEM_NEWSIMAGE));
objItem.setNewsHeading(objJson.getString(Constant.CATEGORY_ITEM_NEWSHEADING));
objItem.setNewsDescription(objJson.getString(Constant.CATEGORY_ITEM_NEWSDESCRI));
objItem.setNewsDate(objJson.getString(Constant.CATEGORY_ITEM_NEWSDATE));
arrayOfRingcatItem.add(objItem);
}
} catch (JSONException e) {
e.printStackTrace();
}
setAdapterToListview();
}
}
}
public void setAdapterToListview() {
//if(arrayOfRingcatItem.size()>0) {
objAllBean = arrayOfRingcatItem.get(0);
str_cid = objAllBean.getCId();
str_cat_name = objAllBean.getCategoryName();
str_cat_image = objAllBean.getCategoryImage();
str_cat_id = objAllBean.getCatId();
str_title = objAllBean.getNewsHeading();
str_desc = objAllBean.getNewsDescription();
str_image = objAllBean.getNewsImage();
str_date = objAllBean.getNewsDate();
news_title.setText(str_title);
news_date.setText(str_date);
news_desc.setBackgroundColor(Color.parseColor("#FFFFFF"));
news_desc.setFocusableInTouchMode(false);
news_desc.setFocusable(false);
news_desc.getSettings().setDefaultTextEncodingName("UTF-8");
WebSettings webSettings = news_desc.getSettings();
Resources res = getResources();
int fontSize = res.getInteger(R.integer.font_size);
webSettings.setDefaultFontSize(fontSize);
String mimeType = "text/html; charset=UTF-8";
String encoding = "utf-8";
String htmlText = str_desc;
String text = "<html><head><style type=\"text/css\">#font-face {font-family: MyFont;src: url(\"file:///android_asset/Roboto-Light.ttf\")}body {font-family: MyFont;font-size: medium; color: #525252;}</style></head><body>"
+ htmlText + "</body></html>";
news_desc.loadData(text, mimeType, encoding);
List<Pojo> pojolist = db.getFavRow(str_cat_id);
if (pojolist.size() == 0) {
img_fav.setImageResource(R.drawable.ic_bookmark_outline);
} else {
if (pojolist.get(0).getCatId().equals(str_cat_id))
;
{
img_fav.setImageResource(R.drawable.ic_bookmark_white);
}
}
img_fav.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
List<Pojo> pojolist = db.getFavRow(str_cat_id);
if (pojolist.size() == 0) {
db.AddtoFavorite(new Pojo(str_cat_id, str_cid, str_cat_name, str_title, str_image, str_desc, str_date));
Toast.makeText(getApplicationContext(), "Leitura Marcada", Toast.LENGTH_SHORT).show();
img_fav.setImageResource(R.drawable.ic_bookmark_white);
interstitial = new InterstitialAd(ActivityDetailStory.this);
interstitial.setAdUnitId(getString(R.string.admob_interstitial_id));
AdRequest adRequest = new AdRequest.Builder().build();
interstitial.loadAd(adRequest);
interstitial.setAdListener(new AdListener() {
public void onAdLoaded() {
if (interstitial.isLoaded()) {
interstitial.show();
}
}
});
} else {
if (pojolist.get(0).getCatId().equals(str_cat_id)) {
db.RemoveFav(new Pojo(str_cat_id));
Toast.makeText(getApplicationContext(), "Leitura desmarcada!", Toast.LENGTH_SHORT).show();
img_fav.setImageResource(R.drawable.ic_bookmark_outline);
}
}
}
});
//}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_story, menu);
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem menuItem) {
switch (menuItem.getItemId()) {
case android.R.id.home:
onBackPressed();
break;
case R.id.menu_share:
Intent sendIntent = new Intent();
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, "Estou lendo vários livro com esse app estou adorando, baixe já, Recomendo "+"https://play.google.com/store/apps/details?id="+getPackageName());
sendIntent.setType("text/plain");
startActivity(sendIntent);
break;
default:
return super.onOptionsItemSelected(menuItem);
}
return true;
}
#Override
protected void onPause() {
// mAdView.pause();
super.onPause();
}
#Override
protected void onResume() {
super.onResume();
//mAdView.resume();
}
#Override
protected void onDestroy() {
//mAdView.destroy();
super.onDestroy();
}
}

You should do this:
public void setAdapterToListview() {
if(arrayOfRingcatItem.size>0){
objAllBean = arrayOfRingcatItem.get(0);
str_cid = objAllBean.getCId();
str_cat_name = objAllBean.getCategoryName();
}
}
EDIT: onResume()
#Override
protected void onResume(){
super.onResume();
arrayOfRingcatItem = new ArrayList<ItemStoryList>();
//imageLoader = new ImageLoader(ActivityDetailStory.this);
if (JsonUtils.isNetworkAvailable(ActivityDetailStory.this)) {
new MyTask().execute(Constant.SERVER_URL + "/api.php?nid=" + Constant.NEWS_ITEMID);
MyApplication.getInstance().trackScreenView("Lendo de cara : " + (Constant.CATEGORY_TITLE));
}
else {
Toast.makeText(getApplicationContext(), "Problema com sua Rede de Internet", Toast.LENGTH_SHORT).show();
}
}
Or you can save the array in the Application class and use it from there, or in a singleton. The error it's because when the activity go to background Android can release some memory and delete your array.
EDIT 2: You can use SharedPreferences to save the id.
You have to put this code in onCreate:
SharedPreferences opc=getSharedPreferences("AppName", 0);
SharedPreferences.Editor editor =opc.edit();
editor.putInt("ID_SAVED",NEWS_ITEMID); editor.commit();
And in the onResume:
SharedPreferences opc=getSharedPreferences("AppName", 0);
NEWS_ITEMID=opc.getInt("ID_SAVED", -1);

Based on what you stated above everything is working fine except:
minimize the app to do something else and then return the app presents this error
You may need to reinitialize code in:
#Override
public void onResume(){
super.onResume();
// put your code here to repopulate arraylist...
refreshMyData();
}
refreshMyData could have:
public void refreshMyData(){
if (JsonUtils.isNetworkAvailable(ActivityDetailStory.this)) {
new MyTask().execute(Constant.SERVER_URL + "/api.php?nid=" + Constant.NEWS_ITEMID);
MyApplication.getInstance().trackScreenView("Lendo de cara : " + (Constant.CATEGORY_TITLE));
}else {
Toast.makeText(getApplicationContext(), "Problema com sua Rede de Internet", Toast.LENGTH_SHORT).show();
}
}
Use this method in your oncreate as well, that way you can have the same method call when creating the activity and resuming.
Sources:
How to use onResume()?

Android, gps. App with GPS's localizzation

I've ha problem: I 'm implementing a secondary Activity that give to me user's position. From Page1.java, through a button, open Track.java when I would like to show the coordinates of the user's location. The problem is when I click on this button: the application is closed!
This is the code of Page1.java:
package com.example.giacomob.myapplication;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
/**
* Created by Giacomo B on 05/08/2015.
*/
public class Page1 extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_page1);
// String dato1 = getIntent().getExtras().getString("NomeDati1");
//Intent intent = getIntent(); // Point 1
// Bundle bundle = intent.getExtras(); // Point 2
// String data1 = bundle.getString("NomeDati1"); // Point 3
String dato1 = getIntent().getExtras().getString("NomeDati1"); //preleva la stringa
Toast.makeText(this, dato1, Toast.LENGTH_SHORT).show(); //PROVA: questo mi fa comparire una specie di label notifica trasparente con il valore di "data1"
Log.d("TAG", "data1:" + dato1); //credo sia una specie di debug
// String salve = getIntent().getExtras().getString("ciao");
// System.out.println("questo è il valore della prima variabile" +salve);
//FARE CONTROLLO IN CASO IL FILE XML E' VUOTO E QUINDI LA STRINGA E' VUOTA
String[] arr = dato1.split("\\|");
for (int i = 0; i < arr.length; i++) {
System.out.println(i + " => " + arr[i]);
}
final ArrayList <String> listp = new ArrayList<String>();
for (int i = 0; i < arr.length; ++i) {
listp.add(arr[i]);
}
// recupero la lista dal layout
final ListView mylist = (ListView) findViewById(R.id.listView1);
// creo e istruisco l'adattatore
final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, listp);
// inietto i dati
mylist.setAdapter(adapter);
Button b_load=(Button)findViewById(R.id.button_send2);
b_load.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
Intent openTrack = new Intent(Page1.this, Track.class);
startActivity(openTrack);
}
});
}
This is the code of Track.java:
package com.example.giacomob.myapplication;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.widget.TextView;
/**
* Created by Giacomo B on 07/08/2015.
*/
public class Track extends ActionBarActivity implements LocationListener {
/* #Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_track);
}
String providerId = Settings.Secure.getString(getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
private final int MIN_DIST=20;
private static final int MIN_PERIOD=30000; */
private String providerId = LocationManager.GPS_PROVIDER;
private LocationManager locationManager=null;
private static final int MIN_DIST=20;
private static final int MIN_PERIOD=30000;
/*if(!providerId.contains("gps"))
{
final Intent intent = new Intent();
intent.setClassName("com.android.settings", "com.android.settings.widget.SettingsAppWidgetProvider");
intent.addCategory(Intent.CATEGORY_ALTERNATIVE);
intent.setData(Uri.parse("3"));
sendBroadcast(intent);
}*/
#Override
protected void onResume()
{
if (!locationManager.isProviderEnabled(providerId))
{
Intent gpsOptionsIntent = new Intent(
android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(gpsOptionsIntent);
}
super.onResume();
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
if (!locationManager.isProviderEnabled(providerId))
{
Intent gpsOptionsIntent = new Intent(
android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(gpsOptionsIntent);
}
else
locationManager.requestLocationUpdates(providerId, MIN_PERIOD, MIN_DIST, this);
}
private void updateGUI(Location location)
{
double latitude=location.getLatitude();
double longitude=location.getLongitude();
String msg="Ci troviamo in coordinate ("+latitude+","+longitude+")";
TextView txt= (TextView) findViewById(R.id.locationText);
txt.setText(msg);
}
#Override
protected void onPause()
{
super.onPause();
locationManager.removeUpdates(this);
}
#Override
public void onLocationChanged(Location location)
{
updateGUI(location);
}
#Override
public void onStatusChanged(String s, int i, Bundle bundle)
{ }
#Override
public void onProviderEnabled(String s)
{ }
#Override
public void onProviderDisabled(String s)
{ }
}
And this is the code of the xml file associate to Track.java, called "activity_track.xml":
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:text="In attesa di essere localizzati..."
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:textSize="25sp"
android:id="#+id/locationText"/>
</RelativeLayout>
This is LogCat's code:
08-08 00:04:23.801 2217-2217/com.example.giacomob.myapplication I/art﹕ Not late-enabling -Xcheck:jni (already on)
08-08 00:04:24.035 2217-2234/com.example.giacomob.myapplication I/OpenGLRenderer﹕ Initialized EGL, version 1.4
08-08 00:04:24.070 2217-2234/com.example.giacomob.myapplication W/EGL_emulation﹕ eglSurfaceAttrib not implemented
08-08 00:04:24.070 2217-2234/com.example.giacomob.myapplication W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xb4398620, error=EGL_SUCCESS
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ Root element :destinazione
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ ----------------------------
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ [ 08-08 00:04:25.762 2217: 2217 I/System.out ]
Current Element :destinazione
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ Coordinata X : 1
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ 1
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ Naziome : Italia
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ Paese : Cannole
08-08 00:04:25.762 2217-2217/com.example.giacomob.myapplication I/System.out﹕ Via : Piazza San Vincenzo
08-08 00:04:25.864 2217-2217/com.example.giacomob.myapplication I/System.out﹕ 0 => 1
08-08 00:04:25.864 2217-2217/com.example.giacomob.myapplication I/System.out﹕ 1 => 2
08-08 00:04:25.864 2217-2217/com.example.giacomob.myapplication I/System.out﹕ 2 => Italia
08-08 00:04:25.864 2217-2217/com.example.giacomob.myapplication I/System.out﹕ 3 => Cannole
08-08 00:04:25.864 2217-2217/com.example.giacomob.myapplication I/System.out﹕ 4 => Piazza San Vincenzo
08-08 00:04:25.919 2217-2234/com.example.giacomob.myapplication W/EGL_emulation﹕ eglSurfaceAttrib not implemented
08-08 00:04:25.919 2217-2234/com.example.giacomob.myapplication W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xa511b960, error=EGL_SUCCESS
08-08 00:04:26.166 2217-2234/com.example.giacomob.myapplication W/EGL_emulation﹕ eglSurfaceAttrib not implemented
08-08 00:04:26.166 2217-2234/com.example.giacomob.myapplication W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xb4398900, error=EGL_SUCCESS
08-08 00:04:26.893 2217-2217/com.example.giacomob.myapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.giacomob.myapplication, PID: 2217
java.lang.RuntimeException: Unable to resume activity {com.example.giacomob.myapplication/com.example.giacomob.myapplication.Track}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.location.LocationManager.isProviderEnabled(java.lang.String)' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2989)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3020)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.location.LocationManager.isProviderEnabled(java.lang.String)' on a null object reference
at com.example.giacomob.myapplication.Track.onResume(Track.java:39)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1257)
at android.app.Activity.performResume(Activity.java:6076)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2978)
            at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3020)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
This is the update of Track.java
package com.example.giacomob.myapplication;
import android.content.Context;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.widget.TextView;
/**
* Created by Giacomo B on 07/08/2015.
*/
public class Track extends ActionBarActivity implements LocationListener {
/* #Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_track);
}
String providerId = Settings.Secure.getString(getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
private final int MIN_DIST=20;
private static final int MIN_PERIOD=30000; */
private String providerId = LocationManager.GPS_PROVIDER;
// private LocationManager locationManager=null;
LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
private static final int MIN_DIST = 20;
private static final int MIN_PERIOD = 30000;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_page1);
this.locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
}
#Override
protected void onResume()
{
if (!locationManager.isProviderEnabled(providerId))
{
Intent gpsOptionsIntent = new Intent(
android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(gpsOptionsIntent);
}
super.onResume();
// LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
if (!locationManager.isProviderEnabled(providerId))
{
Intent gpsOptionsIntent = new Intent(
android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(gpsOptionsIntent);
}
else
locationManager.requestLocationUpdates(providerId, MIN_PERIOD, MIN_DIST, this);
}
private void updateGUI(Location location)
{
double latitude=location.getLatitude();
double longitude=location.getLongitude();
String msg="Ci troviamo in coordinate ("+latitude+","+longitude+")";
TextView txt= (TextView) findViewById(R.id.locationText);
txt.setText(msg);
}
#Override
protected void onPause()
{
super.onPause();
locationManager.removeUpdates(this);
}
#Override
public void onLocationChanged(Location location)
{
updateGUI(location);
}
#Override
public void onStatusChanged(String s, int i, Bundle bundle)
{ }
#Override
public void onProviderEnabled(String s)
{ }
#Override
public void onProviderDisabled(String s)
{ }
}
I don't understand the reason for witch the app is closed! Please, help me! Thanks

You never instantiate your LocationManager reference. This must be done in onCreate like this:
LocationManager manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
The app crashes due to a Null Pointer Exception.

The answer of andrewdleach is correct; and the exact line to add in onCreate is this:
this.locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
EDIT:
ok, try to use this
package com.example.giacomob.myapplication;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.widget.TextView;
/**
* Created by Giacomo B on 07/08/2015.
*/
public class Track extends ActionBarActivity implements LocationListener
{
String providerId = Settings.Secure.getString(getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
private final int MIN_DIST=20;
private static final int MIN_PERIOD=30000; */
private String providerId = LocationManager.GPS_PROVIDER;
private LocationManager locationManager=null;
private static final int MIN_DIST=20;
private static final int MIN_PERIOD=30000;
/*if(!providerId.contains("gps"))
{
final Intent intent = new Intent();
intent.setClassName("com.android.settings", "com.android.settings.widget.SettingsAppWidgetProvider");
intent.addCategory(Intent.CATEGORY_ALTERNATIVE);
intent.setData(Uri.parse("3"));
sendBroadcast(intent);
}*/
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_track);
this.locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
}
#Override
protected void onResume()
{
if (locationManager == null)
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
if (!locationManager.isProviderEnabled(providerId))
{
Intent gpsOptionsIntent = new Intent(
android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(gpsOptionsIntent);
}
super.onResume();
if (!locationManager.isProviderEnabled(providerId))
{
Intent gpsOptionsIntent = new Intent(
android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(gpsOptionsIntent);
}
else
{
locationManager.requestLocationUpdates(providerId, MIN_PERIOD, MIN_DIST, this);
}
}
private void updateGUI(Location location)
{
double latitude=location.getLatitude();
double longitude=location.getLongitude();
String msg="Ci troviamo in coordinate ("+latitude+","+longitude+")";
TextView txt= (TextView) findViewById(R.id.locationText);
txt.setText(msg);
}
#Override
protected void onPause()
{
super.onPause();
if (locationManager != null)
locationManager.removeUpdates(this);
}
#Override
public void onLocationChanged(Location location)
{
updateGUI(location);
}
#Override
public void onStatusChanged(String s, int i, Bundle bundle)
{ }
#Override
public void onProviderEnabled(String s)
{ }
#Override
public void onProviderDisabled(String s)
{ }
}

Can't run my MQTT application on Android Studio

i'm testing a personal MQTT application but it failed when i click on the connect button... There is an exception but i don't know where it comes from.
Here is my code
MainActivity.java :
package com.application.phoste.homecontrol;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity {
private Paho paho = null;
EditText topic = null;
EditText message = null;
Button connect = null;
Button send = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
paho = new Paho();
topic = (EditText) findViewById(R.id.topic);
message = (EditText) findViewById(R.id.message);
connect = (Button) findViewById(R.id.connect);
connect.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
paho.connect();
String res = (paho.isConnected()) ? "Connected" : "Not Connected";
Toast toast = Toast.makeText(getApplicationContext(), res, Toast.LENGTH_SHORT);
toast.show();
}
});
send = (Button) findViewById(R.id.send);
send.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
paho.publish(topic.getText().toString(), message.getText().toString());
Toast toast = Toast.makeText(getApplicationContext(), "Message sent", Toast.LENGTH_SHORT);
toast.show();
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
Paho.java :
package com.application.phoste.homecontrol;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
public class Paho implements MqttCallback {
private MqttClient client;
private static final String BROKER = "tcp://192.168.1.189:1883";
private static final int QOS = 2;
public void connect() {
try {
client = new MqttClient(BROKER, MqttClient.generateClientId());
MqttConnectOptions options = new MqttConnectOptions();
options.setConnectionTimeout(1);
client.setCallback(this);
client.connect();
} catch (MqttException e) {
e.getMessage();
}
}
public void disconnect() {
if (client.isConnected()) {
try {
client.disconnect();
} catch (MqttException e) {
e.getMessage();
}
}
}
public boolean isConnected() {
return client.isConnected();
}
public void publish(String topic, String m) {
try {
MqttMessage message = new MqttMessage(m.getBytes());
message.setQos(2);
client.publish(topic, message);
} catch (MqttException e) {
e.getMessage();
}
}
#Override
public void connectionLost(Throwable throwable) {
}
#Override
public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
}
#Override
public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
}
}
The exception :
07-29 15:17:23.988 15718-15718/com.application.phoste.homecontrol E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.application.phoste.homecontrol, PID: 15718
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean org.eclipse.paho.client.mqttv3.MqttClient.isConnected()' on a null object reference
at com.application.phoste.homecontrol.Paho.isConnected(Paho.java:44)
at com.application.phoste.homecontrol.MainActivity$1.onClick(MainActivity.java:35)
at android.view.View.performClick(View.java:4756)
at android.view.View$PerformClick.run(View.java:19748)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
I also added the <uses-permission android:name="android.permission.internet"/> line into the AndroidManifest.xml
Where am I wrong ?
Edit :
I just realized i had some warning messages even before the exception was thrown... Here they are :
07-29 17:26:52.673 32706-32706/com.application.phoste.homecontrol W/System.err﹕ MqttException (0)
07-29 17:26:52.673 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at org.eclipse.paho.client.mqttv3.persist.MqttDefaultFilePersistence.open(MqttDefaultFilePersistence.java:80)
07-29 17:26:52.673 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at org.eclipse.paho.client.mqttv3.MqttAsyncClient.<init>(MqttAsyncClient.java:286)
07-29 17:26:52.674 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at org.eclipse.paho.client.mqttv3.MqttAsyncClient.<init>(MqttAsyncClient.java:167)
07-29 17:26:52.674 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at org.eclipse.paho.client.mqttv3.MqttClient.<init>(MqttClient.java:224)
07-29 17:26:52.674 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at org.eclipse.paho.client.mqttv3.MqttClient.<init>(MqttClient.java:136)
07-29 17:26:52.675 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at com.application.phoste.homecontrol.MainActivity.onCreate(MainActivity.java:35)
07-29 17:26:52.675 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.app.Activity.performCreate(Activity.java:5933)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2282)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2389)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.app.ActivityThread.access$900(ActivityThread.java:147)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1296)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:102)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.os.Looper.loop(Looper.java:135)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5254)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at java.lang.reflect.Method.invoke(Native Method)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:372)
07-29 17:26:52.676 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898)
07-29 17:26:52.678 32706-32706/com.application.phoste.homecontrol W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
I really hope someone could help me with that.
I also changed my code to do everything in the MainActivity :
package com.application.phoste.homecontrol;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
public class MainActivity extends Activity {
EditText topic = null;
EditText message = null;
Button send = null;
Button debug = null;
MqttClient client;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
try {
client = new MqttClient("tcp://m2m.eclipse.org:1883", MqttClient.generateClientId());
MqttConnectOptions options = new MqttConnectOptions();
options.setConnectionTimeout(1);
client.connect();
} catch (MqttException e) {
e.printStackTrace();
}
topic = (EditText) findViewById(R.id.topic);
message = (EditText) findViewById(R.id.message);
send = (Button) findViewById(R.id.send);
send.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
MqttMessage m = new MqttMessage(message.getText().toString().getBytes());
m.setQos(2);
client.publish(topic.getText().toString(), m);
Toast toast = Toast.makeText(getApplicationContext(), "Message sent", Toast.LENGTH_SHORT);
toast.show();
} catch (MqttException e) {
e.printStackTrace();
}
}
});
debug = (Button) findViewById(R.id.debug);
debug.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String res = (client == null) ? "Null" : "Not Null";
Toast toast = Toast.makeText(getApplicationContext(), res, Toast.LENGTH_SHORT);
toast.show();
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
But it still doesn't work, I get the Null Toast from de debug button.

OK, so you need to set up the MQTT file persistence path and this will require write access to the SD card and the path you give it.
https://www.eclipse.org/paho/files/javadoc/index.html?org/eclipse/paho/client/mqttv3/persist/MqttDefaultFilePersistence.html
You will also need to add the right permission to access the file system.

Your "client" object is not initialized when you are trying to take some action on it.
Move this line: client = new MqttClient(BROKER, MqttClient.generateClientId());
to somewhere else in your application (maybe onCreate() ) to ensure the variable is properly initialized before you access it.i

fatal exception: main java.lang.RuntimeException in android map,

i'm currently working on android maps by following this tutorial http://developer.android.com/training/location/retrieve-current.html, and i keep getting error.there are 4 warnings and i tried to fix it but when i run it again the error message fatal exception still showing
here's the warning messages:
1. the message servicesConnected() from the type LokasiKampus is never used locally
2. the value of local variable kampus is not used
3. the value of local variable laboratorium is not used
4.the value of local variable myCurrentLocation is not used
here's my Java code
package ninth.example.dteinformationcenter;
import android.app.Activity;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.Intent;
import android.content.IntentSender;
import android.location.Location;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesClient;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.location.LocationClient;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.MapView;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
public class LokasiKampus extends FragmentActivity implements
GooglePlayServicesClient.ConnectionCallbacks,
GooglePlayServicesClient.OnConnectionFailedListener{
static final LatLng Kampus = new LatLng (-7.775038, 110.373253);
static final LatLng Laboratorium = new LatLng (-7.765437, 110.374496);
private static final int CONNECTION_FAILURE_RESOLUTION_REQUEST = 9000;
private GoogleMap map;
private GooglePlayServicesClient myLocationClient;
public static class ErrorDialogFragment extends DialogFragment {
private Dialog mDialog;
public ErrorDialogFragment() {
super();
mDialog = null;
}
public void setDialog(Dialog dialog) {
mDialog = dialog;
}
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
return mDialog;
}
public void show(FragmentManager supportFragmentManager, String tag) {
// TODO Auto-generated method stub
}
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch(requestCode) {
case CONNECTION_FAILURE_RESOLUTION_REQUEST :
switch(resultCode) {
case Activity.RESULT_OK : break;
}
}
}
**private boolean servicesConnected()** {
int resultCode = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
if (ConnectionResult.SUCCESS == resultCode) {
Log.d("Location Updated", "Google Play Services is available");
return true;
} else {
Dialog ErrorDialog = GooglePlayServicesUtil
.getErrorDialog(resultCode, this, CONNECTION_FAILURE_RESOLUTION_REQUEST);
if (ErrorDialog != null) {
ErrorDialogFragment errorFragment = new ErrorDialogFragment();
errorFragment.setDialog(ErrorDialog);
errorFragment.show(getSupportFragmentManager(), "Location Updates");
}
return false;
}
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.lokasi_kampus);
map = ((MapFragment) getFragmentManager().findFragmentById(R.id.lokasikampus)).getMap();
if (map != null) {
**Marker kampus = map.addMarker(new MarkerOptions().position(Kampus)
.title("Kampus "));
Marker laboratorium = map.addMarker(new MarkerOptions().position(Laboratorium)
.position(Laboratorium)
.title("Laboratorium")
);**
map.moveCamera(CameraUpdateFactory.newLatLngZoom(Kampus, 18));
map.animateCamera(CameraUpdateFactory.zoomTo(10), 2000, null);
}
LocationClient myLocationClient = new LocationClient(this,this,this);
**Location myCurrentLocation;
myCurrentLocation = myLocationClient.getLastLocation();**
}
#Override
public void onConnected(Bundle dataBundle) {
Toast.makeText(this, "Connected", Toast.LENGTH_SHORT).show();
}
#Override
public void onDisconnected() {
Toast.makeText(this, "Disconnected, please re-connect", Toast.LENGTH_SHORT).show();
}
#Override
public void onConnectionFailed(ConnectionResult connectionResult) {
if(connectionResult.hasResolution()) {
try {
connectionResult.startResolutionForResult(this, CONNECTION_FAILURE_RESOLUTION_REQUEST);
} catch(IntentSender.SendIntentException e) {
e.printStackTrace();
}
} else {
Toast.makeText(this, "Connection Failed", Toast.LENGTH_SHORT).show();
}
}
#Override
protected void onStart() {
super.onStart();
myLocationClient.connect();
}
#Override
protected void onStop() {
myLocationClient.disconnect();
super.onStop();
}
}
this is the error message
FATAL EXCEPTION: main
Process: ninth.example.dteinformationcenter, PID: 1443
java.lang.RuntimeException: Unable to start activity ComponentInfo{ninth.example.dteinformationcenter/ninth.example.dteinformationcenter.LokasiKampus}: java.lang.IllegalStateException: Not connected. Call connect() and wait for onConnected() to be called.
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalStateException: Not connected. Call connect() and wait for onConnected() to be called.
at com.google.android.gms.internal.hb.cn(Unknown Source)
at com.google.android.gms.internal.jg.b(Unknown Source)
at com.google.android.gms.internal.jg$c.cn(Unknown Source)
at com.google.android.gms.internal.jf.getLastLocation(Unknown Source)
at com.google.android.gms.internal.jg.getLastLocation(Unknown Source)
at com.google.android.gms.location.LocationClient.getLastLocation(Unknown Source)
at ninth.example.dteinformationcenter.LokasiKampus.onCreate(LokasiKampus.java:112)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)