Yet another "Can't create handler inside thread that has not called Looper.prepare()" topic - multithreading

Question

I have this code which is an Activity that when started will check for internet connection, if there is a connection, then life goes on. Else a dialog appears to turn on the connection. However I made a thread that each 10 seconds will check for connection and in case the connection was lost it will display the dialog again.
package greensmartcampus.eu.smartcampususerfeedbackapp;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.provider.Settings;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;
import java.net.InetAddress;
public class HomeScreen extends AbstractPortraitActivity {
private static final int WIFI_REQUEST_CODE = 1;
private boolean networkSettingsDialogOpened = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home_screen);
this.runOnUiThread(new Runnable() {
#Override
public void run() {
while (!HomeScreen.this.isInternetAvailable()) {
if (!networkSettingsDialogOpened)
HomeScreen.this.createNetErrorDialog();
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
});
}
(...)
private boolean isInternetAvailable() {
try {
final InetAddress ipAddr = InetAddress.getByName("google.com");
if (ipAddr.equals("")) {
return false;
} else {
return true;
}
} catch (Exception e) {
return false;
}
}
private void createNetErrorDialog() {
networkSettingsDialogOpened = true;
final AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("You need a network connection to use this application. Please turn on mobile network or Wi-Fi in Settings.")
.setTitle("Unable to connect")
.setCancelable(false)
.setPositiveButton("Settings",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
Intent i = new Intent(Settings.ACTION_WIRELESS_SETTINGS);
startActivityForResult(i, WIFI_REQUEST_CODE);
}
}
)
.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
HomeScreen.this.finish();
}
}
);
final AlertDialog alert = builder.create();
alert.show();
}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == WIFI_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
networkSettingsDialogOpened = false;
Toast.makeText(HomeScreen.this, "Returned Ok",
Toast.LENGTH_LONG).show();
}
if (resultCode == RESULT_CANCELED) {
networkSettingsDialogOpened = false;
Toast.makeText(HomeScreen.this, "Returned Canceled",
Toast.LENGTH_LONG).show();
}
}
}
}
However I am getting the following error:
02-03 18:13:14.525 2683-2699/greensmartcampus.eu.smartcampususerfeedbackapp E/AndroidRuntime﹕ FATAL EXCEPTION: Thread-193
Process: greensmartcampus.eu.smartcampususerfeedbackapp, PID: 2683
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:200)
at android.os.Handler.<init>(Handler.java:114)
at android.app.Dialog.<init>(Dialog.java:108)
at android.app.AlertDialog.<init>(AlertDialog.java:125)
at android.app.AlertDialog$Builder.create(AlertDialog.java:967)
at greensmartcampus.eu.smartcampususerfeedbackapp.HomeScreen.createNetErrorDialog(HomeScreen.java:97)
at greensmartcampus.eu.smartcampususerfeedbackapp.HomeScreen.access$200(HomeScreen.java:15)
at greensmartcampus.eu.smartcampususerfeedbackapp.HomeScreen$1.run(HomeScreen.java:29)
Note: Line 97 is the one containing:
final AlertDialog alert = builder.create();
I googled alot, I am already using the cliche answer of runOnUiThread, but it doesn't fix it.
What am I missing?

Answer 1

The way you are checking the internet I guess you are causing your UI thread to sleep. You should do it like this.
Create one Handler and Thread running flag:
Handler mHandler = new Handler();
boolean isRunning = true;
Then, use this thread from your onCreate() method :
new Thread(new Runnable() {
#Override
public void run() {
while (isRunning) {
try {
Thread.sleep(10000);
mHandler.post(new Runnable() {
#Override
public void run() {
if(!HomeScreen.this.isInternetAvailable()){
if (!networkSettingsDialogOpened)
HomeScreen.this.createNetErrorDialog();
}
}
});
} catch (Exception e) {
}
}
}
}).start();
Change this method slightly
private boolean isInternetAvailable() {
try {
final InetAddress ipAddr = InetAddress.getByName("google.com");
if (ipAddr.equals("")) {
return false;
} else {
isRunning = true;
return true;
}
} catch (Exception e) {
return false;
}
}

Answer 2

You can't call Thread.sleep() from code that is running on the UI thread. This is your code:
this.runOnUiThread(new Runnable() {
#Override
public void run() {
while (!HomeScreen.this.isInternetAvailable()) {
if (!networkSettingsDialogOpened)
HomeScreen.this.createNetErrorDialog();
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
});
You jest need to run the bit of code that shows the Dialog on the UI thread. Try this instead:
new Thread(new Runnable() {
#Override
public void run() {
while (!HomeScreen.this.isInternetAvailable()) {
if (!networkSettingsDialogOpened)
// Show the Dialog on the UI thread
HomeScreen.this.runOnUiThread(new Runnable() {
#Override
public void run() {
HomeScreen.this.createNetErrorDialog();
}
});
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();