java – Can't create handler inside thread that has not called Looper.prepare()-ThrowExceptions

Exception or error:

I get this error “Can’t create handler inside thread that has not called Looper.prepare()”

Can you tell me how to fix it?

public class PaymentActivity extends BaseActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.payment);

    final Button buttonBank = (Button) findViewById(R.id.buttonBank);

    buttonBank.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            progressDialog = ProgressDialog.show(PaymentActivity.this, "",
                    "Redirecting to payment gateway...", true, true);

            new Thread() {
                public void run() {
                    try {
                        startPayment("Bank");
                    } catch (Exception e) {
                        alertDialog.setMessage(e.getMessage());
                        handler.sendEmptyMessage(1);
                        progressDialog.cancel();
                    }
                }
            }.start();
        }

    });

StartPayment Method:

    private void startPayment(String id) {
    Bundle b = getIntent().getExtras();
    final Sail sail = b.getParcelable(Constant.SAIL);

    final Intent bankIntent = new Intent(this, BankActivity.class);

    try {
        Reservation reservation = RestService.createReservation(
                sail.getId(),
                getSharedPreferences(Constant.PREF_NAME_CONTACT, 0));
        bankIntent.putExtra(Constant.RESERVATION, reservation);

        // <workingWithDB> Storing Reservation info in Database
        DBAdapter db = new DBAdapter(this);
        db.open();
        @SuppressWarnings("unused")
        long rowid;
        rowid = db.insertRow(sail.getId(), sail.getFrom(),
                sail.getTo(), sail.getShip(), sail.getDateFrom().getTime(),
                sail.getPrice().toString(), reservation.getId().floatValue());
        db.close();
        // </workingWithDB>

        String html = PaymentService.getRedirectHTML(id, reservation);

        bankIntent.putExtra(Constant.BANK, html);
    } catch (Exception e) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        AlertDialog alertDialog = builder.create();
        alertDialog.setMessage(e.getMessage());
        alertDialog.show();
    }

    startActivity(bankIntent);
}
How to solve:

You should know that when you try to modify your UI , the only thread who can do that is the UiThread.

So if you want to modify your UI in another thread, try to use the method: Activity.runOnUiThread(new Runnable);

Your code should be like this :

 new Thread() {
    public void run() {  
        YourActivity.this.runOnUiThread(new Runnable(){

             @Override
             public void run(){
                 try {
                      startPayment("Bank");//Edit,integrate this on the runOnUiThread
                 } catch (Exception e) {
                     alertDialog.setMessage(e.getMessage());
                     handler.sendEmptyMessage(1);
                     progressDialog.cancel();
                 } 
            });                
           }
      }
  }.start();

###

I assume you create a Handler in startPayment() method. You can’t do that, as handlers can be created on th UI thread only. Just create it in your activity class.

###

Instead of new Thread() line, try giving

this.runOnUiThread(new Runnable() {

###

you cant change any UI in thread you can use runOnUIThread or AsyncTask for more detail about this click here

###

I’ve found that most thread handling can be replaced by AsyncTasks like this:

public class TestStuff extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button buttonBank = (Button) findViewById(R.id.button);
        buttonBank.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                new StartPaymentAsyncTask(TestStuff.this).execute((Void []) null);
            }
        });
    }

    private class StartPaymentAsyncTask extends AsyncTask<Void, Void, String> {
        private ProgressDialog dialog;
        private final Context context;

        public StartPaymentAsyncTask(Context context) {
            this.context = context;
        }

        @Override
        protected void onPreExecute() {
            dialog = new ProgressDialog(context);
            // setup your dialog here
            dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            dialog.setMessage(context.getString(R.string.doing_db_work));
            dialog.setCancelable(false);
            dialog.show();
        }

        @Override
        protected String doInBackground(Void... ignored) {
            String returnMessage = null;
            try {
                startPayment("Bank");
            } catch (Exception e) {
                returnMessage = e.getMessage();
            }
            return returnMessage;
        }

        @Override
        protected void onPostExecute(String message) {
            dialog.dismiss();
            if (message != null) {
                // process the error (show alert etc)
                Log.e("StartPaymentAsyncTask", String.format("I received an error: %s", message));
            } else {
                Log.i("StartPaymentAsyncTask", "No problems");
            }
        }
    }

    public void startPayment(String string) throws Exception {
        SystemClock.sleep(2000); // pause for 2 seconds for dialog
        Log.i("PaymentStuff", "I am pretending to do some work");
        throw new Exception("Oh dear, database error");
    }
}

I pass in the Application Context to the Async so it can create dialogs from it.

The advantage of doing it this way is you know exactly which methods are run in your UI and which are in a separate background thread. Your main UI thread isn’t delayed, and the separation into small async tasks is quite nice.

The code assumes your startPayment() method does nothing with the UI, and if it does, move it into the onPostExecute of the AsyncTask so it’s done in the UI thread.

###

Try

final Handler handlerTimer = new Handler(Looper.getMainLooper());
        handlerTimer.postDelayed(new Runnable() {
            public void run() {
                                ...... 

                              }
                                                 }, time_interval});

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