How to input a byte array in an Edittext Dialog in Android

Here is an example of how you could possibly implement this functionality. I've used your code and modified it slightly.

MainActivity.java

package com.example.test;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.text.InputFilter;
import android.text.InputType;
import android.text.method.DigitsKeyListener;
import android.util.Log;
import android.widget.EditText;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        final EditText passtext = new EditText(this);

        // Set the length to 8 characters
        passtext.setFilters(new InputFilter[] { new InputFilter.LengthFilter(8) });

        // Set the keypad to numeric
        passtext.setInputType(InputType.TYPE_CLASS_NUMBER);

        // Only allow the user to enter 0 and 1 numbers
        passtext.setKeyListener(DigitsKeyListener.getInstance("01"));

        new AlertDialog.Builder(this).setTitle("Password Modification").setMessage("Please, introduce the new 8-bit password (with 1 or 0):").setView(passtext).setPositiveButton("OK", new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int which) {

                String binaryDigits = passtext.getText().toString().trim();

                if (binaryDigits != null && !binaryDigits.isEmpty()) {

                    // Convert the entered digits to decimal
                    int decimalValue = Integer.parseInt(binaryDigits, 2);

                    // Convert the entered digits to hex
                    String hex = Integer.toHexString(decimalValue);

                    Log.d(MainActivity.class.getSimpleName(), "Decimal: " + decimalValue);
                    Log.d(MainActivity.class.getSimpleName(), "Hex: " + hex);
                }
            }

        }).show();
    }
}