``java，// MainActivity.java，package com.example.loginapp;，，import android.os.Bundle;，import android.view.View;，import android.widget.Button;，import android.widget.EditText;，import android.widget.Toast;，import androidx.appcompat.app.AppCompatActivity;，，public class MainActivity extends AppCompatActivity {， private EditText usernameEditText, passwordEditText;， private Button loginButton, registerButton;，， @Override， protected void onCreate(Bundle savedInstanceState) {， super.onCreate(savedInstanceState);， setContentView(R.layout.activity_main);，， usernameEditText = findViewById(R.id.username);， passwordEditText = findViewById(R.id.password);， loginButton = findViewById(R.id.login);， registerButton = findViewById(R.id.register);，， loginButton.setOnClickListener(new View.OnClickListener() {， @Override， public void onClick(View v) {， String username = usernameEditText.getText().toString();， String password = passwordEditText.getText().toString();， if (validateLogin(username, password)) {， Toast.makeText(MainActivity.this, "Login Successful", Toast.LENGTH_SHORT).show();， } else {， Toast.makeText(MainActivity.this, "Invalid Credentials", Toast.LENGTH_SHORT).show();， }， }， });，， registerButton.setOnClickListener(new View.OnClickListener() {， @Override， public void onClick(View v) {， String username = usernameEditText.getText().toString();， String password = passwordEditText.getText().toString();， if (registerUser(username, password)) {， Toast.makeText(MainActivity.this, "Registration Successful", Toast.LENGTH_SHORT).show();， } else {， Toast.makeText(MainActivity.this, "Registration Failed", Toast.LENGTH_SHORT).show();， }， }， });， }，， private boolean validateLogin(String username, String password) {， // Add your validation logic here， return true; // Placeholder return value， }，， private boolean registerUser(String username, String password) {， // Add your registration logic here， return true; // Placeholder return value， }，}，`，，`xml，，，，，，，，，，，，``