Create and Login application as above. Validate login data and display Error to user using setError() method

activity_main.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:id="@+id/tvUsername"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Username: "
        android:layout_marginTop="56dp"
        android:layout_marginLeft="20dp"/>

    <EditText
        android:id="@+id/etUsername"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:layout_toRightOf="@+id/tvUsername"
        android:layout_alignBaseline="@+id/tvUsername"/>
    <TextView
        android:id="@+id/tvPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Password: "
        android:layout_marginTop="20dp"
        android:layout_below="@+id/etUsername"
        android:layout_marginLeft="20dp"/>
    <EditText
        android:id="@+id/etPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:layout_below="@+id/etUsername"
        android:layout_toRightOf="@+id/tvPassword"
        android:layout_alignBaseline="@+id/tvPassword"
        android:inputType="textPassword"/>

    <Button
        android:id="@+id/btnLogin"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/etPassword"
        android:layout_marginTop="50dp"
        android:layout_marginLeft="20dp"
        android:text="Login"/>
    <Button
        android:id="@+id/btnCancel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/etPassword"
        android:layout_marginTop="50dp"
        android:layout_marginLeft="20dp"
        android:layout_alignBaseline="@+id/btnLogin"
        android:layout_toRightOf="@+id/btnLogin"
        android:text="Cancel"/>

</RelativeLayout>

MainActivity.java

package com.example.helloworld;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    EditText etUsername,etPassword;
    Button btnLogin,btnCancel;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        etUsername=(EditText)findViewById(R.id.etUsername);
        etPassword=(EditText)findViewById(R.id.etPassword);
        btnLogin=(Button)findViewById(R.id.btnLogin);
        btnCancel=(Button)findViewById(R.id.btnCancel);

        btnLogin.setOnClickListener(this);
        btnCancel.setOnClickListener(this);
    }

    @Override
    public void onClick(View v)
    {
        String na=etUsername.getText().toString();
        String pa=etPassword.getText().toString();
        switch (v.getId()) {
            case R.id.btnLogin:
                if (na.equals("tony"))
                {
                    if (pa.equals("ironman"))
                    {
                        Toast.makeText(this, "Login success", Toast.LENGTH_LONG).show();
                    } else {
                        etPassword.setError("Invalid Password!");
                    }
                }
                else {
                    etUsername.setError("Invalid Username");
                }
                break;

            case R.id.btnCancel:
                etPassword.setText("");
                etUsername.setText("");
                break;
            default:
                break;

        }
    }

}

Output