Login Page Design

 Xml :- 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="20dp"
    tools:context=".Login">
<EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="Enter Email"
    android:id="@+id/email"/>
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter Password"
        android:id="@+id/password"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="Login"
        android:id="@+id/login"/>
    <TextView
        android:id="@+id/gotoregister"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Register Here"
        android:textSize="20sp"
        android:layout_gravity="center"/>
</LinearLayout>

Java : -

package com.niranjan.cloudfirebase;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.FirebaseDatabase;

public class Login extends AppCompatActivity {
EditText email,password;
Button login;
TextView gotoreg;
    FirebaseDatabase firebaseDatabase;
    FirebaseAuth auth;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        firebaseDatabase=FirebaseDatabase.getInstance();
        auth=FirebaseAuth.getInstance();
        email=findViewById(R.id.email);
        password=findViewById(R.id.password);
        login=findViewById(R.id.login);
        gotoreg=findViewById(R.id.gotoregister);
        gotoreg.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(Login.this,Register.class));
            }
        });
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                loginUser();
            }
        });
    }

    private void loginUser() {
        String useremail =email.getText().toString();
        String userpass = password.getText().toString();
        if (TextUtils.isEmpty(useremail))
        {
            Toast.makeText(this, "Email is empty", Toast.LENGTH_SHORT).show();
        }
        if (TextUtils.isEmpty(userpass))
        {
            Toast.makeText(this, "Password is empty", Toast.LENGTH_SHORT).show();
        }
        auth.signInWithEmailAndPassword(useremail,userpass).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isSuccessful()){
                    Toast.makeText(Login.this, "Login Sucessfull", Toast.LENGTH_SHORT).show();
                    startActivity(new Intent(Login.this,MainActivity.class));
                    finish();
                }
            }
        });
    }
}