Main3Activity.java

package com.dannyfirebase.firebase;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
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.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

public class Main3Activity extends AppCompatActivity {

    TextView verifikasi;
    Button btnkeluar;

    FirebaseAuth mAuth;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);

        //Firebase
        mAuth = FirebaseAuth.getInstance();

        btnkeluar = (Button)findViewById(R.id.keluar);
        verifikasi = (TextView)findViewById(R.id.verivikasi);



        btnkeluar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                signout();
            }
        });

        datauser();
    }

    private void signout() {
        FirebaseAuth.getInstance().signOut();
        finish();
        Intent i = new Intent(Main3Activity.this, MainActivity.class);
        startActivity(i);
    }

    private void datauser() {
        final FirebaseUser user = mAuth.getCurrentUser();
        if (user != null){
            if(user.isEmailVerified()){
                verifikasi.setText("Email terferifikasi");
            }else{
                verifikasi.setText("Email Tidak terverifikasi (klik di sini)");
                verifikasi.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        user.sendEmailVerification().addOnCompleteListener(new OnCompleteListener<Void>() {
                            @Override
                            public void onComplete(@NonNull Task<Void> task) {
                                Toast.makeText(Main3Activity.this, "send email, silakan cek email", Toast.LENGTH_SHORT).show();
                            }
                        });
                    }
                });
            }
        }
    }

}