Main2Activity.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.util.Patterns;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
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;


public class Main2Activity extends AppCompatActivity {

    //Firebase
    FirebaseAuth mAuth;

    EditText edtMail,edtPassword;
    Button btndaftar,btnmasuk;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        //Firebase
        mAuth = FirebaseAuth.getInstance();

        edtMail = (EditText)findViewById(R.id.edtuser);
        edtPassword = (EditText)findViewById(R.id.edtpwd);

        btnmasuk = (Button)findViewById(R.id.btnmasuk);
        btndaftar = (Button)findViewById(R.id.btndaftar);


        btndaftar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

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

    private void userlogin() {
        String email = edtMail.getText().toString().trim();
        String password = edtPassword.getText().toString().trim();

        if(email.isEmpty()){
            edtMail.setError("Email sudah salah");
            edtMail.requestFocus();
            return;
        }

        if(!Patterns.EMAIL_ADDRESS.matcher(email).matches()){
            edtMail.setError("silakan masukkan email yang valid");
            edtMail.requestFocus();
            return;
        }

        if(password.isEmpty()){
            edtPassword.setError("Password sudah salah");
            edtPassword.requestFocus();
            return;
        }

        if(password.length()<6){
            edtPassword.setError("minimal 6");
            edtPassword.requestFocus();
            return;
        }


        mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if(task.isSuccessful()){
                    Intent i = new Intent(Main2Activity.this, Main3Activity.class);
                    i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    startActivity(i);
                }else{
                    Toast.makeText(Main2Activity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                }
            }
        });
    }


}