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package com.example.student19.joniapp;

import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
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;
import com.google.firebase.auth.FirebaseUser;



public class MainActivity extends AppCompatActivity {

    private static String  TAG = "MainActivity";
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private EditText editEmail,editPass;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mAuth = FirebaseAuth.getInstance();
        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    // User is signed in
                    Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
                } else {
                    // User is signed out
                    Log.d(TAG, "onAuthStateChanged:signed_out");
                }
                // ...
            }
        };


        editEmail = (EditText)findViewById(R.id.Email);
        editPass = (EditText)findViewById(R.id.Pass);

    }
    @Override
    public void onStart() {
        super.onStart();
        mAuth.addAuthStateListener(mAuthListener);
    }
    @Override
    public void onStop() {
        super.onStop();
        if (mAuthListener != null) {
            mAuth.removeAuthStateListener(mAuthListener);
        }
    }
    public void OnClick(){
        mAuth.createUserWithEmailAndPassword(editEmail.getText().toString(), editPass.getText().toString())
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        Log.d(TAG, "createUserWithEmail:onComplete:" + task.isSuccessful());

                        // If sign in fails, display a message to the user. If sign in succeeds
                        // the auth state listener will be notified and logic to handle the
                        // signed in user can be handled in the listener.
                        if (!task.isSuccessful()) {
                            Toast.makeText(MainActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        }

                        // ...
                    }
                });

    }
}


























<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.student19.joniapp.MainActivity">

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textPersonName"
        android:text="first Name"
        android:ems="10"
        android:layout_marginLeft="51dp"
        android:layout_marginStart="51dp"
        android:layout_marginTop="70dp"
        android:id="@+id/editText"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textPersonName"
        android:text="Last Name"
        android:ems="10"
        android:id="@+id/editText3"
        android:layout_marginTop="16dp"
        android:layout_below="@+id/editText"
        android:layout_alignLeft="@+id/editText"
        android:layout_alignStart="@+id/editText" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textPassword"
        android:ems="10"
        android:id="@+id/Pass"
        android:layout_marginTop="16dp"
        android:layout_below="@+id/editText3"
        android:layout_alignLeft="@+id/editText3"
        android:layout_alignStart="@+id/editText3"
        android:text="password" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textEmailAddress"
        android:ems="10"
        android:layout_below="@+id/Pass"
        android:layout_alignRight="@+id/Pass"
        android:layout_alignEnd="@+id/Pass"
        android:layout_marginTop="13dp"
        android:id="@+id/Email"
        android:text="E-Mail" />

    <Button
        android:text="Registar"
        android:onClick="OnClick"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/Email"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="38dp"
        android:id="@+id/button2" />

</RelativeLayout>