안드로이드 스튜디오, 파이어베이스 구글 로그인 구현하기

1. firebase 프로젝트를 만든다!!

2. 안드로이드 앱과 Firebase를 연동한다. 

3. 연동을 완료 했으면 홈 화면에 Authentication 클릭

4. 로그인 방법 중 구글 로그인 방식을 사용 설정 하고 저장 클릭!

5. 안드로이드 스튜디오로 이동 

package com.moonki.vote;

import android.content.Intent;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import android.view.View;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import com.google.android.gms.auth.api.Auth;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.auth.api.signin.GoogleSignInResult;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.SignInButton;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthCredential;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.GoogleAuthProvider;

public class MainActivity extends AppCompatActivity implements GoogleApiClient.OnConnectionFailedListener{
    SignInButton Google_Login;
    private static final int RC_SIGN_IN = 100;
    private FirebaseAuth mAuth;
    private GoogleApiClient mGoogleApiClient;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(getString(R.string.default_web_client_id))
                .requestEmail()
                .build();
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .enableAutoManage(this, this)
                .addApi(Auth.GOOGLE_SIGN_IN_API,gso)
                .build();
        mAuth = FirebaseAuth.getInstance();
        Google_Login = findViewById(R.id.Google_Login);
        Google_Login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
                startActivityForResult(signInIntent,RC_SIGN_IN);
            }
        });
    }
    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == RC_SIGN_IN) {
            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            if (result.isSuccess()) {
                GoogleSignInAccount account = result.getSignInAccount();
                firebaseAuthWithGoogle(account);
            }
            else{
            }
        }
    }
    private void firebaseAuthWithGoogle(GoogleSignInAccount acct){
        AuthCredential credential = GoogleAuthProvider.getCredential(acct.getIdToken(),null);
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if(!task.isSuccessful()){
                            Toast.makeText(MainActivity.this, "인증 실패", Toast.LENGTH_SHORT).show();
                        }else{
                            Toast.makeText(MainActivity.this, "구글 로그인 인증 성공", Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }
    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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"
    tools:context=".MainActivity">

    <com.google.android.gms.common.SignInButton
        android:id="@+id/Google_Login"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="284dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.1"

    defaultConfig {
        applicationId "com.moonki.vote"
        minSdkVersion 16
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation 'com.google.firebase:firebase-core:17.0.0'
    implementation 'com.google.android.gms:play-services-auth:18.0.0'
    implementation 'com.google.firebase:firebase-auth:19.1.0'
    implementation 'com.google.android.gms:play-services-auth:17.0.0'
    implementation platform('com.google.firebase:firebase-bom:26.5.0')
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    implementation 'com.google.firebase:firebase-analytics'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.google.firebase:firebase-core:16.0.5'
    implementation 'com.firebaseui:firebase-ui-auth:4.2.1'
}
apply plugin: 'com.google.gms.google-services'

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:4.0.1"
        classpath 'com.google.gms:google-services:4.3.5'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.moonki.vote">
    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>