안드로이드 구글 로그인하기 전체 코드

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v4.app.FragmentActivity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

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;

public class MainActivity extends AppCompatActivity implements View.OnClickListener, GoogleApiClient.OnConnectionFailedListener {

    GoogleApiClient mGoogleApiClient;
    int RC_SIGN_IN = 1000;
    String TAG = "TAG";
    TextView mStatusTextView;

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

        // Configure sign-in to request the user's ID, email address, and basic
        // profile. ID and basic profile are included in DEFAULT_SIGN_IN.
        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestEmail()
                .build();
        // Build a GoogleApiClient with access to the Google Sign-In API and the
        // options specified by gso.
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .enableAutoManage(this /* FragmentActivity */,  this /* OnConnectionFailedListener */)
                .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                .build();

        SignInButton signInButton = (SignInButton) findViewById(R.id.sign_in_button);
        signInButton.setSize(SignInButton.SIZE_STANDARD);
        signInButton.setScopes(gso.getScopeArray());

        findViewById(R.id.sign_in_button).setOnClickListener(this);
        mStatusTextView= (TextView) findViewById(R.id.textView);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.sign_in_button:
                signIn();
                break;
        }
    }

    private void signIn(){
        Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
        startActivityForResult(signInIntent, RC_SIGN_IN);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
        if (requestCode == RC_SIGN_IN) {
            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            handleSignInResult(result);
        }else{

        }
    }

    private void handleSignInResult(GoogleSignInResult result) {
        Log.d(TAG, "handleSignInResult:" + result.isSuccess());
        if (result.isSuccess()) {
            // Signed in successfully, show authenticated UI.
            GoogleSignInAccount acct = result.getSignInAccount();
            mStatusTextView.setText(getString(R.string.signed_in_fmt, acct.getDisplayName()));
            updateUI(true);
        } else {
            // Signed out, show unauthenticated UI.
            updateUI(false);
        }
    }
    private void updateUI(boolean signedIn) {
        if (signedIn) {
            findViewById(R.id.sign_in_button).setVisibility(View.GONE);
            mStatusTextView.setText("로그인 성공!!");
        } else {
            findViewById(R.id.sign_in_button).setVisibility(View.VISIBLE);
            mStatusTextView.setText("로그인 실패!!");
        }
    }





    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
        Toast.makeText(getApplicationContext(), ""+connectionResult, 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.zerobin.www.denmatotoapp.MainActivity">

    <com.google.android.gms.common.SignInButton
        android:id="@+id/sign_in_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/textView" />
</RelativeLayout>

앱 수준 bulid.gradle에 하이라이트 한 코드 넣기

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.1.0'
    testCompile 'junit:junit:4.12'
    //google 로그인 과정중 삽입 - 문서참조
    compile 'com.google.firebase:firebase-auth:10.0.1'
   compile 'com.google.android.gms:play-services-auth:10.0.1'
}
apply plugin: 'com.google.gms.google-services'

SHA1 디버그용 지문은 위 그림 오른쪽 빨간상자 부분에 Gradle projects가 작게 있는대 그걸 누르면 저렇게 펼쳐진다.

펼치고 signingReport를 더블 클릭하면 아래처럼 자신의 debug key의 지문이 나온다. 

(테스트 할때 저 지문을 사용, 앱 출시할때는 사용하는 키의 SHA1지문도 등록해야한다!)

위 그림은 파이어베이스 프로젝트에서 지문을 등록한 그림이다.