代码实现 Google SignIn

• 在登录活动的 onCreate 方法中，配置 Google 登录以请求你的应用所需的用户数据。

 GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
        .requestEmail()
        .build();

• 创建一个 GoogleApiClient 对象，可以访问 Google 登录 API 和你指定的选项。

 mGoogleApiClient = new GoogleApiClient.Builder(this)
        .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
        .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
        .build();

• 现在，当用户点击 Google 登录按钮时，请调用此功能。

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

• 实现 OnActivityResult 以获取响应。

 @Override
public 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);
    }
}

• 最后一步处理结果并获取用户数据

   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);
   }
  }