Create Sign-in-with-Google button in Flutter in accordance with the terms

There Is A Pretty Awesome Package Called flutter_signin_button on pub.dev.

You Can Use It It Has Sign In Buttons For

• Email
• Google
• Facebook
• GitHub
• LinkedIn
• Pinterest
• Tumblr
• Twitter
• Apple

With Some Supporting Dark Mode Also With Mini Buttons!

First Add It To Your pubspec.yaml

dependencies:
  ...
  flutter_signin_button:

then import it into your file:

import 'package:flutter_signin_button/flutter_signin_button.dart';

and use the buttons like this:

SignInButton(
  Buttons.Google,
  onPressed: () {},
)

Here Is A Preview Of All The Buttons:

I'm giving you a general idea, replace Android icon with your Google image using Image.asset(google_image)

InkWell(
  onTap: () {},
  child: Ink(
    color: Color(0xFF397AF3),
    child: Padding(
      padding: EdgeInsets.all(6),
      child: Wrap(
        crossAxisAlignment: WrapCrossAlignment.center,
        children: [
          Icon(Icons.android), // <-- Use 'Image.asset(...)' here
          SizedBox(width: 12),
          Text('Sign in with Google'),
        ],
      ),
    ),
  ),
)

you can use Padding property of raised button also use property of Row widget and mainAxisSize of button. Following code may help you to understand clearly.

 new Container(
      margin: EdgeInsets.fromLTRB(30.0, 5.0, 30.0, 5.0),
      child: new RaisedButton(
        padding: EdgeInsets.only(top: 3.0,bottom: 3.0,left: 3.0),
        color: const Color(0xFF4285F4),
        onPressed: () {},
        child: new Row(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            new Image.asset(
              'res/images/icons/google/btn_google_dark_normal_mdpi.9.png',
              height: 48.0,
            ),
            new Container(
              padding: EdgeInsets.only(left: 10.0,right: 10.0),
                child: new Text("Sign in with Google",style: TextStyle(color: Colors.white,fontWeight: FontWeight.bold),)
            ),
          ],
        )
      ),
    ),