Well, since the Other problem(solved) remain unsolved, I was thinking to use POSTMan to do Trial and Error on each steps that the Client library will do.
So I read the Basic steps of Google OAuth2 again, created another OAuth 2 ID at Api Manager > Credentials in Dev Console and ID type is Web Application, and filled them into the POSTMan:
- New tab in POSTMan, then click the Authorization label.
- Choose type as OAuth 2.0 and select "Add token to the url"
- Auth URL: https://accounts.google.com/o/oauth2/v2/auth
- Access Token URL: https://www.googleapis.com/oauth2/v4/token
- Client ID: [the Client ID that I just received]
- Client Secret: [the Client secret that I just received]
- Scope: [empty]
- Grant Type: Authorization Code
- Request access token locally: Selected
- Click "Request Token"
- POSTMan replied me: "Could not complete OAuth2.0 login"
Do I missed something?
(Google redirect URI could be found here)
(API scope could be found here)