Google API, the problem of NULL refresh token

Http://stackoverflow.com/questions/10827920/google-oauth-refresh-token-is-not-being-received

The is only provided on the first authorization from the refresh_token user. Subsequent authorizations, such as the kind you make and testing an OAuth2 integration, would not return the refresh_token again. :)

1. Go to your account security settings:https://www.google.com/settings/u/1/security.
2. Click the Edit button next to "Authorizing applications and sites".
3. Then click the "Revoke Access" next to your app.
4. The next OAuth2 request you to make would return a refresh_token .

Alternatively, you can add the "query parameter to the approval_prompt=force " OAuth redirect (see Google's OAuth 2.0 for Web Server applicat Ions page).

This would prompt the user to authorize the application again and would always return a refresh_token .

Google API, the problem of NULL refresh token