Twitch login/signup for android

API
2

Sounds like you are GETing and showing the Twitch Login page instead of redirecting the user to Twitch?

The following:

GET https://id.twitch.tv/oauth2/authorize
    ?client_id=<your client ID>
    &redirect_uri=<your registered redirect URI>
    &response_type=<type>
    &scope=<space-separated list of scopes>

Should read:

REDIRECT THE USER TO https://id.twitch.tv/oauth2/authorize
    ?client_id=<your client ID>
    &redirect_uri=<your registered redirect URI>
    &response_type=<type>
    &scope=<space-separated list of scopes>