I'm including a web player in Android app webview. Premium Deezer user and free Deezer users will use the application. I don't know the way I can include a list player widget for premium users. I will have users credential because they will authenticated before playing music but in web widget I don't know how to specify user id.
You have a login button on the widget player BUT be careful that on mobile web you'll never be able to stream more than 30 seconds. Logging Premium users in won't do much since that limitation is because Flash isn't available on mobile and we use it for encryption.
The only way to stream full tracks on mobile is either to redirect users to the Deezer native apps, or building your own native app using one of the iOS or Android SDKs.