isTokenValid method
Checks if the stored access token is still valid.
Implementation
Future<bool> isTokenValid() async {
final prefs = await SharedPreferences.getInstance();
final accessToken = prefs.getString('access_token');
final expiresAt = prefs.getInt('expires_at');
if (accessToken != null && expiresAt != null) {
final now = DateTime.now().millisecondsSinceEpoch ~/ 1000;
return now < expiresAt - 60;
}
return false;
}