The translation Google provides is a bit garbled but I will do my best to answer what I think is your question.
Is there a warning can be opened when you attempt a Bluetooth connection fail?
The BluetoothClient's Connect method should return false if the connection fails. If it does, then you could use the notifier component to present a warning/error to the user. If you are looking for a warning/error for when the Bluetooth connection is lost, then the only way to do that currently is to occasionally try to interact with the device and if it has gone away the BluetoothError will run where you can notify the user.
Regards,
Evan