Skip to first unread message
Assigned to by


Apr 18, 2019, 12:34:07 AM4/18/19
to MIT App Inventor Forum

Hello everybody,
I have two weird Ble connection problems.

The first situation is:
If I leave the screen(like click phone back button) after I complete the connection.
When I enter the app again.
Sometimes I can't find any devices in my BLE listpicker.

The second is:
If I repeat the steps of connection and disconnection several times.
Sometimes it will be connection failed because the BLE listpicker is empty like the first situation.

Now my solution is restarting my phone(HTC U11 and SONY).


Chris Ward

Apr 18, 2019, 4:38:41 AM4/18/19
to MIT App Inventor Forum
Hello Roan

If the User just "leaves" the App, everything should be OK but it is possible for things to linger in memory. I suggest you try adding an exit button to the App, and the on-click event cleans things up by ensuring BLE is disconnected and the ListView cleared (create empty list block). Very important to ensure any Clock Timer is set to disabled:


Concerning the ListPicker (or ListView) becoming empty (not updating) MIT are aware of this from a report by another App Inventor User only yesterday. Maybe it was not expected that the User would make several connect-disconnect actions.


Apr 18, 2019, 10:14:05 PM4/18/19
to MIT App Inventor Forum
Hello Chris,

If letting the phone resting a period time, everything seems ok.
So if I can't find the way to clear up the memory in the phone,
I will try to make sure all devices are disconnect before the users leaving the app.

Thank you very much for your suggestions! 

Chris Ward

Apr 19, 2019, 7:18:16 AM4/19/19
to MIT App Inventor Forum
Hi Roan

What I'm not sure about is the repopulation of the List of available devices. We have had three similar (ish) reports this week. So let's wait to see what Evan Patton has to say.
Reply all
Reply to author
0 new messages