Bluetooth Low Energy Multiply times ValueChanged notification

Question

The GattCharacteristic.ValueChanged event handler is triggered multiple times. The same problem with "Windows-universal-samples" in "BluetoothLE" example.

BluetoothLE" example...

For example when I "connect to device"--> Select Service --> Select Characteristic --> (click on) "Subscribe for notification" first time its works OK.

Then I disconnect from device and make new connect "connect to device"--> Select Service --> Select Characteristic --> (click on) "Subscribe for notification" the ValueChanged is Triggered twice an any single notification from BLE device,

Also any click "Unsubscribe / Subscribe to value changes" in demo add one more times to ValueChanged evens 3,4,5,6 times per each notification.

The main my problem when I connect /disconnect form device (when my code dispose BluetoothLEDevice instance).

Answer 1

Hello,

Welcome to Microsoft Q&A!

I've checked the code in the Bluetooth sample that you've mentioned. That's an unexpected behavior and the code you found is the reason causing the behavior.

I've reported this via our channel that there is a mistake in the Bluetooth sample for subscription. Please also submit an issue in the Issues of the GitHub: https://github.com/microsoft/Windows-universal-samples/issues

Thank you.

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Answer 2

Hi. I found the bug in the "Windows-universal-samples" "BluetoothLE" sample...

In "ValueChangedSubscribeToggle_Click()" I just comment the "subscribedForNotifications = false;" line. It placed before 'RemoveValueChangedHandler()' and RemoveValueChangedHandler do nothing when subscribedForNotifications is false...

Best regards.

Vladislav.