Effectively stopping updates and unsubscribing from ValueUpdated events

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Steps to reproduce

1. Connect to bluetooth device, start receiving values from a characteristic with StartUpdatesAsync() and App._characteristics[1].ValueUpdated += (o, args) => { ReceiveData(o, args); }; (The device sends data once per 500 ms) The function that receives the data is on a new page that is loaded with PushModalAsync

2. Attempt to stop/unsubscribe from the event with App._characteristics[1].ValueUpdated -= ReceiveData and App._characteristics[1].StopUpdatesAsync();

3. Reload the page with PushModalAsync and resubscribe to the event exactly the same as in step 1. The previous subscription will still be running, and has not terminated the previous page properly or released the previous event subscription. Data will be received twice every 500 ms (both threads running)

However, Xamarin does not think this other page is running, the Navigation stack does not see any modal pages, so the thread running the previous code is “who knows where”

Expected behavior

I expect to be unsubscribed from the updates and the thread associated with that subscription to be released

Actual behavior

The modal page or thread handling the data receiving is still running somewhere in the app. It appears the subscription to the data being received was never terminated properly

Crashlog

If something causes an exception paste full stack trace + Exception here

Configuration

Version of the Plugin: 1.3.0-alpha1

Platform: e.g. iOS 10.1 / Android 4.4 / … (including version!!! e.g. Android 5.1 / i0S 10) iOS: 10.3.1 Android: 7.0

Device: e.g. HTC Sensation /i Phone 7 … Samsung Galaxy S7 Edge iPhone 5C

[Yelnik]

Ok I think it works now… Thanks

[xabre]

You are using a lanbda to wrap your method and subscribe to the value updated event ( ValueUpdated += (o, args) => { ReceiveData(o, args); };) and then unsbuscribing the actual function delegate ReceiveData. This does not work and causes your memory leak. You should subscribe directly with your delegate ValueUpdated += ReceiveData; otherways there is no way to unsubscribe an anonymous delgate (your lambda). 😃