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Xamarin Forms Android This type of collectionView does not support changes to its sourceCollection from a thread different from the dispatcher thread

Here is the error I'm getting when trying to archive my app for deployment.
This error doesn't show up at any other time. The project builds and runs on emulators and devices without issue. This error has zero context or direction as to where to look to fix it. It also just randomly showed up out of nowhere, last time I built/archived (with zero functional changes) this error did not happen.
Main difference between this archival and the previous one is a newer version of VS 2017. Don't remember exactly the version from before, but am currently on 15.9.4 (stable).
Looking around on the interwebs, I've found that this error seems to have something to do with ObservableCollection's, which there are probably 10-ish in my app. Not really sure what to do here, because this has never been an issue previously, and I'm coming up on a deadline and with the structure of the app, am not in a good position to start making functional changes.
EDIT
I have also cleaned and rebuilt my solution, as well as deleting all bin/obj folders in my xamarin projects. Even tried deleting the .vs folder which can sometimes help. But still no go.
Going to try updating VS to 15.9.5 and see if maybe it was fixed in a release.
EDIT 2
Updating VS 2017 to 15.9.5 made no difference.
EDIT 3
I had my coworker try archiving the exact same project on his machine (running VS 2017: 5.9.3, and it archived fine for him. So far that's the only difference we've been able to find between our environments.

I saw the same problem using VS2017 15.9.9. Even the same code that could be archived a week ago threw the above mentioned error. It seems related to local data in the solution. A "clear" build was not sufficient. However manual deletion of the local obj and bin folders followed by archiving (build is done implicitly) solved the problem for me.

For my part closing Visual studio and deleting the .vs hidden folder did it.
It's actually a fix for many issues using Xamarin.
I had this other issue where I couldn't archive because the build process would just hang and never end. Deleting the .vs folder did it too.
https://github.com/xamarin/xamarin-android/issues/1760

Just go to project property then go to Android options-> Select Advanced then increase the Java Max heap size to 2G/3G -> it's working for me.

Leon Lu's suggestion worked. I don't particularly like it, as it took forever and repairing basically restores you to a base install (no extensions or personalizations). Took about 1.2 hours to complete, but once done I was able to again archive my android application. I guess something went wrong in vs at some point, perhaps during an update. There's no way to tell.

I tried ALL of the ideas above, but had no consistent reliable luck with any of them.
I found that Microsoft has had the problem reported to them (see link below). After a ton of time burn on this, I posted at the link below one way that I've been able to get around this archive-build issue.
Like the other fixes, it's not exactly logical, and nothing that you would think would work, but I've found the process to be repeatable, which is golden for me with tight timelines and having no time for this.
MS Visual Studio Developer Community Problem 507708
Posted on a Saturday morning, a sign of really needing to get around this urgently. I hope it helps you too.

Getting an App APK

Hey guys and girls for a the past week I've grown a lot of interest in android studio (even without knowing quite much about it) I decided to create an app that I deemed quite useful. However the app required maps to be integrated in it and I really did not know what I was doing and at one point I started messing with the settings and then all hell broke loose and I kept getting AAPT2 errors and I even tried to fix this issue with the gradle properties line that you add (I forgot the line of code to add). Anyways it still didnt work. However I rembered that I always kept the good version (before I broke everything) of the app on my phone. So when I go in my phone the app is there and it works just fine. Ive tried so many things to get the source code from the app on my phone without any succes. My question is, how can I get the source code back from the working app onto my laptop to continue coding in android studio? If it helps I am using Linux 18.04 LTS and running the newest version of android studio. Thank you for any help from you guys. This means a lot to me.

You can’t get back the ‘source code’ from an already compiled app.
You should consider using some version control platforms like git from the next time

Android Studio Tests are successful but do not stop junit

I am new to Android and building an app in Android Studio. I have written some tests using JUnit and Mockito.
The tests run successfully and in the run console the text Process finished with exit code 0 is shown.
However, the thread seems to remain active, the stop button is enabled and nothing happens even if I click on it. If I try to start multiple test configurations, they all remain active although the processes finish successfully.
I hope the question is clear enough... I have searched a lot for the answer and mananged to find nothing.

That can be fixed by following these steps:
Open 'Run' tab in Android Studio
Tap 'X' next to test which has just passed

Ok, so after a little more research and some more checking I have concluded that the problem stands in a visual bug of Android Studio. Apparently the tests do indeed stop, the thread running them too. The problem is purely visual.

Android Studio: testing is slow

Every time I want to do a quick test of some code, android studio takes 20-40 minutes loading an emulator which then either crashes my laptop or makes it run very slow. Is there any way to just use the system log without loading the whole app, similar to the System.out.Prinln() feature in net beans?

I understand that the question is about running your app for quick testing and not about automated tests. But you can learn a lot by trying to adapt writing tests, and they can help you to solve your problem.
1) For code without android dependencies you can write JUnit tests and run those just on JVM to test the code. Bonus: you'll start with creating your testsuite!
2) For code with android dependencies: a) Try to be better in separating platform specific code and internal logic so you will be able to cover more code with unit tests. b) You can use roboelectric and test everything without emulator/device for the rest.

INSTALL_FAILED_DEXOPT when using GreenDao

Background
I wanted to simplify the usage of DB in an Android app.
For this, I've compared some third party libraries that create a DAO layer.
I've come up with a nice library called "GreenDao" (presentation about it here) . The website shows that it's faster than other competitors (like ORMLite) and is optimized for Android.
The problem
For some reason, on some device (usually old devices, with GB) , I get the next console error when trying to install the app:
Installation error: INSTALL_FAILED_DEXOPT
Please check logcat output for more details.
Launch canceled!
I've searched for the reason of this error, but couldn't find out how to solve it. Many complain about this error, but I can't find out why it occurs, and what can be done.
The error is quite common and known, but it's never mentioned as the result of using this library, yet when I remove the usage of this library, everything works fine...
Also note that on newer devices (like nexus 4) it installs and works just fine, and that the sample itself also works fine no matter which device I test it on.
The question
Why does it occur?
Is it possible that the structure of the classes is just too much for old devices to load, since we use other libraries ?
Could it be that I've reached the limit of code that is supported by android apps?
The jar file itself takes just 87KB ...
How can I solve this?

Ok, I've found the problem and the solution:
It has nothing to do with GreenDao.
It's because the app uses too many jars, so maybe Android has a limitation of code.
The solution is to either delete un-needed jar files or delete a lot of code.