When adding a control from the Toolbox to the Document Outline window, the designer surface visually shows two instances of the control. If you then go to look at the Source tab, you will see two instances of the control as well. You can also trigger this by going to a different tab such as the MainActivity.cs and going back to the Main.axml file.
Adding an "ImageView" to a "LinearLayout":
Changing back and forth between Source -> Designer:
1. Create a File->New Xamarin.Android Project
2. Open up the Main.axml file in the designer
3. Open up the toolbox and Document Outline windows
4. Add any control from the toolbox to the document outline into a viewgroup such as a LinearLayout.
I have not done a thorough investigation, but it seems all controls I've tested have this behavior. (ImageView, TextView, Spinner, etc)
Visual Studio 15.3.3
I cannot reproduce issue on master (https://www.screencast.com/t/ApKlTPzeasw), however for me the outline window does behave strangely where the first item seems to disappear when a new one is dropped.
@Bret, could you double check this one?
Update: I haven't been able to repro this, on master. I'll get with Jon and we'll go thru the steps together.
Another update: I was eventually able to repro. https://github.com/xamarin/designer/pull/243 should fix it.
Fixed, via https://github.com/xamarin/designer/pull/266
I have tested the bug with d15-5 preview 4 build. The issue is seems to be fixed.
I have not done a thorough investigation, but it seems all controls I've tested have expected behavior i.e. only one control adding at one attempt. Controls tested so far -Button, ImageView, TextView, Spinner, etc.
Microsoft Visual Studio Enterprise 2017
Version 15.5.0 [27109.1.d15rel]
Microsoft .NET Framework
Installed Version: Enterprise
Xamarin 18.104.22.1684 (a773aca)
Xamarin Designer 4.8.152 (5e0da2967)
Xamarin.Android SDK 22.214.171.124 (HEAD/f65f87747)
Xamarin.iOS and Xamarin.Mac SDK 126.96.36.199 (c4240f3)
Complete Build Details:
Hence marking the bug as verified.