visual studio for mac - cannot preview android

Question

I've installed Visual Studio for Mac and started a new Solution. I should be able to preview on the Android screen (see attached) but cannot get it to work. Any ideas? screenshot

Here's the detail: This is the error message inside the Android Preview: System.NullReferenceException: Object reference not set to an instance of an object at Xamarin.AndroidDesigner.CodeInteractions.CodeModelBridge.b__31_0 (Microsoft.CodeAnalysis.AttributeData a) [0x00000] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner.CodeInteractions/CodeModelBridge.cs:403 at System.Linq.ImmutableArrayExtensions.Any[T] (System.Collections.Immutable.ImmutableArray1[T] immutableArray, System.Func2[T,TResult] predicate) [0x00025] in <36486b016d234fca8cd67892bf29c7b5>:0 at Xamarin.AndroidDesigner.CodeInteractions.CodeModelBridge.IsActivityType (Microsoft.CodeAnalysis.INamedTypeSymbol type) [0x00008] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner.CodeInteractions/CodeModelBridge.cs:403 at Xamarin.AndroidDesigner.CodeInteractions.CodeModelBridge.GetAndroidEntityForType (Microsoft.CodeAnalysis.INamedTypeSymbol type) [0x00001] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner.CodeInteractions/CodeModelBridge.cs:120 at Xamarin.AndroidDesigner.CodeInteractions.CodeModelBridge.b__26_2 (Microsoft.CodeAnalysis.INamedTypeSymbol t) [0x00000] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner.CodeInteractions/CodeModelBridge.cs:311 at System.Linq.Utilities+<>c__DisplayClass1_01[TSource].<CombinePredicates>b__0 (TSource x) [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/external/corefx/src/System.Linq/src/System/Linq/Utilities.cs:58 at System.Linq.Enumerable+WhereSelectEnumerableIterator2[TSource,TResult].ToList () [0x0001b] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/external/corefx/src/System.Linq/src/System/Linq/Where.cs:737 at System.Linq.Enumerable.ToList[TSource] (System.Collections.Generic.IEnumerable1[T] source) [0x0000e] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/external/corefx/src/System.Linq/src/System/Linq/ToCollection.cs:30 at Xamarin.AndroidDesigner.CodeInteractions.CodeModelBridge+<GetCustomComponentsInProject>d__26.MoveNext () [0x00147] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner.CodeInteractions/CodeModelBridge.cs:308 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter1[TResult].GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357 at Xamarin.AndroidDesigner.DesignerProject+d__101.MoveNext () [0x00025] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner/DesignerProject.cs:300 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter.GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:113 at Xamarin.AndroidDesigner.DesignerProject+d__102.MoveNext () [0x00020] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner/DesignerProject.cs:307 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter.GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:113 at Xamarin.AndroidDesigner.DesignerProject+d__54.MoveNext () [0x0038a] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner/DesignerProject.cs:141 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter.GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:113 at Xamarin.AndroidDesigner.AndroidDesignerService+d__57.MoveNext () [0x0005a] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Android/Xamarin.AndroidDesigner/Xamarin.AndroidDesigner/AndroidDesignerService.cs:464 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter1[TResult].GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357 at Xamarin.Designer.Forms.XamarinStudioXamlPreviewerView+<InitializeAndroidDesignerProject>d__65.MoveNext () [0x00122] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Forms/Xamarin.FormsPreviewer.MonoDevelop/Xamarin.Designer.Forms/XamarinStudioXamlPreviewerView.cs:542 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter1[TResult].GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357 at Xamarin.Designer.Forms.Preview.AndroidXamlRenderer+d__15.MoveNext () [0x00078] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Forms/Xamarin.Designer.Forms.Preview/Android/AndroidXamlRenderer.cs:78 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter.GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:113 at Xamarin.Designer.Forms.Preview.AndroidXamlRenderer+d__17.MoveNext () [0x0004b] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Forms/Xamarin.Designer.Forms.Preview/Android/AndroidXamlRenderer.cs:122 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2018-02/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357 at Xamarin.Designer.Forms.Preview.AndroidXamlRenderer+d__18.MoveNext () [0x000a0] in /Users/vsts/agent/2.133.3/work/1/s/Xamarin.Designer.Forms/Xamarin.Designer.Forms.Preview/Android/AndroidXamlRenderer.cs:197

Answer 1

Turns out the issue was that the Java version I had was 10 and I needed version 8. Then open preferences in VS and tell it where the new version of Java is. That then allowed me to update the SDKs, update VS (restart) and everything works.

http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html