Android GUI designer config issue in 12.x (idea-IC-122.395)

Hi folks,

I'm new to idea, so apologies if this is a no-brainer.

I'm trying out the GUI designer in 12.x version for Android development, and I think I'm missing a configuration somewhere.  When trying to edit a layout, I'm getting:

org.jetbrains.android.uipreview.RenderingException: Device is not specified

at com.intellij.android.designer.designSurface.AndroidDesignerEditorPanel$8.run(AndroidDesignerEditorPanel.java:279)

at com.intellij.openapi.application.impl.ApplicationImpl$6.run(ApplicationImpl.java:463)

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)

at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)

at java.util.concurrent.FutureTask.run(FutureTask.java:138)

at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)

at java.lang.Thread.run(Thread.java:662)

at com.intellij.openapi.application.impl.ApplicationImpl$1$1.run(ApplicationImpl.java:154)