I got the error message โNo Android SDK Foundโ ... plus the lack of rendering for the Design window, without a cell phone screen.
My path to the SDK was correct, indicating where the SDK lives (downloaded during installation).
During the installation of the Mgr SDK, I did not download the latest version of the preview (version 20) "... (I thought it was better to use the next most recent version (19)). Later I found that there was not a single drop-down option in the AVD Manager to select version 19, only the default value for preview, 20.
I thought: "Maybe the rendering was based on a version that has not yet appeared." So, I downloaded all the "preliminary versions (version 20)" SDK Platform (2) and system images (4) ...
Once the download / installation is complete, RESTARTED Android Studio and viola! success ... error message disappeared, rendering ok.
source share