I started to play with WAB recently. I am following the steps from ESRI's website: Create a custom in-panel widget—Web AppBuilder fo... . Now I can see the custom widget in the widget pool. But after I added the widget to my app and clicked on it to test, it poped up a message saying "Create Widget Error". When I tested it through http://[your host name:3344]/webapp/?config=sample-configs/config-demo.json, I got the same error. (I have downloaded the missing sample-configs folder from GeoNet.). Then I started the steps for creating a custom widget all over again and tested step by step. And it worked fine until Step 8 "Access a map". After I followed the instructions to access a map, I got the Create Widget Error message. I am wondering if anyone has some ideas about how to solve this problem.
Thank you very much!