@qiangxue I will detail it. We remove non static `$themeBundle` and introduce static `$theme`. We distrubute only base theme by `'jui/theme/base/*'` bundles. If user want custom theme he make own `jui/theme/{themeName}/*` bundles. Next he can change theme:

```
\yii\jui\Widget::$theme='red';

//widgets usage

\yii\jui\Widget::$theme='green';

//widgets usage
```