Designing UIs
To create intuitive, modern-looking, fluid user interfaces (UI), use Qt Quick and the integrated Qt Quick Designer.
Use the QML live preview to preview a QML file or an entire Qt Quick application on the desktop, as well as on Android and embedded Linux devices. The changes you make to the UI are instantly visible to you in the preview.
If you need a traditional user interface that has a clear structure and enforces a platform look and feel, use Qt Widgets and the integrated Qt Widgets Designer.
See also How to: Design UIs.