How to realize the internal frame as in Swing? JavaFX has the similar function?
No. The JavaFX 2.2 core platform does not include similar functionality to Swing's JInternalFrame.
See:Like JFrames and JInternalFrames
You could also look at functionality from 3rd parties which provide similar capabilities:
thanks. and what about for system tray ？
For system tray in JavaFX 2.2, you need to use AWT, see =>
Re: How to call Stage’s show/hide methods from AWT-thread
awt - JavaFX app in System Tray - Stack Overflow
Note that the request to get System tray functionality added to JavaFX is:
RT-17503 Provide system tray support
Which is currently scheduled for a feature update release to be delivered *after* Java 8 comes out.