When developing a desktop application, there are times when you want to prevent the user from interacting with the GUI. For example, you may be doing work in the background, and want to make sure you finish before allowing the user to continue. Perhaps the most obvious way to do this is to disable each component in the GUI. This works, but is not a very elegant or maintainable solution. The appearance of each GUI component changes when disabled, and if you add a new component to the window in the future, you will have to remember to disable it as well.

Fortunantly, Swing provides a better way to do this: The glass pane. The glass pane is one of the layers of a JRootPane. It is transparent and normally not visible. However, if you set it as visible, you can effectively block all user interaction with the contents of the window.

Carrying this one step further, it is possible to set the glass pane to be a panel of your own design. By doing this, you can effectively overlay anything you want on top of the current window, including messages to the user, animated progress icons, etc. The screen shot below shows the BlockerPanel in action. The icon and text are on the glass pane, which intercepts all user interaction with the window.

BlockerPanel Demo

The code to implement a BlockerPanel is straightforward, and the resulting class is easy to use. You can download my BlockerPanel class along with a simple demonstration program and use it in any of your projects. The source code is released with no restrictions, so feel free to improve upon it. There are many useful features that could be added, and there are parts of the code that could be improved. I’ll leave this as an exercise for the reader.

BlockerDemo source code and test program.

Further reading:

How to use Root Panes on sun.com