Tips for SWT usage



  • After getting frustrated at work with custom Swing tab-ordering ( a real WTF on its own ) I decided to learn a bit about how SWT does its tab ordering.

    After a bit of googling I came up on this little gem for initializing SWT Controls:


    I Especially like the "Iterate over every Control, catch ClassCastException on each one, and proceed on" .. 



  • Lovely. Because "if ( item instanceof Text) .." is so complicated.. Gah. What a craptastic hack..  



  • What, out of curiosity, is this "custom Swing tab-ordering" problem? The tabs appear in the order you add them. Unless you specify an explicit index, in which case the tab appears at that index. (Of course, having more than a few tabs in your window is not a very good UI design, but I'm sure you already knew that.)



  • He's talking about the order controls get focus when you use the tab key on your keyboard, not just a tab control to show different pages in a dialog.



  • I'm curious as to why you think swing tab traversal is a WTF. It seems pretty straightforward to me:

    http://java.sun.com/j2se/1.5.0/docs/api/java/awt/FocusTraversalPolicy.html

    I've never implemented a custom traversal policy, but I know swing very well. Was the FocusTraversalPolicy hard to implement? 



  • I ran into trouble implementing a custom FocusTraversalPolicy for a single JPanel that is nested in another JPanel. What I specifically needed was a different tabbing order for just one panel's components. Just to clarify, the top 'root' panel has three other panels and I wanted to have custom tab ordering in just one of them. The view I was working with is really really complex, with three regular tabbedpanes each containing 6 - 10 panels, each containing the Components. I'm a contractor in the banking industry at the moment :)

    Implementing the tab ordering for one JPanel is easy, but getting the tab ordering to work between panels was difficult, the focus doesn't seem to want to transfer to the first (or last) element of the following/previous panel.

     I got a workaround by manually adding the components to the custom FocusTraversalPolicy, but that involved some crude hacks (such as including components from other panels). I realize the problem lies somewhere with the cycle root switching focus down and up when it reaches the final element of a focus cycle root. I just thought to hell with it and hacked around it :) In the end it only involved changes in three classes to get it working.
     


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