Egads! An actual Swing Tree-Table!
Four years ago, I went on a hunt for best practices for doing tree table components in Swing. We had a tree-table component in NetBeans, whose maintenance was my never-ending nightmare and the biggest source of bugs on my bug list. It had been written, with the best of intentions, based on Scott Violet's Swing Connection article about how to quickly hack up a tree-table component in Swing (Scott's article was also written with the best of intentions, and I have no intention to ding him here - what he wrote does work for simple use-cases - a debugger is not a simple use-case).When I canvassed folks who had done Swing tree-tables on our mailing lists, most of them were based on that article, as ours was. What I heard back varied between groans of pain and mad rabid howls of pain. There are a few things in that original tree table design that just don't work - not reliably, anyway. Sending events to an offscreen component as if it were on-screen and expecting it to behave sanely is just a really bad idea that happens to work if the look and feel is a subclass of BasicLookAndFeel, and other look and feel implementations have been tormented into supporting this abuse by all the evil Tree-Table implementations in the wild. But the bottom line is, a look-and-feel author would have to be slightly insane to code their TreeUI to behave as if it were a live component when it has no parent and obviously is not one. In other words, the fact that the JTree-as-cell-renderer design works at all is just an accident of how BasicLookAndFeel's TreeUI implementation was designed, which other look and feels inherited. Never mind trying to use said JTree as a cell renderer in a table (I once made a 400% performance improvement in our tired, tortured, hacked-up TreeTable just by having it translate the graphics context instead of repositioning - and thus causing a re-layout) is seriously abusing the component. Now try convincing said offscreen JTree that it has keyboard focus in order to get it to paint appropriately in its role as a cell renderer for another component. On all look and feels. On all platforms. Everywhere. You see what I mean. After doing that canvassing back in '04, it was obvious that Swing needed a real tree-table component. So I started to write one (and the layout cache classes JTree uses were very, very helpful - thanks, Scott!). I started on it, got the basics working, and then moved back to the U.S., changed jobs and ended up travelling the world full-time teaching other people to write NetBeans modules - but it didn't leave time to finish up the Tree Table work. Thankfully, my former office-mate, David Strupl, picked up where I left off when he left Sun to work on Nokia's NetBeans RCP app for managing cellular telephone networks. The really, really great news is: This week, Standa Aubrecht - who took over a bunch of the stuff when I left full-time development of NetBeans in '04 and amazed me with how quickly he was able to get going in a complex codebase - committed it into the main line of NetBeans sources yesterday. So anybody who gets a dev build of NetBeans as of today has a perfectly working Swing Tree Table component they can use (the class name is
Outline- I borrowed the name from Apple's Cocoa library - it's a little less clunky than "tree table" but gets the point across). The JAR file is
org.netbeans.swing.outline.jar. Usage is incredibly easy - you just provide a standard Swing TreeModel of whatever sort you like, and an additional RowModel that can be queried for the other columns contents, editability and so forth. And you never have to worry about cells painted half one color and half another because the tree-cell part got repainted after focus went to a popup menu. It actually works! The real credit here goes to David and Standa for getting this thing production-worthy - I just was pissed-off enough at having a gargantuan list of unfixable bugs (well, fix it on one platform, break it on another, or leave it unfixed everywhere, or semi-fixed some places - pure evil if you hold the illusion that what we do is computer science) four years ago to get the ball rolling. They're the guys who delivered it. I'm incredibly happy to see this finally be real and available not just to people writing NetBeans modules, but anybody doing GUI apps in Java. There has been a need for a real, reliable tree table component for Swing programmers for a long, long, long time. All hail David and Standa!