FlashTips #6: Debug refresh issues in your swf

Most of us know that Flash Builder makes it easy to debug a swf on a server by creating a custom debug configuration. Recently, I had a problem where I needed to be able to debug issues that happened when the browser window was refreshed.
Jeffry Houser, the brains behind Flextras.com, apparently had this very same problem, and resolved it by starting a new debugger session that points to about:blank and then connecting that to the swf after the window has been created.
That's a great solution, but the issue I was having was happening pretty much immediately after the window was refreshed--if I went through his steps, I'd "miss the window." So, after limping along for several hours, trying to figure out the problem without having the direct debug information, I finally figured out that the problem was amazingly simple:

1. Create a new "refresh" debug configuration that doesn't point to a page with a swf in it (I didn't yet know that about:blank was an option).
2. Start the original debug configuration, that points to the swf as normal.
3. Get to the problem point in the application.
4. Launch the "refresh" configuration.
5. Refresh the window.
6. Voilà, we are connected, from the very beginning of the bootstrapping process.

Enjoy!

Debugging itemRenderers

You may have notced that I have spent a lot of time chasing down issues with itemRenderers. It always frustrated me that you could get information on the parent of any component, but I could never figure out how to find out information on the renderers being displayed by a List based control.

I finally realized that if I set a break point in a scope that had a reference to a List control, I could rifle through the properties of that control until I found the rendererArray property, which seems to be an array of arrays. If you're not using a multi-column control, like a DataGrid or an AdvancedDataGrid, the itemRenderer for each row will be at the 0 index of each row index. Otherwise, each row will be the outer index of the rendererArray and each column will be an element in the row array.

I really do view this as my diary of Flex, and I got tired of not ever remembering what the name of the property is. It can take quite a while to fish through all the properties available on a control to try to relocate it. So I wrote it down, since it doesn't seem to be documented. Hope it helps you, too :-).

Debugger and E4X

I had a thingie that I had built in Flex, and I wanted to change it from showing a property of the xml object passed in the data object to the itemRenderer to iterating through child nodes of the xml object to show multiple selections. I thought my problem was with the E4X expression, so I wanted to be able to quickly change the E4X syntax without having to recompile and run my project again. So I decided I'd create a watch expression with my E4X in it and just keep trying until I got it right.

It seemed that no matter what I tried, I kept getting "Errors in Evaluation" for my E4X expression. Finally, in frustration, I put my best guess at the E4X expression in a trace expression, and it worked like a charm. The actual problem was that the logic wasn't even going into the piece I thought it was. So let that be a lesson to me that the debugger expressions window can't actually evaluate E4X!

Oh, and if anyone knows something in the debugger that works like the Immediate pane in VBA, please let me know!

Flex Debugging Tutorial

When I first picked up Flex, I couldn't make heads or tails of the debugger, so finding and fixing problems took forever. I looked everywhere to try to find some documentation on how to use this thing. I finally figured it out on my own, but I've finally found a tutorial on the debugger that will hopefully help other new Flex users from sharing my pain.