Debugging Client-Side Code in Flex Applications

Other Considerations

Be aware of a couple of gotcha’s in client-side debugging in Flex. The following is a list of issues and suggested strategies for handling problems with the debugger.

1. The biggest problem Flex developers have when trying to debug is ensuring that they have the Flash Debug Player installed. If you’re not sure if you have the debug Flash player installed, check the Installing the Flash Debug Player section of this article.
2. Like most application servers, Flex uses a number of reserved words for internal processing. Problems can occur when you use the word "debug" as the name of an MXML or ActionScript file.
3. You may encounter a situation where the SWD files do not generate correctly. If you believe that your SWF is using a cached version of either the SWF or the SWD for a given MXML page, clear the browser cache and restart your Flex server before trying to debug the MXML page again.

   The Flash Debug Player cannot communicate with the fdb debugger. This is evidenced by a pop-up window asking you to indicate where the Flash debugger host is running. If when you execute the run command in fdb or make a request to a given MXML page this pop-up window appears (Figure 1), you will need to ensure that your server configuration settings and the URL used to invoke the MXML file are correct.

   

   Figure 1. If this dialog box appears when you execute the fdb run command or request an MXML page, you'll need to ensure that your server configuration and URL are correct.

4. When you launch an fdb session and the following message appears: "WARNING: The Player that you are using does not support all fdb commands," it means that the Flash Debug Player you have installed in not the correct version.  You need to ensure that you use the Flex version of the Flash Debug Player with fdb.

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