In my recent efforts to create an MP3 downloader application I have been extensively investigating the Adobe Flex browser API to pass through download URLs and other meta data through to my app.

Any sensible person would ensure a web service or suitable server-based XML file was available to AIR requiring only an ID or two to get going but in this instance I had no such luxury.

Typically a flash/flex badge sits on a website and can detect, install and launch an AIR app while passing through simple arguments. It is not widely documented that these arguments may only be alpha-numeric and may not include special characters like dots, slashes, percents and ampersands. This counts simple encoding out.

The way the flash badge fetches content from the page is using the External Interface method whereby the flash badge can call JavaScript functions embedded on the page, which in turn allows XML, also embedded in the page, to be collected and encoded.

I came up with my own encoding mechanism so that XML could be passed through the flash badge and into my AIR app as a string and then decoded there. This meant replacing . with DOT and % with PCNT and / with SLSH etc etc

So everything is working a lot better now, although it would be helpful if Adobe included details about this restriction in their Flex documentation to save wasting time debugging why the flash badge fails to launch the AIR app for no apparent reason. It’s probably a fair restriction for various security reasons due to people running dubious scripts on even more dubious websites that would somehow take hold of your computer via AIR. I had never thought a percent sign could be so dangerous, exclamation marks are much more scary.

Westminster, originally uploaded by Tim Tim Tim.

Saturday night saw us embark on the first London Run for a number of years. The basic premise behind a London run is to navigate around London’s various sights throughout the night, thus avoiding the crowds and using as much petrol as possible, then saving petrol on the return journey by cruising round the M25 at 56mph. The car journey usually passes through Heathrow, all the key sights in central London and finishing at a round about North of the Thames in view of the Millennium Dome.
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Since designing and estimating the work on this downloader app, the time has come to actually build the thing.

The first thing to overcome was using the built-in components to facilitate a download. Searching for assistance on this was made particularly tricky given that my previous article seemed to keep appearing in Google despite providing no actual help.

Huge thanks go out to Elad and his flex download api. This helped me get going enormously. To start with it only supported single downloads, and although I could queue these up, I wanted to be able to support concurrent downloads.
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Working to some kind of Agile methodology can be a great way to deliver web development projects but it can also be a complete nightmare if not done properly. Most people will be familiar with the standard waterfall approach of design, build test and may have heard about the possible benefits of Agile…
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