How to catch file download event in Firefox Extension? [duplicate]

This question already has an answer here: Closed 10 years ago.

Possible Duplicate:

How to hook the download dialog in a Firefox extension?

I have developed a Download Accelerator and now want to create a Firefox Extension for it. What I need to k开发者_运维知识库now is when a file download is requested. I have read about the 'observer-service' events such as 'dl-start'. However, these events are fired after the default download dialog is displayed, I need to catch the download before the default.

Any suggestions?

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I believe the answer to this question is what you are also looking for: How to hook the download dialog in a Firefox extension?