Is there any difference between "on the fly" and "on-the-fly" upon the usage and meaning?
In the following sentence:
You can greatly improve the experience with large content by downloading it on-the-fly and showing slick progress indicators. (Talking about some technology like flash, with which we can using it anytime, anywhere as long as we have a browser like IE or Firefox.)
which meaning should I take for this phrase?
1: in motion : busy
2: while still in the air : without the ball bouncing <the home run
carried 450 feet on the fly>
3: in a hurry and often without preparation : hastily, spontaneously
<making decisions on the fly>
4: simultaneously with another task <software that handles formatting
on the fly>
In my opinion, the 3rd one is the best to this sentence, which means that we don't need to do any preparation for it.
It refers to doing something else while engaged in one's main activity.
'on the fly' :while in motion or progress
I was late for work, so I dashed to catch the train and just grabbed something for breakfast on the fly.
. • Computing : doing something during the running of a computer program without interrupting the run. Downloading in the background while you get on with some other work on the computer.
So, specifically, in this case, the software is continuing to download stuff (the word used in your text is 'content') while the browser is already beginning to display it/reproduce it in some partial way - such as starting with a less high-quality graphic, or starting to play the beginning of a sound clip without first finishing the download.