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Dynamic content in Flash > Checking if a file exists with ActionScript
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Checking if a file exists with ActionScript
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by Guy Watson
www.flashguru.co.uk
Sometimes it is necessary to determine if a file exists using actionscript, for example when you have a preloader cue, that loads a series of .jpgs one after another, if one of the files doesnt exist then the cue wouldnt traverse any further, you could of course use a timeout in that scenario but why not just check if the file exists before loading it, so that if necessary you can move onto the next item in the cue almost instantly. It is possible to determine whether a file exists using the success parameter of the onLoad event handler, the problem lies in the fact that the onLoad event handler for movieclips doesnt work, so to check if an .swf file exists, or an image, you will need to use this method...
Here is a little example, that checks to see if a .swf file exists, and if it does, then it loads it into a movieclip.
fileExists=new LoadVars();
fileExits._parent=this;
fileExists.onLoad=function(success)
{
//success is true if the file exists, false if it doesnt
if(success)
{
//the file exists
var nm=this._parent.createEmptyMovieClip("swfHolder",1); //so create a movieclip
nm.loadMovie("myfile.swf"); //and load our .swf file into it
}
}
fileExists.load("myfile.swf") //initiate the test
You can do the same with any file type, even if flash doesnt support the loading of that filetype. You may also be wondering if the above process means you have to load a file twice, the answer is NO. If you are running you flash movie in the browser, then when you check to see if the file exists, the onLoad even handler wont fire until the file has fully downloaded into the browsers cache, but of course the Loadvars object wont do anything with an image file, sound file, or swf file. The next time round, when it comes to actually loading the file to actually display it(swf,image,text) or play it(sound) the file will load almost instantly from the browsers cache. If your flash movie is running on the local machine, then you dont have to worry about loading times anyway, because, as always the loading of a file locally is almost instant.
(注册日期: 02-18-2004, 点阅人次: 1, 评比积分: 3.68, 票数: 28, 评论篇数: 8)
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fileExists=new LoadVars();
fileExits._parent=this;
fileExists.onLoad=function(success)
{
//success is true if the file exists, false if it doesnt
if(success)
{
//the file exists
var nm=this._parent.createEmptyMovieClip("swfHolder",1); //so create a movieclip
nm.loadMovie("myfile.swf"); //and load our .swf file into it
}
}
fileExists.load("myfile.swf") //initiate the test
(注册日期: 02-27-2007 用户:
访客)
Doesn't work...I am trying to make the movie do something if the file doesn't exist....And this doesn't work...!
(注册日期: 12-02-2006 用户:
访客)
how about loading a file extension of [*.mp3] ? Does it still work?
(注册日期: 08-22-2006 用户:
访客)
>> fileExists.load("myfile.swf") //initiate the test
But this is not a test, it is a real loading statement. So it is for big files not the best practice.
(注册日期: 07-24-2006 用户:
访客)
but with for or while, it's return infinite bucle, i trying to know if "pi1.jpg" to "pic10.jpg" exist.
(注册日期: 03-01-2006 用户:
访客)
Ah. But it loads the file from the server twice
(注册日期: 02-24-2006 用户:
访客)
This is detecting the image/no image pretty cool, but I can not make it load anything into the empty MC or to an existing one on the stage. Any ideas why?
(注册日期: 02-17-2006 用户:
访客)
Thanks, this worked great. I needed to write a script that determines if an flv exists on the CD. Works perfectly.
(注册日期: 10-07-2004 用户:
访客)
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