Question

Flex front-end using AMF to Java back.
Trying to read, in real-time, a file that is being written to. For example, a log.

I’m using Java’s RandomAccessFile class to read the “new” lines of the file and send them back to the UI as a byte array along with the byte offset to start reading from next time.

Using an mx:List to display all lines of the text file.

The problem I’m running into, is Flex, or Flash Player, running out of memory on mildly large files, >25MB.
Is there any preferred method of displaying large amounts of text data in Flex that I’m missing? Or does Flex/Flash just handle this poorly and I’m basically screwed?

Thanks.

Answer 1

If 25MB is only mildly large then I’d say you probably need to page the data into the component, and simple store just a couple of pages in memory at a time. I’d probably pick something like TextArea over List, but creating seamless scrolling for a TextArea could be difficult if you don’t have all the data which sounds like what you’ll have to do. So stick with List for now, and figure out how many lines you want to make a page. And implement your backend as a method like:

// service call interface
public Page getPage( int lineStart, int lines );

// response object from the service call
public class Page {
    private var _totalLines:int;
    private var _lineStart:int;
    private var _lineEnd:int;

    [ArrayElementType("String")]
    private lines:ArrayCollection;
}

Then you can load a page and store X number of pages in memory, but use the totalLines in the file to know how big your model is so the scrollbar can render properly. You’ll just need to build a paging dataprovider that loads pages not yet loaded, and ditches pages if they aren’t displayed or pages that are furthest from what’s being displayed.