Learning Flex – Lesson 23, Printing From Flex

Flex allows for printing from an application by using the FlexPrintJob class which is a wrapper for the flash.printing.PrintJob class. This allows you to specify one or more objects to be printed. The objects can be containers or custom components and you can specify a separate format that is not visible to the user.

The basic process is as follows:

  1. Instantiate a FlexPrintJob object
  2. call it’s start() method to begin the print process – this will cause the OS to display a print dialog and returns  true if they accept or false if they cancel out.
  3. Add the object(s) to be printed using the addObject() method
  4. Send the job to the printer using the send() method
  5. clean up any temporary objects no longer needed.

Between the start() and send() calls, a print job is spooled to the host operating system so only print specific work should be performed at this time.

It’s good practice to check the return of the start() method and abort the print attempt if it returns false.

If you try to hide the print version of a component by setting it’s visible property false, it will still occupy space in the layout. An alternative is to define the print layout in a custom component then define and instance and add it in your print process using the addchild() method of the application. You can then remove it using removeChild() as part of the print job cleanup. Your print code would then look something like this:

var printJob:FlexPrintJob = new FlexPrintJob();
if(printJob.start() != true){
  return;
}
var myPrintcontainer:CustomPrint = new CustomPrint();
addChild(myPrintContainer);
printJob.addObject(myPrintContainer);
printJob.send();
removeChild(myPrintContainer);

The output can be scaled by adding a parameter to the addObject() call. The options are static constants from the FlexPrintJobScaleType class:

  • MATCH_WIDTH – scales the printed output to match the page width. If the height exceeds the width, the output will span multiple pages (default)
  • MATCH_HEIGHT – scales the printed output to fill the page height. If the width exceeds the height, the output will span multiple pages.
  • SHOW_ALL – scales the printed output to fit on a single page, filling the smaller of width or height.
  • FILL_PAGE – scales the printed output to fill at least one page. It selects the larger of width or height.
  • NONE – the printed output matches the dimensions of the object on the screen.

To aid with printing data grids, there are print versions of data grid classes namely PrintDataGrid, PrintAdvancedDataGrid and PrintOLAPDataGrid. These have default appearances designed for printing and methods to support multiple page printing.

A PrintDataGrid will only print the rows that are visible by default. The property sizeToPage specifies that partially visible rows are not printed if it’s set true (default). To print rows below a scrollbar, you must use the nextPage() method and validNextPage boolean property.

While validNextPage is true, call nextPage() and then add the PrintDataGrid object to the print job.

Flex printing can look somewhat blurry on the page and does not always produce the results desired. For a great series of posts on an alternative, (AlivePDF) take a look at these posts from Kalen Gibbons.

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