The system controls the overall printing
process, just like it controls when and how a program can draw. Your application
provides information about the document to be printed, and the printing system
determines when each page needs to be rendered.
This callback printing model enables printing to be supported on a wide range of
printer and systems. It even allows users to print to a bitmap printer from a
computer that doesn't have enough memory or disk space to hold the bitmap of an
entire page. In this situation the printing system will ask your application to
render the page repeatedly so that it can be printed as a series of smaller
images. (These smaller images are typically referred to as bands, and this
process is commonly called banded printing.)
To support printing, an application needs to perform two tasks:
- Job control--managing the print job
- Imaging--rendering the pages to be printed
Job Control
Although the system controls the overall printing process, your application has
to get the ball rolling by setting up a PrinterJob. The PrinterJob , the key
point of control for the printing process, stores the print job properties,
controls the display of print dialogs, and is used to initiate printing.
To steer the PrinterJob through the printing process, your application needs to
- Get a PrinterJob by calling
PrinterJob.getPrinterJob
- Tell the PrinterJob where the rendering code
is by calling setPrintable or setPageable
- If desired, display the Page Setup and Print
dialogs by calling pageDialog and printDialog
- Initiate printing by calling print
The rendering of pages is controlled by the
printing system through calls to the application's imaging code.
Imaging
Your application must be able to render any page when the printing system
requests it. This rendering code is contained in the print method of a page
painter--a class that implements the Printable interface. You implement print to
render page contents by using a Graphics or a Graphics2D rendering context. You
can use either one page painter to render all of the pages in a print job or
different page painters for different types of pages. When the printing system
needs to render a page, it calls print on the appropriate page painter.
When you use a single page painter, the print job is called a printable job.
Using a printable job is the simplest way to support printing. More complex
printing operations that use multiple page painters are referred to as pageable
jobs. In a pageable job an instance of a class that implements the Pageable
interface is used to manage the page painters.
- Printable Jobs
In a printable job all pages use the same page painter and PageFormat, which
defines the size and orientation of the page to be printed. The page painter
is asked to render each page in indexed order, starting the page at index 0.
The page painter might be asked to render a page multiple times before the
next page is requested, but no pages are skipped. For example, if a user
prints pages 2 and 3 of a document, the page painter is asked to render the
pages at indices 0, 1, and 2 even though the page at index 0 will not be
printed.
If a print dialog is presented, it will not display the number of pages,
because that information is not available to the printing system. The page
painter informs the printing system when the end of the document is reached.
- Pageable Jobs
Pageable jobs are useful if your application builds an explicit
representation of a document, page by page. In a pageable job different
pages can use different page painters and PageFormats. The printing system
can ask the page painters to render pages in any order, and pages can be
skipped. For example, if a user prints pages 2 and 3 of a document, the page
painter will be asked to render only the pages at indices 1 and 2.
The multiple page painters in a pageable job are coordinated by a class that
implements the Pageable interface, such as Book. A Book represents a
collection of pages that can use different page painters and that can vary
in size and orientation. You can also use your own implementation of the
Pageable interface if Book does not meet your application's needs.
