CODEWITHSUNDEEP
java
aNNgeL0
aNNgeL0

Reputation: 57

JAVA using Printable print method

I found a usefull code but i don't understand two things from it. The first one is with if (page > 0) . What does that mean ? And also here where it should print job.print(); . Why is it calling this method without any parameter and not this one i created earlier ? : public int print(Graphics g, PageFormat pf, int page)

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.print.*;

public class HelloWorldPrinter implements Printable, ActionListener {


    public int print(Graphics g, PageFormat pf, int page) throws
                                                        PrinterException {

        if (page > 0) {   //Here
            return NO_SUCH_PAGE;
        }



//this one
        System.out.println(pf.getWidth());

        Graphics2D g2d = (Graphics2D)g;
        g2d.translate(pf.getImageableX(), pf.getImageableY());


        g.drawString("Hello world!", 100, 100);


        return PAGE_EXISTS;
    }

    public void actionPerformed(ActionEvent e) {
         PrinterJob job = PrinterJob.getPrinterJob();
         job.setPrintable(this);
         boolean ok = job.printDialog();
         if (ok) {
             try {
                  job.print();  //Here
             } catch (PrinterException ex) {

             }
         }
    }

    public static void main(String args[]) {

        UIManager.put("swing.boldMetal", Boolean.FALSE);
        JFrame f = new JFrame("Hello World Printer");
        f.addWindowListener(new WindowAdapter() {
           public void windowClosing(WindowEvent e) {System.exit(0);}
        });
        JButton printButton = new JButton("Print Hello World");
        printButton.addActionListener(new HelloWorldPrinter());
        f.add("Center", printButton);
        f.pack();
        f.setVisible(true);
    }
}

Upvotes: 1

Views: 3048

Answers (2)

ControlAltDel
ControlAltDel

Reputation: 35011

Q1: if (page > 0) . What does that mean ? - This makes sure only the first page is printed. Because you are using a Printable, rather than a Pageable, it doesn't know how many pages there are to print.

Q2: And also here where it should print job.print(); - It should call job.print where you want to send the print job to the printer. In your case, on the button click

Q3: Why is it calling this method without any parameter and not this one i created earlier ? - These are two different classes and objects. You are calling print() on a PrinterJob, which, calls back your Printable print method to print the page. On the line: job.setPrintable(this); that's how it knows to call back the print method you specified

Upvotes: 0

copeg
copeg

Reputation: 8348

The first one is with if (page > 0) . What does that mean ?

Printing can consist of multiple pages - the PrinterJob does not know how many pages to print, so it will call the print method of your Printable implementation until it is told to do so (eg NO_SUCH_PAGE is returned). One of the parameters passed to your implementation of the print (eg page) is incremented for every page, and indicates the current page number being printed. As a result, this conditional limits the printing to a single page.

And also here where it should print job.print(); . Why is it calling this method without any parameter and not this one i created earlier ?

You first call print on the PrinterJob, PrinterJob then creates the variables which are then passed to your print implementation (sometimes multiple times, depending upon the number of pages) - so you are indirectly calling your Printable implementation (eg the 3 parameter print method).

Oracle has a great printing tutorial worth reading in depth that might further answer questions you have.

Upvotes: 2

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