[Chapter 8] 8.3 Printing

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| Chapter 8 New AWT Features |

## 8.3 Printing

The popup menu visible in Example 8.1 shows that that example application supports a Print command. One of the most exciting new features of Java 1.1 is the ability of programs to generate hardcopy. You draw on a page in Java just as you draw on the screen: by invoking methods of a `Graphics` object. The difference, of course, is in the `Graphics` object. When drawing to the screen, you are given an instance of one subclass of `Graphics`, and when printing, you are given an instance of some other subclass. The two subclasses implement the necessary functionality for on-screen drawing and printing, respectively.

To print in Java 1.1, follow these steps:

- First, you must begin the "print job." You do this by calling the `getPrintJob()` method of the `Toolkit` object. This method displays a dialog box to the user to request information about the print job, such as the name of the printer it should be sent to. `getPrintJob()` returns a `PrintJob` object. You can pass a `Properties` object to `getPrintJob()` and the user's printing preferences are stored in it. If the `Properties` object is used in a subsequent call to `getPrintJob()`, those preferences are reused in the dialog box.

- To begin printing a page, you call the `getGraphics()` method of the `PrintJob` object. This returns a `Graphics` object that implements the `PrintGraphics` interface to distinguish it from an on-screen `Graphics` object.

- Now you can use the various methods of the `Graphics` object to draw your desired output on the page.

- When you are done drawing the page, you call the `dispose()` method of the `Graphics` object to send that page description to the printer. If you need to print another page, you can call the `getGraphics()` method of the `PrintJob` again to obtain a new `Graphics` object for the next page, and repeat the process of drawing and calling `dispose()`.

- When you have printed all of your pages, you end the print job itself by calling the `end()` method of the `PrintJob` object.

Printing AWT components and hierarchies of components is particularly easy. You simply pass a print `Graphics` object to the `print()` method of the component you want to print. By default, `print()` simply passes this `Graphics` object to the `paint()` method. If a component wants to display itself differently on paper than it does on screen, however, it might implement a custom `print()` method. To print a complete hierarchy of components, you simply call the `printAll()` method of the root component of the hierarchy.

An important restriction on printing is that applets cannot initiate print jobs. This does not mean that they cannot define custom `print()` methods to allow themselves to be printed; merely that the Web browser or applet viewer must initiate the print job, and invoke the `printAll()` method of the applet.

The `print()` method of Example 8.1 shows how to generate hardcopy. Note that this `Scribble.print()` method happens to have the same name as the `Component.print()` method discussed above. The two methods have different arguments, however, so `Scribble.print()` does not override `Component.print()`.

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