[Chapter 8] New AWT Features
Author: David Flanagan
Date: Thu Jul 31 15:55:55 1997

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| Chapter 8 |

# 8. New AWT Features

Contents:
The ScrollPane Container
Popup Menus and Menu Shortcuts
Printing
Data Transfer with Cut-and-Paste
New Feature Demo

In addition to the new AWT event model that we saw in Chapter 7, Events, there are a number of important new AWT features in Java 1.1. These new features were outlined in Chapter 4, What's New in Java 1.1. This chapter details many of those new features and demonstrates them in a single extended example application at the end of the chapter. The major features of the example are:

- The new `ScrollPane` component

- Popup menus and menu shortcuts

- Printing

- Data transfer through cut-and-paste

In addition, the example also demonstrates the use of object serialization to save and load application state. This functionality is described in Chapter 9, Object Serialization.

## 8.1 The ScrollPane Container

The new `ScrollPane` container holds a single child component that is usually larger than the `ScrollPane` itself. The `ScrollPane` displays a fixed-size area of the child and provides horizontal and vertical scrollbars so the user can scroll the child component within the "viewport" of the `ScrollPane`. Figure 8.1 shows a top-level window created by the application listed in Example 8.1 at the end of this chapter. As you can see, the application creates a `ScrollPane` container to hold the larger `Scribble` component that supports free-hand drawing.

#### Figure 8.1: New AWT features demo application

The `ScrollPane` is quite easy to use. Simply create it and add a child component as you would with any other container. Note, however, that `ScrollPane` only supports a single child and it cannot have a `LayoutManager` specified. The `ScrollPane` is created in the `ScribbleFrame()` constructor of the example. The important thing to note is that the `ScrollPane` does not have any preferred or natural size of its own, so you should use `setSize()` to specify the size you want it to be. The `ScrollPane` class defines three constants that are legal values of its "scrollbar display policy." Because the example does not specify one of these constants, the policy defaults to `SCROLLBARS_AS_NEEDED`, which indicates that scrollbars are displayed for any dimension in which the contained child is larger than the available "viewport" space of the `ScrollPane` container.

Here is an excerpt of the `ScribbleFrame()` constructor that shows the creation of the `ScrollPane`:

    ScrollPane pane = new ScrollPane();      // Create a ScrollPane.
    pane.setSize(300, 300);                  // Specify its size.
    this.add(pane, "Center");                // Add it to the frame.
    Scribble scribble;
    scribble = new Scribble(this, 500, 500); // Create a bigger scribble area.
    pane.add(scribble);                      // Add it to the ScrollPane.

Inside the Java 1.1 Event Model |  | Popup Menus and Menu Shortcuts