5.6 JScrollPane

The JScrollPane takes somewhat of a special role in Swing. Unlike in AWT, where TextArea and List are by default scrollable (i.e. they have scrollbars), JTextArea, JList, and other Swing components do not. This is a design attempt to create a generic Scrollable interface and any GUI component that implements Scrollable can be added to a ScrollPane.

Simply instantiating a JTextArea or JList does not render them scrollable. The following additional call to the JScrollPane object are required to add scrollbars:

JScrollPane jScrollPane = new JScrollPane(SOME_SCROLLABLE_GUI_COMPONENT);

For JTextArea: JTextArea jTextArea = new JTextArea(); JScrollPane jScrollPane = new JScrollPane(jTextArea); ....add(jScrollPane);

Figure 5.3

For JList: JList jList = new JList(4); JScrollPane jScrollPane = new JScrollPane(jList); ....add(jList);

Figure 5.4