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Shifting Focus Away from a JTextArea with the Tab Key

Shifting Focus Away from a JTextArea with the Tab Key

Under most circumstances, pressing the tab key within a JFC/Swing GUIapplication will cause the focus to shift from the currently focusedComponent to the next focus-traversable Component. This is not thecase, however, if the currently focused Component happens to be aJTextArea object.

A JTextArea is a Component that allows multiple lines of plain text tobe displayed and edited. Unlike the JTextField class, it allows a userto insert tab characters into the text with the tab key. In many caseshowever, the desired behavior is for the user to be able to tab awayfrom a JTextArea without inserting a tab character. Unfortunately, thecreators of JTextArea did not include a way to make a JTextArea objectbehave this way.

One seemingly obvious solution is to write a KeyListener that monitorsKeyEvents within a JTextArea, and shifts the focus to the nextComponent whenever the tab key is pressed while the JTextArea isfocused. The problem with this approach, however, is that the tabcharacter will still get inserted into the JTextArea before the focusis shifted away.

The best solution I’ve found is to use a subclass of JTextArea whoseisManagingFocus() method always returns false, instead of true. Forexample:

 import javax.swing.*;public class NoTabTextArea extends JTextArea {    public boolean isManagingFocus() {        return false;    }}

An instance of NoTabTextArea can be used exactly like a JTextArea,except that the tab key will cause the focus to shift away from itwithout a tab character being inserted.

Unfortunately, you will not be able to visually manipulate instancesof this class within a drag-and-drop-style form designer, like VisualCafe, Visual Age, JBuilder, etc., unless you create a JavaBean basedon the class. You can still hand-code an instance into your formclass, but it will probably not be visible in the form designer.

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