JComboBox : Java Glossary

2009-04-28 by Roedy Green ©1996-2009 Canadian Mind Products
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JComboBox

The Swing equivalent of the AWT Choice. A JComboBox is a component that combines a button or editable field and a drop-down list. The user can select a value from the drop-down list, which appears at the user’s request. If you make the combo box editable, then the combo box includes an editable field into which the user can type a value, thus allowing the user to select something that was not one of the original choices.

The name is misleading. JComboBox does not let you select combinations of options, the way you can with a JList, just a single option. The combo-moniker comes from the fact it has a combination write in field and select from pre-existing choices.

JList is similar to JComboBox, except JComboBox drops down where JList does not. Further, JList permits multiple selections where JComboBox does not.

To control how the choices are displayed, you can write a custom ListCellRenderer, based on BasicComboBoxRenderer.

To control how the new write-in field possibility is keyed, you can write a custom ComboBoxEditor based on BasicComboBoxEditor.

JComboBox uses setSelectedItem instead of select. getSelectedItem returns an Object you must cast to a String. The use of Objects for your choices allows more flexibility in rendering the choices.

Gotchas

Beware of the JComboBox(Vector<?>) constructor. It does not simply make a copy of the Vector. Any changes you make to the JComboBox model will also modify that Vector.
JComboBox.setSelectedItem will trigger an ActionEvent that is immediately dispatched, even before your event handler completes. This is almost never what you want. You usually need to create some mechanism to ignore the event. Otherwise you can get a situation I call fibrillation where events trigger events in an uncontrolled way.

Use

Here in how you use JComboBox:

Learning More

Sun’s Javadoc on the JComboBox class : available:

on the web at java.sun.com
in the current JDK 1.6.0_14 or in the old JDK 1.5.0_19 on your local Windows J: drive.

Sun’s Javadoc on the BasicComboBoxEditor class : available:

on the web at java.sun.com
in the current JDK 1.6.0_14 or in the old JDK 1.5.0_19 on your local Windows J: drive.

Sun’s Javadoc on the BasicComboBoxRenderer class : available:

on the web at java.sun.com
in the current JDK 1.6.0_14 or in the old JDK 1.5.0_19 on your local Windows J: drive.

Sun’s Javadoc on the DefaultComboBoxModel class : available:

on the web at java.sun.com
in the current JDK 1.6.0_14 or in the old JDK 1.5.0_19 on your local Windows J: drive.

adding autocompletion to JComboBox
autocompletion
AWT
Choice
fibrillation
Glazed Lists
JCheckBox
JList
JRadioButton
JToggleButton
List
Swing
ToolTip

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