Java: Radio Buttons
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Radio buttons (javax.swing.JRadioButton) are used in groups (java.awt.ButtonGroup)
where at most one can be selected.
The example below produced this image.
A radio button group starts with all buttons deselected, but after one is
selected the only way to have them appear all off is to have an invisible button
that is selected by the program.
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Source code for above example
This example creates a group of three radio buttons, puts them
in a grid layout on a panel, and puts a titled, etched border around them.
JRadioButton yesButton = new JRadioButton("Yes" , true);
JRadioButton noButton = new JRadioButton("No" , false);
JRadioButton maybeButton = new JRadioButton("Maybe", false);
ButtonGroup bgroup = new ButtonGroup();
bgroup.add(yesButton);
bgroup.add(noButton);
bgroup.add(maybeButton);
JPanel radioPanel = new JPanel();
radioPanel.setLayout(new GridLayout(3, 1));
radioPanel.add(yesButton);
radioPanel.add(noButton);
radioPanel.add(maybeButton);
radioPanel.setBorder(BorderFactory.createTitledBorder(
BorderFactory.createEtchedBorder(), "Married?"));
Testing the status of radio buttons
There are several ways to find out about radio button states:
- Test the radio button with
isSelected
.
- Add an item listener with
addItemListener
. ItemListeners are called both
the button is selected and automatically deselected.
- Add an action listener with
addActionListener
. ActionListeners are called only
when a button is selected.
Common JRadioButton methods
boolean b;
JRadioButton rb = new JRadioButton("Sample", false);
b = rb.isSelected();
rb.setSelected(b);
rb.addActionListener(an-action-listener);
rb.addItemListener(an-item-listener);
Common ButtonGroup methods
The most common method used for a button group is add()
,
but it's also possible to get or set the selected button.
JRadioButton rb = new JRadioButton("Sample", false);
ButtonGroup bgroup = new ButtonGroup();
bgroup.add(JRadioButton rb);
JRadioButton rb = bgroup.getSelectedJRadioButton();
bgroup.setSelectedJRadioButton(rb);