如何从 ButtonGroup 中选择哪个 JRadioButton

I would just loop through your JRadioButtons and call isSelected(). If you really want to go from the ButtonGroup you can only get to the models. You could match the models to the buttons, but then if you have access to the buttons, why not use them directly?

You could use getSelectedObjects() of ItemSelectable (superinterface of ButtonModel) which returns the list of selected items. In case of a radio button group it can only be one or none at all.

jRadioOne = new javax.swing.JRadioButton();
jRadioTwo = new javax.swing.JRadioButton();
jRadioThree = new javax.swing.JRadioButton();

... then for every button:

buttonGroup1.add(jRadioOne);
jRadioOne.setText("One");
jRadioOne.setActionCommand(ONE);
jRadioOne.addActionListener(radioButtonActionListener);

...listener

ActionListener radioButtonActionListener = new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
radioButtonActionPerformed(evt);
}
};

...do whatever you need as response to event

protected void radioButtonActionPerformed(ActionEvent evt) {
System.out.println(evt.getActionCommand());
}

I suggest going straight for the model approach in Swing. After you've put the component in the panel and layout manager, don't even bother keeping a specific reference to it.

If you really want the widget, then you can test each with isSelected, or maintain a Map<ButtonModel,JRadioButton>.

I got similar problem and solved with this:

import java.util.Enumeration;
import javax.swing.AbstractButton;
import javax.swing.ButtonGroup;


public class GroupButtonUtils {


public String getSelectedButtonText(ButtonGroup buttonGroup) {
for (Enumeration<AbstractButton> buttons = buttonGroup.getElements(); buttons.hasMoreElements();) {
AbstractButton button = buttons.nextElement();


if (button.isSelected()) {
return button.getText();
}
}


return null;
}
}

It returns the text of the selected button.

The following code displays which JRadiobutton is selected from Buttongroup on click of a button.
It is done by looping through all JRadioButtons in a particular buttonGroup.

 JRadioButton firstRadioButton=new JRadioButton("Female",true);
JRadioButton secondRadioButton=new JRadioButton("Male");


//Create a radio button group using ButtonGroup
ButtonGroup btngroup=new ButtonGroup();


btngroup.add(firstRadioButton);
btngroup.add(secondRadioButton);


//Create a button with text ( What i select )
JButton button=new JButton("What i select");


//Add action listener to created button
button.addActionListener(this);


//Get selected JRadioButton from ButtonGroup
public void actionPerformed(ActionEvent event)
{
if(event.getSource()==button)
{
Enumeration<AbstractButton> allRadioButton=btngroup.getElements();
while(allRadioButton.hasMoreElements())
{
JRadioButton temp=(JRadioButton)allRadioButton.nextElement();
if(temp.isSelected())
{
JOptionPane.showMessageDialog(null,"You select : "+temp.getText());
}
}
}
}

Add the radiobuttons to a button group then:

buttonGroup.getSelection().getActionCommand

import javax.swing.Action;
import javax.swing.ButtonGroup;
import javax.swing.Icon;
import javax.swing.JRadioButton;
import javax.swing.JToggleButton;


public class RadioButton extends JRadioButton {


public class RadioButtonModel extends JToggleButton.ToggleButtonModel {
public Object[] getSelectedObjects() {
if ( isSelected() ) {
return new Object[] { RadioButton.this };
} else {
return new Object[0];
}
}


public RadioButton getButton() { return RadioButton.this; }
}


public RadioButton() { super(); setModel(new RadioButtonModel()); }
public RadioButton(Action action) { super(action); setModel(new RadioButtonModel()); }
public RadioButton(Icon icon) { super(icon); setModel(new RadioButtonModel()); }
public RadioButton(String text) { super(text); setModel(new RadioButtonModel()); }
public RadioButton(Icon icon, boolean selected) { super(icon, selected); setModel(new RadioButtonModel()); }
public RadioButton(String text, boolean selected) { super(text, selected); setModel(new RadioButtonModel()); }
public RadioButton(String text, Icon icon) { super(text, icon); setModel(new RadioButtonModel()); }
public RadioButton(String text, Icon icon, boolean selected) { super(text, icon, selected); setModel(new RadioButtonModel()); }


public static void main(String[] args) {
RadioButton b1 = new RadioButton("A");
RadioButton b2 = new RadioButton("B");
ButtonGroup group = new ButtonGroup();
group.add(b1);
group.add(b2);
b2.setSelected(true);
RadioButtonModel model = (RadioButtonModel)group.getSelection();
System.out.println(model.getButton().getText());
}
}

Use the isSelected() method. It will tell you the state of your radioButton. Using it in combination with a loop(say for loop) you can find which one has been selected.

You must add setActionCommand to the JRadioButton then just do:

String entree = entreeGroup.getSelection().getActionCommand();

Example:

java = new JRadioButton("Java");
java.setActionCommand("Java");
c = new JRadioButton("C/C++");
c.setActionCommand("c");
System.out.println("Selected Radio Button: " +
buttonGroup.getSelection().getActionCommand());

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MyJRadioButton extends JFrame implements ActionListener
{
JRadioButton rb1,rb2;  //components
ButtonGroup bg;
MyJRadioButton()
{
setLayout(new FlowLayout());
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


rb1=new JRadioButton("male");
rb2=new JRadioButton("female");


//add radio button to button group
bg=new ButtonGroup();
bg.add(rb1);
bg.add(rb2);


//add radio buttons to frame,not button group
add(rb1);
add(rb2);
//add action listener to JRadioButton, not ButtonGroup
rb1.addActionListener(this);
rb2.addActionListener(this);
pack();
setVisible(true);
}
public static void main(String[] args)
{
new MyJRadioButton(); //calling constructor
}
@Override
public void actionPerformed(ActionEvent e)
{
System.out.println(((JRadioButton) e.getSource()).getActionCommand());
}

}

You can put and actionCommand to each radio button (string).

this.jButton1.setActionCommand("dog");
this.jButton2.setActionCommand("cat");
this.jButton3.setActionCommand("bird");

Assuming they're already in a ButtonGroup (state_group in this case) you can get the selected radio button like this:

String selection = this.state_group.getSelection().getActionCommand();

Hope this helps

Typically, some object associated with the selected radio button is required. It is not necessarily a String representing the button's label. It could be an Integer containing the button's index or an object of more complicated type T. You could fill and use a Map<ButtonModel, T> as Tom Hawtin suggested, but I propose to extend the model and place the objects there. Here's an improved ButtonGroup that uses this approach.

import javax.swing.*;


@SuppressWarnings("serial")
public class SmartButtonGroup<T> extends ButtonGroup {
@Override
public void add(AbstractButton b) {
throw new UnsupportedOperationException("No object supplied");
}


public void add(JRadioButton button, T attachedObject) {
ExtendedModel<T> model = new ExtendedModel<>(attachedObject);
model.setSelected(button.isSelected());
button.setModel(model);
super.add(button);
}


@SuppressWarnings("unchecked")
public T getSelectedObject() {
ButtonModel selModel = getSelection();
return selModel != null ? ((ExtendedModel<T>)selModel).obj : null;
}


public static class ExtendedModel<T> extends javax.swing.JToggleButton.ToggleButtonModel {
public T obj;


private ExtendedModel(T object) {
obj = object;
}
}
}

You can use this utility class instead of ButtonGroup. Create an object of this class and add buttons along with associated objects to it. For example,

SmartButtonGroup<Integer> group = new SmartButtonGroup<>();
JPanel panel = new JPanel();


for (int i = 1; i <= 5; i++) {
JRadioButton button = new JRadioButton("Button #" + i, i == 3); // select the 3rd button
group.add(button, i);
panel.add(button);
}

After this, you can get the object associated with the currently selected button anytime you need by simply calling getSelectedObject(), like this:

int selectedButtonIndex = group.getSelectedObject();

In case you need just the buttons themselves, you can use the next non-generic class instead.

import javax.swing.JRadioButton;


@SuppressWarnings("serial")
public class RadioButtonGroup extends SmartButtonGroup<JRadioButton> {
public void add(JRadioButton button) {
super.add(button, button);
}


@Override
public void add(JRadioButton button, JRadioButton attachedObject) {
throw new UnsupportedOperationException("Use the short form of addition instead");
}


public JRadioButton getSelectedButton() {
return getSelectedObject();
}
}

Ale Rojas's answer works fine:

As alternative you can also use the My_JRadiobutton11.addActionListener(this); on your JButton and then make your actions in the actionPerformed function like this (It just uses an extra variable which you have to instantiate (e.g Private String selection;) but it's not a big deal):

public void actionPerformed(ActionEvent arg0) {
if(arg0.getSource() == My_JRadiobutton11){
//my selection
selection = "Become a dolphin";
}else if(arg0.getSource() == My_JRadiobutton12){
//my selection
selection = "Become a Unicorn";
} ..etc
}