java - 未选择单选按钮时调用 ActionEvent

Question

我注意到，即使指定条件语句，ActionEvent 仍会在我的 JRadioButtonMenuItem 组中触发:

if(!button.isSelected())
    //Do stuff

<小时/>

defaultTheme = new JRadioButtonMenuItem("Default theme");
    defaultTheme.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            if(!defaultTheme.isSelected())  
                System.out.println("temp");
        }
    });

<小时/>

我的设置菜单中有多个主题选项，但是如果已经选择了一个说(说默认)，并且已经选择了默认菜单并且我不想执行任何冗余代码用户单击已选择的单选按钮。

Answer 1

ActionListener 会在按钮被“操作”(单击、按下等)时告诉您，但这并不总是会改变其状态。相反，您可以将 ItemListener 附加到按钮模型，这将更准确地告诉您按钮的实际状态何时发生变化，例如...

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class ButtonTest {

    public static void main(String[] args) {
        new ButtonTest();
    }

    public ButtonTest() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;

            ButtonGroup bg = new ButtonGroup();
            final JRadioButton bananas = new JRadioButton("Bananas");
            final JRadioButton apples = new JRadioButton("Apples");
            bg.add(bananas);
            bg.add(apples);

            bananas.getModel().addItemListener(new ItemListener() {
                @Override
                public void itemStateChanged(ItemEvent e) {
                    System.out.println("Bananas " + bananas.isSelected());
                }
            });
            apples.getModel().addItemListener(new ItemListener() {
                @Override
                public void itemStateChanged(ItemEvent e) {
                    System.out.println("Apples " + apples.isSelected());
                }
            });

            add(bananas, gbc);
            add(apples, gbc);

        }

    }

}