如何使 JButton 显示为“翻转”

Question

A JButton has a different appearance when rolled over. That appearance is different from the "selected" appearance.

I want to display my button "as if" it was rolled over, so that user understands that if he hits the Return key, that button will be triggered.

The problem is not the same as setting the default button, because I am in a situation where I really want to get the user to understand that although he wouldn't expect it, if he hits enter that button will be activated. More details below for those who want some. Setting button as default would make button the default one, but wouldn't be significantly signaling to the user.

In my case the strong enough signal is the appearance that the button has when it is rolled over.

How to do that ?

More details on the situation, for those who want some :

• I have a list of buttons representing options, and a text box at the top, which acts as a filter on the buttons
• when filter is such that only one option remains, hitting return directly clicks that option's button
• in reality user would have had to select the button with tab or arrow, and then hit enter.
• since that shortcut is not obvious I want to signal it to user

Answer 1

Based on your question, what you "really" want, is the JRootPane#setDefaultButton , which will highlight the button, in a OS specific manner and if the user presses the default "action" key (Enter in most cases) will call it's ActionListener

For example...

The "normal" button is just a plain old JButton , the Hacked sets the rollOver to enabled and Default has been set as the default button for the JRootPane

As you can see, you're suggest fix does nothing on MacOS, don't know what it might do on other platforms

I suggest you have a look at How to Use Root Panes for more details

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRootPane;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

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

    public Test() {
        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 {

        private JButton asDefault = new JButton("Default");

        public TestPane() {
            JButton hack = new JButton("Hacked");
            hack.getModel().setRollover(true);
            hack.setRolloverEnabled(true);
            asDefault.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("Defaulted");
                }
            });
            add(new JButton("Normal"));

            add(hack);
            add(asDefault);
        }

        @Override
        public void addNotify() {
            super.addNotify();
            JRootPane rootPane = SwingUtilities.getRootPane(this);
            if (rootPane != null) {
                rootPane.setDefaultButton(asDefault);
            }
        }

    }
}

So using button.getModel().setRollover(true); doesn't work on all platforms and on those platforms it does work on, I suspect the user will simply need to move the mouse through it to return it to normal

Answer 2

button.getModel().setRollover(true);