似乎在 FocusListener 中没有读取 JPanel 背景

Question

这个问题出现在my last question here之后。我想将每个按钮的焦点和失去焦点的背景设置为主菜单下方的背景颜色（ContentPane 是 JPanel），所以按钮看起来像标签。在不同的环境中可能会有所不同，所以它是动态的，所以我不能手动设置它。现在，如果我记录 ContentPane 背景，它会显示 238、238、238。如果我在 FocusListener 中记录它 - 它还会显示 238、238、238。如果我直接将按钮的背景设置为 FocusListener 外部的 ContentPane 背景 - 它可以工作，但如果我设置在 FocusListener 内部 - 看起来没有读取和设置值，但如果我手动设置颜色 - 它可以工作。这怎么可能发生？将 FocusListener 设置为按钮是我在主 JPanel 初始化时所做的最后一件事。

private void setButtonDefaults(JButton but) {//calls once for each menu button to set defaults
    but.setBorderPainted(false);
    but.setBackground(Color.DARK_GRAY);
    but.setForeground(Color.WHITE);
    but.setName(but.getText().toLowerCase());
    but.setPreferredSize(buttonSize);
    but.addActionListener(this);
    //add focus listener
    but.addFocusListener(new FocusListener() {
        @Override
        public void focusLost(FocusEvent e) {
            Color clr = ContentPane.getBackground();
            log(clr + "");//logs that color is 238, 238, 238
            JButton button = (JButton) e.getSource();
            button.setBackground(clr);//value is not read
            //button.setBackground(new Color(238, 238, 238)); //value is read
        }

        @Override
        public void focusGained(FocusEvent e) {
            //same as focusLost function
        }
    });
}
private void enableOnlyOne(JButton but) { 
/* calls each time when one of menu buttons are pressed. 
All buttons are unpressed and changed colors to black and one
button is set as pressed and changes background color to
ContentPane background color
*/
    //disable all
    setButtonDisabled(MLibrary);
    setButtonDisabled(MScheduler);
    setButtonDisabled(MBudget);
    setButtonDisabled(MReports);
    setButtonDisabled(MManage);
    setButtonDisabled(MSettings);
    //enable one
    but.getModel().setPressed(true);
    but.setBackground(ContentPane.getBackground());//value is read perfect
    but.setForeground(Color.BLACK);
}
private void setButtonDisabled(JButton but) {
    but.getModel().setPressed(false);
    but.setBackground(Color.DARK_GRAY);
    but.setForeground(Color.WHITE);
}

Answer 1

请不要那样做，因为我看了你之前的帖子...，现在我无法抗拒

更好和最简单的方法是将ChangeListener 添加到预期的JButtons，然后在stateChanged(ChangeEvent changeEvent) 中，您可以确定哪个JButtons 触发了此事件，对于事件类型，您必须从ButtonModel 中提取此事件的类型

（其余由你决定，请把这些JButtons放到Vector, Array or Enumerations），例如

import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;

public class MyButtonGroup {

    private JButton button1 = new JButton("Test Enabled / Disabled");
    private JButton button2 = new JButton("Test Enabled / Disabled");
    private JButton button3 = new JButton("Test Enabled / Disabled");

    public MyButtonGroup() {
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(3, 0, 10, 10));
        button1.addChangeListener(changeListener);
        panel.add(button1);
        button2.addChangeListener(changeListener);
        panel.add(button2);
        button3.addChangeListener(changeListener);
        panel.add(button3);
        JFrame frame = new JFrame("Grouping Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }
    private ChangeListener changeListener = new ChangeListener() {

        public void stateChanged(ChangeEvent changeEvent) {
            JButton abstractButton = (JButton) changeEvent.getSource();
            if (abstractButton == button1) {
                ButtonModel buttonModel = abstractButton.getModel();
                boolean armed = buttonModel.isArmed();
                boolean pressed = buttonModel.isPressed();
                boolean selected = buttonModel.isSelected();
                boolean rolover = buttonModel.isRollover();
                System.out.println("Changed: " + armed + "/" + pressed + "/" + selected + "/" + rolover);
            } else if (abstractButton == button2) {
                ButtonModel buttonModel = abstractButton.getModel();
                boolean armed = buttonModel.isArmed();
                boolean pressed = buttonModel.isPressed();
                boolean selected = buttonModel.isSelected();
                boolean rolover = buttonModel.isRollover();
                System.out.println("Changed: " + armed + "/" + pressed + "/" + selected + "/" + rolover);
            }
        }
    };

    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                MyButtonGroup xxx = new MyButtonGroup();
            }
        });
    }
}

Answer 2

由于某些 L&F 不显示对背景颜色的更改是一种有用的方式，因此您可能需要考虑另一种突出显示形式：不同的边框、更改的前景色、自定义图标或合适的背景面板。更多here.

Answer 3

自己找到答案真是太好了：

private void setButtonDefaults(JButton but) {
    but.setBorderPainted(false);
    but.setBackground(Color.DARK_GRAY);
    but.setForeground(Color.WHITE);
    but.setName(but.getText().toLowerCase());
    but.setPreferredSize(buttonSize);
    but.addActionListener(this);
    //add focus listener
    final Color clr = ContentPane.getBackground();
    final int r = clr.getRed();
    final int g = clr.getGreen();
    final int b = clr.getBlue();
    but.addFocusListener(new FocusListener() {
        @Override
        public void focusLost(FocusEvent e) {
            log("r = " + r + ", g = " + g + ", b = " + b);
            JButton button = (JButton) e.getSource();
            button.setBackground(new Color(r, g, b));
        }

        @Override
        public void focusGained(FocusEvent e) {
            JButton button = (JButton) e.getSource();
            button.setBackground(new Color(r, g, b));
        }
    });
}

感谢所有尝试（并且确实）帮助我的人