LookAndFeel 阻止 JComboBox 背景变化？

Question

目标是当 LookAndFeel 在 main 方法中时改变所有组合框的背景。 但是当 LookAndFeel 存在和不存在时，我会得到不同的结果。

没有 LookAndFeel： JComboBox 在 JFrame 调整大小后可见

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

import static java.awt.Color.WHITE;

public class TestFrame extends JFrame {

    private static final String[] ANIMALS = new String[]{"Cat", "Mouse", "Dog", "Elephant", "Bird", "Goat", "Bear"};

    public TestFrame() {
        setSize(600, 300);
        setVisible(true);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        JComboBox<String> comboBox = new JComboBox<>();
        comboBox.setModel(new DefaultComboBoxModel<>(ANIMALS));
        comboBox.setForeground(WHITE);
        comboBox.setBackground(new Color(71, 81, 93));
        comboBox.getEditor().getEditorComponent().setBackground(new Color(71, 81, 93));
        comboBox.getEditor().getEditorComponent().setForeground(WHITE);
        comboBox.setRenderer(new DefaultListCellRenderer() {
            @Override
            public void paint(Graphics g) {
                setBackground(new Color(71, 81, 93));
                setForeground(WHITE);
                super.paint(g);
            }
        });
        panel.add(comboBox);
        add(panel);
    }

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

使用 LookAndFeel：

import javax.swing.*;
import java.awt.*;
import java.util.logging.Level;
import java.util.logging.Logger;

import static java.awt.Color.WHITE;

public class TestFrame extends JFrame {

    private static final String[] ANIMALS = new String[]{"Cat", "Mouse", "Dog", "Elephant", "Bird", "Goat", "Bear"};

    public TestFrame() {
        setSize(600, 300);
        setVisible(true);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        JComboBox<String> comboBox = new JComboBox<>();
        comboBox.setModel(new DefaultComboBoxModel<>(ANIMALS));
        comboBox.setForeground(WHITE);
        comboBox.setBackground(new Color(71, 81, 93));
        comboBox.getEditor().getEditorComponent().setBackground(new Color(71, 81, 93));
        comboBox.getEditor().getEditorComponent().setForeground(WHITE);
        comboBox.setRenderer(new DefaultListCellRenderer() {
            @Override
            public void paint(Graphics g) {
                setBackground(new Color(71, 81, 93));
                setForeground(WHITE);
                super.paint(g);
            }
        });
        panel.add(comboBox);
        add(panel);
    }

    public static void main(String[] args) {
        try {
            for (UIManager.LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
            Logger.getLogger(TestFrame.class.getName()).log(Level.SEVERE, null, ex);
        }

        /* Create and display the form */
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                new TestFrame();
            }
        });
    }
}

如何在启用 LookAndFeel 的情况下实现组合框的完整绘制？

Answer 1

没有像禁用或启用LookAndFeel 这样的东西。您始终在应用程序中设置外观。您似乎只是设置了另一个LookAndFeel，在您的情况下是Nimbus。但是，为了回答您的问题，Nimbus 将DefaultListCellRenderer 的不透明度属性设置为false，（例如MetalLookAndFeel 将其设置为true），这是视觉效果的原因您正在展示的代表。您应该可以通过覆盖DefaultListCellRenderer 的getListCellRendererComponent 方法来解决此问题，如下所示：

@Override
public Component getListCellRendererComponent(JList list, Object value,
                        int index, boolean isSelected, boolean cellHasFocus) {

    JComponent comp = (JComponent) super.getListCellRendererComponent(list,
                value, index, isSelected, cellHasFocus);

    list.setBackground(COMBO_COLOR);
    list.setForeground(Color.WHITE);
    list.setOpaque(false);
        
    return comp;
}

您还必须将 UIManagers 属性 ComboBox.forceOpaque 设置为 false，如下所示：

UIManager.put("ComboBox.forceOpaque", false);

Nimubs 默认值的完整列表可以在here 找到。

如果需要，提供已解决问题的完整工作示例：

import java.awt.*;
import java.util.Arrays;
import javax.swing.*;

public class JComboBoxExample {
    
    private static final Color COMBO_COLOR = new Color(71, 81, 93);
    private static final String[] COMBO_DATA = {"Get back!", "Go!", "Help!", "Careful!"};
    
    public static void main(String[] args) throws Exception {        
        String nimbus = Arrays.asList(UIManager.getInstalledLookAndFeels())
                .stream()
                .filter(i -> i.getName().equals("Nimbus"))
                .findFirst()
                .get()
                .getClassName();
        
        UIManager.setLookAndFeel(nimbus);
        
        UIManager.put("ComboBox.forceOpaque", false);
        
        JFrame jf = new JFrame();
        jf.setVisible(true);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setLocationRelativeTo(null);
        
        MyComboBox comboBox = new MyComboBox(new DefaultComboBoxModel(COMBO_DATA));
        jf.add(comboBox);
        jf.pack();
    }
    
    private static class MyComboBox extends JComboBox  {

        public MyComboBox(DefaultComboBoxModel model) {
            super(model);
            setForeground(Color.WHITE);
            setFont(new Font("Arial", Font.PLAIN, 30));
            setPreferredSize(new Dimension(350, 50));
            setRenderer(new MyRenderer());
        }

    }

    private static class MyRenderer extends DefaultListCellRenderer {
        
        @Override
        public Component getListCellRendererComponent(JList list, Object value,
                            int index, boolean isSelected, boolean cellHasFocus) {

            JComponent comp = (JComponent) super.getListCellRendererComponent(list,
                    value, index, isSelected, cellHasFocus);

            list.setBackground(COMBO_COLOR);
            list.setForeground(Color.WHITE);
            list.setOpaque(false);
            
            return comp;
        }
    }
    
}

结果：

顺便说一句，我使用 NetBeans IDE 的可视化调试器解决了这个问题。