如何获取 JList 未选定单元格的背景颜色？

Question

我试图找到未选择的单元格使用的颜色。这通常是白色的，但是当我调用 UIManager.getColor("List.background") 时，它似乎与 JPanel 所用的灰色相同。当我调用 new JList().getBackground() 时，我得到了同样可怕的灰色，但当我实际使用该列表时，它是白色的。如何从 JList 或 UIManager 获取这种白色？我目前正在做的查找背景颜色的操作是这样的：

String[] contents = {"Foo", "Bar"};
JList list = new JList(contents);

// Prints true
System.out.println(list.getBackground().equals(new Color(237, 236, 235)));

由于 List.selectionBackground 为我提供了单击单元格时期望看到的蓝色，因此我认为 List.background 将为我提供未选定单元格的颜色。那么 List.background 实际上返回的值是什么？

相关说明，是否有列出这些键的含义？我发现了一个相关问题，但没有一个答案提供按键的描述。

编辑：看来这是执行此操作的正确方法。然而，至少在 GNOME 中，调用 setLookAndFeel 时会出现问题。

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
String[] contents = {"Foo", "Bar"};
JList list = new JList(contents);

// Prints true
System.out.println(list.getBackground().equals(new Color(237, 236, 235)));

// Add list to a pane and display it, and it will actually be white

看起来这可能是一个错误，抱歉各位。

Answer 1

SwingUtilities.updateComponentTreeUI(myFrame);

编辑：

嗯，你能根据这个例子澄清我（我们）你的问题是什么（来自已故的 Old.Good.Forum.Sun.com，:-)，我知道不是珍妮特抵抗）

注意：最好改变这个使用 getListCellRendererComponent

编辑值：请再次使用该检查 camickr UI 默认

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

public class JListDisabledItemDemo implements ItemListener, Runnable {

    private static final String ITEMS[] = {"Black", "Blue", "Green", "Orange", "Purple", "Red", "White", "Yellow"};
    private JList jList;
    private JCheckBox[] checkBoxes;
    private boolean[] enabledFlags;

    @Override
    public void run() {
        JPanel pnlEnablers = new JPanel(new GridLayout(0, 1));
        pnlEnablers.setBorder(BorderFactory.createTitledBorder("Enabled Items"));
        checkBoxes = new JCheckBox[ITEMS.length];
        enabledFlags = new boolean[ITEMS.length];
        for (int i = 0; i < ITEMS.length; i++) {
            checkBoxes[i] = new JCheckBox(ITEMS[i]);
            checkBoxes[i].setSelected(true);
            checkBoxes[i].addItemListener(this);
            enabledFlags[i] = true;
            pnlEnablers.add(checkBoxes[i]);
        }
        jList = new JList(ITEMS);
        jList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        jList.setSelectionModel(new DisabledItemSelectionModel());
        jList.setCellRenderer(new DisabledItemListCellRenderer());
        jList.addListSelectionListener(new ListSelectionListener() {

            @Override
            public void valueChanged(ListSelectionEvent e) {
                if (!e.getValueIsAdjusting()) {
                    System.out.println("selection");
                }
            }
        });
        JScrollPane scroll = new JScrollPane(jList);
        scroll.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        JFrame f = new JFrame("Colors");
        Container contentPane = f.getContentPane();
        contentPane.setLayout(new GridLayout(1, 2));
        contentPane.add(pnlEnablers);
        contentPane.add(scroll);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(240, 280);
        f.setLocationRelativeTo(null);
        UIManager.put("List.background", Color.red);
        UIManager.put("List.selectionBackground", Color.orange);
        UIManager.put("List.selectionForeground", Color.blue);
        UIManager.put("Label.disabledForeground", Color.magenta);
        SwingUtilities.updateComponentTreeUI(f);
        f.setVisible(true);
    }

    @Override
    public void itemStateChanged(ItemEvent event) {
        JCheckBox checkBox = (JCheckBox) event.getSource();
        int index = -1;
        for (int i = 0; i < ITEMS.length; i++) {
            if (ITEMS[i].equals(checkBox.getText())) {
                index = i;
                break;
            }
        }
        if (index != -1) {
            enabledFlags[index] = checkBox.isSelected();
            jList.repaint();
        }
    }

    public static void main(String args[]) {
        SwingUtilities.invokeLater(new JListDisabledItemDemo());
    }

    private class DisabledItemListCellRenderer extends DefaultListCellRenderer {

        private static final long serialVersionUID = 1L;

        @Override
        public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
            if (enabledFlags[index]) {
                return super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
            }
            Component comp = super.getListCellRendererComponent(list, value, index, false, false);
            comp.setEnabled(false);
            return comp;
        }
    }

    private class DisabledItemSelectionModel extends DefaultListSelectionModel {

        private static final long serialVersionUID = 1L;

        /**
         * No need to override addSelectionInterval(int index0, int index1)
         * since we're using SINGLE_SELECTION mode for this demo.
         */
        @Override
        public void setSelectionInterval(int index0, int index1) {
            if (enabledFlags[index0]) {
                super.setSelectionInterval(index0, index0);
            } else {
                /*
                 * The previously selected index is before this one,
                 * so walk forward to find the next selectable item.
                 */
                if (getAnchorSelectionIndex() < index0) {
                    for (int i = index0; i < enabledFlags.length; i++) {
                        if (enabledFlags[i]) {
                            super.setSelectionInterval(i, i);
                            return;
                        }
                    }
                } /*
                 * Otherwise, walk backward to find the next selectable item.
                 */ else {
                    for (int i = index0; i >= 0; i--) {
                        if (enabledFlags[i]) {
                            super.setSelectionInterval(i, i);
                            return;
                        }
                    }
                }
            }
        }
    }
}