具有多行文本和动态高度的 Swing JList

Question

我已经阅读/尝试过这些帖子，但这没有帮助：

• 显示多行Jlist 单元格
• 如何获取 Jlist 的多行文本？
• 显示 JList 组件时出现问题

我需要的是 ListCellRenderer 返回一个面板，左侧有一个图标，右侧有一个动态长度的文本（就像在任何论坛中一样：左侧是用户头像，右侧是帖子文本）。我不知道这些文本，因此我无法设置固定的单元格高度。此外，文本长度因列表单元格而异。因此，每个列表单元格都需要根据文本的长度有自己的高度。实际上这是一个非常常见的布局...但不适用于 Swing。单元格高度不会根据文本长度扩展。

我已经阅读了几乎所有关于 JList 中动态单元格高度和多行文本的帖子，但找不到解决方案。所以我决定参加一个小型的SSCCE。请给我一个关于如何实现我所描述的内容的提示，或者如果您认为这很容易，请修复我的代码。

谢谢

这是 SSCCE：

public class MultiLineList extends JFrame
{

    private static final long serialVersionUID = 1L;

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

    private MultiLineList()
    {
        setTitle("MultiLineList");
        setSize(800, 450);
        setResizable(true);
        setVisible(true);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        this.getContentPane().setLayout(new BorderLayout());

        final DefaultListModel model = new DefaultListModel();
        model.addElement("This is a short text");
        model.addElement("This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. ");
        model.addElement("This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. ");

        final JList list = new JList(model);
        list.setCellRenderer(new MyCellRenderer());

        this.add(list);

        this.getContentPane().invalidate();
        this.getContentPane().validate();

    }

    public class MyCellRenderer extends DefaultListCellRenderer
    {
        @Override
        public Component getListCellRendererComponent(final JList list, final Object value, final int index, final boolean isSelected, final boolean hasFocus)
        {

            final String text = (String) value;

            //create panel
            final JPanel p = new JPanel();
            p.setLayout(new BorderLayout());

            //icon
            final JPanel IconPanel = new JPanel(new BorderLayout());
            final JLabel l = new JLabel("icon"); //<-- this will be an icon instead of a text
            IconPanel.add(l, BorderLayout.NORTH);
            p.add(IconPanel, BorderLayout.WEST);

            //text
            final JTextArea ta = new JTextArea();
            ta.setText(text);
            ta.setLineWrap(true);
            ta.setWrapStyleWord(true);
            p.add(ta, BorderLayout.CENTER);

            return p;

        }
    }

}

Answer 1

编辑1：哎呀 - 看到@Andrew的屏幕截图，意识到这没有按预期工作，文本实际上比显示的要长（忽略了内部评论“PENDING：不适用于JScrollPane中的JList” “;-) 如果我不能很快让它发挥作用，我会挖掘一下并删除这个答案。

编辑2：明白了 - 如下所示的渲染器实现是好的，罪魁祸首是 JList 偶尔小于最佳大小的缓存。 BasicListUI有两部分

• 没有考虑到调整列表大小可能需要清除内部大小（实际上是行高）缓存，应用程序代码必须强制它这样做，fi 在 ComponentListener
• 列表的可滚动实现中 trackViewportWidth 包含逻辑它阻碍了（导致该区域循环拉伸直到它成为一条线），子类返回 true。

使用下面渲染器的代码：

    final JList list = new JList(model) {

        /** 
         * @inherited <p>
         */
        @Override
        public boolean getScrollableTracksViewportWidth() {
            return true;
        }


    };
    list.setCellRenderer(new MyCellRenderer());

    ComponentListener l = new ComponentAdapter() {

        @Override
        public void componentResized(ComponentEvent e) {
            // next line possible if list is of type JXList
            // list.invalidateCellSizeCache();
            // for core: force cache invalidation by temporarily setting fixed height
            list.setFixedCellHeight(10);
            list.setFixedCellHeight(-1);
        }

    };

    list.addComponentListener(l);
    add(new JScrollPane(list));

第一个答案（使用 JTextArea 作为渲染组件的渲染器实现）

TextArea 在调整大小方面有点棘手：它需要初始化为合理的值：

public class MyCellRenderer implements ListCellRenderer {

    private JPanel p;
    private JPanel iconPanel;
    private JLabel l;
    private JTextArea ta;

    public MyCellRenderer() {
        p = new JPanel();
        p.setLayout(new BorderLayout());

        // icon
        iconPanel = new JPanel(new BorderLayout());
        l = new JLabel("icon"); // <-- this will be an icon instead of a
                                // text
        iconPanel.add(l, BorderLayout.NORTH);
        p.add(iconPanel, BorderLayout.WEST);

        // text
        ta = new JTextArea();
        ta.setLineWrap(true);
        ta.setWrapStyleWord(true);
        p.add(ta, BorderLayout.CENTER);
    }

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

        ta.setText((String) value);
        int width = list.getWidth();
        // this is just to lure the ta's internal sizing mechanism into action
        if (width > 0)
            ta.setSize(width, Short.MAX_VALUE);
        return p;

    }
}

Answer 2

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

public class MultiLineList
{
    private static final long serialVersionUID = 1L;

    public static void main(final String[] args)
    {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new MultiLineList();
            }
        });
    }

    private MultiLineList()
    {
        JFrame f = new JFrame("MultiLineList");
        f.setResizable(true);
        f.setVisible(true);
        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        f.getContentPane().setLayout(new BorderLayout());

        final DefaultListModel model = new DefaultListModel();
        model.addElement("This is a short text");
        model.addElement("This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. This is a long text. ");
        model.addElement("This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. This is an even longer text. ");

        final JList list = new JList(model);
        list.setCellRenderer(new MyCellRenderer());

        f.add(list);

        f.pack();
    }

    public class MyCellRenderer extends DefaultListCellRenderer
    {
        final JPanel p = new JPanel(new BorderLayout());
        final JPanel IconPanel = new JPanel(new BorderLayout());
        final JLabel l = new JLabel("icon"); //<-- this will be an icon instead of a text
        final JLabel lt = new JLabel();
        String pre = "<html><body style='width: 200px;'>";

        MyCellRenderer() {
            //icon
            IconPanel.add(l, BorderLayout.NORTH);
            p.add(IconPanel, BorderLayout.WEST);

            p.add(lt, BorderLayout.CENTER);
            //text
        }

        @Override
        public Component getListCellRendererComponent(final JList list, final Object value, final int index, final boolean isSelected, final boolean hasFocus)
        {
            final String text = (String) value;
            lt.setText(pre + text);

            return p;
        }
    }
}