JTree默认箭头图标未移除，需自定义Root图标及点击展开逻辑

问题说明 #

已成功修改JTree的节点（node）和叶子（leaf）图标，但仍存在以下问题：

1. 默认箭头图标（红框标注）未隐藏，破坏界面一致性
2. 仅能点击箭头展开/折叠节点，希望改为点击自定义图标触发展开
3. 需要为Root元素设置与node、leaf不同的专属图标

原界面截图：

修改后界面截图：

现有实现代码 #

自定义TreeCellRenderer #

/** 修改JTree默认图标 **/
private class userRendererForTree extends DefaultTreeCellRenderer {
    private static final long serialVersionUID = 1L;

    public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded,
            boolean leaf, int row, boolean hasFocus) {

        super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
        if (leaf) {
            setIcon(setImageIcon(AppConstants.BOM_ROUTE_NODE_LEAF));
        } else {
            setIcon(setImageIcon(AppConstants.BOM_ROUTE_NODE_RIGHT));
        }
        if (expanded) {
            setIcon(setImageIcon(AppConstants.BOM_ROUTE_NODE_BOTTOM));
        }
        return this;
    }
}

/** 从资源加载图片图标 **/
private ImageIcon setImageIcon(String path){
    Image image = null;
    ImageIcon icon = null;
    try {
        image = LoadResource.getImageFromResourceAsURL(path);
        image = image.getScaledInstance(10, 10, Image.SCALE_SMOOTH);
        icon = new ImageIcon(image);
        return icon;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return icon;
}

Renderer调用代码 #

JTree BomTree = new JTree(createTreeModel());
scrollPane.setColumnHeaderView(BomTree);
BomTree.setCellRenderer(new userRendererForTree());

解决方案 #

1. 为Root节点设置专属图标 #

修改userRendererForTree的逻辑，优先判断Root节点，并调整图标判断顺序（避免expanded状态覆盖leaf判断）：

public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded,
        boolean leaf, int row, boolean hasFocus) {

    super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
    DefaultMutableTreeNode treeNode = (DefaultMutableTreeNode) value;
    
    // 为Root节点设置专属图标
    if (treeNode.isRoot()) {
        setIcon(setImageIcon(AppConstants.BOM_ROUTE_NODE_ROOT)); // 替换为你的Root图标常量
    } else if (leaf) {
        setIcon(setImageIcon(AppConstants.BOM_ROUTE_NODE_LEAF));
    } else if (expanded) {
        setIcon(setImageIcon(AppConstants.BOM_ROUTE_NODE_BOTTOM));
    } else {
        setIcon(setImageIcon(AppConstants.BOM_ROUTE_NODE_RIGHT));
    }
    return this;
}

2. 隐藏默认箭头图标 #

在创建JTree后添加以下代码，隐藏默认的展开箭头和连接线：

// 隐藏JTree默认箭头与连接线
BomTree.putClientProperty("JTree.lineStyle", "None");

3. 实现点击自定义图标展开节点 #

提供两种实现方式，按需选择：

方式一：点击节点任意区域（含图标）展开

设置点击一次即可触发展开/折叠，替代默认的双击节点或点击箭头逻辑：

// 设置点击节点（含图标）一次就展开/折叠
BomTree.setToggleClickCount(1);

方式二：仅点击图标区域时展开

添加鼠标监听器，精确判断点击位置是否在图标区域后触发展开：

BomTree.addMouseListener(new MouseAdapter() {
    @Override
    public void mouseClicked(MouseEvent e) {
        TreePath path = BomTree.getPathForLocation(e.getX(), e.getY());
        if (path != null) {
            Rectangle pathBounds = BomTree.getPathBounds(path);
            // 10为你的图标宽度，根据实际值调整
            if (pathBounds != null && e.getX() <= pathBounds.x + 10) {
                boolean isExpanded = BomTree.isExpanded(path);
                if (isExpanded) {
                    BomTree.collapsePath(path);
                } else {
                    BomTree.expandPath(path);
                }
            }
        }
    }
});

内容的提问来源于stack exchange，提问作者Alpha