Java Swing JTree 完全指南：基礎樹、拖拽編輯與自定義圖標

最簡單的樹：DefaultMutableTreeNode 構建節點

DefaultMutableTreeNode root = new DefaultMutableTreeNode("中國");
DefaultMutableTreeNode guangdong = new DefaultMutableTreeNode("廣東");
guangdong.add(new DefaultMutableTreeNode("佛山"));
guangdong.add(new DefaultMutableTreeNode("汕頭"));
root.add(guangdong);
JTree tree = new JTree(root);
tree.putClientProperty("JTree.lineStyle", "None"); // 無連線
tree.setShowsRootHandles(true); // 顯示根節點展開圖標

可編輯、拖拽、增刪節點

啟用編輯

tree.setEditable(true);

滑鼠拖拽移動節點

TreePath movePath;
MouseListener ml = new MouseAdapter() {
    public void mousePressed(MouseEvent e) {
        movePath = tree.getPathForLocation(e.getX(), e.getY());
    }
    public void mouseReleased(MouseEvent e) {
        TreePath target = tree.getPathForLocation(e.getX(), e.getY());
        if (target != null && movePath != null && !movePath.equals(target)) {
            if (movePath.isDescendant(target)) return; // 禁止拖到子節點
            ((DefaultMutableTreeNode)target.getLastPathComponent())
                .add((DefaultMutableTreeNode)movePath.getLastPathComponent());
            tree.updateUI();
        }
    }
};
tree.addMouseListener(ml);

按鈕操作：新增兄弟/子節點、刪除、重命名

// 新增兄弟節點
DefaultMutableTreeNode parent = (DefaultMutableTreeNode)selected.getParent();
model.insertNodeInto(newNode, parent, parent.getIndex(selected)+1);

// 新增子節點
selected.add(newNode); // 或 model.insertNodeInto(newNode, selected, selected.getChildCount());

// 刪除節點
model.removeNodeFromParent(selected);

// 重命名
tree.startEditingAtPath(tree.getSelectionPath());

自定義節點圖標：擴展 DefaultTreeCellRenderer

封裝節點資料

class NodeData {
    int nodeType; String nodeData;
    NodeData(int t, String d) { nodeType=t; nodeData=d; }
    public String toString() { return nodeData; }
}
interface DBObjectType { int ROOT=0, DATABASE=1, TABLE=2, COLUMN=3, INDEX=4; }

渲染器實現

class MyRenderer extends DefaultTreeCellRenderer {
    ImageIcon rootIcon = new ImageIcon("icon/root.gif");
    ImageIcon dbIcon = new ImageIcon("icon/database.gif");
    ImageIcon tableIcon = new ImageIcon("icon/table.gif");
    ImageIcon colIcon = new ImageIcon("icon/column.gif");
    ImageIcon idxIcon = new ImageIcon("icon/index.gif");

    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 node = (DefaultMutableTreeNode) value;
        NodeData data = (NodeData) node.getUserObject();
        ImageIcon icon = switch (data.nodeType) {
            case DBObjectType.ROOT -> rootIcon;
            case DBObjectType.DATABASE -> dbIcon;
            case DBObjectType.TABLE -> tableIcon;
            case DBObjectType.COLUMN -> colIcon;
            case DBObjectType.INDEX -> idxIcon;
            default -> null;
        };
        setIcon(icon);
        return this;
    }
}

套用渲染器

tree.setCellRenderer(new MyRenderer());
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
SwingUtilities.updateComponentTreeUI(tree);

關鍵提示

• 節點資料請封裝為 `UserObject`，勿直接 `toString()` 硬編碼。
• 拖拽移動本質是「從原父節點移除 → 加入新父節點」，`DefaultMutableTreeNode.add()` 已自動處理移除。
• 大量節點時考慮 `TreeModel` 實作延遲載入（懶加載）。