Swing 工具欄實戰：JToolBar 可拖拽按鈕組與動作回饋

功能描述

構建包含「打開、保存、搜索」三個圖標按鈕的工具欄，按鈕支持工具提示、鍵盤助記符、點擊後在下方文本區輸出操作日誌。工具欄可拖拽浮動/停靠（JToolBar 默認特性）。

完整實現：ToolBarDemo

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

public class ToolBarDemo extends JPanel implements ActionListener {
    private JTextArea logArea;
    private static final String OPEN = "OPEN", SAVE = "SAVE", SEARCH = "SEARCH";
    private final String NL = "\n";

    public ToolBarDemo() {
        super(new BorderLayout());

        // 1. 工具欄
        JToolBar toolBar = new JToolBar();
        toolBar.setFloatable(true); // 允許拖拽浮動
        addButtons(toolBar);
        add(toolBar, BorderLayout.PAGE_START);

        // 2. 日誌輸出區
        logArea = new JTextArea(15, 30);
        logArea.setEditable(false);
        add(new JScrollPane(logArea), BorderLayout.CENTER);

        setPreferredSize(new Dimension(450, 300));
    }

    private void addButtons(JToolBar tb) {
        tb.add(makeButton("Open16", OPEN, "打開一個文件", "打開"));
        tb.add(makeButton("Save16", SAVE, "保存當前文件", "保存"));
        tb.add(makeButton("Search16", SEARCH, "搜索文件內容", "搜索"));
    }

    private JButton makeButton(String imgName, String cmd, String tip, String altText) {
        JButton btn = new JButton();
        btn.setActionCommand(cmd);
        btn.setToolTipText(tip);
        btn.addActionListener(this);

        URL imgUrl = ToolBarDemo.class.getResource("images/" + imgName + ".gif");
        if (imgUrl != null) {
            btn.setIcon(new ImageIcon(imgUrl));
        } else {
            btn.setText(altText); // 圖標缺失時降級顯示文本
            System.err.println("資源未找到: images/" + imgName + ".gif");
        }
        return btn;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String desc = switch (e.getActionCommand()) {
            case OPEN -> "打開文件操作";
            case SAVE -> "保存文件操作";
            case SEARCH -> "搜索字符操作";
            default -> "未知操作";
        };
        logArea.append("執行: " + desc + NL);
        logArea.setCaretPosition(logArea.getDocument().getLength());
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame f = new JFrame("ToolBarDemo");
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setContentPane(new ToolBarDemo());
            f.pack();
            f.setVisible(true);
        });
    }
}

關鍵特性解析

進階擴展：Action 統一管理

將按鈕屬性封裝為 AbstractAction，實現菜單項、工具欄按鈕、鍵盤綁定三位一體：

Action openAction = new AbstractAction("打開", new ImageIcon(...)) {
    @Override public void actionPerformed(ActionEvent e) { /* 打開邏輯 */ }
};
openAction.putValue(Action.SHORT_DESCRIPTION, "打開文件");
openAction.putValue(Action.ACCELERATOR_KEY, KeyStroke.getKeyStroke("ctrl O"));

JMenuItem menuItem = new JMenuItem(openAction);
JButton toolBtn = new JButton(openAction);
inputMap.put(KeyStroke.getKeyStroke("ctrl O"), "open");
actionMap.put("open", openAction);

現代化替代

JavaFX ToolBar + Button 結合 FontAwesome/Material Icons 字體圖標，無需外部圖片文件，支持 CSS 樣式統一風格。