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Java Swing 核心組件大全：從基礎控件到進階對話框實戰

編輯：Java 相關知識

Swing vs AWT：為何選擇 Swing？

Swing 為輕量級、純 Java 實現，跨平台一致性優於 AWT（重量級、依賴原生 Peer）。雖然早期版本效能稍遜，但現代 JVM 優化後差距可忽略。Swing 提供豐富組件：JToolBar、JColorChooser、JFileChooser、JOptionPane 等，AWT 均無對應。

常用組件速覽與綜合範例

基礎輸入與選擇組件

// 按鈕與圖示
Icon okIcon = new ImageIcon("ico/ok.png");
JButton ok = new JButton("確認", okIcon);

// 單選按鈕群組
JRadioButton male = new JRadioButton("男", true);
JRadioButton female = new JRadioButton("女", false);
ButtonGroup bg = new ButtonGroup();
bg.add(male); bg.add(female);

// 複選框
JCheckBox married = new JCheckBox("是否已婚？", false);

// 下拉選單與列表
String[] colors = {"紅色", "綠色", "藍色"};
JComboBox colorChooser = new JComboBox(colors);
JList colorList = new JList(colors);

// 文本域
JTextArea ta = new JTextArea(8, 20);
JTextField name = new JTextField(40);

選單系統：主選單、右鍵選單與風格切換

JMenuBar mb = new JMenuBar();
JMenu file = new JMenu("文件");
JMenu edit = new JMenu("編輯");
JMenu format = new JMenu("格式");

// 快捷鍵設置
newItem.setAccelerator(KeyStroke.getKeyStroke('N', InputEvent.CTRL_MASK));

// 二級選單
edit.add(format);

// 右鍵選單：切換 LookAndFeel
JPopupMenu pop = new JPopupMenu();
ButtonGroup flavorGroup = new ButtonGroup();
JRadioButtonMenuItem metalItem = new JRadioButtonMenuItem("Metal風格", true);
JRadioButtonMenuItem windowsItem = new JRadioButtonMenuItem("Windows風格");
JRadioButtonMenuItem motifItem = new JRadioButtonMenuItem("Motif風格");
flavorGroup.add(metalItem); flavorGroup.add(windowsItem); flavorGroup.add(motifItem);
pop.add(metalItem); pop.add(windowsItem); pop.add(motifItem);

// 事件監聽器統一處理
ActionListener flavorListener = e -> {
    try {
        if ("Metal風格".equals(e.getActionCommand())) changeFlavor(1);
        else if ("Windows風格".equals(e.getActionCommand())) changeFlavor(2);
        else if ("Motif風格".equals(e.getActionCommand())) changeFlavor(3);
    } catch (Exception ex) { ex.printStackTrace(); }
};
metalItem.addActionListener(flavorListener);
windowsItem.addActionListener(flavorListener);
motifItem.addActionListener(flavorListener);

// 安裝右鍵選單
ta.setComponentPopupMenu(pop);

動態切換 LookAndFeel

private void changeFlavor(int flavor) throws Exception {
    switch (flavor) {
        case 1: UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel"); break;
        case 2: UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); break;
        case 3: UIManager.setLookAndFeel("com.sun.java.swing.plaf.motif.MotifLookAndFeel"); break;
    }
    SwingUtilities.updateComponentTreeUI(f.getContentPane());
    SwingUtilities.updateComponentTreeUI(mb);
    SwingUtilities.updateComponentTreeUI(pop);
}

進階組件實戰

JToolBar + Action 共享：工具列、選單、按鈕三位一體

Action copyAction = new AbstractAction("複製", new ImageIcon("ico/copy.png")) {
    public void actionPerformed(ActionEvent e) {
        StringSelection contents = new StringSelection(jta.getSelectedText());
        clipboard.setContents(contents, null);
        if (clipboard.isDataFlavorAvailable(DataFlavor.stringFlavor))
            pasteAction.setEnabled(true);
    }
};
Action pasteAction = new AbstractAction("貼上", new ImageIcon("ico/paste.png")) {
    public void actionPerformed(ActionEvent e) {
        if (clipboard.isDataFlavorAvailable(DataFlavor.stringFlavor)) {
            try {
                String content = (String) clipboard.getData(DataFlavor.stringFlavor);
                jta.replaceRange(content, jta.getSelectionStart(), jta.getSelectionEnd());
            } catch (Exception ex) { ex.printStackTrace(); }
        }
    }
};
// 同一 Action 同時加入工具列、選單、按鈕
jtb.add(copyAction); jtb.add(pasteAction);
edit.add(copyAction); edit.add(pasteAction);
JButton copyBn = new JButton(copyAction);
JButton pasteBn = new JButton(pasteAction);

JColorChooser：模態與非模態顏色選擇器

// 模態對話框（一行搞定）
foreColor = JColorChooser.showDialog(f, "選擇畫筆顏色", foreColor);

// 非模態對話框（可自訂確認/取消回呼）
final JColorChooser colorPane = new JColorChooser(foreColor);
JDialog jd = JColorChooser.createDialog(f, "選擇畫筆顏色", false,
    colorPane, e -> foreColor = colorPane.getColor(), null);
jd.setVisible(true);

JFileChooser：圖片預覽與檔案過濾

JFileChooser chooser = new JFileChooser(".");
ExtensionFileFilter filter = new ExtensionFileFilter();
filter.addExtension("jpg"); filter.addExtension("png"); filter.addExtension("gif");
filter.setDescription("圖片檔案(*.jpg,*.png,*.gif)");
chooser.addChoosableFileFilter(filter);
chooser.setAcceptAllFileFilterUsed(false);
chooser.setFileView(new FileIconView(filter)); // 自訂檔案圖示
chooser.setAccessory(previewLabel); // 預覽區組件

// 監聽選取檔案變更，即時更新預覽
chooser.addPropertyChangeListener(e -> {
    if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(e.getPropertyName())) {
        File f = (File) e.getNewValue();
        if (f != null) {
            ImageIcon icon = new ImageIcon(f.getPath());
            if (icon.getIconWidth() > PREVIEW_SIZE)
                icon = new ImageIcon(icon.getImage().getScaledInstance(PREVIEW_SIZE, -1, Image.SCALE_DEFAULT));
            previewLabel.setIcon(icon);
        }
    }
});