Java AWT 選單實作完全指南：選單列、子選單、核取選單項、動態切換與事件處理

選單架構限制

• 僅限 Frame 應用程式，Applet 無法直接擁有選單列 (無 setMenuBar())
• 解決方案：Applet 建立 Frame 並在其中放置選單
• 四種選單元件：MenuBar、Menu、MenuItem、CheckboxMenuItem

完整範例：Menu1 — 多層選單、核取項、動態切換選單列

//: Menu1.java
import java.awt.*;

public class Menu1 extends Frame {
    String[] flavors = {"Chocolate","Strawberry","Vanilla Fudge Swirl","Mint Chip",
                        "Mocha Almond Fudge","Rum Raisin","Praline Cream","Mud Pie"};
    TextField t = new TextField("No flavor", 30);

    MenuBar mb1 = new MenuBar(), mb2 = new MenuBar();
    Menu f = new Menu("File"), m = new Menu("Flavors"), s = new Menu("Safety");
    CheckboxMenuItem[] safety = {new CheckboxMenuItem("Guard"), new CheckboxMenuItem("Hide")};
    MenuItem[] file = {new MenuItem("Open"), new MenuItem("Exit")};
    Menu fooBar = new Menu("fooBar");
    MenuItem[] other = {new MenuItem("Foo"), new MenuItem("Bar"), new MenuItem("Baz")};
    Button b = new Button("Swap Menus");

    public Menu1() {
        // Flavors 選單動態建構
        for (int i=0; i