如何构建一个java主菜单
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How to build a java Main Menu
提问by Mechanic45
Obviously I am trying to make a main menu using the swing components. I understand that in order to make my menu happen, I have to utilize CardLayout, which I do in the code below:
显然，我正在尝试使用摆动组件制作主菜单。我知道为了让我的菜单出现，我必须使用CardLayout，我在下面的代码中这样做：
(Everything is imported of course)
（当然一切都是进口的）
public class Screen extends JFrame implements ActionListener {
private static final long serialVersionUID = 1L;
int width, height;
JButton play = new JButton("play");
JButton settings = new JButton("settings");
JButton exit = new JButton("exit");
JButton mainMenu = new JButton("main menu");
CardLayout layout = new CardLayout();
JPanel panel = new JPanel();
JPanel game = new JPanel();
JPanel menu = new JPanel();
public Screen(int width, int height) {
this.width = width;
this.height = height;
panel.setLayout(layout);
addButtons();
setSize(width, height);
setResizable(false);
setLocationRelativeTo(null);
setVisible(true);
setTitle("BUILD YOUR EMPIRE");
setDefaultCloseOperation(EXIT_ON_CLOSE);
requestFocus();
}
private void addButtons() {
play.addActionListener(this);
settings.addActionListener(this);
exit.addActionListener(this);
mainMenu.addActionListener(this);
//menu buttons
menu.add(play);
menu.add(settings);
menu.add(exit);
//game buttons
game.add(mainMenu);
//background colors
game.setBackground(Color.MAGENTA);
menu.setBackground(Color.GREEN);
//adding children to parent Panel
panel.add(menu,"Menu");
panel.add(game,"Game");
add(panel);
layout.show(panel,"Menu");
}
public void actionPerformed(ActionEvent event) {
Object source = event.getSource();
if (source == exit) {
System.exit(0);
} else if (source == play) {
layout.show(panel, "Game");
} else if (source == settings){
} else if (source == mainMenu){
layout.show(panel, "Menu");
}
}
}
But when I run it, only the exit button works. When I hit the settings button nothing happens (as expected) but when I hit play button it crashes and gives me this error:
但是当我运行它时，只有退出按钮有效。当我点击设置按钮时没有任何反应（如预期的那样）但是当我点击播放按钮时它崩溃并给我这个错误：
Exception in thread "main" java.lang.IllegalArgumentException: wrong parent for CardLayout
at java.awt.CardLayout.checkLayout(Unknown Source)
at java.awt.CardLayout.show(Unknown Source)
at Screen.Buttons(Screen.java:69)
at Screen.<init>(Screen.java:31)
at Window.main(Window.java:29)
I dont understand what I am doing wrong. Any help on this will be greately appreciated thanks in advance.
我不明白我做错了什么。对此的任何帮助将不胜感激，提前致谢。
采纳答案by DSquare
Found it!
找到了！
It was a matter of wrong order:
这是一个错误的顺序问题：
Buttons();
panel.setLayout(layout);
layout.addLayoutComponent(panel, "Menu");
is wrong because you obviously need to set up the CardLayout in the panelbefore doing anything (like show) with it. So:
是错误的，因为您显然需要在对 CardLayoutpanel进行任何操作（例如show）之前对其进行设置。所以：
panel.setLayout(layout);
layout.addLayoutComponent(panel, "Menu");
Buttons();
Although I don't know why do you need the line:
虽然我不知道你为什么需要这条线：
layout.addLayoutComponent(panel, "Menu");
looking at the tutorialit does not mention the necessity to use it.
查看教程它没有提到使用它的必要性。
Also method names should start in lower case, I was confused for a moment thinking that Buttonswas a class. And you should use more descriptive names:
方法名称也应该以小写开头，我一度认为这Buttons是一个类，我感到很困惑。您应该使用更具描述性的名称：
addButtons()instead of Buttons()
addButtons()代替 Buttons()
gamePanelinstead of game
gamePanel代替 game
and so on.
等等。
Good job providing (not very extensive) relevant code, next time you should try adding a mainalso so we can just execute and test it :)
很好地提供（不是很广泛）相关代码，下次您应该尝试添加一个，main这样我们就可以执行和测试它:)
回答by MadProgrammer
Try swapping these lines...
尝试交换这些行...
panel.setLayout(layout);
addButtons();
Basically, when you try and showthe first screen, the CardLayoutis not associated with your panel, which is, obviously, a invalid parent
基本上，当您尝试show第一个屏幕时，CardLayout与您的 无关panel，这显然是无效的父级
