为什么我的JButton中只有1个显示? [英] Why is only 1 of my JButtons showing?

问题描述

我不明白为什么只有登录现有帐户"是唯一显示的按钮.我只需要显示2个按钮，即使我将其可见性设置为true并移动了它，也不会显示创建帐户"，因此它与登录现有帐户"不重叠.

I don't understand why only "Log in to existing account" is the only button to show. All I want is 2 buttons to show and "Create account" isn't showing even though I set its visibility to true and moved it so it isn't overlapping with "Login to existing account".

public class HotelBookingSystem extends JFrame
{
Container con;
public HotelBookingSystem()
{
    super("Booking System");
    JFrame mainWindow = new JFrame("Booking");
    mainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    mainWindow.setSize(350,400);
    mainWindow.setVisible(true);

    con = getContentPane();
    BorderLayout myLayout = new BorderLayout();
    con.setLayout(myLayout);

    JButton login = new JButton ("Login to existing account");
    JButton register = new JButton ("Create Account");
    JPanel loginPanel = new JPanel();
    JPanel registerPanel = new JPanel();

    loginPanel.add(login, BorderLayout.NORTH);
    registerPanel.add(register, BorderLayout.SOUTH);
    login.setSize(350, 100);
    register.setSize(350, 100);

    loginPanel.setVisible(true);
    registerPanel.setVisible(true);

    mainWindow.add(login);
    mainWindow.add(register);
    mainWindow.add(loginPanel);
    mainWindow.add(registerPanel);

    login.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
              mainWindow.setVisible(false);     
            }
        });

    register.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
              mainWindow.setVisible(false);     
            }
        });
}

public static void main(String[] args) 
{
    HotelBookingSystem dataBaseAccess = new HotelBookingSystem();
}

}

推荐答案

许多问题:

mainWindow.setVisible(true);

在将所有组件添加到框架之后，应该使该框架可见，因此这应该是构造函数中的最后一条语句.

The frame should be made visible AFTER all the components are added to the frame, so this should be the last statement in the constructor.

con = getContentPane();
BorderLayout myLayout = new BorderLayout();
con.setLayout(myLayout);

JFrame的内容窗格的默认布局管理器是BorderLayout，因此不需要此代码.

The default layout manager for the content pane of a JFrame is a BorderLayout, so this code is unnecessary.

login.setSize(350, 100);
register.setSize(350, 100);

不要尝试设置组件的大小.布局管理器的工作是设置每个组件的大小和位置.

Don't try to set the size of a component. It is the job of the layout manager to set the size and location of each component.

JPanel loginPanel = new JPanel();
JPanel registerPanel = new JPanel();

loginPanel.add(login, BorderLayout.NORTH);
registerPanel.add(register, BorderLayout.SOUTH);

为什么要创建两个面板?您可以将按钮直接添加到框架中.

Why are you creating two panels? You can just add the buttons directly to the frame.

此外，JPanel的默认布局管理器是FlowLayout.因此，您不能只是一个BorderLayout约束而期望它起作用.

Also, the default layout manager for a JPanel is the FlowLayout. So you can't just a BorderLayout constraint and expect it to work.

loginPanel.setVisible(true);
registerPanel.setVisible(true);

默认情况下，所有Swing组件(JFrame，JDialog等除外)都是可见的，因此不需要上面的代码.

All Swing component (except JFrame, JDialog etc) are visible by default, so the above code is unnecessary.

mainWindow.add(login);
mainWindow.add(register);
mainWindow.add(loginPanel);
mainWindow.add(registerPanel);

如前所述，框架的默认布局是BorderLayout.如果未指定约束，则组件将转到"CENTER".但是一次只能在中心显示一个组件.

As mentioned earlier the default layout for the frame is a BorderLayout. If you don't specify a constraint, then the component goes to the "CENTER". But only a single component can be displayed in the center at one time.

解决所有其他问题，然后尝试类似的操作:

Fix all the other problems and then try something like:

mainWindow.add(login, BorderLayout.NORTH);
mainWindow.add(register, BorderLayout.SOUTH);
mainWindow.add(loginPanel, BorderLayout.WEST);
mainWindow.add(registerPanel, BorderLayout.EAST);

查看区别.根据需要调整约束.

to see the difference. Adjust the constraints as required.

我建议您阅读 Layout Manager上的Swing教程中的这一节. 的工作示例，向您提供使用每个布局管理器的基础知识.

I suggest you read the section from the Swing tutorial on Layout Manager for working examples to give you the basics of using each of the layout managers.

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