从 JPanel 返回信息

Question

我有一个JFrame，其中有一个Panel 用于JButtons 在两个JPanels（RegistrationPanel 和ConfirmationPanel）之间导航。两个JPanels通过CardPanel/CardLayout相互切换。当用户在RegistrationPanel 中输入信息时，有没有办法将此信息返回到下面列出的StartFrame？

import java.awt.BorderLayout;

public class StartFrame extends JFrame implements ActionListener
{
    JButton nextButton = new JButton("Next");
    JButton previousButton = new JButton("Previous");
    JButton registerButton = new JButton("Register");
    JPanel cardPanel = new JPanel();
    CardLayout cardLayout = new CardLayout(10, 10);

    public StartFrame()
    {
        setLayout(new BorderLayout(5, 5));
        nextButton.addActionListener(this);
        previousButton.addActionListener(this);
        previousButton.setVisible(false);
        registerButton.addActionListener(this);
        registerButton.setVisible(false);

        Panel buttonsPanel = new Panel(new FlowLayout(FlowLayout.CENTER));
        buttonsPanel.add(previousButton);
        buttonsPanel.add(nextButton);
        buttonsPanel.add(registerButton);

        setCardLayout();
        add(BorderLayout.SOUTH, buttonsPanel);
        add(BorderLayout.CENTER, cardPanel);
    }

    private void setCardLayout()
    {       
        cardPanel.setLayout(cardLayout);
        cardPanel.add(new RegistrationPanel(), "registration");
        cardPanel.add(new ConfirmationPanel(), "confirmation");
        cardLayout.show(cardPanel, "registration");
    }

    @Override
    public void actionPerformed(ActionEvent event)
    {
        if (event.getSource().equals(nextButton))
        {
            cardLayout.next(cardPanel);
            previousButton.setVisible(true);
            registerButton.setVisible(true);
            nextButton.setVisible(false);
        }

        else
        {
            cardLayout.previous(cardPanel);
            previousButton.setVisible(false);
            registerButton.setVisible(false);
            nextButton.setVisible(true);
        }
    }
}

Answer 1

这取决于谁在传递此信息时具有“积极”作用。 RegistrationPanel 是否应该将信息传递回 StartFrame（例如，当单击 RegsitrationPanel 上的按钮时？）或者 StartFrame 是否应该从 RegistrationPanel 获取信息（例如，当 StartFrame 上的按钮被点击）？

在第一种情况下，RegistrationPanel 需要对 StartFrame 的引用（最好采用更“抽象”的形式，以避免对这个具体类的依赖）。在第二种情况下，StartFrame 需要对 RegistrationPanel 的引用。

在这里粗略地勾勒出这些方法：

对于第一种情况：

class RegistrationPanel 
{
    private StartFrame startFrame;
    public RegistrationPanel(StartFrame startFrame) 
    {
        this.startFrame = startFrame;
    }

    // Called e.g. when a button was clicked on this panel
    void passBackInformationToStartFrame() 
    {
        startFrame.setInfo(this.getInfo());
    }
}


class StartFrame ...
{
    ...
    private void setCardLayout() 
    {       
        cardPanel.setLayout(cardLayout);

        // Remove: 
        //cardPanel.add(new RegistrationPanel(), "registration");

        // Add: 
        cardPanel.add(new RegistrationPanel(this), "registration");

        ....
    }
}

对于第二种情况

public class StartFrame extends JFrame implements ActionListener
{
    ...
    private RegistrationPanel registrationPanel

    private void setCardLayout()
    {       
        cardPanel.setLayout(cardLayout);

        // Remove: 
        //cardPanel.add(new RegistrationPanel(), "registration");

        // Add:
        registrationPanel = new RegistrationPanel();
        cardPanel.add(registrationPanel, "registration");
    }

    // Called e.g. when a button is clicked on this frame:
    void fetchInformationFromRegistrationPanel()
    {
        Info info = registrationPanel.getInfo();
        ...
    }