Java MVC - 如何更改 View - JPanel

Question

我正在创建学习 Java 中的 MVC。我读到，带有少量 JFrame 的 Java 应用程序是个坏主意，更好的解决方案是使用 JPanel。 JDialog也没有解决问题，因为那时我的数量太多了。我的 MainFrame 有几个按钮，我的问题是 - 单击这些按钮之一后如何更改框架上的 JPanel？如果 View 是框架，我知道如何更改 View ...

//ActionListener in the MainController
public void actionPerformed(ActionEvent e) {

                    TheView theView2 = new TheView(); //TheView extends JFrame
                    TheModel theModel2 = new TheModel();        
                    TheController theController = new TheController(theView2,theModel2);
                    theView.setVisible(false);
                    theView2.setVisible(true);
     }

..但我不知道如何仅更改一帧上的面板？我知道，我必须将监听器添加到 View 中的按钮，然后在 Controller 中添加其余代码(如上)，但是我需要什么来更改 Controller 中的 View ？我应该在 MainController 中还是在 MainFrameController 中执行此操作？以下是该应用程序的工作原理:

1. 一开始显示的是带有可见 Panel1 的 MainFrame。
2. 用户点击 Button1。
3. 其他主机正在显示面板 2。

Panel3、4 依此类推...

感谢您的帮助。

编辑:是的，我知道 CardLayout 和 TabbedPane 并且可以使用它们，但我不知道如何在 MVC 中应用此解决方案。 “我只需要回答随着 JPanel 的变化，这段代码具体应该是什么样子。”以及它应该在哪里。在主 Controller 中？在MainFrameController 中？

Answer 1

I just need answer how specifically should look like this piece of code with the change of the JPanel. I wrote that I can use CardLayout WITHOUT MVC, but I have no idea how to do it in MVC... How to apply it to the MainFrame?

您的 Controller 和模型代码不应该关心 View 采用什么形式，无论它是否扩展 JFrame、JPanel，或者(可能最好)两者都不扩展。大概在上面的控件的 actionPerformed 方法中， View 、模型和 Controller 已经创建并适本地“连接”。在此 actionPerformed 方法中，您要做的就是向模型发送命令以更改其状态。换句话说， Controller 将调用模型上的方法来启动状态更改。我通常让 View 通过监听模型的更改来做出响应。

这还没有完全“连接”，但我想示例代码可能类似于下面的代码。请注意，我更喜欢使用匿名内部类监听器，它们是 View 的一部分，并且它们本身调用 Controller 方法:

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.*;
import javax.swing.event.SwingPropertyChangeSupport;

public class SimpleMVC {
    private static void createAndShowGui() {
        SmvcView view = new SmvcView();
        SmvcModel model = new SmvcModel();
        new SmvcController(view, model);

        view.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

@SuppressWarnings("serial")
class SmvcView {
    private JPanel mainPanel = new JPanel();
    private CardLayout cardLayout = new CardLayout();
    private JPanel cardPanel = new JPanel(cardLayout);
    private ModelListener modelListener = new ModelListener();
    private SmvcController controller;
    private DefaultComboBoxModel<SmvcState> comboModel = new DefaultComboBoxModel<>(
            SmvcState.values());
    private JComboBox<SmvcState> stateCombo = new JComboBox<>(comboModel);

    public SmvcView() {
        stateCombo.setRenderer(new DefaultListCellRenderer() {
            @Override
            public Component getListCellRendererComponent(JList<?> list, Object value, int index,
                    boolean isSelected, boolean cellHasFocus) {
                DefaultListCellRenderer renderer = (DefaultListCellRenderer) super
                        .getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
                SmvcState state = (SmvcState) value;
                if (state != null) {
                    value = state.getText();
                    renderer = (DefaultListCellRenderer) super.getListCellRendererComponent(list,
                            value, index, isSelected, cellHasFocus);
                }
                return renderer;
            }
        });
        stateCombo.addActionListener(evt -> {
            SmvcState state = (SmvcState) stateCombo.getSelectedItem();
            controller.setModelState(state);
        });
        JPanel comboPanel = new JPanel();
        comboPanel.add(stateCombo);

        cardPanel.add(new IntroPanel(), SmvcState.INTRO.toString());
        cardPanel.add(new MainPanel(), SmvcState.MAIN.toString());
        cardPanel.add(new MenuPanel(), SmvcState.MENU.toString());

        mainPanel.setLayout(new BorderLayout());
        mainPanel.add(cardPanel, BorderLayout.CENTER);
        mainPanel.add(comboPanel, BorderLayout.PAGE_END);

    }

    public PropertyChangeListener getModelListener() {
        return modelListener;
    }

    public void setController(SmvcController controller) {
        this.controller = controller;
    }

    public void setVisible(boolean b) {
        JFrame frame = new JFrame("Simple MVC");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private class ModelListener implements PropertyChangeListener {
        @Override
        public void propertyChange(PropertyChangeEvent evt) {
            if (SmvcModel.STATE.equals(evt.getPropertyName())) {
                SmvcState state = (SmvcState) evt.getNewValue();

                cardLayout.show(cardPanel, state.toString());
            }
        }
    }

    private class IntroPanel extends JPanel {
        public IntroPanel() {
            setPreferredSize(new Dimension(400, 300));
            setLayout(new GridBagLayout());
            add(new JLabel(SmvcState.INTRO.toString()), SwingConstants.CENTER);
            setBorder(BorderFactory.createTitledBorder(SmvcState.INTRO.toString()));
        }
    }

    private class MainPanel extends JPanel {
        public MainPanel() {
            setPreferredSize(new Dimension(400, 300));
            setLayout(new GridBagLayout());
            add(new JLabel(SmvcState.MAIN.toString()), SwingConstants.CENTER);
            setBorder(BorderFactory.createTitledBorder(SmvcState.MAIN.toString()));
        }
    }

    private class MenuPanel extends JPanel {
        public MenuPanel() {
            setPreferredSize(new Dimension(400, 300));
            setLayout(new GridBagLayout());
            add(new JLabel(SmvcState.MENU.toString()), SwingConstants.CENTER);
            setBorder(BorderFactory.createTitledBorder(SmvcState.MENU.toString()));
        }
    }

}

class SmvcController {

    private SmvcView view;
    private SmvcModel model;

    public SmvcController(SmvcView view, SmvcModel model) {
        this.view = view;
        this.model = model;
        view.setController(this);

        model.addPropertyChangeListener(view.getModelListener());
    }

    public void setModelState(SmvcState state) {
        model.setState(state);
    }

    public SmvcView getView() {
        return view;
    }

    public SmvcModel getModel() {
        return model;
    }

}

class SmvcModel {
    public static final String STATE = "state";
    private SwingPropertyChangeSupport support = new SwingPropertyChangeSupport(this);
    private SmvcState state = SmvcState.INTRO;

    public void addPropertyChangeListener(PropertyChangeListener modelListener) {
        support.addPropertyChangeListener(modelListener);
    }

    public SmvcState getState() {
        return state;
    }

    // notify listeners whenever state is changed
    public void setState(SmvcState state) {
        SmvcState oldValue = this.state;
        SmvcState newValue = state;
        this.state = state;
        support.firePropertyChange(STATE, oldValue, newValue);
    }

}

enum SmvcState {
    INTRO("Intro"), MENU("Menu"), MAIN("Main");
    private String text;

    private SmvcState(String text) {
        this.text = text;
    }

    public String getText() {
        return text;
    }
}