如何使用多个班级的秋千

Question

我只想知道关于挥杆的一些事情1)如何在挥杆中使用MVC模型？2)说我有一个主窗口,我需要将菜单作为单独的类,所有组件作为单独的类和.which将是集成它的最佳方法

Answer 1

好吧,这被称为回答过度杀戮,所以很抱歉,但这是一个快速的例子,我试图使用一个简单的MVC模式来做一件小事:按一个按钮并更改JTextField中的文本.它太过分了,因为你可以在几行代码中做同样的事情,但它确实在单独的文件中说明了一些MVC以及模型如何控制State.如果有什么令人困惑的话请提问!

将所有内容放在一起并开始工作的主要类:

import javax.swing.*;

public class SwingMvcTest {
   private static void createAndShowUI() {

      // create the model/view/control and connect them together
      MvcModel model = new MvcModel();
      MvcView view = new MvcView(model);
      MvcControl control = new MvcControl(model);
      view.setGuiControl(control);

      // EDIT: added menu capability
      McvMenu menu = new McvMenu(control);

      // create the GUI to display the view
      JFrame frame = new JFrame("MVC");
      frame.getContentPane().add(view.getMainPanel()); // add view here
      frame.setJMenuBar(menu.getMenuBar()); // edit: added menu capability
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   // call Swing code in a thread-safe manner per the tutorials
   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

视图类:

import java.awt.*;
import java.awt.event.*;
import java.beans.*;
import javax.swing.*;

public class MvcView {
   private MvcControl control;
   private JTextField stateField = new JTextField(10);
   private JPanel mainPanel = new JPanel(); // holds the main GUI and its components

   public MvcView(MvcModel model) {
      // add a property change listener to the model to listen and 
      // respond to changes in the model's state
      model.addPropertyChangeListener(new PropertyChangeListener() {
         public void propertyChange(PropertyChangeEvent evt) {
            // if the state change is the one we're interested in...
            if (evt.getPropertyName().equals(MvcModel.STATE_PROP_NAME)) {
               stateField.setText(evt.getNewValue().toString()); // show it in the GUI
            }
         }
      });
      JButton startButton = new JButton("Start");
      startButton.addActionListener(new ActionListener() {
         // all the buttons do is call methods of the control
         public void actionPerformed(ActionEvent e) {
            if (control != null) {
               control.startButtonActionPerformed(e); // e.g., here
            }
         }
      });
      JButton endButton = new JButton("End");
      endButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            if (control != null) {
               control.endButtonActionPerformed(e); // e.g., and here
            }
         }
      });

      // make our GUI pretty
      int gap = 10;
      JPanel buttonPanel = new JPanel(new GridLayout(1, 0, gap, 0));
      buttonPanel.add(startButton);
      buttonPanel.add(endButton);

      JPanel statePanel = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 0));
      statePanel.add(new JLabel("State:"));
      statePanel.add(Box.createHorizontalStrut(gap));
      statePanel.add(stateField);

      mainPanel.setBorder(BorderFactory.createEmptyBorder(gap, gap, gap, gap));
      mainPanel.setLayout(new BorderLayout(gap, gap));
      mainPanel.add(buttonPanel, BorderLayout.CENTER);
      mainPanel.add(statePanel, BorderLayout.PAGE_END);
   }

   // set the control for this view
   public void setGuiControl(MvcControl control) {
      this.control = control;
   }

   // get the main gui and its components for display
   public JComponent getMainPanel() {
      return mainPanel;
   }

}

控制:

import java.awt.event.ActionEvent;

public class MvcControl {
   private MvcModel model;

   public MvcControl(MvcModel model) {
      this.model = model;
   }

   // all this simplistic control does is change the state of the model, that's it
   public void startButtonActionPerformed(ActionEvent ae) {
      model.setState(State.START);
   }

   public void endButtonActionPerformed(ActionEvent ae) {
      model.setState(State.END);
   }
}

该模型使用PropertyChangeSupport对象来允许其他对象(在这种情况下为View)监听状态的变化.因此,该模型实际上是我们的"可观察",而视图是"观察者"

import java.beans.*;

public class MvcModel {
   public static final String STATE_PROP_NAME = "State";
   private PropertyChangeSupport pcSupport = new PropertyChangeSupport(this);
   private State state = State.NO_STATE;

   public void setState(State state) {
      State oldState = this.state;
      this.state = state;
      // notify all listeners that the state property has changed
      pcSupport.firePropertyChange(STATE_PROP_NAME, oldState, state);
   }

   public State getState() {
      return state;
   }

   public String getStateText() {
      return state.getText();
   }

   // allow addition of listeners or observers
   public void addPropertyChangeListener(PropertyChangeListener listener) {
      pcSupport.addPropertyChangeListener(listener);
   }

}

一个简单的枚举,State,用于封装状态的概念:

public enum State {
   NO_STATE("No State"), START("Start"), END("End");
   private String text;

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

   @Override
   public String toString() {
      return text;
   }

   public String getText() {
      return text;
   }
}

编辑:我也看到你提到了菜单,所以我添加了这个类,并在SwingMcvTest类中添加了几行,增加了菜单支持.请注意,由于代码分离,对GUI进行此更改是微不足道的,因为所有菜单需要做的是调用控制方法.它不需要知道模型或视图:

import java.awt.event.ActionEvent;
import javax.swing.*;

public class McvMenu {
   private JMenuBar menuBar = new JMenuBar();
   private MvcControl control;

   @SuppressWarnings("serial")
   public McvMenu(MvcControl cntrl) {
      this.control = cntrl;

      JMenu menu = new JMenu("Change State");
      menu.add(new JMenuItem(new AbstractAction("Start") {
         public void actionPerformed(ActionEvent ae) {
            if (control != null) {
               control.startButtonActionPerformed(ae);
            }
         }
      }));
      menu.add(new JMenuItem(new AbstractAction("End") {
         public void actionPerformed(ActionEvent ae) {
            if (control != null) {
               control.endButtonActionPerformed(ae);
            }
         }
      }));

      menuBar.add(menu);
   }

   public JMenuBar getMenuBar() {
      return menuBar;
   }
}

上帝,这是一个很简单的代码!我提名自己和我的代码为本周的Stackoverflow Rube Goldberg奖.

Answer 2

Swing 具有简化 MVC 实现的内置机制。它有行动框架。负责构建视图的类应该关心 JComponent 子类的实例化并将它们放置到面板上。每个对用户活动做出反应的组件都应该有相应的 Action ( b.setAction(myAction))。我通常创建包com.myapp.actions并将所有操作放在那里。有时我也会创建抽象动作，但它是特定于应用程序的。操作允许您将逻辑与表示层分开。将行动视为“模型”的入口点。

典型的应用程序具有比操作更多的控件。某些控件重复使用相同的操作。例如，您可以通过键入 Ctrl-S、单击菜单项或工具栏按钮、使用上下文菜单等来保存文件。但所有这些控件都将调用相同的操作SaveFileAction。

关于你的第二个问题，有两种不同的方法。首先是基于继承。有人在需要框架时扩展 JFrame 并将所有布局实现到这个特殊的类中。

其他方法是创建一组生成布局的实用方法。我个人比较喜欢这个。我认为如果您确实需要某个东西的子类，例如当您希望重写超类方法之一时（例如paint()） ，则应该使用继承

我希望我的描述有所帮助。祝你好运。