在两个 JPanel 对象之间发送消息

Question

我有一个包含 JPanel 的 Java JFrame。在该 JPanel 中，有两个独立的 JPanel。当用户单击第一个 JPanel 中的按钮时，需要向另一个 JPanel 发送一条消息，通知它单击了哪个按钮。在这样的对象之间发送消息的最简单方法是什么？

Answer 1

对于 mKorbel（以及原始海报）：
我建议的是松散耦合，即一个 JPanel 不了解另一个 JPanel，并且所有连接都是通过某种控件完成的。例如，借用您的一些代码：

CopyTextNorthPanel2.java

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

public class CopyTextNorthPanel2 extends JPanel {

   private static final long serialVersionUID = 1L;
   public JTextField northField;

   public CopyTextNorthPanel2() {
      northField = new JTextField("Welcome World");
      northField.setFont(new Font("Serif", Font.BOLD, 20));
      northField.setPreferredSize(new Dimension(300, 25));
      add(northField);
   }

   public String getNorthFieldText() {
      return northField.getText();
   }
}

CopyTextSouthPanel2.java

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

public class CopyTextSouthPanel2 extends JPanel {

   private static final long serialVersionUID = 1L;
   private JTextField firstText = new JTextField("Desired TextField");
   private JButton copyButton = new JButton("Copy text from JTextFields");
   private CopyTextControl2 control;

   public CopyTextSouthPanel2() {
      copyButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            if (control != null) {
               control.copyAction();
            }
         }
      });

      add(firstText);
      add(copyButton);
   }

   public void setControl(CopyTextControl2 control) {
      this.control = control;
   }

   public void setFirstText(String text) {
      firstText.setText(text);
   }
}

CopyTextControl2.java

public class CopyTextControl2 {
   private CopyTextNorthPanel2 northPanel;
   private CopyTextSouthPanel2 southPanel;

   public void copyAction() {
      if (northPanel != null && southPanel != null) {
         southPanel.setFirstText(northPanel.getNorthFieldText());
      }
   }

   public void setNorthPanel(CopyTextNorthPanel2 northPanel) {
      this.northPanel = northPanel;
   }

   public void setSouthPanel(CopyTextSouthPanel2 southPanel) {
      this.southPanel = southPanel;
   }

}

CopyText2.java

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

public class CopyText2 {

   private static void createAndShowUI() {
      CopyTextNorthPanel2 northPanel = new CopyTextNorthPanel2();
      CopyTextSouthPanel2 southPanel = new CopyTextSouthPanel2();
      CopyTextControl2 control = new CopyTextControl2();

      southPanel.setControl(control);
      control.setNorthPanel(northPanel);
      control.setSouthPanel(southPanel);

      JPanel mainPanel = new JPanel(new BorderLayout());
      mainPanel.add(northPanel, BorderLayout.NORTH);
      mainPanel.add(Box.createRigidArea(new Dimension(100, 100)), BorderLayout.CENTER);
      mainPanel.add(southPanel, BorderLayout.SOUTH);

      JFrame frame = new JFrame("Copy Text");
      frame.getContentPane().add(mainPanel);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

Answer 2

您可以创建一个自定义事件，并将一个或多个侦听器附加到该事件。

正确的实现方法是让 Button ActionListener 触发事件，然后让两个面板成为该事件的侦听器。

Answer 3

但实际上

public MyClass implements ActionListener {

...
myButton.addActionListener(this);
...

public void actionPerformed(ActionEvent e) {
      //for example if you have more than one events that you need to handle
      if(e.getSource().equals(myButton) {
           //update your do some work on you jpanels
      }
}

，我认为是时候开始考虑设计模式了。您所描述的内容是 观察者模式和可能的命令模式

Answer 4

例如，通过在类之间使用构造函数或（用于调试问题）使用 getParent() 从所需的 JComponent 中提取值

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

public class CopyTextFrame extends JFrame {

    private static final long serialVersionUID = 1L;
    private CopyTextNorthPanel northPanel;
    private CopyTextCenterPanel centerPanel;
    private CopyTextSouthPanel southPanel;

    public void makeUI() {
        northPanel = new CopyTextNorthPanel();
        centerPanel = new CopyTextCenterPanel();
        southPanel = new CopyTextSouthPanel();
        northPanel.setName("northPanel");
        centerPanel.setName("centerPanel");
        southPanel.setName("southPanel");
        centerPanel = new CopyTextCenterPanel();
        centerPanel.setPreferredSize(new Dimension(300, 40));
        southPanel = new CopyTextSouthPanel();
        southPanel.setSourceTextField(northPanel.desText);
        northPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK, 1));
        centerPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK, 1));
        southPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK, 1));
        setLayout(new BorderLayout(5, 5));
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        add(northPanel, BorderLayout.NORTH);
        add(centerPanel, BorderLayout.CENTER);
        add(southPanel, BorderLayout.SOUTH);
        pack();
        setVisible(true);
    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new CopyTextFrame().makeUI();
            }
        });
    }
}  

+

import javax.swing.*;

public class CopyTextCenterPanel extends JPanel {

    private static final long serialVersionUID = 1L;

    public CopyTextCenterPanel() {
    }
}

+

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

public class CopyTextNorthPanel extends JPanel {

    private static final long serialVersionUID = 1L;
    public JTextField desText;

    public CopyTextNorthPanel() {
        desText = new JTextField("Welcome World");
        desText.setFont(new Font("Serif", Font.BOLD, 20));
        desText.setPreferredSize(new Dimension(300, 25));
        desText.setBorder(BorderFactory.createLineBorder(Color.BLACK, 1));
        desText.addComponentListener(null);
        desText.setName("desText");
        add(desText);
    }

    public JTextField getDesText() {
        return desText;
    }
}

+

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

public class CopyTextSouthPanel extends JPanel {

    private static final long serialVersionUID = 1L;
    private JTextField firstText;
    private JButton copyButton;
    private JTextField sourceTextField;
    private String lds = "";

    public CopyTextSouthPanel() {
        firstText = new JTextField("Desired TextField");
        firstText.setMinimumSize(new Dimension(300, 25));
        firstText.setPreferredSize(new Dimension(300, 25));
        firstText.setMaximumSize(new Dimension(300, 25));

        copyButton = new JButton("Copy text from JTextFields");
        copyButton.setMinimumSize(new Dimension(200, 25));
        copyButton.setPreferredSize(new Dimension(200, 25));
        copyButton.setMaximumSize(new Dimension(200, 25));
        copyButton.addActionListener(new java.awt.event.ActionListener() {

            @Override
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                copyButtonActionPerformed(evt);
            }

            private void copyButtonActionPerformed(ActionEvent evt) {
                System.out.print("Button pressed" + "\n");
                Component[] comp = CopyTextSouthPanel.this.getParent().getComponents();
                int nO = comp.length;
                for (int i = 0; i < comp.length; ++i) {
                    if (comp[i] instanceof JPanel) {
                        String name = ((JPanel) comp[i]).getName();
                        if (name.equals("northPanel")) {
                            JPanel panel = (JPanel) comp[i];
                            Component[] comp1 = panel.getComponents();
                            int nO1 = comp1.length;
                            for (int ii = 0; ii < comp1.length; ++ii) {
                                if (comp1[ii] instanceof JTextField) {
                                    String name1 = ((JTextField) comp1[ii]).getName();
                                    if (!(name1 == null)) {
                                        if (name1.equals("desText")) {
                                            JTextField text = (JTextField) comp1[ii];
                                            String str = text.getText();
                                            firstText.setText(str);
                                            System.out.print("set value -> " + str + "\n");
                                            break;
                                        }
                                    }
                                }
                            }
                            break;
                        }
                    }
                }
                lds = sourceTextField.getText();
                if (lds != null || (!(lds.isEmpty()))) {
                    firstText.setText(" Msg -> " + lds);
                }
            }
        });
        add(firstText, BorderLayout.EAST);
        add(copyButton, BorderLayout.WEST);
    }

    public void setSourceTextField(JTextField source) {
        this.sourceTextField = source;
    }
}