java关闭和重新显示帧的频率随着每次按下按钮的频率的增加而增加

Question

我正在使用自制的工具栏浏览我的应用程序，该工具栏显示在所有页面上。每次显示新页面时，我都会使用以下代码关闭当前帧并打开新帧：

java.awt.Window win[] = java.awt.Window.getWindows(); 
for(int i=0;i<win.length;i++){ 
win[i].dispose(); 
}

我这样做是因为ActionListeners是在toolbar类中声明的，而每个页面的框架是在运行时声明的，不是静态的

除了一个特殊情况“取消”按钮外，这一切都可以正常工作，第一次访问帧时，它将关闭一次。第二次将关闭并重新打开2次，第三次将关闭并重新打开3次，依此类推。我使用代码中的“计数器”跟踪了这一点

我已将代码最小化，以重新创建相同的行为，如下所示：

工具栏类

 public class Toolbar {

    static JButton buttonCancel = new JButton("Cancel");
    static int counter;

    public static JPanel Toolbar(String panelname){

        FlowLayout layout = new FlowLayout();

        JPanel Toolbar = new JPanel(new BorderLayout());
        Toolbar.setLayout(layout);

        GridLayout GLayout = new GridLayout(2,1);
        GLayout.setVgap(0);

        JPanel container2 = new JPanel();

        if(panelname.matches("Customers")){

        container2.setLayout(GLayout);
        JButton buttonAddCust = new JButton("Add Cust");
        container2.add(buttonAddCust, BorderLayout.PAGE_START);

        buttonAddCust.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {

                java.awt.Window win[] = java.awt.Window.getWindows(); 
                for(int i=0;i<win.length;i++){ 
                win[i].dispose(); 
                }

             Customers.AddCustomersGui();           
            }
        });
        }


        JPanel container21 = new JPanel();
        if(panelname.matches("Add Customers")){ 
            container21.setLayout(GLayout);
            container21.add(buttonCancel, BorderLayout.PAGE_START);

            buttonCancel.addActionListener(new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {

                    counter ++;                 
                    java.awt.Window win[] = java.awt.Window.getWindows(); 
                    for(int i=0;i<win.length;i++){ 
                    win[i].dispose(); 
                    }                       
                    System.out.println("Coutner " + counter);                   
                    Customers.CustomersGui();   

                }
                });
        }

        Toolbar.add(container2);      
        Toolbar.add(container21);

        return Toolbar;

    }



}

GUI类

public class Customers extends Toolbar{

    public static void CustomersGui(){

        final JFrame frame = new JFrame("Customers");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel customers = new JPanel();

        customers.add(Toolbar.Toolbar(frame.getTitle()));

        frame.setContentPane(customers);

        frame.setSize(1200,500);

        frame.setVisible(true);

    }

    public static void AddCustomersGui(){

        final JFrame frame1 = new JFrame("Add Customers");
        frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel Addcustomers = new JPanel();

        Addcustomers.add(Toolbar.Toolbar(frame1.getTitle()));

        frame1.setContentPane(Addcustomers);

        frame1.setSize(1200,500);

        frame1.setVisible(true);
    }
    }

主类

public static void main(String[] args) {

    Customers.CustomersGui();

}

Answer 1

随着代码的每次迭代，您将向buttonCancel添加一个新的ActionListener，这就是程序行为的原因

---

另外，根据我的评论，你说

Each time a new page is displayed I am closing the current frame and opening a new one.

更好的设计可能不是交换可能令人讨厌的窗口，而是使用CardLayout交换JPanel视图。请阅读The Use of Multiple JFrames, Good/Bad Practice?

---

例如，将这行代码添加到程序中：

  if (panelname.matches("Add Customers")) {
     container21.setLayout(GLayout);
     container21.add(buttonCancel, BorderLayout.PAGE_START);
     buttonCancel.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
           counter++;
           java.awt.Window win[] = java.awt.Window.getWindows();
           for (int i = 0; i < win.length; i++) {
              win[i].dispose();
           }
           System.out.println("Coutner " + counter);
           Customers.CustomersGui();
        }
     });

     // ***** add this here **********
     System.out.println("buttonCancel ActionListener count: "
           + buttonCancel.getListeners(ActionListener.class).length);
  }

您将看到ActionListeners被多次添加到此按钮

---

交换视图的一个示例：

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

@SuppressWarnings("serial")
public class SwapPanels extends JPanel {
   public static final String CUSTOMER = "customer";
   public static final String ADD_CUSTOMER = "Add Customer";
   protected static final int PREF_W = 800;
   protected static final int PREF_H = 600;
   public static final String CANCEL = "Cancel";
   private CardLayout cardLayout = new CardLayout();

   public SwapPanels() {
      setLayout(cardLayout);

      add(createCustomerPanel(CUSTOMER), CUSTOMER);
      add(createAddCustomerPanel(ADD_CUSTOMER), ADD_CUSTOMER);
   }

   public void showCard(String key) {
      cardLayout.show(this, key);
   }

   public JPanel createAddCustomerPanel(String name) {
      JPanel addCustPanel = new JPanel() {
         @Override
         public Dimension getPreferredSize() {
            if (isPreferredSizeSet()) {
               return super.getPreferredSize();
            }
            return new Dimension(PREF_W, PREF_H);
         }
      };
      addCustPanel.setName(name);
      addCustPanel.setBorder(BorderFactory.createTitledBorder(name));
      addCustPanel.add(new JButton(new AbstractAction(CANCEL) {
         {
            int mnemonic = (int)getValue(NAME).toString().charAt(0);
            putValue(MNEMONIC_KEY, mnemonic);
         }

         @Override
         public void actionPerformed(ActionEvent e) {
            if (CANCEL.equals(e.getActionCommand())) {
               SwapPanels.this.showCard(CUSTOMER);
            }
         }
      }));
      return addCustPanel;
   }

   private JPanel createCustomerPanel(String name) {
      JPanel custPanel = new JPanel() {
         @Override
         public Dimension getPreferredSize() {
            if (isPreferredSizeSet()) {
               return super.getPreferredSize();
            }
            return new Dimension(PREF_W, PREF_H);
         }
      };
      custPanel.setName(name);
      custPanel.setBorder(BorderFactory.createTitledBorder(name));
      custPanel.add(new JButton(new AbstractAction(ADD_CUSTOMER) {
         {
            int mnemonic = (int)getValue(NAME).toString().charAt(0);
            putValue(MNEMONIC_KEY, mnemonic);
         }

         @Override
         public void actionPerformed(ActionEvent e) {
            if (ADD_CUSTOMER.equals(e.getActionCommand())) {
               SwapPanels.this.showCard(ADD_CUSTOMER);
            }
         }
      }));
      return custPanel;
   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("SwapPanels");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new SwapPanels());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}