写入值并单击按钮打开浏览器

Question

我尝试从JComboBox 中选择一个案例，然后写入一个值并打开该网站“案例+值”。但是当我点击按钮时得到这个错误信息：

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.awt.Button cannot be cast to javax.swing.JComboBox
    at Deneme1.actionPerformed(Deneme1.java:52)
    at java.awt.Button.processActionEvent(Button.java:409)
    at java.awt.Button.processEvent(Button.java:377)
    at java.awt.Component.dispatchEventImpl(Component.java:4889)
    at java.awt.Component.dispatchEvent(Component.java:4711)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

有我的源代码：

import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import java.net.URI;
import javax.swing.*;
import java.net.URISyntaxException;

public class Deneme1 extends Frame implements WindowListener, ActionListener {

    JTextField Value = new JTextField(20);
    Button Try;

    public static void main(String[] args) {
        Deneme1 Windows = new Deneme1("Deneme1 ");
        Windows.setSize(400, 200);
        Windows.setLocation(430, 100);
        Windows.setVisible(true);
        Windows.setTitle("Title");
    }

    public Deneme1(String title) {

        JLabel Text2 = new JLabel("Pick one: ");
        add(Text2);
        JComboBox Select = new JComboBox();
        Select.addItem("A");
        Select.addItem("B");
        add(Select);
        JLabel Text1 = new JLabel("Enter Value:");
        setLayout(new FlowLayout());
        addWindowListener(this);
        Try = new Button("Try");
        add(Text1);
        add(Value);
        add(Try);
        Try.addActionListener(this);
    }

    public void actionPerformed(ActionEvent E) {

        JComboBox<String> Select = (JComboBox<String>) E.getSource();
        String Selected = (String) Select.getSelectedItem();
        switch (Selected) {
            case "A":
                try {
                    URI AcilacakSite = new URI("https://A" + Value.getText());
                    Desktop.getDesktop().browse(AcilacakSite);
                } catch (URISyntaxException | IOException ex) {
                    JOptionPane.showMessageDialog(null, "ERR");
                }
                break;
            case "B":
                try {
                    URI AcilacakSite = new URI("https://B" + Value.getText());
                    Desktop.getDesktop().browse(AcilacakSite);
                } catch (URISyntaxException | IOException ex) {
                    JOptionPane.showMessageDialog(null, "ERR");
                }
                break;
            default:
                JOptionPane.showMessageDialog(null, "ERR");
                break;
        }
    }

    @Override
    public void windowOpened(WindowEvent e) {
    //throw new UnsupportedOperationException("Not supported yet."); //To     change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void windowClosing(WindowEvent e) {
        dispose();
        System.exit(0);

    }

    @Override
    public void windowClosed(WindowEvent e) {
    //throw new UnsupportedOperationException("Not supported yet."); //To     change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void windowIconified(WindowEvent e) {
    //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void windowDeiconified(WindowEvent e) {
    //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void windowActivated(WindowEvent e) {
    //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void windowDeactivated(WindowEvent e) {
    //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

Answer 1

此代码通过将组合框声明为类属性并直接在执行的操作方法中访问它来修复ClassCastException。

import java.awt.*;
import java.awt.event.*;
import java.net.*;
import javax.swing.*;
import java.io.IOException;

public class Deneme1 extends JFrame implements ActionListener {

    JTextField value = new JTextField(20);
    JButton tryFetch;
    // declared as a class attribute, this can be accessed 
    // in the action performed method
    JComboBox select; 

    public static void main(String[] args) {
        Deneme1 windows = new Deneme1("Deneme1 ");
        windows.setSize(400, 200);
        windows.setLocation(430, 100);
        windows.setVisible(true);
        windows.setTitle("Title");
    }

    public Deneme1(String title) {
        JLabel text2 = new JLabel("Pick one: ");
        add(text2);
        select = new JComboBox();
        select.addItem("A");
        select.addItem("B");
        add(select);
        JLabel text1 = new JLabel("Enter value:");
        setLayout(new FlowLayout());
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        tryFetch = new JButton("Try");
        add(text1);
        add(value);
        add(tryFetch);
        tryFetch.addActionListener(this);
    }

    public void actionPerformed(ActionEvent E) {
        String selected = (String) select.getSelectedItem();
        switch (selected) {
            case "A":
                try {
                    URI AcilacakSite = new URI("https://A" + value.getText());
                    Desktop.getDesktop().browse(AcilacakSite);
                } catch (URISyntaxException | IOException ex) {
                    JOptionPane.showMessageDialog(null, "ERR");
                }
                break;
            case "B":
                try {
                    URI AcilacakSite = new URI("https://B" + value.getText());
                    Desktop.getDesktop().browse(AcilacakSite);
                } catch (URISyntaxException | IOException ex) {
                    JOptionPane.showMessageDialog(null, "ERR");
                }
                break;
            default:
                JOptionPane.showMessageDialog(null, "ERR");
                break;
        }
    }
}

注意：我修复了 cmets 中提到的大部分问题。这段代码还是有问题。