javax.swing.JComboBox 无法转换为 javax.swing.JButton

Question

这是我使用的代码：

public void actionPerformed(ActionEvent arg0) {
    JButton buttonPressed = (JButton) arg0.getSource();
    JComboBox selectedOption = (JComboBox) arg0.getSource();

    if (buttonPressed.getText() == "Spam!") {
        if(emailModeBoolean)
            sendSpam(sendBox.getText(), "Not Spam", messageBox.getText());
        else
            sendTextMessage(sendBox.getText(), messageBox.getText());
    }
    if(selectedOption.getSelectedItem().toString() == "Phone Mode") {
        emailModeBoolean = false;
    } else if(selectedOption.getSelectedItem().toString() == "Email Mode"){
        emailModeBoolean = true;
    }
}

当我尝试将 JComboBox 从 "Phone Mode" 更改为 "Email Mode" 时抛出此错误：

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: javax.swing.JComboBox cannot be cast to javax.swing.JButton
at Spammer.actionPerformed(Spammer.java:77)
at javax.swing.JComboBox.fireActionEvent(Unknown Source)
at javax.swing.JComboBox.setSelectedItem(Unknown Source)
at javax.swing.JComboBox.setSelectedIndex(Unknown Source)
at javax.swing.plaf.basic.BasicComboPopup$Handler.mouseReleased(Unknown Source)
at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at javax.swing.plaf.basic.BasicComboPopup.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access0(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.awt.EventQueue.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

提前感谢您的帮助！

Answer 1

您有：

JButton buttonPressed = (JButton) arg0.getSource();
JComboBox selectedOption = (JComboBox) arg0.getSource();

所以在同一个调用中，您试图将接收到的值转换为 JButton 和 JComboBox.

如果您确实将相同的 ActionListener 分配给了两个不同的控件，那么您需要有逻辑来区分它们，方法是在目标上使用 typeof 或 getClass() 之类的东西.

您可能还想完成 How to Write an Action Listener 教程。

Answer 2

你可以...

为按钮和组合框使用单独的 ActionListener...

aButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent evt) {
        // Button specific code
    }
});
aComboBox.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent evt) {
        // Combobox specific code
    }
});

你可以...

使用instanceof确定您正在处理的对象类型...

public void actionPerformed(ActionEvent evt) {
    Object source = evt.getSource();
    if (source instanceof JButton) {
        // Button specific code
    } else if (soruce instanceof JComboBox) {
        // Combobox specific code
    }