javax.swing.JPanel 无法转换为 javax.swing.JLayeredPane

Question

我遇到了一个小问题，我的代码中有一个异常。

我有一个基本框架类:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class BaseFrame extends JFrame {

    private BaseListener listener = new BaseListener();

    public static final String BTN_END = "Ende";
    public static final String BTN_OK = "Ok";

    private JButton bu_end      = null;
    private JButton bu_ok       = null;

    public BaseFrame() {
        super();
        initialize();
    }

    private void initialize() {

       JPanel pa_01 = new JPanel();
       JPanel pa_02 = new JPanel();
       JPanel pa_03 = new JPanel();

       this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

       this.setLayout(new BorderLayout(0, 0));
       this.setPreferredSize(new Dimension(800, 600));
       this.setMinimumSize(new Dimension(800, 600));

       this.add(pa_01, BorderLayout.NORTH);
       this.add(pa_02, BorderLayout.CENTER);
       this.add(pa_03, BorderLayout.SOUTH);

       pa_01.setLayout(new FlowLayout(FlowLayout.CENTER,10,5));
       pa_01.add(new JLabel("Rennwagenverwaltung"));
       pa_01.setPreferredSize(new Dimension(800, 60));

       pa_02.setLayout(new GridLayout(8, 2));

       pa_02.add(new JLabel("Rennwagenid"));
       pa_02.add(new JTextField());
       pa_02.add(new JLabel("Modell"));
       pa_02.add(new JTextField());
       pa_02.add(new JLabel("Hersteller"));
       pa_02.add(new JTextField());
       pa_02.add(new JLabel("Leistung"));
       pa_02.add(new JTextField());
       pa_02.add(new JLabel("Hubraum"));
       pa_02.add(new JTextField());
       pa_02.add(new JLabel("maximaler Tankinhalt"));
       pa_02.add(new JTextField());
       pa_02.add(new JLabel("aktueller Tankinhalt"));
       pa_02.add(new JTextField());

       bu_end = new JButton(BaseFrame.BTN_END);
       bu_end.addActionListener(listener);
       bu_ok = new JButton(BaseFrame.BTN_OK);
       bu_ok.addActionListener(listener);

       pa_02.add(bu_end);
       pa_02.add(bu_ok);

       pa_02.setPreferredSize(new Dimension(800, 350));

       pa_03.setBackground(Color.WHITE);
       pa_03.setPreferredSize(new Dimension(800, 200));


       this.setTitle("Rennwagen");
       this.setVisible(true);
       this.pack();
       this.setLocationRelativeTo(null);
    }
}

我的听众类:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.JRootPane;

public class BaseListener
implements ActionListener
{
    public void actionPerformed(ActionEvent e) 
    {
        Object  object  = e.getSource();
        JButton bu_work = null;
        JFrame  frame   = null; 
        String  text    = null;

        if (object instanceof JButton)
        {
           bu_work = (JButton) object;
           text = bu_work.getText();
           frame = this.getMyJFrame(bu_work);

           if(text == BaseFrame.BTN_OK) {
               Rennwagen rw = null;

           } else if(text == BaseFrame.BTN_END) {
               frame.dispatchEvent(new WindowEvent(frame, WindowEvent.WINDOW_CLOSING));
           }
        }
    }

    /**
     * @param button
     * @return
     */
    private BaseFrame getMyJFrame(JButton button)
    {
        JPanel       contenpane  = null;
        JLayeredPane layeredpane = null;
        JRootPane    rootpane    = null;
        BaseFrame    myframe     = null; 

        contenpane  = (JPanel)       button.getParent();
        layeredpane = (JLayeredPane) contenpane.getParent();
        rootpane    = (JRootPane)    layeredpane.getParent();
        myframe     = (BaseFrame)    rootpane.getParent();

        return myframe;
    }
}

我现在在这一行有这样的期望:

layeredpane = (JLayeredPane) contenpane.getParent();

这就是整个错误日志:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: javax.swing.JPanel cannot be cast to javax.swing.JLayeredPane
    at Rennwagen.BaseListener.getMyJFrame(BaseListener.java:50)
    at Rennwagen.BaseListener.actionPerformed(BaseListener.java:27)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.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.access$400(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.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)

为什么这是不可能的，我在这里做错了什么？

Answer 1

如果您想获取JFrame，请调用getTopLevelAncestor .