Jlist和DefaultListModel的问题

Question

我有很多麻烦让这个Jlist工作。当我试图构造JList时，问题就出现了。当我编译时，我得到一条消息说:

"error: constructor JList in class JList cannot be applied to given types; list = new JList(model);
required: no arguments
found: DefaultListModel
reason: actual and formal argument lists differ in length"

此外，我有麻烦添加元素到DefaultListModel。如果您取消注释我试图向模型添加字符串的代码，我得到一条消息说:

JList.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

下面我复制了我的整个程序，所以如果你愿意，你可以复制这个并自己编译。谢谢你！

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.lang.*;
import java.awt.event.*;
import javax.swing.filechooser.*;
import java.io.*;
public class JList
{
  public static void main (String args[])
  {
    new MyFrameClass();
  }
}
class MyFrameClass extends JFrame implements ActionListener
{
JMenuBar menuBar;
JMenu fileMenu, itemMenu;
JMenuItem loadMenuItem, saveMenuItem, saveAsMenuItem, newMenuItem, deleteMenuItem, deleteAllMenuItem;
JPanel menuBarPanel;
JFileChooser fc;
File file;
JList list;
DefaultListModel model;
MyFrameClass()
{
    Container cp;
    fc = new JFileChooser();
    menuBar = new JMenuBar();
    menuBar.setLayout(new FlowLayout());
    fileMenu = new JMenu("File");
    itemMenu = new JMenu("Item");
    loadMenuItem = new JMenuItem("Load");
    loadMenuItem.addActionListener(this);
    saveMenuItem = new JMenuItem("Save");
    saveMenuItem.addActionListener(this);
    saveAsMenuItem = new JMenuItem("SaveAs");
    saveAsMenuItem.addActionListener(this);
    newMenuItem = new JMenuItem("New");
    newMenuItem.addActionListener(this);
    deleteMenuItem = new JMenuItem("Delete");
    deleteMenuItem.addActionListener(this);
    deleteAllMenuItem = new JMenuItem("DeleteAll");
    deleteAllMenuItem.addActionListener(this);
    fileMenu.add(loadMenuItem);
    fileMenu.add(saveMenuItem);
    fileMenu.add(saveAsMenuItem);
    itemMenu.add(newMenuItem);
    itemMenu.add(deleteMenuItem);
    itemMenu.add(deleteAllMenuItem);
    menuBar.add(fileMenu);
    menuBar.add(itemMenu);
    menuBarPanel = new JPanel();
    menuBarPanel.setLayout(new FlowLayout());
    menuBarPanel.add(menuBar);
    model = new DefaultListModel();
    list = new JList(model);
    //model.addElement("USA");
    /*model.addElement("India");
    model.addElement("Vietnam");
    model.addElement("Canada");
    model.addElement("Denmark");
    model.addElement("France");
    model.addElement("Great Britain");
    model.addElement("Japan");
    */
    cp = getContentPane();
    cp.add(menuBarPanel);
    setupMainFrame();
}
void setupMainFrame()
{
    Toolkit    tk;
    Dimension   d;
    tk = Toolkit.getDefaultToolkit();
    d = tk.getScreenSize();              // Get screen resolution.
    setSize(d.width/2, d.height/2);      // Set size and location based
    setLocation(d.width/4, d.height/4);  // on the resolution.
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setTitle("JList Project");  // For the title bar
    setVisible(true);
}
public void actionPerformed(ActionEvent e)
{
    if( e.getSource() == loadMenuItem )
    {
        System.out.print("load");
        int decision = fc.showOpenDialog(this);
        if (decision == JFileChooser.APPROVE_OPTION) {
            file = fc.getSelectedFile();
            System.out.print("Opening: " + file.getName() + "." + "n");
        }
    }
    else if( e.getSource() == saveMenuItem )
    {
        System.out.print("save");
        int decision = fc.showSaveDialog(this);
        if (decision == JFileChooser.APPROVE_OPTION) {
            file = fc.getSelectedFile();
        }
    }
    else if( e.getSource() == saveAsMenuItem )
    {
        System.out.print("save as");
        int decision = fc.showSaveDialog(this);
        if (decision == JFileChooser.APPROVE_OPTION) {
            file = fc.getSelectedFile();
        }
    }
    else if( e.getSource() == newMenuItem )
    {
        System.out.print("new");
    }
    else if( e.getSource() == deleteMenuItem )
    {
        System.out.print("delete");
    }
    else if( e.getSource() == deleteAllMenuItem )
    {
        System.out.print("delete all");
    }
}
}

Answer 1

叹息....

您已经将自己的类命名为JList:

public class JList
{
  public static void main (String args[])
  {
    new MyFrameClass();
  }
}

等为编译器创建了一个名称类。因此，当您创建JList变量时，它是您的 JList类型，而不是javax.swing.JList，并且当您调用构造函数时，编译器会为您自己的JList类查找一个不存在的构造函数。

解决方案:不要这样做，不要给你的类名与那些关键的核心Java类名冲突，而是把你的类名改为其他的，例如

public class JListTest
{
  public static void main (String args[])
  {
    new MyFrameClass();
  }
}