但是,我认为我的大多数代码都能工作,但是我相信我只在函数updatedJList()
下只缺少一行,请帮忙,谢谢。
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;
import javax.swing.SwingConstants;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.JList;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Ex1 extends JFrame {
private JTextField txtName;
private JList nameList;
private String[] nameArr;
private int arrCounter = 0;
private JLabel lblDisplayName;
public Ex1(){
this.setTitle("Exercise01");
this.setSize(300, 266);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
getContentPane().setLayout(null);
this.nameArr = new String[10];
JLabel lblName = new JLabel("Name:");
lblName.setBounds(10, 11, 264, 14);
getContentPane().add(lblName);
this.txtName = new JTextField();
this.txtName.setBounds(10, 25, 264, 20);
getContentPane().add(this.txtName);
this.txtName.setColumns(10);
JButton btnAddName = new JButton("Add Name to List");
btnAddName.setBounds(10, 49, 264, 23);
getContentPane().add(btnAddName);
btnAddName.addActionListener(new AddNameListener());
//Create ScrollPane
JScrollPane scrollPane = new JScrollPane();
scrollPane.setBounds(10, 75, 264, 126);
getContentPane().add(scrollPane);
//Create and Add JList
this.nameList = new JList();
nameList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
this.updateJList();
this.nameList.addListSelectionListener(new DisplayListener());
this.lblDisplayName = new JLabel("(Name will be shown here)");
this.lblDisplayName.setHorizontalAlignment(SwingConstants.CENTER);
this.lblDisplayName.setBounds(10, 203, 264, 14);
getContentPane().add(this.lblDisplayName);
this.setVisible(true);
}
private class AddNameListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
updateJList();
}
}
private void updateJList(){
//I think I am missing something on this line.. HELP
String name = this.txtName.getText();
this.txtName.setText(name);
this.arrCounter++;
this.txtName.setText("");
DefaultListModel model = new DefaultListModel();
for(int i =0;i<this.nameArr.length;i++)
{
model.addElement(name);
}
this.nameList.setModel(model);
}
private class DisplayListener implements ListSelectionListener {
@Override
public void valueChanged(ListSelectionEvent arg0) {
displayName();
}
}
private void displayName()
{
int index = this.nameList.getSelectedIndex();
String name = this.nameArr[index];
this.lblDisplayName.setText(name);
}
public static void main(String[] args) {
Ex1 gui = new Ex1();
}
}
在这一点上,我非常迷失,我似乎无法弄清楚出什么问题了,我学习Java已有大约8周的时间,而我也一直在研究这个问题4个小时。我确实认为我错过了一行,但如果您有其他意见,请随时发表评论。谢谢你,好人!
编辑:经过一番讨论,OP指出的问题如下:
[无论何时运行代码,它都会起作用,但是,当我在文本框中键入名称以将其存储在数组中并显示它时,它不会显示在文本框中,因此,我无法显示该名称。
将以下代码与您的问题进行比较。更改将在代码后进行描述。
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;
import javax.swing.SwingConstants;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.JList;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Ex1 extends JFrame {
private JTextField txtName;
private JList<Object> nameList;
private String[] nameArr;
private int arrCounter = 0;
private JLabel lblDisplayName;
public Ex1() {
this.setTitle("Exercise01");
this.setSize(300, 266);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
getContentPane().setLayout(null);
this.nameArr = new String[10];
JLabel lblName = new JLabel("Name:");
lblName.setBounds(10, 11, 264, 14);
getContentPane().add(lblName);
this.txtName = new JTextField();
this.txtName.setBounds(10, 25, 264, 20);
getContentPane().add(this.txtName);
this.txtName.setColumns(10);
JButton btnAddName = new JButton("Add Name to List");
btnAddName.setBounds(10, 49, 264, 23);
getContentPane().add(btnAddName);
btnAddName.addActionListener(new AddNameListener());
// Create and Add JList
DefaultListModel<Object> model = new DefaultListModel<>();
this.nameList = new JList<>(model);
nameList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
// Create ScrollPane
JScrollPane scrollPane = new JScrollPane(nameList);
scrollPane.setBounds(10, 75, 264, 126);
getContentPane().add(scrollPane);
this.nameList.addListSelectionListener(new DisplayListener());
this.lblDisplayName = new JLabel("(Name will be shown here)");
this.lblDisplayName.setHorizontalAlignment(SwingConstants.CENTER);
this.lblDisplayName.setBounds(10, 203, 264, 14);
getContentPane().add(this.lblDisplayName);
this.setVisible(true);
}
private class AddNameListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
updateJList();
}
}
private void updateJList() {
// I think I am missing something on this line.. HELP
String name = this.txtName.getText();
this.txtName.setText(name);
this.arrCounter++;
this.txtName.setText("");
DefaultListModel<Object> model = (DefaultListModel<Object>) nameList.getModel();
model.addElement(name);
}
private class DisplayListener implements ListSelectionListener {
@Override
public void valueChanged(ListSelectionEvent arg0) {
displayName();
}
}
private void displayName() {
int index = this.nameList.getSelectedIndex();
if (index >= 0) {
ListModel<Object> model = nameList.getModel();
Object obj = model.getElementAt(index);
String name = obj == null ? "" : obj.toString();
this.lblDisplayName.setText(name);
}
}
public static void main(String[] args) {
Ex1 gui = new Ex1();
}
}
首先为JList
创建一个模型,然后将其传递给JList
构造函数。
DefaultListModel<Object> model = new DefaultListModel<>();
this.nameList = new JList<>(model);
您要添加一个空的JScrollPane
。您需要将JList
传递给JScrollPane
构造函数。
JScrollPane scrollPane = new JScrollPane(nameList);
在方法updateJList()
中,您不需要新模型,只需要通过向其中添加元素来更新现有模型。
DefaultListModel<Object> model = (DefaultListModel<Object>) nameList.getModel();
model.addElement(name);
[对不起,我没有注意显示从nameList
中选择的值的代码部分。
我将上面代码中的方法displayName()
更改为以下内容:
private void displayName() {
int index = this.nameList.getSelectedIndex();
if (index >= 0) {
ListModel<Object> model = nameList.getModel();
Object obj = model.getElementAt(index);
String name = obj == null ? "" : obj.toString();
this.lblDisplayName.setText(name);
}
}
您不需要nameArr
,也不需要arrCounter
。
不需要数组。
使用Swing组件时,数据存储在“模型”中,在这种情况下为DefaultListModel
。因此,数据已添加到模型中,并且如果每个人都想访问JList中的数据,则可以从模型中获取数据。
DefaultListModel model = new DefaultListModel();
该代码是错误的。您不想每次单击按钮都继续创建新模型。您想向现有模型添加项目,以便可以显示所有项目。
请阅读Swing教程中有关How to Use Lists的部分。 ListDemo
代码将向您展示如何更好地构造类,以便您可以动态添加和删除模型中的项目。因此,请下载代码并根据您的要求进行修改。