当您按下JButton Ny 时，用户输入应该作为对象（类Deltagare）添加到ArrayList中，当用户稍后按JButton 签证，它应显示在JTextArea。
问题是textArea只显示一个空的Arraylist，不知何故输入没有添加到Arraylist。
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
class Tävling extends JFrame
{
public static ArrayList<Deltagare> list = new ArrayList<Deltagare>();
JTextArea text = new JTextArea();
JRadioButton rb1 = new JRadioButton("Startnr", true);
JRadioButton rb2 = new JRadioButton("Namn", false);
JRadioButton rb3 = new JRadioButton("Ålder", false);
JRadioButton rb4 = new JRadioButton("Tid", false);
Tävling()
{
super ("DSV Kista Marathon");
setLayout(new BorderLayout());
//NORTH
JPanel north = new JPanel();
north.add(new JLabel("DSV Kista Marathon"));
add(north, BorderLayout.NORTH);
//CENTER
add(new JScrollPane(text), BorderLayout.CENTER);
text.setEditable(false);
//EAST
JPanel east = new JPanel();
east.setLayout(new BoxLayout(east, BoxLayout.Y_AXIS));
east.add(new JLabel("Sortering"));
east.add(rb1);
east.add(rb2);
east.add(rb3);
east.add(rb4);
ButtonGroup group = new ButtonGroup();
group.add(rb1);
group.add(rb2);
group.add(rb3);
group.add(rb4);
add(east, BorderLayout.EAST);
//SOUTH
JPanel south = new JPanel();
JButton b1 = new JButton("Ny");
b1.addActionListener(new B1());
south.add(b1);
JButton b2 = new JButton("Visa");
b2.addActionListener(new B2());
south.add(b2);
JButton b3 = new JButton("Tid");
b3.addActionListener(new B3());
south.add(b3);
add(south, BorderLayout.SOUTH);
//Set
setLocation(500,200);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(300,350);
setVisible(true);
}
//Metod för att skapa startnr
public int getStartnr()
{
int startnr = list.size()+1;
return startnr;
}
public static void main(String[] args)
{
new Tävling();
}
//Huvudklass slut ------------------------------------------------------
//b1 - Ny
class B1 implements ActionListener
{
public void actionPerformed(ActionEvent ave)
{
new F1();
}
}
//b2 - Visa
class B2 implements ActionListener
{
public void actionPerformed(ActionEvent ave)
{
if (rb1.isSelected())
text.append(list.toString() + "\n");
else if (rb2.isSelected())
text.setText("Namn");
else if (rb3.isSelected())
text.setText("Ålder");
else if (rb4.isSelected())
text.setText("Tid");
}
}
//b3 - Tid
class B3 implements ActionListener
{
public void actionPerformed(ActionEvent ave)
{
new F2();
}
}
//JOptionPane - Ny (Deltagare)
class F1 implements ActionListener
{
JTextField nfield = new JTextField(12);
JTextField cfield = new JTextField(12);
JTextField afield = new JTextField(3);
F1()
{
JPanel form = new JPanel();
form.add(new JLabel("Startnr "+ getStartnr()));
form.setLayout(new BoxLayout(form, BoxLayout.Y_AXIS));
JPanel r1 = new JPanel();
r1.add(new JLabel ("Namn:"));
r1.add(nfield);
form.add(r1);
nfield.addActionListener(this);
JPanel r2 = new JPanel();
r2.add(new JLabel ("Land:"));
r2.add(cfield);
form.add(r2);
cfield.addActionListener(this);
JPanel r3 = new JPanel();
r3.add(new JLabel ("Ålder:"));
r3.add(afield);
form.add(r3);
afield.addActionListener(this);
JOptionPane.showConfirmDialog(null, form, "Ny Tävlande"
, JOptionPane.OK_CANCEL_OPTION);
}
public void actionPerformed(ActionEvent ave)
{
String name = nfield.getText();
String country = cfield.getText();
int age = Integer.parseInt(afield.getText());
int startnr = getStartnr();
list.add(new Deltagare(name, country, age, startnr));
}
}
//JOptionPane - Tid (Registrera ny)
class F2
{
JTextField field1 = new JTextField(6);
JTextField field2 = new JTextField(6);
F2()
{
JPanel form = new JPanel();
form.setLayout(new BoxLayout(form, BoxLayout.Y_AXIS));
JPanel r1 = new JPanel();
r1.add(new JLabel ("Startnr:"));
r1.add(field1);
form.add(r1);
JPanel r2 = new JPanel();
r2.add(new JLabel ("Tid:"));
r2.add(field2);
form.add(r2);
JOptionPane.showConfirmDialog(null, form, "Registrera Tid"
, JOptionPane.OK_CANCEL_OPTION);
}
}
}
Class Deltagare：
public class Deltagare
{
public String name,country;
public int age,startnr;
public Deltagare(String n, String c, int a, int b)
{
this.name = "n";
this.country = "c";
this.age = a;
this.startnr = b;
}
public void setStartnr(int b)
{
startnr = b;
}
public int getStartnr()
{
return startnr;
}
public String getName()
{
return name;
}
public String getCountry()
{
return country;
}
public int getAge()
{
return age;
}
public String toString()
{
return startnr + "" + name + " " + country + " " + age;
}
}
答案 0 :(得分：4)
首先，Deltagare类的构造函数做错了，替换
public Deltagare(String n, String c, int a, int b)
{
this.name = "n";
this.country = "c";
this.age = a;
this.startnr = b;
}
带
public Deltagare(String n, String c, int a, int b)
{
// removed quotes to assign value of n to name and same for country.
this.name = n;
this.country = c;
this.age = a;
this.startnr = b;
}
然后，您已将actionListener添加到JTextField课程中的所有F1，但如果用户点击确定按钮或 CANCEL 按钮。为此，请执行以下操作：在F1：
F1()
{
JPanel form = new JPanel();
form.add(new JLabel("Startnr "+ getStartnr()));
form.setLayout(new BoxLayout(form, BoxLayout.Y_AXIS));
JPanel r1 = new JPanel();
r1.add(new JLabel ("Namn:"));
r1.add(nfield);
form.add(r1);
nfield.addActionListener(this);
JPanel r2 = new JPanel();
r2.add(new JLabel ("Land:"));
r2.add(cfield);
form.add(r2);
cfield.addActionListener(this);
JPanel r3 = new JPanel();
r3.add(new JLabel ("Ålder:"));
r3.add(afield);
form.add(r3);
afield.addActionListener(this);
int choice = JOptionPane.showConfirmDialog(null, form, "Ny Tävlande"
, JOptionPane.OK_CANCEL_OPTION);
// If the value of the user is OK, then do this, else do nothing.
if (choice == JOptionPane.OK_OPTION)
{
String name = nfield.getText();
String country = cfield.getText();
int age = Integer.parseInt(afield.getText());
int startnr = getStartnr();
list.add(new Deltagare(name, country, age, startnr));
}
else if (choice == JOptionPane.CANCEL_OPTION)
{
System.out.println("CANCEL OPTION SELECTED, DO SOMETHING NOW :-)");
}
}
答案 1 :(得分：2)
在你的班级F1中，你在JOptionPane中显示一个表格，但是你没有对用户的回答做任何事情（确定或取消）。你有一个方法actionPerformed但是它适用于ActionListener，但是你永远不会在任何地方注册你的ActionListener。我认为你应该简单地处理JOptionPane的结果。如果正常，则调用actionPerformed中的代码（可以重命名）。
注意：showConfirmDialog是一个阻止调用。