错误：很奇怪，我没有收到任何错误。
我想要做什么：（我还添加了 // 解释我的代码功能的消息。）
我想做的很简单。
1) 在 JTextField 中填写一个名称，按回车键，该名称应出现在 JTextArea 中。名称在 JTextArea 中后，JTextField 变为空，因此您可以填写另一个名称，依此类推，在 JTextArea 中应该出现名称列表。
2) 按下按钮 kiesWin 使程序从列表中随机选择一个人。（这里出错了）
3) 按下按钮 resetL 来重置程序，这样我就可以创建一个新列表来从中随机选择一个获胜者。
问题：当我按下按钮 Kies（翻译：选择）时，它应该从 ArrayList 中选择一个随机名称并在 JTextField textvak2 中显示随机名称。但是当我按下按钮 Kies 时，程序什么也不做。它应该向我显示从 ArrayList 中随机选择的名称。
这是不能正常工作的类：（我认为）
// This is the button that chooses a random name from the ArrayList.
// The random chosen name should appear in the JTextField textvak2. (but it doesn't)
// This is also the part where it goes wrong at the moment.
class Kies extends OnthoudNaam implements ActionListener {
public void actionPerformed( ActionEvent e ) {
Random r = new Random();
if (lijst.size() > 0) {
int n = r.nextInt(lijst.size());
Naam kiesNaam = lijst.get(n);
textvak2.setText(kiesNaam.getIngevoerdNaam());
}
}
}
如果您需要整个代码：
import javax.swing.*;
import javax.swing.border.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
// Main method to make the frame.
public class Loterij3 extends JFrame {
public static void main( String args[] ) {
JFrame frame = new Loterij3();
frame.setExtendedState( frame.MAXIMIZED_BOTH );
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.setTitle( "My Lottery!" );
frame.setContentPane( new Paneel() );
frame.setVisible( true );
}
}
// This is the Panel that goes into the frame.
class Paneel extends JPanel {
private Boven boven;
JTextArea textvak1;
JTextField textvak2;
OnthoudNaam onthoudNaam = new OnthoudNaam();
JTextField invoervak1; // JTextField from class Boven.
public Paneel() {
setLayout( new BorderLayout() ); // using border Layout.
setBackground( Color.LIGHT_GRAY );
boven = new Boven();
textvak1 = new JTextArea();
add( new JScrollPane( textvak1 ) );
textvak1.setBackground( Color.WHITE );
textvak2 = new JTextField();
textvak2.setHorizontalAlignment(JTextField.CENTER);
add( boven, BorderLayout.NORTH ); // Where the class Boven should be.
add( textvak1, BorderLayout.CENTER );
add( textvak2, BorderLayout.SOUTH );
}
// This is the class Boven (Translation up or upper).
// This is where the JButtons, JTextField and JLabels are.
public class Boven extends JPanel {
JButton kiesWin, resetL;
JLabel label1;
public Boven() {
setBackground( Color.LIGHT_GRAY );
setLayout( new GridLayout( 1, 4, 100, 5 ) ); // using GridLayout.
Border border =
BorderFactory.createEmptyBorder( 10, 10, 10, 10 );
setBorder( border );
kiesWin = new JButton("Kies een Winnaar!");
kiesWin.addActionListener( new Kies() );
resetL = new JButton("Reset alles");
resetL.addActionListener( new Reset() );
label1 = new JLabel("Voer Persoon in en druk op enter: ", JLabel.RIGHT);
invoervak1 = new JTextField( 20 );
invoervak1.addActionListener( new InvoerVakHandler() );
add( label1 );
add( invoervak1 );
add( kiesWin );
add( resetL );
}
}
// The class Naam (translation = name).
// This is what the ArrayList should remember
// In other words ArrayList should remember the Names I put in the JTextField.
class Naam {
private String ingevoerdNaam;
public Naam( String ingevoerdNaam) {
this.ingevoerdNaam = ingevoerdNaam;
}
public String getIngevoerdNaam() {
return ingevoerdNaam;
}
public String toString() {
return ingevoerdNaam;
}
}
// This is my ArrayList,
// This should remember the names I type in the JTextField.
class OnthoudNaam extends JPanel {
protected ArrayList<Naam> lijst;
public OnthoudNaam() {
lijst = new ArrayList<Naam>();
}
public void voegNaamToe(Naam x ) {
lijst.add(x);
}
public String toString() {
StringBuffer buffer = new StringBuffer();
for(Naam x : lijst ) {
buffer.append( x );
buffer.append( "\n" );
}
return buffer.toString();
}
}
// This is the JTextField where I enter the names.
// The Name I fill in the JTextField should be remembered by the ArrayList.
// The Name I fill in should be put in the JTextArea.
public class InvoerVakHandler implements ActionListener {
public void actionPerformed( ActionEvent e ) {
String invoer = invoervak1.getText();
Naam Naam = new Naam( invoer );
onthoudNaam.voegNaamToe( Naam );
textvak1.setText( onthoudNaam.toString() );
invoervak1.setText( "" );
}
}
// This is the button that chooses a random name from the ArrayList.
// This is also the part where it goes wrong at the moment.
class Kies extends OnthoudNaam implements ActionListener {
public void actionPerformed( ActionEvent e ) {
Random r = new Random();
if (lijst.size() > 0) {
int n = r.nextInt(lijst.size());
Naam kiesNaam = lijst.get(n);
textvak2.setText(kiesNaam.getIngevoerdNaam());
}
}
}
// This should become the button that resets everything so you can start over.
class Reset implements ActionListener {
public void actionPerformed( ActionEvent e ) {
}
}
}