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我写了这个简单的JApplet（是的，我是一个初学者）。它左侧有4个按钮，中央有一个cardLayout。左侧的每个按钮应在中央打开不同的面板。我的程序编译时没有错误（使用Drjava和Eclipse），但显示的appletviewer完全是空白的。谁能帮我弄清楚我做错了什么？面板不显示在小程序查看器中，但没有错误
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ApplicationCentre extends JApplet implements ActionListener {
JButton b1, b2, b3, b4, b5, b6;
JRadioButton rb1 ;
JLabel l1, l2, l3, l4, l5, l6, l7, l8, l9, l10, l11;
JTextField t1,t2,t3,t4,t5,t6;
JTextArea ta1, ta2;
JList j1;
JComboBox studentList;
JRadioButton accept[], reject[];
ButtonGroup radioGroup[];
JPanel deck;
CardLayout cardManager = new CardLayout();
Student s[];
String uniList [] = {"Toronto", "York", "Western", "Brock", "Guelph", "Waterloo", "McGill", "Concordia", "Laval", "Macmaster"};
public void init(){
s= new Student [100];
Container container = getContentPane();
deck = new JPanel();
cardManager = new CardLayout();
deck.setLayout(cardManager);
//add panels to deck
deck.add(inputPanel(), "input");
deck.add(admitPanel(), "admit");
deck.add(allPanel(), "displayAll");
deck.add(onePanel(), "displayOne");
//Left-side Buttons
JPanel P1 = new JPanel();
P1.setLayout (new GridLayout(4, 1));
b1 = new JButton("INPUT");
b1.addActionListener(this);
P1.add(b1);
b2 = new JButton("ADMIT");
b2.addActionListener(this);
P1.add(b2);
b3 = new JButton("DISPLAY ALL");
b3.addActionListener(this);
P1.add(b3);
b4 = new JButton("DISPLAY ONE");
b4.addActionListener(this);
P1.add(b4);
container.add(P1, BorderLayout.WEST);
// add deck to container
container.add(deck, BorderLayout.CENTER);
}
// Input panel
public JPanel inputPanel(){
JPanel P2 = new JPanel();
P2.setLayout (new GridLayout(6,2));
l1 = new JLabel ("Name");
P2.add(l1);
t1 = new JTextField (15);
P2.add(t1);
l2 = new JLabel ("Name of Program");
P2.add(l2);
t2 = new JTextField();
P2.add(t2);
l3 = new JLabel ("Average Mark");
P2.add(l3);
t3 = new JTextField();
P2.add(t3);
l4 = new JLabel ("Type of postgrad degree");
P2.add(l4);
t4 = new JTextField();
P2.add(t4);
l5 = new JLabel ("Universities (select 3)");
P2.add(l5);
j1 = new JList (uniList);
j1.setVisibleRowCount(3);
j1.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
P2.add(j1);
b5 = new JButton ("Submit");
P2.add(b5);
l7 = new JLabel();
P2.add(l7);
return P2;
}
// Admit panel
public JPanel admitPanel(){
JPanel P3 = new JPanel();
P3.setLayout (new BorderLayout());
studentList = new JComboBox(s);
studentList.setMaximumRowCount(8);
P3.add(studentList, BorderLayout.NORTH);
JPanel P3a = new JPanel();
P3a.setLayout (new GridLayout (3,3));
for (int j=0; j<3; j++) {
radioGroup[j] = new ButtonGroup();
accept[j] = new JRadioButton("Accept", false);
reject[j] = new JRadioButton("Reject", true);
radioGroup[j].add(accept[j]);
radioGroup[j].add(reject[j]);
}
l8 = new JLabel();
P3a.add(l8);
P3a.add(accept[1]);
P3a.add(reject[1]);
l9 = new JLabel();
P3a.add(l9);
P3a.add(accept[2]);
P3a.add(reject[2]);
l10 = new JLabel();
P3a.add(l10);
P3a.add(accept[3]);
P3a.add(reject[3]);
P3.add(P3a, BorderLayout.CENTER);
b6 = new JButton ("Submit");
P3.add(b6, BorderLayout.SOUTH);
return P3;
}
// DisplayAll panel
public JPanel allPanel(){
JPanel P4 = new JPanel();
ta1 = new JTextArea();
ta1.setFont(new Font("Serif", Font.ITALIC, 12));
ta1.setEditable(false);
P4.add(ta1);
return P4;
}
//DisplayOne Panel
public JPanel onePanel(){
JPanel P5 = new JPanel();
P5.setLayout (new BorderLayout());
JPanel P5a = new JPanel();
l11 = new JLabel ("Enter Student's name");
P5a.add(l11);
t6 = new JTextField();
P5a.add(t6);
P5.add(P5a, BorderLayout.NORTH);
ta2 = new JTextArea();
ta2.setFont(new Font("Arial", Font.PLAIN, 14));
ta2.setEditable(false);
P5.add(ta2, BorderLayout.CENTER);
return P5;
}
public void actionPerformed(ActionEvent e) {
if (e.getSource() == b1)
cardManager.show(deck,"input");
else if (e.getSource() == b2)
cardManager.show(deck,"admit");
else if (e.getSource() == b3)
cardManager.show(deck,"displayAll");
else if (e.getSource() == b4)
cardManager.show(deck,"displayOne");
}
}
// student class and extensions
abstract class Student {
private String name, programName, uni1, uni2, uni3;
public boolean u1a=false;
public boolean u2a=false;
public boolean u3a=false;
public Student (String n, String p, String u1, String u2, String u3){
setName(n);
setProgramName(p);
setUni1(u1);
setUni2(u2);
setUni3(u3);
}
public String getProgramName() {
return programName;
}
public void setProgramName(String programName) {
this.programName = programName;
}
public String getUni3() {
return uni3;
}
public void setUni3(String uni3) {
this.uni3 = uni3;
}
public String getUni2() {
return uni2;
}
public void setUni2(String uni2) {
this.uni2 = uni2;
}
public String getUni1() {
return uni1;
}
public void setUni1(String uni1) {
this.uni1 = uni1;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
class Postgrad extends Student{
private double avgMark;
private String degree;
public Postgrad (String n, String p, String u1, String u2, String u3, double avg, String d){
super(n, p, u1, u2, u3);
setAvgMark(avg);
setDegree(d);
}
public double getAvgMark() {
return avgMark;
}
public void setAvgMark(double avgMark) {
this.avgMark = avgMark;
}
public String getDegree() {
return degree;
}
public void setDegree(String degree) {
this.degree = degree;
}
}
class Undergrad extends Student {
private double avgMark;
public Undergrad (String n, String p, String u1, String u2, String u3, double avg){
super(n, p, u1, u2, u3);
setAvgMark(avg);
}
public double getAvgMark() {
return avgMark;
}
public void setAvgMark(double avgMark) {
this.avgMark = avgMark;
}
}
*“我已经写了这个简单的JApplet”*小程序从来不简单，这个有> 300 LOC。 –
欢迎来到Stackoverflow！对于未来的问题：请提供一个简短的例子，而不是整个源代码。 –
我会尽我所能去做，但我不知道问题出在哪里。现在我确实......谢谢你。 – AshkanMil