我正在尝试写一个由U.F.O组成的小游戏。它飞向各个方向（基于按钮）并在它触及屏幕底部时爆炸。我有4个班级，其中2个我不允许编辑。他们是：
显示窗口
import javax.swing.*;
import java.awt.*;
public class DisplayWindow extends JFrame{
private Container c;
public DisplayWindow(){
super("Display");
c = this.getContentPane();
}
public void addPanel(JPanel p){
c.add(p);
}
public void showFrame(){
this.pack();
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
不明飞行物的驱动程序。
import javax.swing.*;
public class SaucerDriver{
public static void main(String[] args){
DisplayWindow d = new DisplayWindow();
JMenuBar menuBar = new JMenuBar();
d.setJMenuBar(menuBar);
SaucerPanel p = new SaucerPanel(menuBar);
d.addPanel(p);
d.showFrame();
}
}
我正在尝试添加一个菜单栏，但它不会显示出来。我做错了什么？
这是我的班级，用于绘制所有建筑物以及诸如此类
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class SaucerPanel extends JPanel implements ActionListener{
JButton quitButton;
JButton upButton;
JButton leftButton;
JButton rightButton;
JButton downButton;
int xLoc;
int yLoc;
boolean explode;
public SaucerPanel(JMenuBar menuBar){
xLoc = 20;
yLoc = 200;
explode = false;
this.setPreferredSize(new Dimension(850,500));
this.setBackground(Color.white);
quitButton = new JButton("Quit");
this.add(quitButton);
quitButton.addActionListener(this);
downButton = new JButton("Down");
this.add(downButton);
downButton.addActionListener(this);
upButton = new JButton("Up");
this.add(upButton);
upButton.addActionListener(this);
leftButton = new JButton("Left");
this.add(leftButton);
leftButton.addActionListener(this);
rightButton = new JButton("Right");
this.add(rightButton);
rightButton.addActionListener(this);
}
public void paintComponent(Graphics g){
super.paintComponent(g);
g.setColor(Color.green);
g.fillRect(0,440,850,60);
g.setColor(Color.gray);
g.fillRect(80,420,210,100);
g.fillRect(100,410,170,100);
g.fillRect(120,400,130,100);
g.fillOval(130,350,110,150);
int[] aPoints = {170,200,185};
int[] bPoints = {370,370,320};
g.fillPolygon(aPoints,bPoints, 3);
g.setColor(Color.black);
g.fillRect(135,410,20,100);
g.fillRect(175,410,20,100);
g.fillRect(215,410,20,100);
g.setColor(Color.blue);
g.fillRect(460,140,120,360);
g.setColor(Color.red);
g.fillRect(700,400,100,150);
g.setColor(Color.yellow);
int[] xPoints = {700,800,750};
int[] yPoints = {400,400,350};
g.fillPolygon(xPoints, yPoints, 3);
g.setColor(Color.black);
g.fillRect(730,450,40,50);
g.setColor(Color.darkGray);
if(explode == false){
g.fillOval(xLoc,yLoc,80,40);
g.drawString("hovering...",xLoc,yLoc - 10);
}else{
for(int i = 0; i < 2000; i++){
int x = (int)(Math.random()*850);
int y = (int)(Math.random()*850);
g.setColor(Color.orange);
g.fillOval(x,y,5,5);
int a = (int)(Math.random()*850);
int b = (int)(Math.random()*850);
g.setColor(Color.red);
g.fillOval(a,b,5,5);
int c = (int)(Math.random()*850);
int d = (int)(Math.random()*850);
g.setColor(Color.yellow);
g.fillOval(c,d,5,5);
}
}
}
public void actionPerformed(ActionEvent e){
if(e.getSource() == quitButton){
System.exit(0);
}
else if(e.getSource() == downButton){
yLoc += 5;
if(yLoc == 400){
explode = true;
}
}
else if(e.getSource() == upButton){
yLoc -= 5;
}
else if(e.getSource() == leftButton){
xLoc -= 5;
}
else if(e.getSource() == rightButton){
xLoc += 5;
}
repaint();
}
}
这是我的菜单栏类
import javax.swing.*;
public class menuBar extends JFrame{
public menuBar(){
JFrame frame = new JFrame("Menu");
frame.setVisible(true);
frame.setSize(850,200);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JMenuBar menuBar = new JMenuBar();
frame.setJMenuBar(menuBar);
JMenu file = new JMenu("File");
menuBar.add(file);
JMenuItem open = new JMenuItem("Open");
file.add(open);
JMenuItem neww = new JMenuItem("New");
file.add(neww);
JMenu edit = new JMenu("Edit");
menuBar.add(edit);
JMenuItem color = new JMenuItem("Change Color");
edit.add(color);
JMenu help = new JMenu("Help");
menuBar.add(help);
JMenuItem about = new JMenuItem("About");
help.add(about);
frame.setVisible(true);
}
}
答案 0 :(得分：2)
您需要做一些小改动。
你的MenuBar类不应该扩展JFrame，它应该扩展JMenuBar。
您的SaucerDriver类需要添加您的MenuBar类，而不是创建一个新的JMenuBar，因为它是空的，并且不会在您的代码中的任何位置填充。
您的代码应如下所示
import javax.swing.*;
public class menuBar extends JMenuBar{
public menuBar(){
JMenu file = new JMenu("File");
this.add(file);
JMenuItem open = new JMenuItem("Open");
file.add(open);
JMenuItem neww = new JMenuItem("New");
file.add(neww);
JMenu edit = new JMenu("Edit");
this.add(edit);
JMenuItem color = new JMenuItem("Change Color");
edit.add(color);
JMenu help = new JMenu("Help");
this.add(help);
JMenuItem about = new JMenuItem("About");
help.add(about);
}
}
和SaucerDriver这样
import javax.swing.*;
public class SaucerDriver{
public static void main(String[] args){
DisplayWindow d = new DisplayWindow();
d.setJMenuBar(new menuBar());
SaucerPanel p = new SaucerPanel(menuBar);
d.addPanel(p);
d.showFrame();
}
}
编辑：因为你无法更改SauceDriver并且JMenuBar对象被传递到SaucerPanel对象，然后你可以从SaucerPanel类操作MenuBar。因此，请执行以下操作...
public SaucerPanel(JMenuBar menuBar){
setMenuBarItems(menuBar);
//...rest of the JPANEL code here
}
并将此方法添加到您的SaucerPanel类
public void setMenuBarItems(JMenuBar menuBar) {
JMenu file = new JMenu("File");
menuBar.add(file);
JMenuItem open = new JMenuItem("Open");
file.add(open);
JMenuItem neww = new JMenuItem("New");
file.add(neww);
JMenu edit = new JMenu("Edit");
menuBar.add(edit);
JMenuItem color = new JMenuItem("Change Color");
edit.add(color);
JMenu help = new JMenu("Help");
menuBar.add(help);
JMenuItem about = new JMenuItem("About");
help.add(about);
}