我正在开发一个applet，我没有这方面的经验.. 我想绘制两个对象，插入图像并将背景颜色更改为黑色。如果我不改变颜色，一切都很好，问题来自我决定改变背景颜色。 我得到的是没有图纸和图片的黑色屏幕。如果我最小化或重新调整窗口大小，那么我得到了一切。 下面是我的代码，一个简化版本。
import javax.swing.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class JAlienHunt extends JApplet implements ActionListener {
private JButton button = new JButton();
JLabel greeting = new JLabel("Welcome to Alien Hunt Game!");
JLabel gameOverMessage = new JLabel(" ");
JPanel displayPanel = new JPanel(new GridLayout(2, 4));
private int[] alienArray = new int[8];
int countJ = 0, countM = 0;
private ImageIcon image = new ImageIcon("earth.jpg");
private int width, height;
Container con = getContentPane();
Font aFont = new Font("Gigi", Font.BOLD, 20);
public void init() {
/** Setting the Layout and adding the content. */
width = image.getIconWidth();
height = image.getIconHeight();
greeting.setFont(aFont);
greeting.setHorizontalAlignment(SwingConstants.CENTER);
con.setLayout(new BorderLayout());
con.add(greeting, BorderLayout.NORTH);
con.add(displayPanel, BorderLayout.CENTER);
/** Add Buttons to the Applet */
displayPanel.add(button);
String text = Integer.toString(i+1); // convert button # to String adding 1.
buttons.setText(text);
buttons.addActionListener(this);
}
public void actionPerformed(ActionEvent event) {
/** Shows the Alien representing the selected button and deactivate the button. */
if(event.getSource() == buttons)
button.setText("Jupiterian");
else
buttons[i].setText("Martian");
button.setEnabled(false);
con.remove(greeting);
displayPanel.remove(button);
displayPanel.setLayout(new FlowLayout());
gameOverMessage.setHorizontalAlignment(SwingConstants.CENTER);
con.add(gameOverMessage, BorderLayout.NORTH);
repaint();
}
public void paint(Graphics gr) {
super.paint(gr);
/** Condition when user loses the game. Two Jupiterians will be painted on the screen*/
Jupiterian jupit = new Jupiterian();
displayPanel.setBackground(Color.BLACK);
gameOverMessage.setFont(new Font ("Calibri", Font.BOLD, 25));
gameOverMessage.setText("The Earth has been destroyed!");
jupit.draw(gr, 250, 120);
gr.copyArea(190, 40, 465, 300, 500, 0);
gr.drawImage(image.getImage(), 400, 400, width, height, this); //+
}
}
----------------来自Jupiterian类的方法draw（）
public void draw(Graphics g, int x, int y) {
g.setColor(Color.WHITE);
g.drawOval(x, y, 160, 160); // Body of the alien
g.drawLine(x, y + 80, x - 40, y + 170); // Left hand
g.drawLine(x - 40, y + 170, x - 40, y + 180); // Left hand fingers
g.drawLine(x - 40, y + 170, x - 55, y + 180);
Font aFont = new Font ("Chiller", Font.BOLD, 30); // Description text.
g.setFont(aFont);
g.drawString(toString(), 230, 60);
}
---抽象类
public abstract class Aliena {
protected String name;
protected String planet;
/** Constructor for the class. Creates the Alien object with the parameters provided */
public Aliena(String nam, int eyes, String hair, String plan){
name = nam;
planet = plan;
}
/** Method that returns a String with a complete description of the Alien. */
public String toString(){
String stringAlien = "I am " + name + " from " + planet;
return stringAlien;
}
}
提前致谢！
答案 0 :(得分：0)
请勿在任何displayPanel.setBackground(Color.BLACK);方法中调用gameOverMessage.setFont(new Font("Calibri", Font.BOLD, 25));，gameOverMessage.setText("The Earth has been destroyed!");，paint或任何其他任何UI组件的更新。
这只会导致repaint被重新安排，并且将开始一个恶性循环的更新，这将消耗你的CPU并将世界吸入一个黑暗的厄运......
相反，在调用repaint
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ImageIcon;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
public class JAlienHunt extends JApplet implements ActionListener {
private JButton button = new JButton();
JLabel greeting = new JLabel("Welcome to Alien Hunt Game!");
JLabel gameOverMessage = new JLabel(" ");
JPanel displayPanel = new JPanel(new GridLayout(2, 4));
private int[] alienArray = new int[8];
int countJ = 0, countM = 0;
private ImageIcon image = new ImageIcon("earth.jpg");
private int width, height;
Container con = getContentPane();
Font aFont = new Font("Gigi", Font.BOLD, 20);
public void init() {
/**
* Setting the Layout and adding the content.
*/
width = image.getIconWidth();
height = image.getIconHeight();
greeting.setFont(aFont);
greeting.setHorizontalAlignment(SwingConstants.CENTER);
con.setLayout(new BorderLayout());
con.add(greeting, BorderLayout.NORTH);
con.add(displayPanel, BorderLayout.CENTER);
/**
* Add Buttons to the Applet
*/
displayPanel.add(button);
// String text = Integer.toString(i + 1); // convert button # to String adding 1.
button.setText("!");
button.addActionListener(this);
}
public void actionPerformed(ActionEvent event) {
/**
* Shows the Alien representing the selected button and deactivate the
* button.
*/
// if (event.getSource() == buttons) {
// button.setText("Jupiterian");
// } else {
//// buttons[i].setText("Martian");
// }
button.setEnabled(false);
con.remove(greeting);
displayPanel.remove(button);
displayPanel.setLayout(new FlowLayout());
gameOverMessage.setHorizontalAlignment(SwingConstants.CENTER);
con.add(gameOverMessage, BorderLayout.NORTH);
displayPanel.setBackground(Color.BLACK);
gameOverMessage.setFont(new Font("Calibri", Font.BOLD, 25));
gameOverMessage.setText("The Earth has been destroyed!");
repaint();
}
public void paint(Graphics gr) {
super.paint(gr);
/**
* Condition when user loses the game. Two Jupiterians will be painted on
* the screen
*/
Jupiterian jupit = new Jupiterian();
// displayPanel.setBackground(Color.BLACK);
// gameOverMessage.setFont(new Font("Calibri", Font.BOLD, 25));
// gameOverMessage.setText("The Earth has been destroyed!");
jupit.draw(gr, 250, 120);
// gr.copyArea(190, 40, 465, 300, 500, 0);
gr.drawImage(image.getImage(), 400, 400, width, height, this); //+
}
public class Jupiterian {
public void draw(Graphics g, int x, int y) {
g.setColor(Color.WHITE);
g.drawOval(x, y, 160, 160); // Body of the alien
g.drawLine(x, y + 80, x - 40, y + 170); // Left hand
g.drawLine(x - 40, y + 170, x - 40, y + 180); // Left hand fingers
g.drawLine(x - 40, y + 170, x - 55, y + 180);
Font aFont = new Font("Chiller", Font.BOLD, 30); // Description text.
g.setFont(aFont);
g.drawString(toString(), 230, 60);
}
}
}