Hangman游戏背景图像无效

Question

我正在制作一个Hangman游戏，我的代码似乎没有给我提供太多使用布局的自由。我在我的JFrame中添加了一个图像，然后在我的图像中添加了JPanel，我正在为所有的JLabels和JTextFields使用它，但在我看来，这是低效的，因为为了改变我的JTextField或JLabels的布局，我必须改变我的图像布局，这会打乱游戏的整个外观。我如何才能让这段代码更有效率，让自己有更多的自由来更改JLabels和JTextFields的布局，而不会把一切都搞砸？提前感谢您的帮助。

/*PACKAGE DECLARATION*/
package Game;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

/************************
* GAME MECHANICS CLASS *
* **********************/
public class GameStructure {
/* INSTANCE DECLARATIONS */
private String []wordList = {"computer","java","activity","alaska","appearance","article",
"automobile","basket","birthday","canada","central","character","chicken","chosen",
"cutting","daily","darkness","diagram","disappear","driving","effort","establish","exact",
"establishment","fifteen","football","foreign","frequently","frighten","function","gradually",
"hurried","identity","importance","impossible","invented","italian","journey","lincoln",
"london","massage","minerals","outer","paint","particles","personal","physical","progress",
"quarter","recognise","replace","rhythm","situation","slightly","steady","stepped",
"strike","successful","sudden","terrible","traffic","unusual","volume","yesterday"};
private int []length = new int [64];
private JTextField tf;//text field instance variable (used)
private JLabel jl2;//label instance variable (used)
private JLabel jl3;//label instance (working on)
private String letter;

/*****************
* LENGTH METHOD *
* ***************/
public void length(){
jl3 = new JLabel();
int j = 0;
for(j = 0; j<64; j++) {
length[j] = wordList[j].length();//gets length of words in wordList
}//end for
int l = 0;
String line = "";
//create line first then put into .setText
for(int m = 0; m<length[l]; m++) {
line += "__ ";
l++;
}//end for
jl3.setText(line);
}//end length method

/*****************
* WINDOW METHOD *
* ***************/
public void window() {
LoadImageApp i = new LoadImageApp();//calling image class
JFrame gameFrame = new JFrame();//declaration
JPanel jp = new JPanel();
//JPanel jp2 = new JPanel();//jpanel for blanks
JLabel jl = new JLabel("Enter a Letter:");//prompt with label
jl.setFont(new Font("Rockwell", Font.PLAIN, 20));//set font
tf = new JTextField(1);//length of text field by character
jl2 = new JLabel("Letters Used:    ");
tf.setFont(new Font("Rockwell", Font.PLAIN, 20));//set font
jl2.setFont(new Font("Rockwell", Font.PLAIN, 20));//set font
jp.add(jl);//add label to panel
jp.add(tf);//add text field to panel
jp.add(jl2);//add letters used
gameFrame.add(i); //adds background image to window
i.add(jp); // adds panel containing label to background image panel
gameFrame.setTitle("Hangman");//title of frame window
gameFrame.setSize(850, 600);//sets size of frame
gameFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//exit when 'x' button pressed
gameFrame.setIconImage(new ImageIcon("Hangman-Game-grey.png").getImage());//set the frame icon to an image loaded from a file
gameFrame.setLocationRelativeTo(null);//window centered
gameFrame.setResizable(false);//user can not resize window
gameFrame.setVisible(true);//display frame
}//end window method

/*********************
* USER INPUT METHOD *
* *******************/
public void userInput() {
tf.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {//when enter key pressed
JTextField tf = (JTextField)e.getSource();
letter = tf.getText();
jl2.setText(jl2.getText() + letter + " ");//sets jlabel text to users entered letter
}//end actionPerformed method
});
}//end userInput method
}//end GameMechanics class

/*PACKAGE DECLARATION*/
package Game;

/***********************
* IMPORT DECLARATIONS *
* *********************/
import java.awt.BorderLayout;
import java.awt.Graphics;
import javax.swing.ImageIcon;
import javax.swing.JPanel;

/***************
* IMAGE CLASS *
* *************/
public class LoadImageApp extends JPanel {
private static final long serialVersionUID = 1L;
private ImageIcon image;

/***********************
* PAINT IMAGE METHOD *
* *********************/
public void paintComponent (Graphics g) {
//setLayout(new BorderLayout());
super.paintComponent(g);
image = new ImageIcon("hangman.png");//image name & type
image.paintIcon(this, g, 270, 20);
}//end paintComponent method
}//end LoadImageApp class
/*PACKAGE DECLARATION*/
package Game;

/*******************
* GAME MAIN CLASS *
* *****************/
public class GameMain {

/***************
* MAIN METHOD *
* *************/
public static void main (String []args) {
GameStructure game = new GameStructure();//declaration
game.length();
game.window();
game.userInput();
}//end main method
}//end GameMain class

Answer 1

一些建议：

• 不要覆盖JPanel的paint(...)方法，而是覆盖它的paintComponent(Graphics g)方法，除非你需要改变它渲染子组件或边界的方式(你不需要)。通过这样做，您还可以获得一些Swing图形的优势，包括自动双缓冲
• 切勿将图像读入paint或paintComponent方法。这些方法是GUI对用户的响应程度的主要决定因素之一，因此您永远不想在该方法中进行文件I/O。此外，为什么每当调用paint或paintComponent时，代码都会低效地重新读取相同的图像？为什么不简单地将图像或ImageIcon存储在一个变量中一次，然后使用它呢
• 学习和使用布局管理器
• 处理绘图或图像渲染的JPanel JPanel通常应该是非不透明的，所以一定要在它们上调用setOpaque(false)，也要在其他一些覆盖的Swing组件上调用

____________________

编辑

例如，这里是我的SSCCE，它显示了在类构造函数中获取图像(这里是从互联网上获取的)的示例。还要注意，我的SSCCE可以在任何连接到互联网的计算机上工作，因为它不需要图像文件，不像你的。此外，与显示GUI无关的代码也被删除，使得剩余的代码与问题更加相关。下次发布SSCCE时，请考虑这样做。

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
class GameStructure {
private JTextField tf;
private JLabel jl2;
public void window() {
LoadImageApp loadImageApp = new LoadImageApp();
JFrame gameFrame = new JFrame();
JPanel jp = new JPanel();
jp.setOpaque(false); //!!
jp.setBorder(BorderFactory.createTitledBorder("jp"));
JLabel jl = new JLabel("Enter a Letter:");
jl.setFont(new Font("Rockwell", Font.PLAIN, 20));
tf = new JTextField(1);
jl2 = new JLabel("Letters Used:    ");
tf.setFont(new Font("Rockwell", Font.PLAIN, 20));
jl2.setFont(new Font("Rockwell", Font.PLAIN, 20));
jp.add(jl);
jp.add(tf);
jp.add(jl2);
gameFrame.add(loadImageApp);
loadImageApp.add(jp);
gameFrame.setTitle("Hangman");
gameFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// gameFrame.setIconImage(
// new ImageIcon("Hangman-Game-grey.png").getImage());
gameFrame.setResizable(false);
gameFrame.pack();
gameFrame.setLocationRelativeTo(null);
gameFrame.setVisible(true);
}
}
class LoadImageApp extends JPanel {
private static final long serialVersionUID = 1L;
private static final int PREF_W = 850;
private static final int PREF_H = 600;
private BufferedImage img;
public LoadImageApp() {
// just used as an example public image
String spec = "https://duke.kenai.com/"
+ "SunRIP/.Midsize/SunRIP.png.png";    
URL url;
try {
url = new URL(spec);
img = ImageIO.read(url);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}  
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
g.drawImage(img, 0, 0, getWidth(), getHeight(), this);
}
}
}
public class GameMain {
public static void main(String[] args) {
GameStructure game = new GameStructure();
game.window();
}
}