我正在尝试制作跳棋游戏。我知道在 JLabel 中插入 ImageIcon 并将其放入 的基础知识的JPanel
我这里有一个网格，每个单元格都有一个JPanel。我设法通过将代码放在drawsBoard()方法（不在下面的代码中）中，将JLabel数组分配给JPanel。
然而，我需要以单独的方法做到这一点，以使事情看起来更好。当我尝试运行下面的代码时，没有芯片出现在板上，这与之前不同。我错过了什么？你可以自己编译并查看。
这是我的代码：
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Image;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.Color;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferedImage;
import java.awt.image.ImageObserver;
import java.io.File;
import java.io.IOException;
import javax.swing.JTextField;
public class Main extends JFrame {
private JPanel contentPane;
ImageIcon p1Chip;
JPanel[][] board = new JPanel[8][8];
JLabel[][] label = new JLabel[8][8];
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Main frame = new Main();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public Main() throws IOException {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 800, 800);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
startGame();
}
//Start Game!
public void startGame() throws IOException{
getAssets();
drawBoard();
drawChips();
}
//ASSETS
public void getAssets(){
System.out.println("Getting assets!");
p1Chip = new ImageIcon("C:/Users/Trifecta/Desktop/Java Exercises/Checkers/src/checkers/P1ChipNormal.png");
}
//******************************DRAWS BOARD******************************\\
//Draws the board
public void drawBoard() throws IOException{
System.out.println("Start Drawing Board!");
getContentPane().setLayout(new GridLayout(8,8));
int colorAssignRow = 0;
int colorAssignCol = 0;
for(int r = 0; r < 8; r++){
colorAssignRow++;
colorAssignCol = 0;
for(int c = 0; c < 8; c++){
colorAssignCol++;
board[r][c] = new JPanel();
if(colorAssignRow%2!=0){
if(colorAssignCol%2==0)board[r][c].setBackground(Color.RED);
else board[r][c].setBackground(Color.BLACK);
}
else if(colorAssignRow%2==0){
if(colorAssignCol%2==0)board[r][c].setBackground(Color.BLACK);
else board[r][c].setBackground(Color.RED);
}
getContentPane().add(board[r][c]);
}
}
System.out.println("Board Drawing Done!");
}
//******************************END OF DRAWING BOARD******************************\\
//THIS IS THE PART THAT IS NOT WORKING
//******************************DRAWING CHIPS******************************\\
public void drawChips(){
/*
* Put Chip When: (r and c)
* 0 and even
* 1 and odd
* 2 and even
*/
//Drawing Player One Chips\\
for(int r = 0; r < 8; r++){
for(int c = 0; c < 8; c++){
label[r][c].setIcon(p1Chip);
label[r][c] = new JLabel();
board[r][c] = new JPanel();
if(r==0 && c%2==0){
board[r][c].add(label[r][c]);
}
else if(r==1 && c%2!=0 && c!=0){
board[r][c].add(label[r][c]);
}
else if(r==2 && c%2==0){
board[r][c].add(label[r][c]);
}
revalidate();
repaint();
}
}
//End Of Drawing Player One Chips\\
}
//******************************END OF DRAWING CHIPS******************************\\
}
更新：
这是我删除时收到的错误
label[r][c] = new JLabel();
board[r][c] = new JPanel();
java.lang.NullPointerException
at checkers.Main.drawChips(Main.java:145)
at checkers.Main.startGame(Main.java:69)
at checkers.Main.<init>(Main.java:60)
at checkers.Main$1.run(Main.java:43)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
调用drawChips（）方法时会停止。
答案 0 :(得分：3)
您的代码绘制了主板，初始化了所有面板，然后执行以下操作：
label[r][c].setIcon(p1Chip); // set the icon of the label
label[r][c] = new JLabel(); // replace the label in the array, containing the icon, by a new one, without any icon
board[r][c] = new JPanel(); // replace the already initialized panel in the board by a new, empty one
...
board[r][c].add(label[r][c]); // add the empty label to the empty panel.
所以，删除这些没有意义的行：
label[r][c] = new JLabel();
board[r][c] = new JPanel();
并删除这些无用的行：
revalidate();
repaint();
编辑，基于你的代码，我认为标签数组已经填充。情况并非如此，因此您需要删除
board[r][c] = new JPanel();
并翻转这两条指令：
label[r][c].setIcon(p1Chip); // set the icon of the label
label[r][c] = new JLabel(); // create the label
必须在设置其图标之前创建标签。所以它应该是
label[r][c] = new JLabel(); // create the label
label[r][c].setIcon(p1Chip); // set the icon of the label