我试图在JFrame中制作国际象棋游戏。我有一个问题，我正在使用drawImage渲染碎片。
这是每个部分代码的一部分
private Image img;
private int x, y;
public Tura(int x, int y)
{
this.x = x;
this.y = y;
this.img = new ImageIcon("C:/Users/Rares/Documents/PieseSah/cal.png").getImage();
}
这就是我展示的方式：
for(int y=0;y<8;y++)
for(int x=0;x<8;x++)
g.drawImage(p[y][x].getImage(), 37+x*81, 62+y*81, this);
如果我为每件作品使用相同的图像，一切都OK。如果我为每个部分使用正确的图像，我会在drawImage行获得NullPointerException。
p阵列的种群：
for(int y=0;y<8;y++)
for(int x=0;x<8;x++)
{
if(y == 1 || y == 6)
p[y][x] = new Pion(x,y);
else if(y == 0 || y == 7)
switch(x)
{
case 0: case 7: p[y][x] = new Tura(x,y);break;
case 1: case 6: p[y][x] = new Cal(x,y);break;
case 2: case 5: p[y][x] = new Nebun(x,y);break;
case 3: p[y][x] = new Regina(x,y);break;
case 4: p[y][x] = new Rege(x,y);break;
}
else p[y][x] = new PiesaBlank(x,y);
}
此代码适用于我的jframe
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package tablasah;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.util.Scanner;
import javax.swing.JFrame;
/**
*
* @author Rares
*/
public class Tabla extends JFrame {
private PiesaSah[][] p = new PiesaSah[8][8];
private Image dbImage;
private Graphics dbg;
public Tabla()
{
setTitle("Joc Sah");
setSize(700,725);
setResizable(false);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
initializare();
}
public void paint(Graphics g) {
dbImage = createImage(getWidth(), getHeight());
dbg = dbImage.getGraphics();
paintComponent(dbg);
g.drawImage(dbImage, 0, 0, this);
}
public void paintComponent(Graphics g) {
g.setColor(Color.LIGHT_GRAY);
g.fillRect(0, 0, getWidth(), getHeight());
g.setColor(Color.DARK_GRAY);
g.fillRect(27, 52, 648, 648);
g.setColor(Color.LIGHT_GRAY);
g.drawLine(27, 133, 675, 133);
g.drawLine(27, 214, 675, 214);
g.drawLine(27, 295, 675, 295);
g.drawLine(27, 376, 675, 376);
g.drawLine(27, 457, 675, 457);
g.drawLine(27, 538, 675, 538);
g.drawLine(27, 619, 675, 619);
g.drawLine(108, 52, 108, 700);
g.drawLine(189, 52, 189, 700);
g.drawLine(270, 52, 270, 700);
g.drawLine(351, 52, 351, 700);
g.drawLine(432, 52, 432, 700);
g.drawLine(513, 52, 513, 700);
g.drawLine(594, 52, 594, 700);
for(int y=0;y<8;y++)
for(int x=0;x<8;x++)
g.drawImage(p[y][x].getImage(), 37+x*81, 62+y*81, this);
}
public void initializare()
{
for(int y=0;y<8;y++)
for(int x=0;x<8;x++)
{
if(y == 1 || y == 6)
p[y][x] = new Pion(x,y);
else if(y == 0 || y == 7)
switch(x)
{
case 0: case 7: p[y][x] = new Tura(x,y);break;
case 1: case 6: p[y][x] = new Cal(x,y);break;
case 2: case 5: p[y][x] = new Nebun(x,y);break;
case 3: p[y][x] = new Regina(x,y);break;
case 4: p[y][x] = new Rege(x,y);break;
}
else p[y][x] = new PiesaBlank(x,y);
}
}
public PiesaSah[][] getPiesaSah()
{
return p;
}
public void afisareTabla()
{
System.out.println("\n------------------------------------------\nAfisez:");
for(int y=7;y>=-1;y--)
{
if(y==-1)
System.out.print(" y/x");
else
System.out.print(" " + y + " ");
for(int x=0;x<8;x++)
{
if(y==-1)
System.out.print(" " + x);
if(y>-1)
System.out.print(" " + p[y][x].getChar());
}
System.out.print("\n");
}
System.out.println("------------------------------------------");
}
public int mutarePiesa()
{
Scanner scanner = new Scanner(System.in);
System.out.print("\nCe piesa vreti sa mutati?\nx=");
int x = scanner.nextInt();
System.out.print("y=");
int y = scanner.nextInt();
if (p[y][x].getChar() == '-') {
System.out.println("\nError: Nu exista piesa la acea locatie.");
return 0;
} else {
System.out.println("\nPiesa selectata: " + p[y][x].getType() + "[" + p[y][x].getPosX() + "][" + p[y][x].getPosY() + "]");
System.out.print("\nLa ce locatie vreti sa o mutati?\nx=");
int z = scanner.nextInt();
System.out.print("y=");
int w = scanner.nextInt();
if (x == z && y == w) {
System.out.println("\nError: Nu ai mutat piesa (aceeasi locatie).");
return 0;
} else if (p[w][z].getChar() != '-') {
System.out.println("\nError: Exista deja o piesa pe acea locatie.");
return 0;
} else {
if (p[y][x].verificareMutare(z, w) == 1) {
p[w][z] = p[y][x];
p[y][x] = new PiesaBlank(x, y);
System.out.println("\nMutare efectuata cu succes.");
this.afisareTabla();
} else return 0;
}
}
System.out.println("Continuam? Da=1/Nu=0");
return scanner.nextInt();
}
}
这是我女王的示例代码
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package tablasah;
import java.awt.Image;
import javax.swing.ImageIcon;
/**
*
* @author Rares
*/
public class Regina implements PiesaSah {
private final String type = "Regina";
private final char c = 'r';
private Image img;
private int x, y;
public Regina(int x, int y)
{
this.x = x;
this.y = y;
this.img = new ImageIcon("C:/Users/Rares/Documents/PieseSah/regina.png").getImage();
}
public char getChar()
{
return c;
}
public String getType()
{
return type;
}
public Image getImage()
{
return img;
}
public int getPosX()
{
return this.x;
}
public int getPosY()
{
return this.y;
}
public int verificareMutare(int x, int y)
{
if(y < 0 || x < 0 || y > 8 || x > 8)
{
System.out.println("Error mutare " + this.getType());
return 0;
}
else if ((x-this.x == y-this.y) || (this.x == x && ((y > this.y) || (y < this.y))) || (this.y == y && ((x > this.x) || (x < this.x))))
{
this.x = x;
this.y = y;
return 1;
}
else
{
System.out.println("Error mutare " + this.getType());
return 0;
}
}
}
我的作品界面
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package tablasah;
import java.awt.Image;
/**
*
* @author Rares
*/
public interface PiesaSah {
public int verificareMutare(int x, int y);
public int getPosX();
public int getPosY();
public Image getImage();
public String getType();
public char getChar();
}
例外 - ＆gt;
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at tablasah.Tabla.paintComponent(Tabla.java:65)
at tablasah.Tabla.paint(Tabla.java:36)
at javax.swing.RepaintManager$3.run(RepaintManager.java:819)
at javax.swing.RepaintManager$3.run(RepaintManager.java:796)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:769)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:718)
at javax.swing.RepaintManager.access$1100(RepaintManager.java:62)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1677)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
答案 0 :(得分：0)
我通过从代码的构造函数中删除这部分代码
来解决这个问题this.img = new ImageIcon("C:/Users/Rares/Documents/PieseSah/cal.png").getImage();
并将其添加到我的getImage方法
喜欢
public Image getImage()
{
this.img = new ImageIcon("C:/Users/Rares/Documents/PieseSah/cal.png").getImage();
return img;
}
这不奇怪吗？我们所称的所有构造函数都是......