在 Java 小程序中加载/显示图像时出现问题。不确定我是否错误地加载了图像，或者我是否错误地访问了它。这是绘制船和背景的代码（这是一个类似小行星的游戏）。背景绘制正确，但船没有。这是我正在处理的主要类方法：
public void paintFrame(Graphics g) {
Dimension d = size();
g.fillRect(0, 0, d.width, d.height);
g.drawImage(ship.getImage(), d.width/2, d.height/2, null);
}
我在类的开头创建了一个 ship 类的实例。但是，如果我尝试在方法中实例化船类（例如“Ship ship = new Ship();”），它会说从未使用过变量“ship”。
这是整个船级：
public class Ship {
private int dx;
private int dy;
private int x;
private int y;
private Image image;
public Ship() {
ImageIcon ii = new ImageIcon("ship1.png");
image = ii.getImage();
}
public Image getImage() {
return image;
}
}
如果我按原样运行它，它运行没有错误，但它不显示船。如果我尝试在除顶部以外的其他任何地方创建船的实例，它会给我一个 NullPointerException。
更新
这是我的整个主要课程：
import java.applet.Applet;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
public class RunGame extends Applet implements Runnable {
int frame;
int delay;
Thread animator;
Ship ship = new Ship();
Level level;
Dimension offDimension;
Image offImage;
Graphics offGraphics;
/**
* Initialize the applet and compute the delay between frames.
*/
public void init() {
String str = getParameter("fps");
int fps = (str != null) ? Integer.parseInt(str) : 10;
delay = (fps > 0) ? (1000 / fps) : 100;
}
/**
* Method is called when the applet becomes visible on
* the screen.
*/
public void start() {
animator = new Thread(this);
animator.start();
}
/**
* This method is called by the thread that was created in
* the start method. It does the main animation.
*/
public void run() {
// Remember the starting time
long tm = System.currentTimeMillis();
while (Thread.currentThread() == animator) {
// Display the next frame of animation.
repaint();
// Delay depending on how far we are behind.
try {
tm += delay;
Thread.sleep(Math.max(0, tm - System.currentTimeMillis()));
} catch (InterruptedException e) {
break;
}
// Advance the frame
frame++;
}
}
/**
* This method is called when the applet is no longer
* visible. Set the animator variable to null so that the
* thread will exit before displaying the next frame.
*/
public void stop() {
animator = null;
offImage = null;
offGraphics = null;
}
/**
* Update a frame of animation.
*/
public void update(Graphics g) {
Dimension d = size();
// Create the offscreen graphics context
if ((offGraphics == null) || (d.width != offDimension.width) || (d.height != offDimension.height)) {
offDimension = d;
offImage = createImage(d.width, d.height);
offGraphics = offImage.getGraphics();
}
// Erase the previous image
offGraphics.setColor(getBackground());
offGraphics.fillRect(0, 0, d.width, d.height);
offGraphics.setColor(Color.black);
// Paint the frame into the image
paintFrame(offGraphics);
// Paint the image onto the screen
g.drawImage(offImage, 0, 0, null);
}
/**
* Paint the previous frame (if any).
*/
public void paint(Graphics g) {
if (offImage != null) {
g.drawImage(offImage, 0, 0, null);
}
}
/**
* Paint a frame of animation.
*/
public void paintFrame(Graphics g) {
Dimension d = size();
g.fillRect(0, 0, d.width, d.height);
//g.drawImage(level.getImage(), 0, 0, null);
g.drawImage(ship.getImage(), 400, 300, null);
}
}