作業中のゲームに画像をロードしようとしています。クラスで作成したグループ ゲームをパターン化しています。私のパネルクラスでは、画像をロードして背景に描画します。これは機能し、画像を見つけて描画します。
ただし、宇宙船クラスに入れている画像をどのようにロードし、宇宙船のインスタンスを使用して描画しても、null ポインター例外が発生します。画像が見つからないと思いますが、背景画像が正常に取得されたソースフォルダーの同じ場所に配置しました。また、ゲーム画面クラスに空間イメージをロードしてパネルに描画すると、正常に動作します。
2 つのクラスのコードを以下に示します。で画像を読み込んでみました
spaceship = ImageIO.read(new File("Background.png"));
としても：
Image img = Toolkit.getDefaultToolkit().createImage("spaceShip.png");
ただし、両方の方法で同じ null ポインターを取得します。私は迷っており、誰かが助けてくれることを願っています。
package temp;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.ArrayList;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class GameScreen extends JFrame {
//Create an instance of a spaceship object
SpaceShip spaceship;
//Create an instance of a missile object
Missile missile;
//Create an instance of a launcher object
Launcher launcher;
//create an array that holds missile objects
ArrayList<Missile> missileArray = new ArrayList<Missile>();
//Creates an array to hold spaceship objects
ArrayList<SpaceShip> enemyArray = new ArrayList<SpaceShip>();
int lives = 3;
public GameScreen() {
//sets up the panel and the parent frame
//sets the default specs of the JFrame and adds the panel to it
this.setSize(600, 700);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
//Creates a panel object and adds it to the main frame
panel panel1 = new panel(launcher, enemyArray, missileArray);
this.add(panel1);
}
}
class panel extends JPanel {
//creates a new launcher object
Launcher launcher;
//creates a spaceship object
SpaceShip space;
//creates an arraylist of spaceship objects
static ArrayList<SpaceShip> ships;
//creates an arraylist of missile objects
ArrayList<Missile> missiles;
//loads images to draw
Image backGround;
public panel(Launcher la, ArrayList<SpaceShip> ss, ArrayList<Missile> mi) {
try {
launcher = la;
ships = ss;
missiles = mi;
backGround = ImageIO.read(new File("Background.png"));
} catch (Exception e) {
e.printStackTrace();
}
}
public void paintComponent(Graphics g) {
BufferedImage x = new BufferedImage(600, 700, BufferedImage.TYPE_INT_RGB);
Graphics g2 = x.getGraphics();
g2.drawImage(backGround, 0, 0, this);
g2.drawImage(space.img, 0, 0, this);
System.out.println(ships.size());
g.drawImage(x, 0, 0, this);
}
}
宇宙船.java
import java.awt.Image;
import java.awt.Toolkit;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
/**
* @author WymoreJW
*/
class SpaceShip extends Character {
Image img = Toolkit.getDefaultToolkit().createImage("spaceShip.png");
public void SpaceShip() {
this.health = 10;
this.speed = 2;
}
}
スタック トレース エラー
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at missiledefense.panel.paintComponent(GameScreen.java:108)
at javax.swing.JComponent.paint(JComponent.java:1029)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JLayeredPane.paint(JLayeredPane.java:567)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5131)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered
(RepaintManager.java:1479)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1410)
at javax.swing.RepaintManager.paint(RepaintManager.java:1224)
at javax.swing.JComponent.paint(JComponent.java:1015)
at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
at java.awt.Container.paint(Container.java:1780)
at java.awt.Window.paint(Window.java:3375)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:713)
at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:693)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run
(SystemEventQueueUtilities.java:125)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters
(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy
(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)