Java 加载和显示图像时命令提示出错
我正在开发我的第一个Java应用程序，一个游戏。 我现在编译的东西很好，但当我在命令提示符下运行它时，命令提示符会反复打印：Java 加载和显示图像时命令提示出错,java,swing,nullpointerexception,Java,Swing,Nullpointerexception,我正在开发我的第一个Java应用程序，一个游戏。 我现在编译的东西很好，但当我在命令提示符下运行它时，命令提示符会反复打印： Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at Spike.loadpic(Spike.java:50) at Spike.paintspi
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Spike.loadpic(Spike.java:50)
at Spike.paintspike(Spike.java:55)
at Move.paint(Move.java:106)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5217)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1532)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1455)
at javax.swing.RepaintManager.paint(RepaintManager.java:1252)
at javax.swing.JComponent._paintImmediately(JComponent.java:5165)
at javax.swing.JComponent.paintImmediately(JComponent.java:4976)
at javax.swing.RepaintManager$3.run(RepaintManager.java:811)
at javax.swing.RepaintManager$3.run(RepaintManager.java:794)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:794)
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:1680)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
@SuppressWarnings("serial")
public class Move extends JPanel implements Runnable {
private synchronized void start(){
if(running){
return;
}
running = true;
thread = new Thread(this);
thread.start();
}
public void run(){
private Thread thread;
boolean running = false;
long tijd = System.nanoTime();
double ticks = 60.0;
double ns = 1000000000/ticks;
double delta=0;
while(running){
long tijd2 = System.nanoTime();
delta+=(tijd2-tijd)/ns;
tijd=tijd2;
if(delta>1){
player.move();
for(int i=0;i<zappelin.length;i++){
zappelin[i].movezappelin();
}
repaint();
delta--;
}
}
}
@Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
if(player.x<400){g2d.translate(0,0);}
else if(player.x+400>levellength){g2d.translate(-levellength+800,0);}
else{g2d.translate(-(player.x-400),0);}
player.paintplayer(g2d);
for(int i=0;i<ground.length;i++){
ground[i].paintground(g2d);
}
for(int j=0;j<spike.length;j++){
spike[j].paintspike(g2d);
}
for(int k=0;k<zappelin.length;k++){
zappelin[k].paintzappelin(g2d);
}
}
public static void main(String[] args){
/*Set frame, create Move game, etc */
game.start();
}
/*Some other stuff*/
}
public class Player{
loaded=false;
private void loadpic(){
player[0] = new ImageIcon("Images/Playa.png").getImage();
player[1] = new ImageIcon("Images/Playal.png").getImage();
player[2] = new ImageIcon("Images/Playar.png").getImage();
loaded = true;
game.repaint();
}
public void paintplayer(Graphics2D g){
if(!loaded){
loadpic();
}
if(loaded){
if(xa==-1){
g.drawImage(player[1], x, y, null);
}
else if(xa==1){
g.drawImage(player[2], x, y, null);
}
else{
g.drawImage(player[0], x, y, null);
}
}
}
/*Other stuff*/
}
public class Zappelin{
private void loadpic(){
zappelin[0] = new ImageIcon("Images/zappelinl.png").getImage();
zappelin[1] = new ImageIcon("Images/zappelinr.png").getImage();
zappelin[2] = new ImageIcon("Images/explosion.png").getImage();
loaded = true;
game.repaint();
}
public void paintzappelin(Graphics2D g) {
if(dead){return;}
if(!loaded){
loadpic();
}
else{
if(xaz==-1||xaz==0){g.drawImage(zappelin[0], xz, yz, null);}
else{g.drawImage(zappelin[1],xz,yz,null);
//g.drawImage(zappelin[2], 10,10, 64, 64, 0,0,64,64,null);
}
}
if(bullet){
g.setColor(Color.RED);
g.fillOval(xbullet,ybullet,4,4);
}
}
/*Other stuff*/
}
public class Spike{
private void loadpic(){
switch (dimension){
case "normaal":
spike = new ImageIcon("Images/Spike.png").getImage();
test=1337;
break;
case "links":
spike = new ImageIcon("Images/spikel.png").getImage();
break;
case "rechts":
spike = new ImageIcon("Images/spiker.png").getImage();
break;
case "boven":
spike = new ImageIcon("Images/spikeb.png").getImage();
break;
default:
spike = new ImageIcon("Images/Spike.png").getImage();
break;
}
loaded = true;
game.repaint();
}
public void paintspike(Graphics2D g) {
if(!loaded){
loadpic();
}
else{
if(dimension=="normaal"||dimension=="boven"){
for(int i=0; i<amount;i++){
g.drawImage(spike, xg+15*i, yg, null);}
}
if(dimension=="links"||dimension=="rechts"){
for(int i=0; i<amount;i++){
g.drawImage(spike, xg, yg+20*i, null);
}
}
}
}
}
@SuppressWarnings（“串行”）
公共类移动扩展JPanel实现可运行{
私有同步的void start（）{
如果（正在运行）{
返回；
}
运行=真；
线程=新线程（此）；
thread.start（）；
}
公开募捐{
私有线程；
布尔运行=假；
long tijd=System.nanoTime（）；
双刻度=60.0；
双纳秒=100000000/滴答；
双增量=0；
（跑步时）{
long tijd2=System.nanoTime（）；
delta+=（tijd2 tijd）/ns；
tijd=tijd2；
如果（增量>1）{
player.move（）；
对于（int i=0；i您的paint（）-方法中有一个NPE（NullPointerException）。这意味着您使用了一个未初始化的变量（它只是null）。因为您的代码不完整，我们不知道第50行在哪里，所以我无法告诉您问题的确切位置
另一个注意事项：从线程内部调用JPanel的重绘方法是不好的做法。Swing不是线程安全的。您需要使用SwingUtilities.invokeAndWait（runnable）
或SwingUtilities.invokeLater（runnable）
。检查Spike.java文件中的第50行。您有一个空指针异常。（1）-（2）Images
文件夹是否在“工作目录”中？如果不是，则您的图像将为空“这意味着您使用了未初始化的变量”不一定为真。图像可能为空。尝试g.drawImage（空，…）
将导致NPEYes-您完全正确。但是，请注意，异常应指向另一个堆栈中的此调用。