I cant get it to work! NullPointerExeption at first awt.Graphics Object

Question

I am writing a game with AWT having it as an applet. I intend NOT to use anything outside of Java 1.1
For my Game i thought that i ATLEAST need the following classes:
MainGame, Level, Unit.
I Started writing Level. wrote a fewe methods for it such as
drawGras(int grastype) And started to write MainGame to see if they would work together. it's is/is going to be my first Java application where i actually know what object orienting is... I have already wrote a game in Java but with out knowing what a class or what object orienting realy is(the game works rather good to) but this time i wanted to use object orienting but came up with problems =( if first posted in "New to Javaprogramming" but they couldn't help me and advice me here
My previous post: http://forum.java.sun.com/thread.jsp?forum=54&thread=290558
Here's my code:
import java.awt.*;
public class MainGame extends java.applet.Applet
     implements Runnable {
     Thread runner;
     Image ImgLevel, ImgUnit;
     public MainGame() {
          Level nr1 = new Level();
          nr1.init();
          nr1.setGround(300);
          nr1.drawGras(1);
          nr1.CalcGraphics();
          nr1.drawSky(1);
          Image ImgLevel = nr1.getLevelImage();
     public void paint(Graphics g) {
          g.drawImage(ImgLevel,0,0,this);
     public void update(Graphics g) {
          paint(g);
     public void init() {
          MainGame Game = new MainGame();
     public void stop() {
          runner = null;
          System.exit(1);
     public void start() {
          if(runner == null) {
               runner = new Thread(this);
               runner.start();
     void Pause(int time) {
         try {
             Thread.sleep(time);
         } catch(InterruptedException e) {
           System.out.println(e.toString());
     public void run() {
          Thread thisThread = Thread.currentThread();
               while(thisThread == runner) {
class Level extends java.applet.Applet {
    Font BigText = new Font("Arial", Font.PLAIN, 36);
    Font Normal = new Font("Arial", Font.PLAIN, 14);
    Font Bold = new Font("Arial", Font.BOLD, 14);
    Graphics GrLevel;
    int pattern, sky, GroundtoWalk, Ground;
    Color BgColor = new Color(166,202,240);
    Color gras1 = new Color(0,255,0);
    Color gras2 = new Color(0,200,0);
    Color gras3 = new Color(0,100,0);
    Image ImgLevel;
    void setBgColor(int r, int g, int b) {
        BgColor = new Color(r,g,b);
    void CalcGraphics() {
        ImgLevel = createImage(800,600);
        GrLevel = ImgLevel.getGraphics();
    void setGround(int GrounD) {
        Ground = GrounD;
    void GroundToWalkADD(int addToGround) {
        GroundtoWalk = Ground + addToGround;
    void setGroundToWalk(int GrToWalk) {
        GroundtoWalk = GrToWalk;
    public void init() {
          System.out.println("Init 1"); // This was placed here when i was checking how far it got when debuging
          CalcGraphics();
          System.out.println("Init 2");
          drawGras(1);
          System.out.println("Init 3");
          repaint();
          System.out.println("Init 4");
    Image getLevelImage() {
        return ImgLevel;
    public void paint(Graphics g) {
          g.drawImage(ImgLevel,0,0,this);
    public void update(Graphics g) {
        paint(g);
    void drawGras(int pt) {
     GrLevel.setColor(BgColor);
     GrLevel.fillRect(0,0,800,600);
     switch(pt) {
          case 1:
               GrLevel.setColor(gras1);
               GrLevel.fillRect(0,GroundtoWalk,800,300);
               GrLevel.setClip(0,GroundtoWalk,800,300);
               for(int i = 0; 890>i;i=i+5) {
                    GrLevel.setColor(gras2);
                    GrLevel.drawLine(0+i,GroundtoWalk,-190+i,GroundtoWalk+300);
               for(int i=950; 0<i; i=i-5) {
                    GrLevel.setColor(gras3);
                    GrLevel.drawLine(890-i,GroundtoWalk,1000-i,GroundtoWalk+300);
          break;
          case 2:
               GrLevel.setColor(gras2);
               GrLevel.fillRect(0,GroundtoWalk+5,800,300);
               for(int i = 0; 890>i;i=i+5) {
                    GrLevel.setColor(gras3);
                    GrLevel.drawLine(0+i,GroundtoWalk,-190+i,GroundtoWalk+300);
               for(int i=950; 0<i; i=i-5) {
                    GrLevel.setColor(gras1);
                    GrLevel.drawLine(890-i,GroundtoWalk,1000-i,GroundtoWalk+300);
          break;
          case 3:
               GrLevel.setColor(gras3);
               GrLevel.fillRect(0,GroundtoWalk+10,800,300);
               for(int i = 0; 800>i; i=i+20) {
                    GrLevel.fillArc(0+i,GroundtoWalk,20,20,180,-180);
          break;
     pattern = pt;
    int getGrasPattern() {
         return pattern;
    void drawSky(int cl) {
            GrLevel.setColor(BgColor);
            GrLevel.fillRect(0,0,800,155);
            switch(cl) {
                case 1:
               for(int y = 0;y<7;y++) {
               for(int x = 0;x<800;x=x+20) {
                            GrLevel.setColor(Color.white);
                            GrLevel.drawArc(x,y*20,20,20,180,180);
                            GrLevel.setColor(Color.red);
                            GrLevel.drawArc(x,y*20+4,20,20,180,180);
                            GrLevel.setColor(Color.yellow);
                            GrLevel.drawArc(x,y*20+2,20,20,180,180);
                            GrLevel.setColor(Color.green);
                            GrLevel.drawArc(x,y*20+8,20,20,180,180);
                            GrLevel.setColor(Color.blue);
                            GrLevel.drawArc(x,y*20+12,20,20,180,180);
                            GrLevel.setColor(Color.pink);
                            GrLevel.drawArc(x,y*20+16,20,20,180,180);
          break;
          case 2:
                    GrLevel.setColor(Color.gray);
          break;
     sky = cl;
     GrLevel.setFont(BigText);
     GrLevel.setColor(Color.black);
     GrLevel.fillRect(0,0,800,50);
     GrLevel.setColor(Color.white);
     GrLevel.drawString("Score Tabel - comming someday",((size().width)/2)-260, 40);
    int getSkyTyp() {
         return sky;
}I tested running the code of class Level by puting it into Level.java and compiled it...ran it with appletviewer and it worked as it was intended to.
But when i compiled it with MainGame... and in the HTML started MainGame.class,.....applet didn't intializeand i got the following error messege:
Init 1
java.lang.NullPointerException
        at Level.CalcGraphics(MainGame.java:84)
        at MainGame.<init>(MainGame.java:11)Line 82: void CalcGraphics() {
Line 83: ImgLevel = createImage(800,600);
Line 84: GrLevel = ImgLevel.getGraphics(); // The First awt.Graphics object
Line 85: }
Line 9:      public MainGame() {
Line 10:     Level nr1 = new Level();
Line 11:     nr1.CalcGraphics(); // calling the method above -> same error first awt.Graphics Object.
If i change it os that "drawGras" comes first it's first awt.Graphics Line will show the same error
Hope some one can and will help me

Answer 1

As per the documentation of
java.awt.Component.createImage(int,int):
Creates an off-screen drawable image to be used for
double buffering.
Parameters:
width - the specified width
height - the specified height
Returns:
an off-screen drawable image, which can be used for
double buffering. The return value may be null if the
component is not displayable. This will always happen
if GraphicsEnvironment.isHeadless() returns true.
Since:
JDK1.0 its not
ImgLevel = createImage(800,600); that's making the problem but The first awt.Graphics Object in class Level, no mather which on it is =((
>
The key part is '...may be null if the component is
not displayable.'
You should put your graphics initialization code in
start(), which will be called when your applet is
ready to go. Before then, your applet is not
displayable. (Also, remember to dispose() your
graphics in your stop() method, if not sooner.)for the part writen above...I'll try to change it like you are saying.
Thanx for your help!