NullPointerException

Landon Brand · 2012-01-13T02:43:08

Well, I've been trying to learn some Java for a while, but I'm having some trouble with the following code: package net.devox.basic; import java.awt.Canvas; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Toolkit; import java.awt.image.BufferedImage; /* * Title: Game * Version: 1.0.0 * Desc: This class is used to control and pack together the * methods required to run the games logic in a central * location. */ public class Game extends Canvas { //buffer for off screen drawing private BufferedImage buffer; private static final long serialVersionUID = 1L; private void init() { //turn paint off this.setIgnoreRepaint(true); //set size this.setSize(GUI.WIDTH, GUI.HEIGHT); //set Focusable this.setFocusable(true); //create buffer buffer = new BufferedImage(GUI.WIDTH, GUI.HEIGHT, BufferedImage.TYPE_INT_ARGB); } public void start() { //initialize game this.init(); //start loop while(true){ try{ this.update(); this.drawbuffer(); this.drawscreen(); }catch(Exception e){e.printStackTrace(); Main.close();} } } private void update() { return; } private void drawbuffer() { //set buffer Graphics buff = buffer.createGraphics(); //do drawing logic drawrect(buff, 10, 10, 10, 10); //clear buffer buff.dispose(); } private void drawscreen() { Graphics2D g2d = (Graphics2D)getGraphics(); // Render Buffer to Screen g2d.drawImage(buffer, 0, 0, this); Toolkit.getDefaultToolkit().sync(); // Dispose of Graphics2D g2d.dispose(); } //Generic render method. Change this. private void drawrect(Graphics buff, int x, int y, int width, int height) { buff.setColor(Color.BLACK); buff.drawRect(x, y, width, height); } } ( http://pastebin.com/A8hEgMMf ) I get the error: java.lang.NullPointerException at net.devox.basic.Game.drawscreen(Game.java:81) at net.devox.basic.Game.start(Game.java:57) at net.devox.basic.Main.main(Main.java:19) when I run it. Does anyone have any advice or know how to fix the error? I'd greatly appreciate any feedback. Thank you for your time.

For Beginners

Started by Eckhart January 08, 2012 07:15 AM

9 comments, last by Eckhart 12 years, 3 months ago

Eckhart

107

Author

January 13, 2012 02:43 AM

Because if you call it in your main method the Graphics object from the GUI might not be initialized yet. You've created a race situation because your main method is in one thread and the GUI (i assume it's a JFrame or something) runs in the GUI thread.

Thanks, I think that's why.

NullPointerException

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

NullPointerException

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines