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  NullPointerException Problem...  (Read 1211 times)
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Offline LucaSeem

Senior Newbie





« Posted 2012-10-06 21:12:16 »

Hi Guys,

lets get straight to the point. I have this problem:

Exception in thread "Thread-2" java.lang.NullPointerException
   at javax.swing.JComponent.getComponentGraphics(Unknown Source)
   at javax.swing.JComponent.paint(Unknown Source)
   at Display.Display.run(Display.java:39)
   at java.lang.Thread.run(Unknown Source)


So.. here is my code for one class:
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package Display;

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;

import javax.swing.JPanel;

public class Display extends JPanel implements Runnable {

   private Graphics g;
   private Thread gameThread;
   private boolean running = false;

   public Display() {
      gameThread = new Thread();
   }

   public void init() {
      running = true;
      gameThread = new Thread(this);
      gameThread.start();

   }

   public void update() {

   }

   public void draw(Graphics g){
     
   }

   @Override
   public void run() {
      while (running) {
         update();
         paint(g);
      }
   }

}


and the other class:
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package fullscreen;

import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;

import javax.swing.JFrame;

import Display.Display;

public class MainFrame extends JFrame {

   private static final long serialVersionUID = -485903859773002276L;
   private GraphicsDevice device;
   private boolean isFullScreen = false;
   private Display display = new Display();

   public MainFrame(GraphicsDevice device) {
      setTitle("SeemRang Fullscreen API");
      setDefaultCloseOperation(EXIT_ON_CLOSE);

      this.device = device;

      add(display);
      display.init();
   }

   public void begin() {
      isFullScreen = device.isFullScreenSupported();
      setUndecorated(isFullScreen);
      setResizable(!isFullScreen);

      if (isFullScreen) {
         // Full-screen mode
        device.setFullScreenWindow(this);
      } else {
         // Windowed mode
        pack();
         setVisible(true);
      }
   }

   public static void main(String[] args) {
      GraphicsEnvironment env = GraphicsEnvironment
            .getLocalGraphicsEnvironment();
      GraphicsDevice[] devices = env.getScreenDevices();

      for (int i = 0; i < 1; i++) {
         MainFrame test = new MainFrame(devices[i]);
         test.begin();
      }
   }
}


and the last.
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package fullscreen;

import java.awt.DisplayMode;

public class FullscreenInit {
   private DisplayMode modes;

   public FullscreenInit(DisplayMode modes) {
      this.modes = modes;
   }

   public DisplayMode getDisplayMode() {
      return modes;
   }

}


any solutions??? Any help will be appreciated.

Thnx,

LucaSeem Grin Grin Grin Grin Grin Grin Grin Grin
Offline Best Username Ever

Junior Member





« Reply #1 - Posted 2012-10-06 22:51:18 »

Use repaint, not paint.
Offline KittenKoder

Senior Member


Medals: 7



« Reply #2 - Posted 2012-10-06 22:58:15 »

First, as stated already, use repaint not paint. Second, just declaring a member doesn't fill that member if it's an object, you have to actually create or get an object to fill it.

I am no one else.
Games published by our own members! Check 'em out!
Legends of Yore - The Casual Retro Roguelike
Offline GabrielBailey74
« Reply #3 - Posted 2012-10-07 05:25:25 »

Revised the class a little bit, removed the Graphics g object.
Added the repaint/paint methods Grin
Removed the double 'gameThread = new GameThread(this).
The NullPointerException was caused by your 'Graphics g' object being nulled, therefor when you called 'paint(g);' it throws the NullPointerException Kiss

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package Display;

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;

import javax.swing.JPanel;

public class Display extends JPanel implements Runnable {

   private Thread gameThread;
   private boolean running = false;

   public Display() {
   }

   public void init() {
      running = true;
      gameThread = new Thread(this);
      gameThread.start();
   }

   public void update() {
      // Do Game Logic before you Render o,O
     draw();
   }

   public void paint(Graphics g) {
      super.paint(g);
   }

   public void draw() {
      repaint();
   }

   @Override
   public void run() {
      while (running) {
         update();
      }
   }

}

Offline LucaSeem

Senior Newbie





« Reply #4 - Posted 2012-10-07 09:08:55 »

Thanx guys!!!!
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