Null Pointer Exeption

I'm new to all these things and I am trying to do 'double buffering' in my game so that the pictures would not flicker.

Then when I tried to run the game, eclipse said that it had a NullPointerExeption. When I debugged it, it said that it had an error on this line "bufferGraphics = offscreen.getGraphics();".

Please Help :)

Code:

---


public class Board extends Canvas
{
        Image[] backgrounds;
        Image[] bloatMeter;
        Character pig;
       
        Graphics bufferGraphics;
        Image offscreen;
       
        int backgroundNo;
        int meter;
       
        //Perks Pictures (Sample Only)
        Image[] perks;
       
        public Board()
        {
                offscreen = createImage(600, 700);
                [B]bufferGraphics = offscreen.getGraphics(); [/B]
               
                //Background Pictures
                backgroundNo = 0;
                backgrounds = new Image[5];
               
                backgrounds[0] = new ImageIcon("Farm Background.png").getImage();
                backgrounds[1] = new ImageIcon("Background Blue.png").getImage();
               
                //Bloat Meter Pictures
                meter = 0;
                bloatMeter = new Image[4];
               
                bloatMeter[0] = new ImageIcon("Bloat Meter 1.png").getImage();
                bloatMeter[1] = new ImageIcon("Bloat Meter 2.png").getImage();
                bloatMeter[2] = new ImageIcon("Bloat Meter 3.png").getImage();
                bloatMeter[3] = new ImageIcon("Bloat Meter 4.png").getImage();
               
                //Perk Pictures (Sample Only) -Create new class
                perks = new Image[3];
               
                perks[0] = new ImageIcon("Cake.png").getImage();
                perks[1] = new ImageIcon("Watermelon.png").getImage();
                perks[2] = new ImageIcon("Donut.png").getImage();
               
                //New Pig Object
                pig = new Character();
               
                addMouseListener(new MouseEvents());
                addMouseMotionListener(new MouseEvents());
                addKeyListener(new KeyboardEvents());
        }
       
        public void paint(Graphics g)
        {
                //Background
                bufferGraphics.drawImage(backgrounds[backgroundNo], 0, 0, this);
               
                //Height - Sample Only
                bufferGraphics.drawString("Height: 00000", 5, 20);
       
                //Bloat Meter
                bufferGraphics.drawImage(bloatMeter[meter], 480, 5, this);
               
                //Perks - Sample Only
                bufferGraphics.drawImage(perks[0], 200, 70, this);
                bufferGraphics.drawImage(perks[0], 350, 70, this);
               
                bufferGraphics.drawImage(perks[1], 150, 300, this);
                bufferGraphics.drawImage(perks[1], 270, 300, this);
                bufferGraphics.drawImage(perks[1], 400, 300, this);
               
                //Character
                bufferGraphics.drawImage(pig.pigPictures[meter], pig.x - 40, pig.y, this);
               
                g.drawImage(offscreen, 0, 0, this);
               
                /** Old "Non buffered" stuff

                //Background
                g.drawImage(backgrounds[backgroundNo], 0, 0, this);
               
                //Height - Sample Only
                g.drawString("Height: 00000", 5, 20);
       
                //Bloat Meter
                g.drawImage(bloatMeter[meter], 480, 5, this);
               
                //Perks - Sample Only
                g.drawImage(perks[0], 200, 70, this);
                g.drawImage(perks[0], 350, 70, this);
               
                g.drawImage(perks[1], 150, 300, this);
                g.drawImage(perks[1], 270, 300, this);
                g.drawImage(perks[1], 400, 300, this);
               
                //Character
                g.drawImage(pig.pigPictures[meter], pig.x - 40, pig.y, this);

                **/
        }
       
        public void update(Graphics g)
    {
        paint(g);
    }

    ....

---

Why are you using java.awt.Canvas and not javax.swing.JComponent/JPanel? Swing components are double buffered by default.

As for your present problem, read the API for createImage(int, int) inherited from java.awt.Component.

db

Wow! That was a quick fix :) I used canvas because our teacher used it as an example so I just copied him :P Thank You Very Much! :)

If you've changed over to Swing, make sure you do the custom painting the correct way.
Lesson: Performing Custom Painting (The Java™ Tutorials > Creating a GUI With JFC/Swing)

Also, avoid any concurrency issues if you do any animation
Lesson: Concurrency in Swing (The Java™ Tutorials > Creating a GUI With JFC/Swing)

db