Hi all. I looked around here for the proper way to double buffer an applet, and I think I’ve got it, but it’s realllly choppy when it runs. (It’s a little 2d jump 'n run game with not much in it yet). If you have any idea why, please tell =) Thanks!
public class Game extends JApplet implements KeyListener, Runnable
{
//doublebuffer stuff
Graphics bufferGraphics;
Image offscreenImage;
Dimension dim;
//constants
int SCREEN_WIDTH = 800;
int SCREEN_HEIGHT = 600;
int SPRITE_SIZE = 64;
Color BGColor = Color.white;
int PLAYER_SPEED_X = 10;
int PLAYER_JUMP_SPEED = 20;
int GRAVITY_ACCEL = 1;
//directional constants
int LEFT = -1;
int RIGHT = 1;
int STOPPED = 0;
int UP = -1;
int DOWN = 1;
//images
Image playerImage;
//movement
boolean freeFall = true;
int playerDirX = STOPPED;
int playerVelY = 0;
int playerPosX = 0;
int playerPosY = 0;
//game control variables
boolean gameIsRunning = false;
Thread t;
int i = 0;
public void init()
{
addKeyListener(this);
gameIsRunning = true;
//prepare offscreen image for double buffering
setSize(800,600);
dim = getSize();
offscreenImage = createImage(dim.width,dim.height);
bufferGraphics = offscreenImage.getGraphics();
playerImage = getImage(getDocumentBase(),"images/playerRight.gif");
t = new Thread(this);
t.start();
}
public void run()
{
while(gameIsRunning)
{
try
{
t.sleep(33);
}
catch (InterruptedException e) {}
playerPosX += playerDirX*PLAYER_SPEED_X;
playerPosY -= playerVelY;
if(freeFall)
{
playerVelY -= GRAVITY_ACCEL;
}
//wraparound
if(playerPosX < 0)
{
playerPosX = 0;
}
if(playerPosX > SCREEN_WIDTH - SPRITE_SIZE)
{
playerPosX = SCREEN_WIDTH - SPRITE_SIZE;
}
//stop at the floor
if(playerPosY > SCREEN_HEIGHT - SPRITE_SIZE)
{
freeFall = false;
playerVelY = 0;
playerPosY = SCREEN_HEIGHT - SPRITE_SIZE;
}
repaint();
}
}
public void keyPressed(KeyEvent e)
{
//move right
if(e.getKeyCode() == KeyEvent.VK_RIGHT ||
e.getKeyCode() == KeyEvent.VK_D)
{
playerImage = getImage(getDocumentBase(),"images/playerRight.gif");
playerDirX = RIGHT;
}
//move left
if(e.getKeyCode() == KeyEvent.VK_LEFT ||
e.getKeyCode() == KeyEvent.VK_A)
{
playerImage = getImage(getDocumentBase(),"images/playerLeft.gif");
playerDirX = LEFT;
}
//jump
if(e.getKeyCode() == KeyEvent.VK_SPACE ||
e.getKeyCode() == KeyEvent.VK_W ||
e.getKeyCode() == KeyEvent.VK_UP)
{
//allow jumping if we're standing on a surface
if(playerPosY == SCREEN_HEIGHT - SPRITE_SIZE ||
playerPosX == 0 ||
playerPosX == SCREEN_WIDTH - SPRITE_SIZE)
{
if(playerPosX == 0)
{
playerDirX = RIGHT;
playerImage =
getImage(getDocumentBase(),"images/playerRight.gif");
}
if(playerPosX == SCREEN_WIDTH - SPRITE_SIZE)
{
playerDirX = LEFT;
playerImage =
getImage(getDocumentBase(),"images/playerLeft.gif");
}
freeFall = true;
playerVelY = PLAYER_JUMP_SPEED;
}
}
}
public void keyReleased(KeyEvent e)
{
//stop moving right
if(e.getKeyCode() == KeyEvent.VK_RIGHT ||
e.getKeyCode() == KeyEvent.VK_D)
{
if(playerDirX == RIGHT)
{
playerDirX = STOPPED;
}
}
//stop moving left
if(e.getKeyCode() == KeyEvent.VK_LEFT ||
e.getKeyCode() == KeyEvent.VK_A)
{
if(playerDirX == LEFT)
{
playerDirX = STOPPED;
}
}
}
public void keyTyped(KeyEvent e)
{
}
public void paint(Graphics g)
{
//clear screen
bufferGraphics.setColor(Color.white);
bufferGraphics.fillRect(0,0,SCREEN_WIDTH,SCREEN_HEIGHT);
//draw the player
bufferGraphics.drawImage(playerImage,playerPosX,playerPosY,this);
g.drawImage(offscreenImage,0,0,this);
}
public void stop()
{
t.stop();
}
public void update(Graphics g)
{
paint(g);
}
}