I'm working on a ping-pong style game (2d of course) and want to make it so the player can hit harder to make the ball go faster. I will only post the code that is relevant to the momentum. This is my current code for the paddle:
and for the ball:
I can compile without error but when I run it and the ball hits the player paddle I get the error terminal saying
"java.lang.NullPointerException
at Ball.checkPaddleCollision(Ball.java:62) <-- if(playerpaddle.getPaddleMomentumX() != 999999 && playerpaddle.getPaddleMomentumY() != 999999)
at Ball.act(Ball.java:29) <-- checkPaddleCollision();
"
This might be because of the mouse.getX() thing, so if it is do you think I should just use getX() of the paddle, since it follows the mouse?
public class PlayerPaddle extends Actor
{
private int mouseYcalc, mouseXcalc;
public int mouseX5, mouseX4, mouseX3, mouseX2, mouseX1, mouseY5, mouseY4, mouseY3, mouseY2, mouseY1 = 0;
public void act()
{
calculatePaddleMomentum();
}
public void calculatePaddleMomentum()
{
MouseInfo mouse = Greenfoot.getMouseInfo();
if(mouse != null)
{
mouseXcalc = mouse.getX();
mouseYcalc = mouse.getY();
mouseX5 = mouseX4;
mouseX4 = mouseX3;
mouseX3 = mouseX2;
mouseX2 = mouseX1;
mouseX1 = mouseXcalc;
mouseY5 = mouseY4;
mouseY4 = mouseY3;
mouseY3 = mouseY2;
mouseY2 = mouseY1;
mouseY1 = mouseYcalc;
}
}
public int getPaddleMomentumX()
{
MouseInfo mouse = Greenfoot.getMouseInfo();
if(mouse != null)
{
return ((int)(mouseX5 - mouseX1));
}
else
return 999999; // for error detection in Ball class
}
public int getPaddleMomentumY()
{
MouseInfo mouse = Greenfoot.getMouseInfo();
if(mouse != null)
{
return ((int)(mouseY5 - mouseY1));
}
else
return 999999; // for error detection in Ball class
}
}public class Ball extends Actor
{
private String xDirection = "right";
Table world = (Table)getWorld();
PlayerPaddle playerpaddle = (PlayerPaddle)world.playerpaddle;
//Physics:
private double yMomentum = 10;
private double xMomentum = 5;
public void checkPaddleCollision()
{
if(wait5 == 0)
{
PlayerPaddle collidedBlue = (PlayerPaddle)getOneIntersectingObject(PlayerPaddle.class);
if (collidedBlue != null && xDirection == "left")
{
if(playerpaddle.getPaddleMomentumX() != 999999 && playerpaddle.getPaddleMomentumY() != 999999)
{
xMomentum = playerpaddle.getPaddleMomentumX();
yMomentum = playerpaddle.getPaddleMomentumY();
xDirection = "right";
}
}
public void act()
{
if(wait5 > 0)
{
wait5 = (wait5 - 1);
}
checkPaddleCollision();
calcPhysics();
moveBall();
}
}
EnemyPaddle collidedRed = (EnemyPaddle)getOneIntersectingObject(EnemyPaddle.class);
if (collidedRed != null && xDirection == "right")
{
xMomentum = ((Greenfoot.getRandomNumber(7) + 3) * -1);
yMomentum = (((Greenfoot.getRandomNumber(3) - 4) * (Greenfoot.getRandomNumber(3) + 1)));
xDirection = "left";
}
}
}
}
