Null pointer exception

Core Library Questions

paritydnb

in Core Library Questions • 7 months ago

I get a null pointer exception error message and all i am trying to do is apply text to the programe with an int for the player score... However when i call upon the function of the ScoreUp class in draw, i get the error. Seems silly for such a simple thing!!!

Any hep appreciatted, ill just pop the code up....

//Main class

Star [] star = new Star [50];//Declare as a collection/array of stars and the size - 50.
Enemy [] enemy = new Enemy[3];//Declare classes
Planet [] planet = new Planet[6];

ArrayList bulletCollection;

Score score;
User user;

import ddf.minim.*;

Minim minim;
AudioPlayer player;
AudioSample crash;

void setup() {
size(1000, 700, P3D);
smooth();

minim = new Minim(this);
player = minim.loadFile("theme.mp3");
//player.play();
crash = minim.loadSample("crash.mp3");

bulletCollection = new ArrayList();

for (int i = 0; i < 6; i ++) {
planet [i] = new Planet(random(0, width), random(0, height), 15, 15);
}

for (int i = 0; i < enemy.length; i ++) {
enemy [i] = new Enemy(1050, random(100, 600), 50, 50);//initialize parameters in here
}

PImage simg = loadImage("ship.jpg");
user = new User(75, 350, simg);

for (int i = 0; i < 50; i ++) {
star [i] = new Star(random (0, width), random(0, height), 5, 5);
}
}

void draw() {

background(0);
noStroke();

score.displayScore();

for (int i = 0; i < bulletCollection.size() ; i ++) {
Bullets bullets = (Bullets) bulletCollection.get(i);
bullets.run();

}

for (int i = 0; i < 50; i ++) {
    star[i].run();//call upon all elements of the array. If i was a 0 itwould call one star
    star[i].move();
    if (star[i].x < 0) {
      star [i] = new Star( width, random(0, height), 5, 5);
    }
}

for (int i = 0; i < enemy.length; i ++) {
enemy[i].run();
}

for (int i = 0; i < 6; i ++) {
    planet[i].display();
    planet[i].move();
    if (planet[i].x < 0) {
      planet [i] = new Planet(random(1000, 1200), random(0, height), 15, 15);
    }
}

user.run();

}

void keyPressed() {
//println(user.playerSpeedX);
user.move();
}

void mousePressed() {

Bullets bullets = new Bullets(user.imgX + 172, user.imgY + 42, 5, 2);
bulletCollection.add(bullets);
}

void stop()
{
// always close Minim audio classes when you are done with them
player.close();
crash.close();
minim.stop();

super.stop();
}

//Bullet Class

class Bullets {

float x, y, w, h;
float bulletSpeed = 8;
boolean hit = false;
boolean active = true;
int playerScore = 0;

Bullets(float posX, float posY, float Width, float Height) {

    x = posX;
    y = posY;
    w = Width;
    h = Height;
}

void run() {
    display();
    moveBullet();
    collision();

}

void display() {
fill (255, 255, 44);
rect(x, y, w, h);
}

void moveBullet() {
    x += bulletSpeed;
    if (x >= width) {
      active = false;
    }
}

void collision() {
    for (int i = 0; i < bulletCollection.size();i++) {
      Bullets bullets = (Bullets) bulletCollection.get(i);
      for (int j = 0; j < enemy.length ; j ++) {
        if (x+w >= enemy[j].x && x <= enemy[j].x + enemy[j].w
          && y+h >= enemy[j].y && y <= enemy[j].y + enemy[j].h && active != false) {
          enemy[j].x = width;
          hit = true;
          bulletCollection. remove(i);
          println(playerScore);
        }
        else {
          hit = false;
        }
      }
    }
}
}

//Enemy Class

class Enemy {

float x, y, w, h;
float Xspeed = -7;
float Yspeed = -5;
float YspeedC = 2;
boolean collide = false;
float collideFall = 8;
float fillCol = 0;

Enemy (float posX, float posY, float Width, float Height) {
    x = posX;
    y = posY;
    w = Width;
    h = Height;
}

void run() {
    show();
    move();
    changeover();
    collide();
    boom();
    reset();
}

void show() {
fill(255, 255, fillCol);
rect(x, y, w, h);
}

void move() {
x += Xspeed;
y += Yspeed;
}

void changeover() {
    if (y <= 100|| y >= 600) {
      Yspeed = Yspeed *-1;
    }
}

void collide() {
    if (x >= user.imgX && x <= user.imgX + 172
      && y >= user.imgY && y <= user.imgY + 90) {
      Xspeed = 0;
      Yspeed = 0;
      collide = true;
    }
}

void boom() {
    if ((collide)) {
      user.imgY += collideFall;
      //crash.trigger();
    }
    else {
      collide = false;
    }
}

void reset() {
    if (x <= 0) {
      x = width;
      y = random(0,700);
    }
}
}

//planet class

class Planet{

float x,y,w,h;
float planetSpeed = 5;

Planet(float PosX, float PosY, float Width, float Height){
    x = PosX;
    y = PosY;
    w = Width;
    h = Height;

}

void display(){
    fill(random(0,255),random(0,255), random(0,255));
    ellipse(x,y,w,h);
    noStroke();
}

void move(){
    x -= planetSpeed;
}
}

//Score class

class Score {

int playerScore = 0;

void displayScore() {
    fill(255);
    textSize(30);
    text (playerScore, 50, 50);
}
}

//Star Class

class Star {
float x, y, w, h;
float starSpeed = 7;
Star( float posx, float posy, float posw, float posh ) {
    x = posx;
    y = posy;
    w = posw;
    h = posh;
}

void run(){
    display();
}

void display(){
    fill(255);
    ellipse(x,y,w,h);
    strokeWeight(2);
}

void move(){
    x -= starSpeed;

}
}

//User Class

class User {

float x, y, w, h;
float playerSpeedY = 15;
float playerSpeedX = 15;
PImage img;
float imgX = 75;
float imgY = 350;

User (float posX, float posY, PImage img) {
    this.x = posX;
    this.y = posY;
    this.img = img;
}

void run() {
display();
bulletTracker();
}

void display() {

image(img, imgX, imgY);
}

void bulletTracker() {
fill(255, 255, 0);
ellipse(imgX + 172, imgY + 45, 10, 10);
}

void move() {
    if (keyCode == UP) {
      imgY -= playerSpeedY;
    }
    else if (keyCode == DOWN) {
      imgY += playerSpeedY;
    }
    else if (keyCode == LEFT) {
      imgX -= playerSpeedX;
    }
    else if (keyCode == RIGHT) {
      imgX += playerSpeedX;
    }
}
}

Many thanks!

Replies(7)

ramin

Re: Null pointer exception

7 months ago

Is the score initialized? did you call the constructor?

paritydnb

Re: Re: Null pointer exception

7 months ago

How do you mean??? i havent got a constructor in the score class??? do i need one?? if so how do you call the variables in the constructor???

ramin

Re: Null pointer exception

7 months ago

You don't necessarily need a constructor. You can always call the default constructor, which has no parameters, like

Score score = new Score();

If you just write

Score score;

and want access variables of this object you will get a nullpointerException.

I wonder how and why you managed to write so much code, apparently without knowing much about

Object Oriented Programming.

Look into that topic, if you want to know about Classes, Objects, Constructors, Fieldvariables and so forth

paritydnb

Re: Re: Null pointer exception

7 months ago

Ive started at university learning this stuff.... cheers for your help.

paritydnb

Re: Null pointer exception

7 months ago

Also, the only real problem now is that the score wont go up every time there is a collision between the bullet and the enemy.... any ideas, it sometimes detects the collision and others not meaning the score doesnt go up every time an enemy is killed.

ramin

Re: Null pointer exception

7 months ago

hehe and welcome to the world of debugging. So a collision makes the score go up?

Check if the collision works correctly.

Is there something else changing the Score? Consider that everytime you create Score Object, playerScore is set to 0.

Also, why is there a playerScore in the Bullet class?

paritydnb

Re: Null pointer exception

7 months ago

Appreciatte the help bud. Im pretty certain its something to do with the collision as the boolean i set to true when a collision occurs very rarely does that. Mot of the time when an element in the array is hit, it still says false!!!