myClass.move does not exist (but it does)

gleister

Hey all, I'm making a game for my online Processing class and I am a bit stuck. I'm very new to the program (and programming in general) so bare with me. I have called move() in my Ball class but when I call ball.move(); in void draw(), I get an error that says.move() doesn't exist. If anyone could look at my code to see whats wrong with it, I would appreciate it a lot!

My code:

float ballSpeed=5;
float PaddleSpeed=6;
gamePieces paddle;
gamePieces ball;
boolean mousePressed = false;


//paddle p1;

int playerscore = 0;
int cpuscore = 0;
int lastlevel = 3;
boolean keypress = false;
boolean endgame = false;

void setup () {
  size(800, 800);
  smooth();
  background(255);
  ball = new ball();
}

void draw() {
  //table
  background(0);


  //displays

  ball.display();
  if (endgame) {
    textSize(30);
    textAlign(CENTER);
    fill (255);
    text("Click to Start", 400, 100);
  } else {
    if (mousePressed == true) {
      ball.move();
      //paddle.moveX(moveX);

      //paddle.intersectTop(ball);
    }
  }
}

Ball clas (was in a separate tab)

class ball extends gamePieces {

  // processing.org/examples/bounce.html
  int rad = 20;
  float xpos, ypos;

  float xspeed = 2.6;
  float yspeed = 2.5;

  int xdirection = 1;
  int ydirection = 1;


  ball() {
    super();
  }

  void display() {
    stroke(255);
    strokeWeight(3);
    fill(#FFFEE8);
    frameRate(30);
    ellipseMode(RADIUS);
    ellipse(xpos, ypos, rad, rad);
  }

  void move () {
    xpos = width/2;
    ypos = height/2;

    xpos = xpos + (xspeed * xdirection);
    ypos=+ ypos + (yspeed * ydirection);

    if (xpos > width-rad || ypos < rad) {
      xdirection *= -1;
    }
    if (ypos > height-rad || ypos < rad) {
      ydirection *= -1;
    }
  }
}

Dinoswarleafs

Highlight all the code in your text and click the 'C' icon to format multiple lines of code. The ` only works for a single line.

gleister

Thank You Dinoswarleafts! I fixed the formatting now I believe

GoToLoop

• By Java's standards, classes and interfaces should follow the UpperCaseNaming.
• And it's advisable for the name be singular too.
• So ball should be Ball instead.
• And gamePieces should be named as GamePiece.
• The reason method move() doesn't "exist" is b/c you've declared variable ball as gamePieces.
• Even though variable ball holds an instance of ball, Java "sees" it as being gamePieces instead.
• Solution: declare ball as of datatype ball instead of gamePieces.
• Even better, rename those types as Ball & GamePiece. :-bd

gleister

GoToLoop, Thank you for the advice! I have looked at other forums where you have answered and your feedback has helped me on many projects during this class, so I really appreciate all your help.

I switched the class names to UpperCaseNaming. For the project I am working on, I have to include a class and a subclass. I have used GamePiece as the top class, and ball as the subclass (and eventually will add Paddle as another subclass of GamePiece). Will I still be able to use the Ball subclass and call the Ball.move ? Is that done in the main tab still? Or would I have to call it (or some part of Ball) in the GamePiece class tag?

Hope that makes some sense... Thanks again for your help.

GoToLoop

• Since GamePiece is your base class, a good idea is to declare it abstract.
• Doing so allows you to declare abstract methods inside it.
• For example, you can declare abstract void move();.
• Now any class which extends it gotta implement its own method move().
• And that also allows variables declared as GamePiece to be able to invoke method move().

/** 
 * Abstract Inheritance (v1.0)
 * GoToLoop (2017/Aug/17)
 *
 * Forum.Processing.org/two/discussion/23842/
 * myclass-move-does-not-exist-but-it-does#Item_5
 */

final GamePiece ball = new Ball(), paddle = new Paddle();

void setup() {
  frameRate(1);
}

void draw() {
  background((color) random(#000000));
  ball.move();
  paddle.move();
  println("ball:", ball.x, "\tpaddle:", paddle.x);
}

abstract class GamePiece {
  int x;
  abstract void move();
}

class Ball extends GamePiece {
  static final int SPD = 5;

  @ Override void move() {
    x += SPD;
  }
}

class Paddle extends GamePiece {
  static final int SPD = 3;

  @ Override void move() {
    x += SPD;
  }
}

gleister

GoToLoop, I was able to get the ball to appear in the center of my sketch now so that's a step in the right direction! Now the problem I am facing is that that new Ball wont move from the center. This is what I got so far: Pong Game (main tab)

GamePiece Paddle;
GamePiece Ball;
boolean mousePressed = false;

//for Ball 
int rad = 15;
float xPos, yPos;

float xSpeed = 3;
float ySpeed = 2;

int xDirection = 2;
int yDirection = 1;

int SPD = 5;


int playerscore = 0;
boolean keypress = false;
boolean endgame = false;

final GamePiece ball = new Ball(), paddle = new Paddle();

void setup () {
  size(800, 800);
  smooth();
  background(0);
  Ball = new Ball();
}

void draw() {
  //table

  background (0);
  //displays & moves
  Ball.move();
  Ball.display();

  //Paddle.move();
  //Paddle.display();
}

gamePiece Tab

        abstract class GamePiece {

          GamePiece () {
          }


          abstract void move();
          abstract void display();
        }

Ball Tab

class Ball extends GamePiece {

  //https://processing.org/examples/bounce.html
  Ball() {
    super();
  }

  void display() {
    stroke(255);
    strokeWeight(3);
    fill(#FFFEE8);
    frameRate(30);
    ellipseMode(RADIUS);
    xPos = width/2;
    yPos = height/2;

    ellipse(xPos, yPos, rad, rad);
  }

  void move () {
    //scales ball position
    ellipse(xPos, yPos, rad, rad);
    xPos = xPos + (xSpeed * xDirection);
    yPos = yPos + (ySpeed * yDirection);

    if (xPos > width-rad || xPos < rad) {
      xDirection *= -1;
    }
    if (yPos > height-rad || yPos < rad) {
      yDirection *= -1;
    }
  }
}

And Paddle tab (which isnt working either.. getting the dreaded nullpointerexception error when i try to call the display and move... but thats the next thing I have to tackle)

class Paddle extends GamePiece {
  float xPos;
  float yPos = 700;

  Paddle () {
  }

  void display () {
    rectMode(CENTER);
    rect(xPos, yPos, 50, 20);
  }
  void move () {
    xPos = mouseX;
  }
}

GoToLoop

You need to define the coordinate, dimension, speed & direction pairs inside class as well.
You can even define them directly in abstract class GamePiece.
So its children classes automatically inherit them all. *-:)

abstract class GamePiece {
  float x, y, w, h, vx, vy, dx, dy;

  abstract void move();
  abstract void display();
}

class Ball extends GamePiece {
  @ Override void move() {
  }

  @ Override void display() {
  }
}

class Paddle extends GamePiece {
  @ Override void move() {
  }

  @ Override void display() {
  }
}