Question

I’m working on a problem I’m having lots of trouble with. The concept of the question is to build a pyramid using bricks. The entire pyramid of bricks is centered in the window. I can draw one brick, then two, then three all the way up until 12 which makes up the base of the pyramid but all of the bricks are alined on the left edge on the left of the window instead of being centered in the window.

Using getWidth() and getHeight() i can do (getWidth()-BRICK_WIDTH) / 2; to get the center for the x coordinate of the brick. And then (getHeight() -BRICK_HEIGHT) / 2; for the center of the y coordinate of one brick. The only problem is i don’t understand where to enter that code so it applies to all the bricks so each row of bricks is centered in the window.

import acm.program.*;
import acm.graphics.*;

public class Pyramid extends GraphicsProgram {
  public void run() {
    double xCoordinate = (getWidth() - BRICKWIDTH) / 2;
    double yCoordinate = (getHeight() - BRICK_HEIGHT / 2);
    for (int i = 0; i < BRICKS_IN_BASE; i++) {
      for (int j = 0; j < i; j++) {
        double x = j * BRICK_WIDTH;
        double y = i * BRICK_HEIGHT;
        GRect square = new GRect(x, y, BRICK_WIDTH, BRICK_HEIGHT);
        add(square);
      }
    }
  }
  private static final int BRICK_WIDTH = 50;
  private static final int BRICK_HEIGHT = 25;
  private static final int BRICKS_IN_BASE = 12;
}

Answer 1

You should try something like this :

import acm.program.*;
import acm.graphics.*;

public class Pyramid extends GraphicsProgram
{
    public void run()
    {
        // We calculate some values in order to center the pyramid vertically
        int pyramidHeight = BRICKS_IN_BASE * BRICK_HEIGHT;
        double pyramidY = (getHeight() - pyramidHeight) / 2;

        // For each brick layer...
        for (int i=BRICKS_IN_BASE ; i >= 1; i--)
        {
            // We calculate some values in order to center the layer horizontally
            int layerWidth = BRICKWIDTH * i;
            double layerX = (getWidth() - layerWidth) / 2;
            double layerY = pyramidY + (i-1) * BRICK_HEIGHT;

            // For each brick in the layer...
            for(int j=0 ; j<i ; j++)
            {
                GRect square = new GRect(layerX + j*BRICK_WIDTH, layerY, BRICK_WIDTH, BRICK_HEIGHT);
                add(square);
            }
        }
    }

    private static final int BRICK_WIDTH = 50;
    private static final int BRICK_HEIGHT = 25;
    private static final int BRICKS_IN_BASE = 12;
}

In this implementation, we first calculate the global width of the layer (because we already know how many bricks there will be in it) and we use it to find a global “point of start” of the layer, from which we find all the coordinates for all the rectangles.