Conway's Game Of Life specific view for a tutorial on the SSaurel's Blog

GameOfLifeView.java

package com.ssaurel.gameoflife;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.Display;
import android.view.MotionEvent;
import android.view.SurfaceView;
import android.view.WindowManager;

public class GameOfLifeView extends SurfaceView implements Runnable {
  
 // Default size of a cell
 public static final int DEFAULT_SIZE = 50;
 // Default color of an alive color (white in our case)
 public static final int DEFAULT_ALIVE_COLOR = Color.WHITE;
 // Default color of a dead color (black in our case)
 public static final int DEFAULT_DEAD_COLOR = Color.BLACK;
 // Thread which will be responsible to manage the evolution of the World
 private Thread thread;
 // Boolean indicating if the World is evolving or not
 private boolean isRunning = false;
 private int columnWidth = 1;
 private int rowHeight = 1;
 private int nbColumns = 1;
 private int nbRows = 1;
 private World world;
 // Utilitaries objects : a Rectangle instance and a Paint instance used to draw the elements
 private Rect r = new Rect();
 private Paint p = new Paint();
  
 public GameOfLifeView(Context context) {
  super(context);
  initWorld();
 }
  
 public GameOfLifeView(Context context, AttributeSet attrs) {
  super(context, attrs);
  initWorld();
 }
  
 @Override
 public void run() {
  // while the world is evolving
  while (isRunning) {
   if (!getHolder().getSurface().isValid())
    continue;
    
   // Pause of 300 ms to better visualize the evolution of the world
   try {
    Thread.sleep(300);
   } catch (InterruptedException e) {
   }
   
    Canvas canvas = getHolder().lockCanvas();
    world.nextGeneration();
    drawCells(canvas);
    getHolder().unlockCanvasAndPost(canvas);
  }
 }
  
 public void start() {
  // World is evolving
  isRunning = true;
  thread = new Thread(this);
  // we start the Thread for the World's evolution
  thread.start();
 }
  
 public void stop() {
  isRunning = false;
  
   while (true) {
   try {
    thread.join();
   } catch (InterruptedException e) {
   }
   break;
  }
   
 }
  
 private void initWorld() {
  WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
  Display display = wm.getDefaultDisplay();
  Point point = new Point();
  display.getSize(point);
  // we calculate the number of columns and rows for our World
  nbColumns = point.x / DEFAULT_SIZE;
  nbRows = point.y / DEFAULT_SIZE;
  // we calculate the column width and row height
  columnWidth = point.x / nbColumns;
  rowHeight = point.y / nbRows;
  world = new World(nbColumns, nbRows);
 }
  
 // Method to draw each cell of the world on the canvas
 private void drawCells(Canvas canvas) {
   for (int i = 0; i < nbColumns; i++) {
    for (int j = 0; j < nbRows; j++) {
     Cell cell = world.get(i, j);
     r.set((cell.x * columnWidth) - 1, (cell.y * rowHeight) - 1,
           (cell.x * columnWidth + columnWidth) - 1, 
           (cell.y * rowHeight + rowHeight) - 1);
     // we change the color according the alive status of the cell
     p.setColor(cell.alive ? DEFAULT_ALIVE_COLOR : DEFAULT_DEAD_COLOR);
     canvas.drawRect(r, p);
    }
   }
 }
  
 // We let the user to interact with the Cells of the World
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  if (event.getAction() == MotionEvent.ACTION_DOWN) {
   // we get the coordinates of the touch and we convert it in coordinates for the board
   int i = (int) (event.getX() / columnWidth);
   int j = (int) (event.getY() / rowHeight);
   // we get the cell associated to these positions
   Cell cell = world.get(i, j);
   // we call the invert method of the cell got to change its state
   cell.invert();
   invalidate();
  }
  return super.onTouchEvent(event);
 }
}