Working bitmap

WhirlView.java

package ru.ifmo.md.lesson1;

import android.content.Context;
import android.graphics.Canvas;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.graphics.Bitmap;

import java.util.Random;

/**
 * Created by thevery on 11/09/14.
 * Modified by heat-wave on 15/09/14
 */

class WhirlView extends SurfaceView implements Runnable {
    int [][] field = null;
    int width = 0;
    int height = 0;
    int scale = 4;
    final int MAX_COLOR = 10;
    int[] palette = {0xFFFF0000, 0xFF800000, 0xFF808000, 0xFF008000, 0xFF00FF00, 0xFF008080, 0xFF0000FF, 0xFF000080, 0xFF800080, 0xFFFFFFFF};
    Bitmap screen;
    SurfaceHolder holder;
    Thread thread = null;
    volatile boolean running = false;

    public WhirlView(Context context) {
        super(context);
        holder = getHolder();
    }

    public void resume() {
        running = true;
        thread = new Thread(this);
        thread.start();
    }

    public void pause() {
        running = false;
        try {
            thread.join();
        } catch (InterruptedException ignore) {}
    }

    public void run() {
        while (running) {
            if (holder.getSurface().isValid()) {
                long startTime = System.nanoTime();
                Canvas canvas = holder.lockCanvas();
                updateField();
                onDraw(canvas);
                holder.unlockCanvasAndPost(canvas);
                long finishTime = System.nanoTime();
                Log.i("TIME", "FPS: " + (1000000000.0 / (finishTime - startTime)));
                try {
                    Thread.sleep(16);
                } catch (InterruptedException ignore) {}
            }
        }
    }

    @Override
    public void onSizeChanged(int w, int h, int oldW, int oldH) {
        width = w/scale;
        height = h/scale;
        screen = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
        field = new int[width][height];
        initField();
    }

    void initField() {
        field = new int[width][height];
        Random rand = new Random();
        for (int x=0; x<width; x++) {
            for (int y=0; y<height; y++) {
                field[x][y] = rand.nextInt(MAX_COLOR);
                screen.setPixel(x, y, palette[field[x][y]]);
            }
        }
    }

    void updateField() {
        int[][] field2 = new int[width][height];
        for (int x=0; x<width; x++) {
            for (int y=0; y<height; y++) {
                field2[x][y] = field[x][y];
                for (int dx=-1; dx<=1; dx++) {
                    for (int dy=-1; dy<=1; dy++) {
                        int x2 = x + dx;
                        int y2 = y + dy;
                        if (x2<0) x2 += width;
                        if (y2<0) y2 += height;
                        if (x2>=width) x2 -= width;
                        if (y2>=height) y2 -= height;
                        if ( (field[x][y]+1) % MAX_COLOR == field[x2][y2]) {
                            field2[x][y] = field[x2][y2];
                            screen.setPixel(x, y, palette[field[x][y]]);
                        }
                    }
                }
            }
        }
        field = field2;
    }

    @Override
    public void onDraw(Canvas canvas) {
        canvas.drawBitmap(Bitmap.createScaledBitmap(screen, canvas.getWidth(), canvas.getHeight(), true), 0, 0, null);
    }
}