How to create a Scratch Card in Android?
<p>I need to create a "Scratch Card" App for my final project in school and can't find the way how to implement the scratching event (How do I create background image and put Grey rectangles over it, so when I will scratch those rectangles I will see the picture under them)</p>

<p>The Implementation must be in Android because I don't how to develop In Objective-C yet.</p>

<p>I saw a reference for Objective-C Implementation, but it's no good as I don't understand it.</p>

<p>My Code is:</p>

<pre><code>public class FingerPaint extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        try {
            MyView myView = new MyView(this);
            myView.requestFocus();
            myView.PaintObjectInit();
            // setContentView(myView);

            LinearLayout upper = (LinearLayout) findViewById(R.id.LinearLayout01);
            upper.addView(myView);
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }

        // MyImageView myImageView = new MyImageView(this);
        // setContentView(myImageView);
    }
}



public class MyView extends View {

    private Paint mPaint;
    private Bitmap mBitmap;
    private Canvas mCanvas;
    private Path mPath;
    private Paint mBitmapPaint;

    public MyView(Context context) {
        super(context);
        this.mPaint = new Paint();
        mPath = new Path();
        mBitmapPaint = new Paint(Paint.DITHER_FLAG);
    }

    protected void PaintObjectInit() {
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        //mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
        //mPaint.setColor(0xFFFF0000);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(12);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        try
        {


        //Bitmap bm1 = BitmapFactory.decodeResource(this.getResources(),R.drawable.scratch).copy(Bitmap.Config.ARGB_8888, true);;
        //Bitmap bm2 = BitmapFactory.decodeResource(this.getResources(),R.drawable.main).copy(Bitmap.Config.ARGB_8888, true);;

        //mBitmap = toTransparency(bm1, 0xFFAAAAAA, true, bm2);

        mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
        }
        catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {

        canvas.drawColor(0xFFAAAAAA);
        canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
        canvas.drawPath(mPath, mPaint);
    }

    private float mX, mY;
    private static final float TOUCH_TOLERANCE = 4;

    private void touch_start(float x, float y) {
        // mPath.reset();
        mPath.moveTo(x, y);
        mX = x;
        mY = y;
    }

    private void touch_move(float x, float y) {
        float dx = Math.abs(x - mX);
        float dy = Math.abs(y - mY);
        if (dx &gt;= TOUCH_TOLERANCE || dy &gt;= TOUCH_TOLERANCE) {
            mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
            mX = x;
            mY = y;
        }
    }

    private void touch_up() {
        mPath.lineTo(mX, mY);
        // commit the path to our offscreen
        mCanvas.drawPath(mPath, mPaint);
        // kill this so we don't double draw
        // mPath.reset();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();

        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            touch_start(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_MOVE:
            touch_move(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_UP:
            touch_up();
            invalidate();
            break;
        }
        return true;
    }
}
</code></pre>

<p>Please help regarding this.</p>
