아래 소스와 같이 그리고지우는것은 성공 하였는데

지울떄 paint를   mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); 로

바꾸고 지우면 지우는 순간(move) 지워지지 않고  손을떄는순간(touch_up)하는순간 지워지더군요

move할때 계속 지원지게 하려면 어떻한 방법이 있을까요?

조언 부탁 드리겠습니다

 mPaint = new Paint();
  mPaint.setAntiAlias(true);
  mPaint.setDither(true);
  mPaint.setColor(0xFF000000);
  mPaint.setStyle(Paint.Style.STROKE);
  mPaint.setStrokeJoin(Paint.Join.ROUND);
  mPaint.setStrokeCap(Paint.Cap.ROUND);
  mPaint.setStrokeWidth(12);

class MyView extends View {
  Context context;
  private Canvas mCanvas;
  private static final String TAG = "MyView";

  public MyView(Context context) {
   super(context);
   this.context = context;
   mBitmap = Bitmap.createBitmap(480, 800, Bitmap.Config.ARGB_8888);
   mBitmapPaint = new Paint(Paint.DITHER_FLAG);
   mPath = new Path();
   mCanvas = new Canvas(mBitmap);
  }

  public void onDraw(Canvas canvas) {

   Log.i(TAG, "onDraw");
   canvas.drawColor(Color.WHITE);
   // canvas.
   // for (int i = 0; i < list.size(); i++) {
   // if (list.get(i).isDraw) {
   // canvas.drawLine(list.get(i - 1).x, list.get(i - 1).y,
   // list.get(i).x, list.get(i).y, mPaint);
   // }
   // }
   canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);

   canvas.drawPath(mPath, mPaint);
  }

  public void setColor(int color) {
   mPaint.setColor(color);
  }

  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 >= TOUCH_TOLERANCE || dy >= 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;
  }
 }