안드로이드 그림판 초기화하는 법 질문이요

Question

최근 안드로이드 스튜디오를 책으로 공부하고 있는 대학생입니다.

제가 책을보면서 그림판 어플 소스를 작성 중인데

도전과제 중 그렸던 그림을 초기화하는 기능을 도무지 찾아봐도 모르겠어서 질문을 드립니다. 

DrawView.java

public class DrawView extends View {
    private Paint paint = new Paint();
    private Path path = new Path();
    private int paintColor = 0xFF000000;
    private Paint canvasPaint;
    private Canvas drawCanvas;
    private Bitmap canvasBitmap;
    private LinearLayout Lin;

    public DrawView(Context context, AttributeSet attrs) {
        super(context, attrs);
        paint.setAntiAlias(true);
        paint.setStrokeWidth(10f);
        paint.setColor(paintColor);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
    }
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        drawCanvas = new Canvas(canvasBitmap);
        canvasPaint = new Paint(Paint.DITHER_FLAG);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
        canvas.drawPath(path, paint);
    }
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float touchX = event.getX();
        float touchY = event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                path.moveTo(touchX, touchY);
                break;
            case MotionEvent.ACTION_MOVE:
                path.lineTo(touchX, touchY);
                break;
            case MotionEvent.ACTION_UP:
                drawCanvas.drawPath(path, paint);
                path.reset();
                break;
            default:
                return false;
        }
        invalidate();
        return true;
    }

    public void setColor(String newColor) {
        invalidate();
        paintColor = Color.parseColor(newColor);
        paint.setColor(paintColor);
    }
}

Mainactivity.java

public class MainActivity extends AppCompatActivity {
    private DrawView drawView;
    private ImageButton currPaint;

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

        drawView = (DrawView) findViewById(R.id.drawing);
        LinearLayout paintLayout = (LinearLayout) findViewById(R.id.paint_colors);
        currPaint = (ImageButton) paintLayout.getChildAt(0);
    }

    public void clicked(View view) {
        if (view != currPaint) {
            String color = view.getTag().toString();
            drawView.setColor(color);
            currPaint = (ImageButton) view;
        }
    }
}