How to create method Eraser in class custom ImageView?

Question

• I have created a custom imageview class. Here I use the function

public void setNewImage(Bitmap alteredBitmap, Bitmap bmp, float paintSize, int paintColor)

in which alteredBitmap is a bitmap that does not contain an image, bmp is a bitmap that contains an image to initialize Paint and Canvas. Then i will use void onTouch() to draw on the image.

• Problem: when I changed the mode to eraser mode using the void isDrawing(boolean b, int color, float size) function, it erased both the path and the bitmap drawn below.

• Desired result: I only want to delete the path, not the bitmap drawn below.

• Note: in this class I use void setImageBitmap(alteredBitmap); to assign images rather than using functions @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); }

This is my class:

public class DrawableImageView2 extends androidx.appcompat.widget.AppCompatImageView implements View.OnTouchListener, MultiTouchListener.OnMultiTouchListener {
 
   public DrawableImageView2(Context context, AttributeSet attrs,
                              int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        int action = event.getAction();

        switch (action) {
            case MotionEvent.ACTION_DOWN:
                downx = getPointerCoords(event)[0];//event.getX();
                downy = getPointerCoords(event)[1];//event.getY();
  
                if (isDrawing) {
                    
                    path.reset();
                    path.moveTo(downx, downy);
                } else {
                    path.reset();
                    path.moveTo(downx, downy);
                }
                break;
            case MotionEvent.ACTION_MOVE:
                upx = getPointerCoords(event)[0];//event.getX();
                upy = getPointerCoords(event)[1];//event.getY();


                    path.lineTo(upx, upy);
                    canvas.drawPath(path, paint);


                invalidate();
                downx = upx;
                downy = upy;

                break;
            case MotionEvent.ACTION_UP:
                upx = getPointerCoords(event)[0];//event.getX();
                upy = getPointerCoords(event)[1];//event.getY();

                if (isDrawing) {
                    undoList.add(new MapEntry<>(paint, path));

                    canvas.drawPath(path, paint);
                    path = new Path();
                } else {
                    path.lineTo(upx, upy);
                    canvas.drawPath(path, paint);
                }


                Log.d(TAG, "onTouch: ACTION_UP: upx = " + upx + " upy = " + upy);

                invalidate();
                break;
            case MotionEvent.ACTION_CANCEL:
                break;
            default:
                break;
        }
        return true;
    }


    public void setNewImage(Bitmap alteredBitmap, Bitmap bmp, float paintSize, int paintColor) {
        canvas = new Canvas(alteredBitmap);
        paint = new Paint();
        paint.setColor(paintColor);
        paint.setStrokeWidth(paintSize);
        paint.setAntiAlias(true);
        paint.setDither(true);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OVER));
        matrix = new Matrix();

        originalBitmap = bmp;
        canvas.drawBitmap(bmp, matrix, paint);

        setImageBitmap(alteredBitmap);

        Rect rect = getDrawable().getBounds();
        Log.d(TAG, "drawBorder: rect: " + rect);

    }


    final float[] getPointerCoords(MotionEvent e) {
        final int index = e.getActionIndex();
        final float[] coords = new float[]{e.getX(index), e.getY(index)};
        Matrix matrix = new Matrix();
        getImageMatrix().invert(matrix);
        matrix.postTranslate(getScrollX(), getScrollY());
        matrix.mapPoints(coords);
        return coords;
    }

   



    public void isDrawing(boolean b, int color, float size) {
        isDrawing = b;
        if (b) {
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OVER)); // Chuyển về chế độ vẽ bằng cách xóa Xfermode
            paint.setColor(color); // Thiết lập màu sắc cho chế độ vẽ
            paint.setStrokeWidth(size);
        } else {
            paint.setMaskFilter(null); // Xóa MaskFilter
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); // Chuyển sang chế độ xóa
            paint.setAntiAlias(true);
        }
    }

    public void setOptionPaint(int mValue, float mSize) {
        paint = new Paint();
        paint.setColor(mValue);
        paint.setStrokeWidth(mSize);
        paint.setAntiAlias(true);
        paint.setDither(true);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DARKEN));

    }
}