Android : How do I undo a bitmap which has been drawn to a canvas?

I am dropping drawables on a canvas like markers, setting the final bitmap to an ImageView. How do I add an undo functionality where I can undo one drawable at a time? Please help.

This is my code:

Bitmap bitmap = ((BitmapDrawable) prescription.getDrawable()).getBitmap();

//Create a new image bitmap and attach a brand new canvas to it
Bitmap tempBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.RGB_565);

 Canvas tempCanvas = new Canvas(tempBitmap);

 //Draw the image bitmap into the canvas
 tempCanvas.drawBitmap(bitmap, 0, 0, null);

 Bitmap marker = BitmapFactory.decodeResource(getResources(), R.drawable.check);

 //Draw into the canvas
 tempCanvas.drawBitmap(marker, x, y, null);

 //Attach the canvas to the ImageView
 imageView.setImageDrawable(new BitmapDrawable(getResources(), tempBitmap));