How can I get the bitmap of the canvas I get in onDraw?

While there is no getBitmap() function for a canvas, since you are making a custom view, what you can do instead is write a function like this inside your view class.

public Bitmap get(){
   return this.getDrawingCache();
}

This returns the Bitmap of the view, but it is important that in all your constructors you add this,

this.setDrawingCacheEnabled(true);

Otherwise getDrawingCache will return null

There is no way to extract the Bitmap out of a Canvas. The only way you can access it is to pass it yourself when creating the canvas like this new Canvas(myBitmap) and keep the reference.

EDIT2: see @Alex comment blow - the approach of passing a Bitmap to the Canvas does not seem to work for more recent versions of Android.

EDIT : If you don't create the Canvas yourself, you could create a screen-sized Bitmap (or whatever size you need) and then pass it to the Canvas in onDraw calls like this: canvas.setBitmap(myBitmap).

I found out that Canvas has a setBitmap function, but not a getBitmap one. It's strange, but anyway, it enables me to create the bitmap myself and pass it to the canvas, retaining the reference.