Android: adding a bitmap texture to a non rectangular item

I have a widget which looks like this:

Every cone is a "touchable element". Now I want to put a bitmap texture above each cone. However, bitmap images are all rectangular, so a bitmap texture above one cone would interfere with the bitmap texture above another cone.

I'm wondering what is the best solution to this approach. Should I just create an image which fits (as a rectangle) exactly above the cone and make the non used areas transparent?

A second question is, how do bitmap textures work with stretching? Because this whole circle draws itself to fit the whole screen size, while bitmap textures are pretty much one size.

Offhand I can't think of a better way to draw bitmaps over those cones than your own suggestion of using transparent zones.

However, I can help with your second question as stretching bitmaps is not hard. You've got a few options in the Canvas class. For example:

canvas.save();
canvas.scale(xRatio, yRatio);
canvas.drawBitmap(....);
canvas.restore();

You can also use a Matrix, using matrix.postScale(xRatio, yRatio), to then generate either a larger bitmap and draw it normally, or pass the matrix in to your canvas.drawBitmap(....) command to make it scale while it draws.

All of these methods assume you have access to the drawing canvas itself. If you are using a view, you can subclass it and override the onDraw(Canvas canvas) method to grab the canvas before it starts drawing it. If you're using a SurfaceHolder, then you should already know how to get the canvas.

Edit: I forgot the third method I was going to describe. You can use the canvas.drawBitmap(bitmap, srcRect, dstRect, paint) to also make the canvas scale the bitmap to fit the destination rectangle. In short, there are lots of methods to do this - pick the one that's easiest based on your application!