Leave the method onDraw clean

[ppamorim]

Hi Harjot.

I would like to say to leave this method clean, try to move any instantiation of values or heavy operations to out of the scope of this element. You can reduce the CPU and battery usage doing this. This method was build just to read values and draw on canvas.

Of course, this is not a problem:

void onDraw(Canvas canvas) {
  canvas.draw(x + diff, y + diff, paint)
}

You can do it, the performance will be not affected when the calculation of values is not that heavy.
To create some values based on the bounds of its view, you can use the method onLayout(...).