From android docs, the GradientDrawable.setCornerRadii (float[] radii) method:
Specifies radii for each of the 4 corners. For each corner, the array contains 2 values
Why are there 2 values for each corner? What is the meaning of two values for a single corner?
One value is for the X_radius the other for the Y_Radius. If they are equal you'll get an even radius. If they are different it will be distorted in one dimension or the other (look more like a logarithmic curve for example).