given that you don't know that much about OpenGL, I would say the easiest way for you to achieve this is with a simple texture.
I will give you three possible implementation ideas ordered from easy to "hard"
- Just create a gradient texture of the size you need in your prefered image application, then use the standard libgdx sprite batcher
- create an Image in your app of the size 1x2 with the two colors you like to have a gradient with. Upload this image as a texture and set the filtering option to linear. then use it as before, this approach gives you the nice benefit to work perfect with every background size
- If you know a bit OpenGL you could just create an Quad with the Color-Attribute set to the colors you want and let OpenGL interpolate them for you.
first of all thanks for the great answer!
I really don't know nothing about opengl but i'm interessed in it, can you suggest me some tutorial or other? i want to implement the 3th way, there is some explaination about it?