Assuming you want to load on obj model you need to:
1 create an array of object3d
2 load that obj into an input stream
3 load the mtl in another input stream
4 inizialize array with the right function
an example of code here:
public Object3D[] model;
public AssetManager mngr;
public InputStream objStream = null;
public InputStream mtlStream = null;
//into your constructor
public yourconstructor()
{
.
.
.
mngr = instanceofactivity.getAssets();
try {
objStream = mngr.open("file.obj");
} catch (IOException e) {
e.printStackTrace();
}
try {
mtlStream = mngr.open("file.mtl");
} catch (IOException e) {
e.printStackTrace();
}
model = Loader.loadOBJ(objStream, mtlStream, x);
.
.
.
}
In this case i put my file into the assets folder.
Hope can be helpful!