DexClassLoader - invoke method with parameter

Question

I have met some tutorials on the web, which are invoking simple methods and all I need is to invoke method "startDownload" which accepts Context as a parameter. I am now calling it:

Class<?> loaded = cl.loadClass("com.test.someclass");
Method m = loaded.getDeclaredMethod("startDownload", null);
m.invoke(this, null); 

where c1 is DexClassLoader. But no success. I am getting error of NoSuchMethodException, I know I have to add parametres somewhere, but don't know where... any advices?

Thanks