Random Number Generator for iOS and Android

I'm building an app for both Android and iOS. In the app, I need to generate psuedorandom numbers that match in both the iOS version and the Android version. I'be seen many implementations of custom random number generators but some are in C++ or PHP... I only know Java and Swift. Can someone help me and point me to a random generator that would work on both iOS and Android or can someone tell em the steps on how to create my own random number generator?