ControllerManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// <summary>
// Splash screen.cs
// Bj Thomas
// 8/15/2018
// <summary>

public class ControllerManager : MonoBehaviour {

    public Texture2D _controllerNotDetected;                                   //Creates slot in inspector to assign controller not detected warning test

    public bool _pS4Controller;                                               //Creates bool for when a ps4 controller is connected
    public bool _XboxController;                                              //Creates bool for when a xbox controller is connected
    public bool _controllerDetected;                                          //Creates bool for when a controller is connected

    public static bool _startUpFinished;                                      //Creates bool for when start up is finished

    private void Awake(){
        _pS4Controller = false;                                              //PS4 controller is false on awake
        _XboxController = false;                                             //Xbox controller is false on awake
        _controllerDetected = false;                                         //controller is false on awake
    }

    // Use this for initialization
    void Start () {
        DontDestroyOnLoad(this);                                           //Don't destroy this gameobject when loading a new scene
	}

	// Update is called once per frame
	void Update () {

	}

    void LateUpdate(){
        string[] _joyStickNames = Input.GetJoystickNames();               //_joyStickNames equals get joystick names from inbuilt input

        for(int _js = 0; _js < _joyStickNames.Length; _js++){           //increase counter _js based on joystick names length
            if(_joyStickNames [_js].Length == 19){                       //if joystick name equals code 19
                _pS4Controller = true;                                   //set ps4 controller to true
                _controllerDetected = true;                              //set a controller detected to true
            }

            if(_joyStickNames [_js].Length == 33){                       //if joystick name equals code 33
                _XboxController = true;                                   //set xbox controller to true
                _controllerDetected = true;                              //set a controller detected to true
            }

             if (_joyStickNames[_js].Length != 0)                         //if joystick names does not equal 0
                    return;                                               //then do nothing and return

                if (string.IsNullOrEmpty(_joyStickNames[_js]))           //if string is null/empty ie no controller detected
                    _controllerDetected = false;                         //then set controller detected to false
        }
    }

    private void OnGUE(){
        if (_startUpFinished == false)                                   //if start up finished equals false
            return;                                                      //then do nothing and return

        if(_controllerDetected == true)                                 //if controller detected equals true
            return;                                                     //then do nothing and return

        if (_controllerDetected == false)                              //if controller detected equals false
            GUI.DrawTexture(new Rect(                                  //Draw texture
                0, 0,                                                  //at this position
                Screen.width, Screen.height),                         //by these dimensions
                _controllerNotDetected);                              //draw the controller not detected texture
    }
}