public class Utils {
        public static void fullscreen(){
            UnityPlayer.currentActivity.getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_IMMERSIVE | View.SYSTEM_UI_FLAG_FULLSCREEN | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
        }

        public static void toast(String text){
            Toast.makeText(UnityPlayer.currentActivity, text, Toast.LENGTH_SHORT).show();
        }

        public static boolean test1(int code,String[] text){
            return true;
        }

        public static int test2(){
            return 1;
        }
    }

using UnityEngine;

public class Utils : MonoBehaviour {
    private void Init(){
        #if UNITY_ANDROID && !UNITY_EDITOR
        javaClass = new AndroidJavaClass("com.unity.plugin.Utils");
        #endif
    }

    void Awake () {
        Init();
        Fullscreen ();
    }

    public void Fullscreen(){
        #if UNITY_ANDROID && !UNITY_EDITOR
        if (javaClass != null)
        javaClass.CallStatic ("fullscreen");
        #endif
    }

    public void Toast(string text){
        #if UNITY_ANDROID && !UNITY_EDITOR
        if (javaClass != null)
        javaClass.CallStatic ("toast",text);
        #endif
    }

    public bool Test1(int code,string[] text){
        #if UNITY_ANDROID && !UNITY_EDITOR
        if (javaClass != null)
        return javaClass.CallStatic<bool> ("test1",code,text);
        #endif
        return false;
    }

    public int Test2(){
        #if UNITY_ANDROID && !UNITY_EDITOR
        if (javaClass != null)
        return javaClass.CallStatic<int> ("test2");
        #endif
        return 0;
    }

    public void clickBtn1(){
        if (Test1 (11, new string[]{ "text" }))
            Toast ("true clickBtn1");
        else
            Toast ("false clickBtn1");
    }

    public void clickBtn2(){
        if (Test2 () == 1)
            Toast ("Равно 1 clickBtn2");
        else
            Toast ("Неравно clickBtn2");
    }

    public void clickBtn3(){
        Fullscreen ();
        Toast ("Fullscreen clickBtn3");
    }
}