using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
     void OnGUI() {
         string[] names = QualitySettings.names;
         GUILayout.BeginVertical();
         int i = 0;
         while (i < names.Length) {
             if (GUILayout.Button(names[i]))
                 QualitySettings.SetQualityLevel(i, true);
              
             i++;
         }
         GUILayout.EndVertical();
     }
}