I used this code given by the official site of unity [URL]
using UnityEngine;
using System.Collections;
public class animFov : MonoBehaviour
{
void Start()
{
AnimationClip fovc = new AnimationClip();
AnimationCurve curve = AnimationCurve.Linear(0.0f, 60.0f, 10.0f, 90.0f);
fovc.SetCurve("", typeof(Camera), "field of view", curve);
fovc.legacy = true;
GetComponent<Animation>().AddClip(fovc, "animfov");
GetComponent<Animation>().Play("animfov");
}
}
It is working in the editor but not in an android device.