Unity RGB Split变成黑屏android

Question

Shader "Custom/ChromaticAberration" {
    Properties {
        _MainTex ("Base (RGB)", 2D) = "white" {}
    }
    SubShader
    {
        Pass
        {
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag
            #pragma fragmentoption ARB_precision_hint_fastest
            #include "UnityCG.cginc"

            uniform sampler2D _MainTex;
            uniform float _AberrationOffset;

            float4 frag(v2f_img i) : COLOR
            {

                float2 coords = i.uv.xy;

                _AberrationOffset /= 300.0f;

                //Red Channel
                float4 red = tex2D(_MainTex , float2(coords.x - _AberrationOffset, coords.y));
                //Green Channel
                float4 green = tex2D(_MainTex, coords.xy );
                //Blue Channel
                float4 blue = tex2D(_MainTex, float2(coords.x + _AberrationOffset, coords.y));

                float4 finalColor = float4(red.r, green.g, blue.b, 1.0f);
                return finalColor;
            }
            ENDCG
        }
    }
}

这是我的RGB拆分着色器 我正在android中对其进行测试。问题是当方向改变时，屏幕变黑。为什么？

我的脚本如下：

using UnityEngine;

namespace _MyScripts
{
    [ExecuteInEditMode]
    [RequireComponent(typeof(Camera))]
    public class ChromaticAberration : MonoBehaviour
    {
        public Shader shader;
        private float ChromaticAberrationOffset = 1.0f;
        public float ChromaticAberrationMaxOffset = 1.0f;
        private Material _material;
        private float _flickerTime = 0.5f;
        private float flicker;

        private void Start()
        {
            _material = new Material(shader);
        }

        private void OnRenderImage(RenderTexture sourceTexture, RenderTexture destTexture)
        {
            flicker += Time.deltaTime;
            if (flicker > _flickerTime)
            {
                flicker = 0;
                _flickerTime = Random.value;
            }

            ChromaticAberrationOffset = flicker * ChromaticAberrationMaxOffset; //(Mathf.PingPong(Time.time, 1) * ChromaticAberrationMaxOffset) - ChromaticAberrationMaxOffset / 2;
            _material.SetFloat("_AberrationOffset", ChromaticAberrationOffset);

            Graphics.Blit(sourceTexture, destTexture, _material);
        }

    }
}