一、Player Settings 设置
Player Settings>Player>Other Settings> Android > Write Permission > External (SDCard).

二、代码

using System.Collections;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
using UnityEngine.Android;
using System;
using UnityEngine.UI;
public class VideoPlayManager : MonoBehaviour
{private void Awake(){}void Start(){SetAndroid();}private void SetAndroid(){
#if UNITY_ANDROID// 控制音频和视频的权限，在Android设备上需要申请权限// Permission.RequestUserPermission(Permission.ExternalStorageRead);// Permission.RequestUserPermission(Permission.ExternalStorageWrite);if (!Permission.HasUserAuthorizedPermission(Permission.ExternalStorageRead)){Permission.RequestUserPermission(Permission.ExternalStorageRead);}//请求 写入外部存储（如 SD 卡）的权限       if (!Permission.HasUserAuthorizedPermission(Permission.ExternalStorageWrite)){Permission.RequestUserPermission(Permission.ExternalStorageWrite);}
#endif}
}

三、修改AndroidManifest
打开AndroidManifest
Player Settings>Player>Other Settings> Android >Publishing Settings> Build>Custom Main Manifest

在Assets\Plugins\Android\AndroidManifest打开AndroidManifest添加权限代码

	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" tools:remove="android:maxSdkVersion" /><uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" tools:remove="android:maxSdkVersion" />