最简单的就是用androidStudio 进行编辑，打个aar 包，在Unity中调用方法，很便捷

以下内容均转载Unity论坛，Android API24版本下可用，android API 24以上版本未进行测试

void Start()

{

    StartCoroutine(downLoadFromServer());

}

IEnumerator downLoadFromServer()

{

    string url = "http://apkdl.androidapp.baidu.com/public/uploads/store_2/f/f/a/ffaca37aaaa481003d74725273c98122.apk?xcode=854e44a4b7e568a02e713d7b0af430a9136d9c32afca4339&filename=unity-remote-4.apk";

    string savePath = Path.Combine(Application.persistentDataPath, "data");

    savePath = Path.Combine(savePath, "AntiOvr.apk");

    Dictionary<string, string> header = new Dictionary<string, string>();

    string userAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36";

    header.Add("User-Agent", userAgent);

    WWW www = new WWW(url, null, header);

    while (!www.isDone)

    {

        //Must yield below/wait for a frame

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Stat: " + www.progress;

        yield return null;

    }

    byte[] yourBytes = www.bytes;

    GameObject.Find("TextDebug").GetComponent<Text>().text = "Done downloading. Size: " + yourBytes.Length;

    //Create Directory if it does not exist

    if (!Directory.Exists(Path.GetDirectoryName(savePath)))

    {

        Directory.CreateDirectory(Path.GetDirectoryName(savePath));

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Created Dir";

    }

    try

    {

        //Now Save it

        System.IO.File.WriteAllBytes(savePath, yourBytes);

        Debug.Log("Saved Data to: " + savePath.Replace("/", "\\"));

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Saved Data";

    }

    catch (Exception e)

    {

        Debug.LogWarning("Failed To Save Data to: " + savePath.Replace("/", "\\"));

        Debug.LogWarning("Error: " + e.Message);

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Error Saving Data";

    }

    //Install APK

    installApp(savePath);

}

public bool installApp(string apkPath)

{

    try

    {

        AndroidJavaClass intentObj = new AndroidJavaClass("android.content.Intent");

        string ACTION_VIEW = intentObj.GetStatic<string>("ACTION_VIEW");

        int FLAG_ACTIVITY_NEW_TASK = intentObj.GetStatic<int>("FLAG_ACTIVITY_NEW_TASK");

        AndroidJavaObject intent = new AndroidJavaObject("android.content.Intent", ACTION_VIEW);

        AndroidJavaObject fileObj = new AndroidJavaObject("java.io.File", apkPath);

        AndroidJavaClass uriObj = new AndroidJavaClass("android.net.Uri");

        AndroidJavaObject uri = uriObj.CallStatic<AndroidJavaObject>("fromFile", fileObj);

        intent.Call<AndroidJavaObject>("setDataAndType", uri, "application/vnd.android.package-archive");

        intent.Call<AndroidJavaObject>("addFlags", FLAG_ACTIVITY_NEW_TASK);

        intent.Call<AndroidJavaObject>("setClassName", "com.android.packageinstaller", "com.android.packageinstaller.PackageInstallerActivity");

        AndroidJavaClass unityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer");

        AndroidJavaObject currentActivity = unityPlayer.GetStatic<AndroidJavaObject>("currentActivity");

        currentActivity.Call("startActivity", intent);

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Success";

        return true;

    }

    catch (System.Exception e)

    {

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Error: " + e.Message;

        return false;

    }

}

//For API 24 and above

private bool installApp(string apkPath)

{

    bool success = true;

    GameObject.Find("TextDebug").GetComponent<Text>().text = "Installing App";

    try

    {

        //Get Activity then Context

        AndroidJavaClass unityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer");

        AndroidJavaObject currentActivity = unityPlayer.GetStatic<AndroidJavaObject>("currentActivity");

        AndroidJavaObject unityContext = currentActivity.Call<AndroidJavaObject>("getApplicationContext");

        //Get the package Name

        string packageName = unityContext.Call<string>("getPackageName");

        string authority = packageName + ".fileprovider";

        AndroidJavaClass intentObj = new AndroidJavaClass("android.content.Intent");

        string ACTION_VIEW = intentObj.GetStatic<string>("ACTION_VIEW");

        AndroidJavaObject intent = new AndroidJavaObject("android.content.Intent", ACTION_VIEW);

        int FLAG_ACTIVITY_NEW_TASK = intentObj.GetStatic<int>("FLAG_ACTIVITY_NEW_TASK");

        int FLAG_GRANT_READ_URI_PERMISSION = intentObj.GetStatic<int>("FLAG_GRANT_READ_URI_PERMISSION");

        //File fileObj = new File(String pathname);

        AndroidJavaObject fileObj = new AndroidJavaObject("java.io.File", apkPath);

        //FileProvider object that will be used to call it static function

        AndroidJavaClass fileProvider = new AndroidJavaClass("android.support.v4.content.FileProvider");

        //getUriForFile(Context context, String authority, File file)

        AndroidJavaObject uri = fileProvider.CallStatic<AndroidJavaObject>("getUriForFile", unityContext, authority, fileObj);

        intent.Call<AndroidJavaObject>("setDataAndType", uri, "application/vnd.android.package-archive");

        intent.Call<AndroidJavaObject>("addFlags", FLAG_ACTIVITY_NEW_TASK);

        intent.Call<AndroidJavaObject>("addFlags", FLAG_GRANT_READ_URI_PERMISSION);

        currentActivity.Call("startActivity", intent);

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Success";

    }

    catch (System.Exception e)

    {

        GameObject.Find("TextDebug").GetComponent<Text>().text = "Error: " + e.Message;

        success = false;

    }

    return success;

}