unity+android：大版本更新安装下好的apk，兼容任意安卓5.0,7.0,8.0版本

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <root-path name="root" path="" />
    <external-path name="external_storage_root" path="." />
    <external-path name="external_storage_download" path="Download" />
</paths>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.luoyikun.installapk">

<uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES"/>

    <application
        android:allowBackup="true">

    <provider
        android:name="android.support.v4.content.FileProvider"
        android:authorities="cn.com.woong.resultbackdemo.fileProvider"
        android:exported="false"
        android:grantUriPermissions="true"
        tools:ignore="WrongManifestParent">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/file_paths"/>
    </provider>

    </application>
</manifest>

package com.luoyikun.installapk;

import android.app.Activity;
import android.app.Fragment;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.content.FileProvider;

import com.unity3d.player.UnityPlayer;

import java.io.File;

public class InstallApk extends Fragment {
    private static final String TAG = "InstallApk";

    String m_gameObjectName;
    String m_funcName;

    private Context unityContext;
    private Activity unityActivity;


    public void UnityFunc(String gameObjectName, String funcName)
    {
        m_gameObjectName = gameObjectName;
        m_funcName = funcName;
    }

    public static InstallApk GetInstanceByAndroid(Activity activity,Context context)
    {
        if (Instance == null)
        {
            Instance = new InstallApk();
            Instance.unityActivity = activity;
            Instance.unityContext = context;

            activity.getFragmentManager().beginTransaction().add(Instance, TAG).commit();
        }
        return Instance;
    }

    private static InstallApk Instance = null;

    public static InstallApk GetInstance()
    {
        if(Instance == null)
        {
            Instance = new InstallApk();
            Instance.unityActivity = UnityPlayer.currentActivity;
            Instance.unityContext = Instance.unityActivity.getBaseContext();
            UnityPlayer.currentActivity.getFragmentManager().beginTransaction().add(Instance, TAG).commit();

        }
        return Instance;
    }

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);  // 这一句很重要，保存对该Fragment的引用，防止在旋转屏幕等操作时时丢失引用（Fragment隶属于Activity）
    }

    // 调用 Unity
    // gameObjectName 为接受消息的Unity 中 GameObject 的名字
    // functionName   为接受消息的GameObject 挂载 C# 脚本中的函数名
    // _content       为发送给Unity 的内容
    public void CallUnity( String _content)
    {
        UnityPlayer.UnitySendMessage(m_gameObjectName, m_funcName, _content);
    }

    public void installApp(String path){
        File pFile = new File(path);
        if (null == pFile)
            return;
        if (!pFile.exists())
            return;
        Intent _Intent = new Intent();
        _Intent.setAction(Intent.ACTION_VIEW);
        Uri _uri;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            _Intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
            _uri = FileProvider.getUriForFile(unityContext, unityContext.getPackageName() + ".fileProvider", pFile);
        }else {
            _uri = Uri.fromFile(pFile);
            _Intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        }
        _Intent.setDataAndType(_uri, "application/vnd.android.package-archive");
        unityContext.startActivity(_Intent);
    }

}

    public static void InstallApk(string path)
    {
        AndroidJavaObject pluginObject = new AndroidJavaClass("com.luoyikun.installapk.InstallApk").CallStatic<AndroidJavaObject>("GetInstance");
        pluginObject.Call("installApp", path);
    }

            string path = dataPath + apkName;
            path = path.Replace(":", "");
            AndroidFunc.InstallApk(path);