Unity使用native读取streamingasset里文件

需求是，使用native方式，读取apk包里的lua代码，读进c#，做解密

一准备unity工程

public class GameMain : MonoBehaviour {
    public const string libName = "TGNative";
    public Text content;
    [DllImport(libName)]
    public static extern int ReadAsset(string fileName, byte[] buffer, int size);
    // Use this for initialization
    void Start () {
        Debug.Log("Start################");
        var size =  * ;
        var buffer = new byte[size];
        var num = ReadAsset("test.txt", buffer, size);
        Debug.Log("ReadAsset ################"+ num);
        if (num >  )
        {
            Debug.Log("Read succ");
            var str = UTF8Encoding.UTF8.GetString(buffer,, num);
            content.text = str;
            Debug.Log(str);
        }
    }

    // Update is called once per frame
    void Update () {

    }
}

二unity导出android工程

注意playersetting 里设置包名

三android studio 打开导出的工程

四 添加代码

UnityPlayerActivity里

新增TGNative.java,增加native方法

public native static void InitAssetManager( AssetManager am );

五使用javah生成头文件

javah -d jni -classpath D:\work\ndkread\AssetMgr\AndroidAssetMgr\NativeAssetMgr\build\intermediates\classes\debug;C:\Users\Topjoy\AppData\Local\Android\Sdk\platforms\android-\android.jar com.topjoy.JniTest.TGNative

六新增NativeUtil.c和Android.mk Applicatioin,mk ,build.bat

build.bat

ndk-build NDK_PROJECT_PATH=. NDK_APPLICATION_MK=Application.mk APP_BUILD_SCRIPT=Android.mk APP_PLATFORM=android-

NativeUtil.c

//
// Created by Topjoy on 2018/12/7.
//
#include <jni.h>
#include <assert.h>
#include <string.h>
#include <malloc.h>
#include <android/asset_manager.h>
#include <android/asset_manager_jni.h>
#include <android/log.h>
#include "com_topjoy_JniTest_TGNative.h"

#define LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,"Unity",__VA_ARGS__) // 定义LOGD类型
#define LOGW(...)  __android_log_print(ANDROID_LOG_WARN,"Unity",__VA_ARGS__)

static AAssetManager* mgr = NULL;
JNIEXPORT void JNICALL Java_com_topjoy_JniTest_TGNative_InitAssetManager
  (JNIEnv * env, jclass tis, jobject assetmanager){
    mgr = AAssetManager_fromJava(env, assetmanager);
}

extern int ReadAsset(char* fileName, char* buffer, int size)
{
    if(mgr == NULL)
    {
        LOGW( "mgr is null" );
        return ;
    }
    AAsset* asset = AAssetManager_open(mgr, fileName, AASSET_MODE_UNKNOWN);
    if( asset == NULL )
    {
        LOGW( "open asset (%s) failed" , fileName);
        return ;
    }
    int len = (int)AAsset_getLength(asset);
    if(len >size)
    {
        LOGW("Buffer less than length");
        return ;
    }
    int nread = AAsset_read(asset, buffer, size);
    AAsset_close(asset);
    if(nread != len)
    {
        LOGW("Read num %d not equal length %d", nread, len);
        return ;
    }
    return nread;
}

七运行build.bat 生成so文件

八使用jar命令生成jar文件

@echo off
set app=%cd%
set debugp=%cd%\build\intermediates\classes\debug
set classp=%debugp%\com\topjoy\JniTest
cd %classp%

pause
for %%x in (*) do (
    if not "%%x"=="UnityPlayerActivity.class" (
        if not "%%x"=="TGNative.class" (
        del %%x
        )
    )
)

cd %debugp%
jar  -cvf  class.jar com

move class.jar %app%\

九把生成的class.jar 和so文件拷贝进unity工程

十生成apk，拷贝进木木测试

成功！