NDK，在JNI层使用AssetManager读取文件

NDK，二进制文件数据读取，在JNI层，通过AAssetManager读取asset内部的资源：

1，首先传个AssetManager到JNI层；
AssetManager assetManager = getAssets();
2，将你的数据放到assets文件夹中，然后和对应的文件名字一起，通过JNI Native函数传递到JNI:
readFromAssets(assetManager, "yourdata.bin");
3，然后在JNI的Native实现函数中读取：(也可直接在对应的C函数调用，调用方法类似fopen，fread)

JNIEXPORT  jstring JNICALL Java_com_lib_MyLib_readFromAssets(JNIEnv* env, jclass clazz,
jobject assetManager, jstring dataFileName) {

AAssetManager* mManeger = AAssetManager_fromJava(env, assetManager);
jboolean iscopy;
const char *dataFile = env->GetStringUTFChars(dataFileName, &iscopy);

int c = dataRead(mManeger, dataFile);  //call the C function

env->ReleaseStringUTFChars(dataFileName, dataFile);

jstring resultStr;
resultStr = env->NewStringUTF("success");
return resultStr;
}
int dataRead(AAssetManager* mManeger, const char *dataFile){

AAsset* dataAsset = AAssetManager_open(mManeger, dataFile, AASSET_MODE_UNKNOWN);//get file read AAsset
off_t dataBufferSize = AAsset_getLength(dataAsset);

int num = dataBufferSize/sizeof(float);

//float *data = (float*) malloc(num * sizeof(float));  //allocate the data, the same with the later line
float *data = (float*) malloc(dataBufferSize);

int numBytesRead = AAsset_read(dataAsset, data, dataBufferSize);  //begin to read data once time
　　//note: numBytesRead is the total bytes, then num = dataBufferSize/sizeof(float) = numBytesRead/sizeof(float)

if (numBytesRead<0) {
LOGI("read data failed");
}
else{
LOGI("numBytesRead: %d", numBytesRead);
}

//int numBytesRead;
//for (int i = 0; i < num; i++) {
//    numBytesRead = AAsset_read(dataAsset, (char*) (&data[i]), sizeof(float));   //or read the data one by one
//    if (numBytesRead<0) {
//        LOGI("read data failed");
//    }
//    else{
//        LOGI("numBytesRead: %d", numBytesRead);
//    }
//}

AAsset_close(dataAsset);
free(data);

return 0;
}