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AlphaNext/CppStruct_to_Android_JNI

Last active July 10, 2020 12:57
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Android_JNI
Raw
cpp_struct.hpp
struct PassResult{
int errorID;
string errorMsg;
float* pointArray;
int width;
int height;
int dataLength;
// imageArray could be seemed as a opencv cv::Mat
unsigned char* imageArray;
};
Raw
cpp_struct_jni.cpp
// PassResult: doc_out is the result which will be passed to java part
// https://stackoverflow.com/questions/8541568/c-and-jni-how-to-pass-an-array-into-a-jfloatarray
// http://stackz.ru/en/1610045/how-to-return-an-array-from-jni-to-java
// 转移存储结果
jobject docResult_array = NULL;
jclass objectClass = env->FindClass("com/image/demo/PassResult");
jmethodID construction_id = env->GetMethodID(objectClass, "<init>", "()V");
jfieldID field_PointBoxs = env->GetFieldID(objectClass, "pointArray", "[F");
jfieldID field_errorMsg = env->GetFieldID(objectClass, "errorMsg", "Ljava/lang/String;");
jfieldID field_errorID = env->GetFieldID(objectClass, "errorID", "I");
jfieldID field_width = env->GetFieldID(objectClass, "width", "I");
jfieldID field_height = env->GetFieldID(objectClass, "width", "I");
jfieldID field_length = env->GetFieldID(objectClass, "dataLength", "I");
jfieldID field_image = env->GetFieldID(objectClass, "imageArray", "[B");
docResult_array = env->NewObject(objectClass, construction_id);
// points part
jfloatArray pointsArray = env->NewFloatArray(8);
env->SetFloatArrayRegion(pointsArray, 0, 8, (const jfloat*) doc_out.pointArray);
env->SetObjectField(docResult_array, field_PointBoxs, pointsArray);
env->DeleteLocalRef(pointsArray);
env->SetIntField(docResult_array, field_errorID, doc_out.errorID);
// https://stackoverflow.com/questions/11621449/send-c-string-to-java-via-jni/24564937
// https://juejin.im/post/5afd694ef265da0b96727210
// int byteCount = doc_out.errorMsg.length();
// const jbyte* pNativeMsg = reinterpret_cast<const jbyte*>(doc_out.errorMsg.c_str());
// jbyteArray Msgbytes = env->NewByteArray(byteCount);
// env->SetByteArrayRegion(Msgbytes, 0, byteCount, pNativeMsg);
jstring Msg = env->NewStringUTF(doc_out.errorMsg.c_str());
env->SetObjectField(docResult_array, field_errorMsg, Msg);
env->DeleteLocalRef(Msg);
// return image part
env->SetIntField(docResult_array, field_height, doc_out.height);
env->SetIntField(docResult_array, field_width, doc_out.width);
env->SetIntField(docResult_array, field_length, doc_out.dataLength);
jbyteArray imageArray = env->NewByteArray(doc_out.dataLength);
env->SetByteArrayRegion(imageArray, 0, doc_out.dataLength, (jbyte*)doc_out.pointArray);
env->SetObjectField(docResult_array, field_image, imageArray);
env->DeleteLocalRef(imageArray);
free(buf);
return docResult_array;
Raw
CppStruct_to_Android_JNI
pass cpp struct result to android part using android JNI
Raw
struct_to_java.java
package com.image.demo;
public class PassResult{
int errorID;
String errorMsg;
float[] pointArray;
int width;
int height;
int dataLength;
byte[] imageArray;
DetectResult(){}
};
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