Java JNI 将本机无符号字符数组转换为 jbyte 数组
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JNI converting native unsigned char arry to jbyte array
提问by Roy08
í have JNI function that needs to return a jbyte array. The array contains byte data of a c struct with data. But i get an error when i pass the data form the unsinged char array to the jbyte array.
í 有需要返回 jbyte 数组的 JNI 函数。该数组包含带有数据的 ac 结构的字节数据。但是当我将数据从 unsinged char 数组传递到 jbyte 数组时出现错误。
The C struct is defined as followed:
C 结构体定义如下：
// ObjectInfo struct definition
struct ObjectInfo {
int ObjectXCor;
int ObjectYCor;
int ObjectMass;
};
// ObjectInfo struct definition
struct SensorDataStruct{
int PingData;
int IRData;
int ForceData;
int CompassData;
};
// ObjectInfo struct definition
union PackedSend{
struct CommStruct{
ObjectInfo VisionData;
SensorDataStruct SensorData;
} CommData;
unsigned char bytes[28];
}SendData;
The JNI method is defined as followed:
JNI方法定义如下：
JNIEXPORT jbyteArray JNICALL Java_com_example_communicationmodule_MainActivity_Convert(
JNIEnv *env, jobject,
jint var1,
jint var2,
jint var3,
jint var4,
jint var5,
jint var6,
jint var7)
{
// Array to fill with data
jbyteArray Array;
// Init java byte array
Array = env->NewByteArray(28);
SendData.CommData.SensorData.PingData = var1;
SendData.CommData.SensorData.IRData = var2;
SendData.CommData.SensorData.ForceData = var3;
SendData.CommData.SensorData.CompassData = var4;
SendData.CommData.VisionData.ObjectXCor = var5;
SendData.CommData.VisionData.ObjectYCor = var6;
SendData.CommData.VisionData.ObjectMass = var7;
//Put the native unsigned chars in the java byte array
for(int Index=0; Index < 28; Index++){
Array[Index] = SendData.bytes[Index];
}
// Return java array
return Array;
}
The error that i get is: jni/HelperFunctions.cpp:44:38: error: no match for 'operator=' in '*(Array + ((unsigned int)Index)) = SendData.PackedSend::bytes[Index]'
我得到的错误是：jni/HelperFunctions.cpp:44:38: error: no match for 'operator=' in '*(Array + ((unsigned int)Index)) = SendData.PackedSend::bytes[Index] '
My question is wat is the proper way to convert the native unsigned char array to the a jbyte array? Doe anyboy have a suggestion? All tips are welcome!
我的问题是 wat 是将本机无符号字符数组转换为 jbyte 数组的正确方法吗？有大佬给点建议吗？欢迎所有提示！
Update
更新
After casting to (jbyte) i get the the following errors: jni/HelperFunctions.cpp:54:46: error: no match for 'operator=' in '*(Array + ((unsigned int)Index)) = (jbyte)SendData.PackedSend::bytes[Index]' jni/HelperFunctions.cpp:54:46: note: candidate is: C:/android-ndk-r9/platforms/android-8/arch-arm/usr/include/jni.h:66:7: note: _jbyteArray& _jbyteArray::operator=(const _jbyteArray&)
转换为 (jbyte) 后，我收到以下错误：jni/HelperFunctions.cpp:54:46: error: no match for 'operator=' in '*(Array + ((unsigned int)Index)) = (jbyte) SendData.PackedSend::bytes[Index]' jni/HelperFunctions.cpp:54:46：注意：候选是：C:/android-ndk-r9/platforms/android-8/arch-arm/usr/include/jni。 h:66:7: 注意：_jbyteArray& _jbyteArray::operator=(const _jbyteArray&)
The casting code is as followed:
铸造代码如下：
//Put the native unsigned chars in the java byte array
for(int Index=0; Index < 28; Index++){
Array[Index] = (jbyte) SendData.bytes[Index];
}
Does anybody have a idea or suggestion? Everthing is welcome!
有人有想法或建议吗？什么都欢迎！
采纳答案by afpro
env->SetByteArrayRegion(Array, 0, 28, (jbyte*)SendData.bytes)
