Android-与JNI有关的问题

Question

static void convert(unsigned int &c, const float &temp1, const float &temp2, const float &temp3) {
    if ( (temp3 * 6) < 1) c = (unsigned int) ((temp2 + (temp1 - temp2) * 6 * temp3) * 100);

    else if ((temp3 * 2) < 1) c = (unsigned int) (temp1 * 100);

    else if ((temp3 * 3) < 2) c = (unsigned int) ((temp2 + (temp1 - temp2) * (.66666 - temp3) * 6) * 100);

    else c = (unsigned int) (temp2 * 100);

    return;
}

convert(r, temp1, temp2, temp3);

但是，当我使用命令行中的ndk-build命令编译它时，会出现以下错误：

Android NDK:APP_PLATFORM未设置。默认为最小支持版本Android-16。[arm64-v8a]编译:com_celik_abdullah_imageprocessingpart_processors_NativeImageProcessor<=com_celik_Abdullah_ImageProcessPart_ProcessPart_NativeImageProcessor.c jni/com_celik_Abdullah_ImageProcessPart_ProcessPart_NativeImageProcessor.c jni/com_celik_Abdullah_ImageProcessingPart_ProcessPart_ProcessPart_NativeImageProcessor.c const float&temp1,const float...^JNI/com_celik_abdullah_imageprocessingpart_processors_NativeImageProcessor.c:193:47:错误：参数名称省略静态空转换（无符号int&c,const float&temp1,const float...^JNI/com_celik_abdullah_imageprocessingpart_processors_NativeImageProcessor.c:194:11:如果((temp3*6)<1)c=（无符号int）_NativeimagEprocessor.c:194:27:错误：如果((temp3*6)<1)c=（无符号int）((temp2+(Temp1-Temp2)*6*temp3...^JNI/COM_CELIK_ABDULLAH_ImageProcessingPart_Processors_NativeImageProcessor.c:194:57:错误：如果((temp3*6)<1)c=（无符号int）((temp2+(Temp1-Temp2)*6*temp3...^JNI/COM_Celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:194:65:错误：未声明标识符'temp2'的使用如果((temp3*6)<1)c=（无符号int)((temp2+(Temp1-Temp2)*6*temp3)*...^JNI/COM_Celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:194:48:错误：未声明标识符'temp2'的使用如果((temp3*6)<1)c=（无符号^jni/com_celik_abdullah_imageprocessingpart_processors_nativeimageProcessor.c:194:78:错误：使用未声明的标识符'temp3'...(temp3*6)<1)c=（无符号int）((temp2+(Temp1-temp2)*6*temp3)*100)；^jni/com_celik_abdullah_imageprocessingpart_processors_nativeimageProcessor.c:196:15:错误：使用未声明的标识符'temp3'否则，如果((temp3*2)<1)c=（无符号int）(temp1*100)；^jni/com_celik_abdullah_imageprocessingpart_processors_nativeimageprocessor.c:196:31:错误：使用未声明的标识符“c”否则，如果((temp3*2)<1)c=（无符号int）(temp1*100)；^jni/com_celik_abdullah_imageprocessingpart_processors_nativeimageprocessor.c:196:51:错误：使用未声明的标识符'temp1'否则，如果((temp3*2)<1)c=（无符号int）(temp1*100)；^JNI/COM_Celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:198:15:错误：使用未声明的标识符'temp3'否则如果((temp3*3)<2)c=（无符号int）((temp2+(Temp1-Temp2)*(.666..)^JNI/COM_CELIK_ABDULLAH_ImageProcessingPart_Processors_NativeImageProcessor.c:198:31:错误：使用未声明的标识符“c”否则，如果((temp3*3)<2)c=（无符号int）((temp2+(Temp1-Temp2)*(.666..)^JNI/COM_Celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:198:61:错误：使用未声明的标识符'temp1'否则如果((temp3*3)<2)c=（无符号int）((temp2+(Temp1-Temp2)*(.666...^JNI/COM_Celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:198:69:错误：使用未声明的标识符“temp2”...如果((temp3*3)<2)c=（无符号int）((temp2+(Temp1-Temp2)*(.66666-temp.)^JNI/COM_Celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:198:52:错误：使用未声明的标识符'temp2'否则((temp3*3)<2)c=（无符号int)((temp2+(Temp1-Temp2)*(.666...^JNI/COM_Celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:198:88:错误：使用未声明的标识符'temp3'...<2)c=（无符号H_ImageProcessingPart_Processors_NativeImageProcessor.c:200:10:错误：使用未声明的标识符'c'else c=（无符号int）(temp2*100)；^JNI/com_celik_Abdullah_ImageProcessingPart_Processors_NativeImageProcessor.c:200:30:错误：使用未声明的标识符'temp2'else c=（无符号int）(temp2*100)；

我从一个。cpp文件中得到了代码。当我删除签名中的地址运算符(&)时，一切都很好（没有错误），但我不知道算法是否会工作。

有人能帮忙吗？

Answer 1

您试图用C编译器编译C++代码，但这是行不通的。

显而易见的解决方案是使用C++编译器编译它（例如，通过为源文件提供.cpp扩展名）。

如果出于某种原因必须使用C编译器，那么必须用C重写函数。
首先，可以通过值而不是引用传递所有const float参数（通过去掉&)。我不知道为什么它们首先是引用。
第一个参数(C)被用作输出参数，结果被写入其中。因此，必须将它从引用更改为指针（即无符号int*c)。或者更好的方法是跳过输出参数，让函数返回它的结果：

static int convert(const float temp1, const float temp2, const float temp3) {
    unsigned int c;

    if ( (temp3 * 6) < 1) c = (unsigned int) ((temp2 + (temp1 - temp2) * 6 * temp3) * 100);
    else if ((temp3 * 2) < 1) c = (unsigned int) (temp1 * 100);
    else if ((temp3 * 3) < 2) c = (unsigned int) ((temp2 + (temp1 - temp2) * (.66666 - temp3) * 6) * 100);
    else c = (unsigned int) (temp2 * 100);

    return c;
}

r = convert(temp1, temp2, temp3);