通过jni将2d矩阵从Java传递到C ++文件 [英] passing a 2d matrix from java to C++ file through jni

问题描述

我在java_method()方法的MyClass.java文件中的Java中有一个二维矩阵，并且我已经声明了一个本机方法c_method().矩阵是浮点型的，例如:

I have a 2d matrix in java say in a file MyClass.java in the method java_method() and I have declared a native method say c_method(). the matrix is float type like:

    float[][] pos_matrix;

大小为3by4的

，我已经在Java中初始化了矩阵.现在，我想将此矩阵传递给jni中的cpp文件.该怎么做?

of size 3by4 and I have initialized the matrix in java. Now I want to pass this matrix to my cpp file in the jni. How to do that?

推荐答案

两个选项:

1. 将矩阵编码为长度为12的一维数组，作为float []传递.在本机端结果为jfloatArray.无法直接使用，请阅读Get/ReleaseFloatArrayElements
2. 使用方法float GetValueAt(int,int)(或类似方法)将Java矩阵包装在Facade类中，并通过传递实例(本机端jobject中的结果)然后调用该方法(GetMethodID/CallFloatMethod)在本机端进行访问

1. encode the matrix in 1D array of length 12, pass as float[]. Results in jfloatArray on native side. Cannot be used directly, read about Get/ReleaseFloatArrayElements
2. wrap the Java matrix in a facade class with method float GetValueAt(int,int) (or similar) and access on native side by passing the instance (results in jobject on native side) and then calling that method (GetMethodID/CallFloatMethod)

选项1更简单(编码更少)，选项2以"OO方式"更简洁-关注点分离.使用选项1，您几乎可以在JVM不显示时修改阵列.

Option 1 is simpler (less coding), option 2 is cleaner in "OO way" - separation of concerns. With option 1 you can practically modify the array when JVM is not looking.

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