What is the method for calling JNI in Android?

In Android, the usual way to make JNI calls is by using the Java Native Interface (JNI). Here are some common JNI calling methods:

1. Creating a JNI function prototype involves declaring a method with the “native” keyword in Java code and providing the corresponding JNI function prototype. For example, declaring a native method in Java code.

public native void myNativeMethod();

Next, generate the corresponding JNI function prototype header file using the command javah.

javah -jni com.example.MyClass

1. Implement JNI functions: Implement JNI functions in C or C++ code. By including the generated JNI function prototype header file, you can define JNI functions and implement their corresponding functionality in C or C++ code.

#include <jni.h>

JNIEXPORT void JNICALL Java_com_example_MyClass_myNativeMethod(JNIEnv* env, jobject obj) {
    // 实现JNI函数的功能
}

1. Load the JNI library: Loading the compiled JNI library in Java code to use JNI functions. This can be done using the System.loadLibrary method.

static {
    System.loadLibrary("mylibrary");
}

Among them, “mylibrary” is the name of the compiled JNI library.

1. Invoke JNI functions: Calling functions defined through JNI in Java code. Directly call the JNI functions wherever needed.

myNativeMethod();

It is important to note that JNI calls involve interaction between Java and C/C++, requiring data type conversion and memory management. These operations can be performed using functions and macros provided by JNI.