Use javah (javah generates the JNI header file)

C:/users/archfree> javah
Usage: javah [Option] <class>

[Options] include:

-Help: output the help message and exit.
-Classpath <path> indicates the path used to load the class.
-Bootclasspath <path> is used to mount the path of the boot class.
-D <directory> output directory
-O <File> output file (only one of-D or-O can be used)
-JNI: JNI-style header file (default)
-Version: Output version information.
-Verbose enables detailed output
-Force always writes data to the output file

Use a fully qualified name to specify the <class> (example:

First, we need to compile our android project, because javah is a decompilation tool and must be used for compiled files. The compiled files are stored in the bin directory under the android project directory by default. So we open cmd

Cd d:/Works/Android-SerialPort-API/project/bin/

Assume that the project directory contains the bin folder, and the bin stores the compiled class file;
In the bin directory,

Enter the bin directory under the project directory and enter

Javah-JNI Android. SerialPort. SerialPort

Under the JNI directory, android_serialport_serialport.h is generated.