Android Studio uses JNI

1. Add Native Interface

static{
System.loadlibrary ("Jnitest");
}

Private native int Add (double num1,double num2);
Private native int Sub (double num1,double num2);
Private native int Mul (double num1,double num2);
Private native int Div (double num1,double num2);

2.build->make Project
Verify that there are no other errors in the project and compile the project to generate a. class file
Inside the Build/intermediates/classes/debug.

3.javah generate the. h file

Under the App/src/main/java directory of the Project
CMD executes the Javah com.example.caculate.MainActivity command, the. h file is generated
Create the JNI directory and copy the. h

4.jni directory implementation. C
Create a new. C implementation. Functions in the. h

5.build->make Project

Will error
Add the NDK path to the Local.properties file
Sdk.dir=c\:\\users\\alif\\appdata\\local\\android\\sdk
ndk.dir=i\:\\android\\android-ndk-r11c

Add the name of so in the build.gradle below the app
\app\build.gradle
NDK {
ModuleName "Jnitest"
Abifilters "Armeabi", "armeabi-v7a", "x86"
}

6.build->make Project can compile the so file.
The resulting so is below app/build/intermediates/ndk/debug/lib

We add a android.mk file under the JNI directory
Local_path: = $ (call My-dir)
Include $ (clear_vars)
Local_module: = Jnitest
Local_src_files: = main.c
Include $ (build_shared_library)

Then ndk-build generate the Libs directory

Changing the Libs directory name to Jnilibs will be automatically packaged into the APK.

. h and. c Files

/*Do not EDIT this file-it are machine generated*/#include<jni.h>/*Header for Class com_example_caculate_mainactivity*/#ifndef _included_com_example_caculate_mainactivity#define_included_com_example_caculate_mainactivity#ifdef __cplusplusextern "C" {#endif/** class:com_example_caculate_mainactivity * method:add * Signature: (DD) I*/jniexport jint jnicall java_com_example_caculate_mainactivity_add (jnienv*, Jobject, jdouble, jdouble);/** class:com_example_caculate_mainactivity * method:sub * Signature: (DD) I*/jniexport jint jnicall java_com_example_caculate_mainactivity_sub (jnienv*, Jobject, jdouble, jdouble);/** class:com_example_caculate_mainactivity * Method:mul * Signature: (DD) I*/jniexport jint jnicall java_com_example_caculate_mainactivity_mul (jnienv*, Jobject, jdouble, jdouble);/** class:com_example_caculate_mainactivity * method:div * Signature: (DD) I*/jniexport jint jnicall java_com_example_caculate_mainactivity_div (jnienv*, Jobject, jdouble, jdouble); #ifdef __cplusplus}#endif#endif#include<jni.h>#defineJintjnicall#ifndef _included_com_example_caculate_mainactivity#define_included_com_example_caculate_mainactivity#ifdef __cplusplusextern "C" {#endifjniexport jintjnicall java_com_example_caculate_mainactivity_add (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {    return(Jint) (NUM1 +num2);} Jniexport jintjnicall java_com_example_caculate_mainactivity_sub (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {    return(Jint) (NUM1-num2);} Jniexport jintjnicall Java_com_example_caculate_mainactivity_mul (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {    return(Jint) (NUM1 *num2);} Jniexport jintjnicall java_com_example_caculate_mainactivity_div (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {    if(num2 = =0)return 0; return(Jint) (NUM1/num2);} #ifdef __cplusplus}#endif#endif

Using dynamic Enrollment JNI

1. The function name is too long because it is a Javah generated header file, the name is too long
2. Every class has to be javah once, very troublesome

Generate write in the JNI directory. C

#include <jni.h>#include<stdio.h>//#include <assert.h>#include <stdlib.h>#include<unistd.h>#include<sys/types.h>#include<sys/stat.h>#include<fcntl.h>jniexport jint jnicall native_add (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {return(Jint) (NUM1 + num2 +1);} Jniexport jint jnicall native_sub (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {    return(Jint) (Num1-num2 +1);} Jniexport jint jnicall Native_mul (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {    return(Jint) (NUM1 * num2 +1);} Jniexport jint jnicall native_div (jnienv*env, Jobject obj, jdouble num1, jdouble num2) {    if(num2 = =0)return 0; return(Jint) (Num1/num2 +1);}//binding Tables for Java and JNI functionsStaticJninativemethod gmethods[] = {        {"ADD","(DD) I", (void*) Native_add}, {"Sub","(DD) I", (void*) Native_sub}, {"Mul","(DD) I", (void*) Native_mul}, {"Div","(DD) I", (void*) Native_div},};//registering the native method in JavaStatic intRegisternativemethods (jnienv* env,Const Char*ClassName, Jninativemethod* Gmethods,intnummethods)    {Jclass clazz; Clazz= (*env)Findclass (env, className); if(Clazz = =NULL) {        returnJni_false; }    if(*env)->registernatives (env, Clazz, Gmethods,nummethods) <0){        returnJni_false; }    returnjni_true;}intRegister_ndk_load (JNIENV *env) {    returnRegisternativemethods (ENV,"com/example/caculate/mainactivity", Gmethods,sizeof(gmethods)/sizeof(gmethods[0])); //Nelem (Gmethods));}jniexport jint jni_onload (JAVAVM* VMS,void*reserved) {jnienv* env =NULL; Jint result= -1; if((*VM)->getenv (VM, (void* *) &env, jni_version_1_4)! =JNI_OK) {        returnresult;    } register_ndk_load (env); //returns the version of JNI    returnjni_version_1_4;}

Writing android.mk files

Local_path: = $ (call My-dir)
Include $ (clear_vars)
Local_prelink_module: = False
Local_module: = Jnitest_jni
Local_src_files: = myjnicalc.c
Local_shared_libraries: = Libandroid_runtime
Include $ (build_shared_library)

Generating so files using Ndk-build

or move it to the Jnilibs directory.

Last Successful modification

78+11 +1 = 90

Source: http://pan.baidu.com/s/1kULyvDd Password M8ns

Android Studio uses JNI