前些天发现了一个蛮有意思的人工智能学习网站,8个字形容一下"通俗易懂,风趣幽默",感觉非常有意思,忍不住分享一下给大家。
👉点击跳转到教程
第一步首先配置Android studio的NDK开发环境,首先在Android studio中下载NDK包
第二步在local.properties文件中,配置对应的NDK路径
第三歩,在app目录下的build.gradle文件中的,android{}闭包中,指定CMakeLists.txt路径
// 在android节点下
// 指定CMakeLists.txt路径
externalNativeBuild {
cmake {
// 在该文件种设置所要编写的c源码位置,以及编译后so文件的名字
path 'CMakeLists.txt'
}
}
在defaultConfig闭包下配置
// 增加cmake控制属性
externalNativeBuild {
cmake {
// 指定编译架构
abiFilters 'arm64-v8a', 'armeabi-v7a', 'x86', 'x86_64'
}
}
在app目录下,指定CmakeLists.txt文件,根据注释进行相应添加
# CMakeLists.txt
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
# Sets the minimum version of CMake required to build the native library.
#CMakeLists.txt
cmake_minimum_required(VERSION 3.4.1)
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
add_library(
# 设置so文件名称.
Hello
# 设置这个so文件为共享.
SHARED
# Provides a relative path to your source file(s).
src/main/jni/Hello.c)
add_library(
# 设置so文件名称.
Test
# 设置这个so文件为共享.
SHARED
# Provides a relative path to your source file(s).
src/main/jni/Test.c)
add_library(
# 设置so文件名称.
CCallJava
# 设置这个so文件为共享.
SHARED
# Provides a relative path to your source file(s).
src/main/jni/CCallJava.c)
# 添加 log 库的链接
target_link_libraries(CCallJava log)
target_link_libraries(Test log)
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
find_library( # Sets the name of the path variable.
log-lib
# Specifies the name of the NDK library that
# you want CMake to locate.
log )
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
# 制定目标库.
Hello
# Links the target library to the log library
# included in the NDK.
${log-lib} )
第四步,首先进行Java代码C代码的操作
1.JNI2.java代码如下
/**
* @Author: ly
* @Date: 2023/8/6
* @Description: java调C代码
*/
public class JNI2 {
static {
System.loadLibrary("Test"); //加载动态链接库
}
/**
* 让C代码做加法运算,把结果返回
* 场景:大量运算,编解码之类的,需要性能很高的情况下,可以用C代码
*
* @param x
* @param y
* @return
*/
public native int add(int x, int y);
/**
* 从java传入字符串,C代码进行拼接
*
* @param s I am from java
* @return I am from java and I am from c
*/
public native String sayHello(String s);
/**
* 让C代码给每个元素都加上10
*
* @param intArray
* @return
*/
public native int[] increaseArrayEles(int[] intArray);
/**
* 应用:检查密码是否正确,如果正确返回200,否则返回400
*
* @param pwd
* @return
*/
public native int checkPwd(String pwd);
}
2.根据命令行javah +JNI2的全类名,生成Test.c对应的C代码头文件com_example_jniproject_JNI2.h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_jniproject_JNI2 */
#ifndef _Included_com_example_jniproject_JNI2
#define _Included_com_example_jniproject_JNI2
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_example_jniproject_JNI2
* Method: add
* Signature: (II)I
*/
JNIEXPORT jint JNICALL Java_com_example_jniproject_JNI2_add
(JNIEnv *, jobject, jint, jint);
/*
* Class: com_example_jniproject_JNI2
* Method: sayHello
* Signature: (Ljava/lang/String;)Ljava/lang/String;
*/
JNIEXPORT jstring JNICALL Java_com_example_jniproject_JNI2_sayHello
(JNIEnv *, jobject, jstring);
/*
* Class: com_example_jniproject_JNI2
* Method: increaseArrayEles
* Signature: ([I)[I
*/
JNIEXPORT jintArray JNICALL Java_com_example_jniproject_JNI2_increaseArrayEles
(JNIEnv *, jobject, jintArray);
/*
* Class: com_example_jniproject_JNI2
* Method: checkPwd
* Signature: (Ljava/lang/String;)I
*/
JNIEXPORT jint JNICALL Java_com_example_jniproject_JNI2_checkPwd
(JNIEnv *, jobject, jstring);
#ifdef __cplusplus
}
#endif
#endif
3.根据jni协议,去写对应的c代码,创建Test.c文件,代码如下
//
// Created by DELL on 2023/8/6.
//
#include "com_example_jniproject_JNI2.h"
#include "string.h"
#include <stdlib.h>
#include <android/log.h>
#define TAG "luyu"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,TAG ,__VA_ARGS__) // 定义LOGD类型
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,TAG ,__VA_ARGS__) // 定义LOGI类型
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN,TAG ,__VA_ARGS__) // 定义LOGW类型
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG ,__VA_ARGS__) // 定义LOGE类型
#define LOGF(...) __android_log_print(ANDROID_LOG_FATAL,TAG ,__VA_ARGS__) // 定义LOGF类型
JNIEXPORT char *JNICALL Java_com_example_MyClass_myMethod(JNIEnv *env, jobject obj, jstring jstr) {
const char *cstr = (*env)->GetStringUTFChars(env, jstr, NULL);
// 使用 cstr 进行操作,并获取结果(假设结果为 result)
(*env)->ReleaseStringUTFChars(env, jstr, cstr);
char *result = (char *) malloc(strlen(cstr) + 1);
strcpy(result, cstr);
return result;
}
/**
* jint:返回值
* Java_全类名_方法名
* JNIEnv *env
*/
jint Java_com_example_jniproject_JNI2_add
(JNIEnv *env, jobject jobj, jint ji, jint jj) {
int result = ji + jj;
return result;
};
/**
* 从java传入字符串,C代码进行拼接
*
* @param s I am from java
* @return I am from java and I am from c
*/
jstring Java_com_example_jniproject_JNI2_sayHello
(JNIEnv *env, jobject jobj, jstring jstring1) {
char *fromJava = Java_com_example_MyClass_myMethod(env, jobj, jstring1);
char *fromC = " and I am from C";
//拼接函数,拼接后得到的结果放到第一个参数里面
strcat(fromJava, fromC);//把拼接的结果放在第一个参数里面
//jstring (*NewStringUTF)(JNIEnv*, const char*);
LOGE("fromJava==%s\n", fromJava);
return (*env)->NewStringUTF(env, fromJava);
};
/**
* 给每个元素加10
* 场景:图片处理,颜色矩阵(就是数组),进行数组的处理
*/
jintArray Java_com_example_jniproject_JNI2_increaseArrayEles
(JNIEnv *env, jobject jobj, jintArray jintArray1) {
//1.得到数组的长度
//jsize (*GetArrayLength)(JNIEnv*, jarray);
jsize size = (*env)->GetArrayLength(env, jintArray1);
//2.得到数组的元素
// jint* (*GetIntArrayElements)(JNIEnv*, jintArray, jboolean*);
jint *intArray = (*env)->GetIntArrayElements(env, jintArray1,
JNI_FALSE);//这里传0 false表示 在同一份内存操作,不开辟新的内存
//3.遍历数组,给每个元素加10
int i;
for (i = 0; i < size; i++) {
*(intArray + i) += 10;
}
// 4. 同步修改到 Java 层
(*env)->ReleaseIntArrayElements(env, jintArray1, intArray, 0);
//4.返回结果
return jintArray1;
};
/**
* 应用:检查密码是否正确,如果正确返回200,否则返回400
*/
jint Java_com_example_jniproject_JNI2_checkPwd
(JNIEnv *env, jobject jobj, jstring jstring1) {
//假设服务器的密码是123456
char *origin = "123456";
char *fromUser = Java_com_example_MyClass_myMethod(env, jobj, jstring1);
//函数比较字符串是否相同
int code = strcmp(origin, fromUser);
LOGE("code==%d\n", code);
if (code == 0) {
return 200;
} else {
return 400;
}
};
第五步,C代码调用Java代码,首先创建JNI3.java
/**
* @Author: ly
* @Date: 2023/8/6
* @Description: C代码调用Java代码
*/
public class JNI3 {
static {
System.loadLibrary("CCallJava"); //加载动态链接库
}
//当执行这个方法的时候,让C代码调用
//public int add(int x, int y)
public native void callbackAdd();
/**
* 当执行这个方法的时候,让C代码调用
* public void helloFromJava()
*/
public native void callbackHelloFromJava();
/**
* 当执行这个方法的时候,让C代码调用
* public void printString(String s)
*/
public native void callbackPrintString();
/**
* 当执行这个方法的时候,让C代码调用
* public static void sayHello(String s)
*/
public native void callbackSayHello();
public int add(int x, int y) {
Log.e("TAG", "add() x=" + x + " y=" + y);
return x + y;
}
public void helloFromJava() {
Log.e("TAG", "helloFromJava");
}
public void printString(String s) {
Log.e("TAG", "C中输入的:" + s);
}
public static void sayHello(String s) {
Log.e("TAG", "我是java代码中的JNI" +
".java中的sayHello(String s)静态方法,我被C调用了:" + s);
}
}
2.根据命令行,javah +JNI3全类名,生成CCallJava.c对应的头文件
com_example_jniproject_JNI3.h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_jniproject_JNI3 */
#ifndef _Included_com_example_jniproject_JNI3
#define _Included_com_example_jniproject_JNI3
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_example_jniproject_JNI3
* Method: callbackAdd
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_com_example_jniproject_JNI3_callbackAdd
(JNIEnv *, jobject);
/*
* Class: com_example_jniproject_JNI3
* Method: callbackHelloFromJava
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_com_example_jniproject_JNI3_callbackHelloFromJava
(JNIEnv *, jobject);
/*
* Class: com_example_jniproject_JNI3
* Method: callbackPrintString
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_com_example_jniproject_JNI3_callbackPrintString
(JNIEnv *, jobject);
/*
* Class: com_example_jniproject_JNI3
* Method: callbackSayHello
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_com_example_jniproject_JNI3_callbackSayHello
(JNIEnv *, jobject);
#ifdef __cplusplus
}
#endif
#endif
3.对应的CCallJava.c文件中的代码如下
//
// Created by DELL on 2023/8/6.
//
#include "com_example_jniproject_JNI3.h"
#include <stdlib.h>
#include <stdio.h>
#include <android/log.h>
#define TAG "luyu"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,TAG ,__VA_ARGS__) // 定义LOGD类型
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,TAG ,__VA_ARGS__) // 定义LOGI类型
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN,TAG ,__VA_ARGS__) // 定义LOGW类型
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG ,__VA_ARGS__) // 定义LOGE类型
#define LOGF(...) __android_log_print(ANDROID_LOG_FATAL,TAG ,__VA_ARGS__) // 定义LOGF类型
/**
* 让C代码调用Java中JNI类的public int add(int x ,int y)
*/
JNIEXPORT void Java_com_example_jniproject_JNI3_callbackAdd(JNIEnv *env, jobject jobj) {
//1.得到字节码
//jclass (*FindClass)(JNIEnv*, const char*);
jclass jclazz = (*env)->FindClass(env, "com/example/jniproject/JNI3");
//2.得到方法
//jmethodID (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);
//最后一个参数是方法签名
jmethodID jmethodId = (*env)->GetMethodID(env, jclazz, "add", "(II)I");
//3.实例化该类
jobject jobject1 = (*env)->AllocObject(env, jclazz);
//4.调用方法
//jint (*CallIntMethod)(JNIEnv*, jobject, jmethodID, ...);
jint value = (*env)->CallIntMethod(env, jobject1, jmethodId, 99, 1);
//成功调用
LOGE("value==%d\n", value);
};
/***
* 让C代码调用
* public void helloFromJava()
*/
JNIEXPORT void JNICALL Java_com_example_jniproject_JNI3_callbackHelloFromJava
(JNIEnv *env, jobject jobj) {
//1.得到字节码
//jclass (*FindClass)(JNIEnv*, const char*);
jclass jclazz = (*env)->FindClass(env, "com/example/jniproject/JNI3");
//2.得到方法
//jmethodID (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);
//最后一个参数是方法签名
jmethodID jmethodIds = (*env)->GetMethodID(env, jclazz, "helloFromJava", "()V");
//3.实例化该类
jobject jobject1 = (*env)->AllocObject(env, jclazz);
//4.调用方法
//jint (*CallIntMethod)(JNIEnv*, jobject, jmethodID, ...);
(*env)->CallVoidMethod(env, jobject1, jmethodIds);
};
/***
* 让C代码调用
* public void printString(String s)
*
*/
JNIEXPORT void JNICALL Java_com_example_jniproject_JNI3_callbackPrintString
(JNIEnv *env, jobject jobj) {
//1.得到字节码
//jclass (*FindClass)(JNIEnv*, const char*);
jclass jclazz = (*env)->FindClass(env, "com/example/jniproject/JNI3");
//2.得到方法
//jmethodID (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);
//最后一个参数是方法签名
jmethodID jmethodIds = (*env)->GetMethodID(env, jclazz, "printString", "(Ljava/lang/String;)V");
//3.实例化该类
jobject jobject1 = (*env)->AllocObject(env, jclazz);
//4.调用方法
//jint (*CallIntMethod)(JNIEnv*, jobject, jmethodID, ...);
// jstring (*NewStringUTF)(JNIEnv*, const char*);
jstring jst = (**env).NewStringUTF(env, "I am Android!");
(*env)->CallVoidMethod(env, jobject1, jmethodIds, jst);
};
/**
* 让C代码调用
* public static void sayHello(String s)
*
*/
JNIEXPORT void JNICALL Java_com_example_jniproject_JNI3_callbackSayHello
(JNIEnv *env, jobject jobj){
//1.得到字节码
//jclass (*FindClass)(JNIEnv*, const char*);
jclass jclazz = (*env)->FindClass(env, "com/example/jniproject/JNI3");
//2.得到方法
// jmethodID (*GetStaticMethodID)(JNIEnv*, jclass, const char*, const char*);
//最后一个参数是方法签名
jmethodID jmethodIds = (*env)->GetStaticMethodID(env, jclazz, "sayHello", "(Ljava/lang/String;)V");
jstring jst = (**env).NewStringUTF(env, "I am Android!");
(*env)->CallStaticVoidMethod(env,jclazz,jmethodIds,jst);
};
之后,在MainActivity中调用对应的方法即可
public class MainActivity extends AppCompatActivity {
private JNI2 jin2;
private static final String TAG = "MainActivity";
private JNI3 mJNI3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
jin2 = new JNI2();
mJNI3 = new JNI3();
}
/******以下是Java代码调用C*****/
public void checkPwd(View view) {
int result = jin2.checkPwd("12345678");
Log.i(TAG, "result==" + result);
}
public void increaseArrayEles(View view) {
int array[] = {1, 2, 3, 4};
jin2.increaseArrayEles(array);
for (int i = 0; i < array.length; i++) {
Log.i(TAG, "result[" + i + "]:" + array[i]);
}
}
public void sayHello(View view) {
String result = jin2.sayHello("I am from java");
Log.i(TAG, "result==" + result);
}
public void add(View view) {
int result = jin2.add(99, 1);
Log.i(TAG, "result==" + result);
}
/******以下是C调Java代码*****/
public void callbackAdd(View view) {
mJNI3.callbackAdd();
}
public void callbackHelloFromJava(View view) {
mJNI3.callbackHelloFromJava();
}
public void callbackPrintString(View view) {
mJNI3.callbackPrintString();
}
public void callbackSayHello(View view) {
mJNI3.callbackSayHello();
}
}
点击按钮便可输出对应的日志,表示调用成功。