C/C++ enables hybrid programming on Java projects, Android, and Objective-C platforms

Since I work on a MAC, here's how to do JNI development on a MAC, and Virtual Studio on Windows is very simple.

Path:

/System/Library/Frameworks/JavaVM.framework/Frameworks/JavaNativeFoundation.framework/

JNIEXPORT jint JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_add(JNIEnv *, jclass, jint param1, jint param2)
    jint result = param1 + param2;
    return result;
    JNIEXPORT void JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_say(JNIEnv *env, jclass, jstring param)
    const char *param_char = env->GetStringUTFChars(param, NULL);
    std::string str = param_char;
    JNIEXPORT jstring JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_getInfo(JNIEnv *env, jclass)
    std::string str = "Hi,I am C++.";
    jstring result =  env->NewStringUTF(str.c_str());
    return result;
    JNIEXPORT void JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_nativeToJava(JNIEnv * env, jclass, jobject obj)
    jclass cls = env->FindClass("cn/taoweiji/nativemodule/NativeDemo");
    jmethodID mid = env->GetMethodID(cls, "subtract", "(II)I");
    int result = (int) env->CallIntMethod(obj, mid, 10, 2);Copy the code

package cn.taoweiji.nativemodule; Cn_taoweiji_nativemodule_nativedemo. h public class NativeDemo {public static native int add(int param1, int param2); public static native void say(String name); public static native String getInfo(); public static native void nativeToJava(NativeDemo nativeDemo); public int subtract(int param1, int param2) { System.out.println("NativeDemo:" + String.format("%s - %s = %s", param1, param2, param1 - param2)); return param1 - param2;Copy the code

Android JNI development, C++ files must be written in a separate module, Java interface code can be written in app(module), and C++ in the same module, through gradle association. Detailed code please download demo to browse

Gradle configuration (NativeModule) apply plugin: Library 'android {compileSdkVersion 23 buildToolsVersion "24.0.0rc2" defaultConfig {minSdkVersion 14 TargetSdkVersion 23 versionCode 1 versionName "1.0" buildTypes {release {minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' NDK {moduleName "joyrun" STL "stlport_static" ldLibs "log"// used to resolve __android_log_print abiFilters "armeabi", "armeabi-v7a", "x86", "x86_64", "arm64-v8a" //add -fexceptions to allow throw error //add -w to "format not a string literal and no format arguments [-Werror=format-security" cFlags "-w -fexceptions" dependencies { compile fileTree(dir: 'libs', include: ['*.jar'])Copy the code

Write the JNI interface

// NativeDemo.java
package cn.taoweiji.nativemodule;
public class NativeDemo {
    public static native int add(int param1, int param2);Copy the code

Write C++ interface code, JNI file directory default is module/ SRC /main/ JNI, can be changed through gradle configuration

// cn_taoweiji_nativemodule_NativeDemo.h
#include 
#ifndef _Included_cn_taoweiji_nativemodule_NativeDemo
#define _Included_cn_taoweiji_nativemodule_NativeDemo
#ifdef __cplusplus
extern "C" {
#endif
 * Class:     cn_taoweiji_nativemodule_NativeDemo
 * Method:    add
 * Signature: (II)I
 JNIEXPORT jint JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_add(JNIEnv *, jclass, jint, jint);
#ifdef __cplusplus
#endif
#endifCopy the code

// NativeDemo.cpp
#include "cn_taoweiji_nativemodule_NativeDemo.h"
JNIEXPORT jint JNICALL Java_cn_taoweiji_nativemodule_NativeDemo_add(JNIEnv *, jclass, jint param1, jint param2)
    jint result = param1 + param2;
    return result;Copy the code

call

Static {system.loadLibrary ("joyrun"); Int result = nativedemo.add (1,2); Log.i("1+2=",String.valueOf(result));Copy the code

Zip: jNI: armeabi, armeabi-v7a, x86, x86_64, arm64-v8a, etc. To open so you can see in the lib prefix format file, it is the native is compiled file, we usually refer to third-party libraries (baidu map) is also to add these files to our libs folder, different names represents a different platform related to compile files, most of mobile phones on the market are the arm CPU, X86 phones are almost not used (GenyMotion emulator belongs to x86 platform), so we usually release APP without considering x86 platform and just add armeabi file. However, it is suggested to add X86 SO file during development to facilitate us to run on the emulator.

1. STL runtime reference
2. Armeabi, Armeabi-V7A, x86, X86_64, ARM64-V8A and other platform configurations
3. C++ output logcat configuration
4. A compilation exception resolved
5. Exception handling

   STL "stlport_static"//gnustl_static // abiFilters "armeabi", "armeabi-v7a", "x86", "x86_64", Add-fexceptions to allow throw error //add -w to "format not a string literal and no format arguments [-Werror=format-security" cFlags "-w -fexceptions"Copy the code

// std::string -> jstring std::string str = "Hello World"; jstring result = env->NewStringUTF(str.c_str()); // jstring -> std::string jstring param; const char *param_char = env->GetStringUTFChars(param, NULL); std::string str = param_char; // jboolean Two values JNI_TRUE and JNI_FALSECopy the code

File: autojavah. Sh

#! /bin/sh export ProjectPath=$(cd ".. /$(dirname "$1")"; pwd) export TargetClassName="co.runner.app.jni.NativeDemo" export SourceFile="${ProjectPath}/app/src/main/java" export TargetPath="${ProjectPath}/jni-joyrun/src/main/jni" cd "${SourceFile}" javah -d ${TargetPath} -classpath "${SourceFile}"  "${TargetClassName}" echo -d ${TargetPath} -classpath "${SourceFile}" "${TargetClassName}"Copy the code

class Demo{
public:
    std::string name;
    int age = 0;
    void say();
    static int add(int param1,int param2)
        return param1 + param2;Copy the code