Jni的笔记一，简单的通信

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开发环境

SDK:
android 7.1.1
Tool:
Android studio 2.1.1
NDK

配置开发环境

设置系统NDK系统环境变量
NDK_ROOT = E:\android_sdk\ndk-bundle
PATH = %NDK_ROOT%
PATH = C:\Program Files\Java\jdk1.8.0_111\bin （如果不配置，Javah、java、javac不可用）

代码

步骤一，建立工程，声明要调用的模块libhellojni.so,用native 声明要调用的JNI的方法。

public class MainActivity extends AppCompatActivity {    private TextView text1;    private TextView text2;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        text1 = (TextView) findViewById(R.id.text1);        text2 = (TextView) findViewById(R.id.text2);        text1.setText("Return String is:  "+returnString());        text2.setText("Return add value is :  "+add(55,11));    }    static {        System.loadLibrary("hellojni");    }    private native int add(int a, int b);    private native String  returnString();}

步骤二，配置build.gradle

    defaultConfig {        applicationId "com.adc.tiny4412.adc"        minSdkVersion 15        targetSdkVersion 25        versionCode 1        versionName "1.0"        ndk{            moduleName "hellojni"        }        sourceSets.main{            jni.srcDirs = []            jniLibs.srcDir "src/main/libs"        }    }

配置gradle.properties:

android.useDeprecatedNdk=true

编译 Build->Make Project

步骤三 ,生成 javah -jni com.adc.tiny4412.adc.MainActivity

/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>/* Header for class com_adc_tiny4412_adc_MainActivity */#ifndef _Included_com_adc_tiny4412_adc_MainActivity#define _Included_com_adc_tiny4412_adc_MainActivity#ifdef __cplusplusextern "C" {#endif/* * Class:     com_adc_tiny4412_adc_MainActivity * Method:    add * Signature: (II)I */JNIEXPORT jint JNICALL Java_com_adc_tiny4412_adc_MainActivity_add  (JNIEnv *, jobject, jint, jint);/* * Class:     com_adc_tiny4412_adc_MainActivity * Method:    returnString * Signature: ()Ljava/lang/String; */JNIEXPORT jstring JNICALL Java_com_adc_tiny4412_adc_MainActivity_returnString  (JNIEnv *, jobject);#ifdef __cplusplus}#endif#endif

在studio里面创jni文件夹
创建main.c

#include <jni.h>/* * Class:     com_adc_tiny4412_adc_MainActivity * Method:    add * Signature: (II)I */JNIEXPORT jint JNICALL Java_com_adc_tiny4412_adc_MainActivity_add  (JNIEnv *env, jobject jobj, jint a, jint b){    return a+b;  }/* * Class:     com_adc_tiny4412_adc_MainActivity * Method:    returnString * Signature: ()Ljava/lang/String; */JNIEXPORT jstring JNICALL Java_com_adc_tiny4412_adc_MainActivity_returnString  (JNIEnv *env, jobject jobj){    return (*env)->NewStringUTF(env,"Hi man,I come from JNI!");  }

添加脚本文件Android.mk

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE    := hellojniLOCAL_SRC_FILES := main.cinclude $(BUILD_SHARED_LIBRARY)

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