android java层通过jni加载使用第三方的so库

1、例如我们自己编译一个so库，我们的其他模块要加载如何操作了

首先在c盘新建立一个文件夹sb，在sb下面新建立一个文件夹jni，如果你要使用ndk编译so库，必须需要有jni目录

2、在jni目录下面建立下面几个文件

我们来看看c文件

//
// Created by wei.yuan on 2017/11/2.
//
#include<jni.h>
#include<logback_ecmapplication_cetcs_com_myapplicationkldsk_JNI.h>
#include <jni.h>
#include <string.h>
#include <pthread.h>
JNIEXPORT jstring JNICALL Java_logback_ecmapplication_cetcs_com_myapplicationkldsk_JNI_getStringFromC
  (JNIEnv *env, jobject obj){
    int *a = (int *) (NULL);
    *a = ;
    return (*env)->NewStringUTF(env,"I'm comes from 5454552444444to Native Function!");
  }

然后是头文件

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity */

#ifndef _Included_logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity
#define _Included_logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity
#ifdef __cplusplus
extern "C" {
#endif
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_ABOVE_CLIENT
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_ABOVE_CLIENT 8L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_ADJUST_WITH_ACTIVITY
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_ADJUST_WITH_ACTIVITY 128L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_ALLOW_OOM_MANAGEMENT
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_ALLOW_OOM_MANAGEMENT 16L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_AUTO_CREATE
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_AUTO_CREATE 1L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_DEBUG_UNBIND
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_DEBUG_UNBIND 2L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_IMPORTANT
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_IMPORTANT 64L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_NOT_FOREGROUND
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_NOT_FOREGROUND 4L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_WAIVE_PRIORITY
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_BIND_WAIVE_PRIORITY 32L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_CONTEXT_IGNORE_SECURITY
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_CONTEXT_IGNORE_SECURITY 2L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_CONTEXT_INCLUDE_CODE
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_CONTEXT_INCLUDE_CODE 1L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_CONTEXT_RESTRICTED
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_CONTEXT_RESTRICTED 4L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_APPEND
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_APPEND 32768L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING 8L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_MULTI_PROCESS
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_MULTI_PROCESS 4L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_PRIVATE
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_PRIVATE 0L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_WORLD_READABLE
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_WORLD_READABLE 1L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_WORLD_WRITEABLE
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_MODE_WORLD_WRITEABLE 2L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_DIALER
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_DIALER 1L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_DISABLE
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_DISABLE 0L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_SEARCH_GLOBAL
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_SEARCH_LOCAL
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_SHORTCUT
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_DEFAULT_KEYS_SHORTCUT 2L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_RESULT_CANCELED
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_RESULT_CANCELED 0L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_RESULT_FIRST_USER
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_RESULT_FIRST_USER 1L
#undef logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_RESULT_OK
#define logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity_RESULT_OK -1L
/*
 * Class:     logback_ecmapplication_cetcs_com_myapplicationkldsk_MainActivity
 * Method:    getStringFromC
 * Signature: ()Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_logback_ecmapplication_cetcs_com_myapplicationkldsk_JNI_getStringFromC
  (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

现在我们要生成so库，需要配置android.mk文件和application.mk文化

android.mk文件内容如下所示：

ROOT_PATH := $(call my-dir)

LOCAL_PATH := $(ROOT_PATH)
include $(CLEAR_VARS)

LOCAL_MODULE    := sb_jni
LOCAL_SRC_FILES := logback_ecmapplication_cetcs_com_myapplicationkldsk_JNI.c
LOCAL_CFLAGS :=  -Wl,-g
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)

application.mk文件如下所示：

APP_STL := stlport_static
APP_ABI := all
APP_CXXFLAGS := -std=c++ -D__STDC_LIMIT_MACROS
APP_PLATFORM := android-

有了上面的配置之后，我们就可以在cgwin环境中生成对应的so库文件了，cgwin进入到对应的jni目录，使用ndk-build命令

编译成功之后会在jni的目录下产生下面的两个文件夹

libs文件下面的so库就是可以提高给第三方使用的so库，obj目录下生成的so库就是具有调试信息的so库，当发现奔溃的时候，可以使用工具arm-linux-androideabi-addr2line.exe解决该obj目录下的so库来定位文件

现在我们在android studio下面新建立一个工程

我们将上面的libs目录拷贝到工程和src同级别的目录下

然后在工程的gradle文件中配置下面的代码

sourceSets {
    main {
        jniLibs.srcDirs = ['libs']
    }
}
完成的gradle代码如下

apply plugin: 'com.android.application'

android {
    compileSdkVersion
    buildToolsVersion "24.0.2"
    defaultConfig {
        applicationId "cn.onlinecache.breakpad"
        minSdkVersion
        targetSdkVersion
        versionCode
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    sourceSets {
        main {
            jniLibs.srcDirs = ['libs']
        }
    }
}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile project(':breakpad')

    compile 'com.android.support:appcompat-v7:24.2.1'
    compile 'com.jakewharton:butterknife:8.4.0'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.4.0'
}

通过上面的配置，我们编译工程就会自动生成jNIlibs目录

然后我们要在代码中使用so库中的函数，如何使用了

JNIEXPORT jstring JNICALL Java_logback_ecmapplication_cetcs_com_myapplicationkldsk_JNI_getStringFromC
  (JNIEnv *env, jobject obj){
    int *a = (int *) (NULL);
    *a = 1;
    return (*env)->NewStringUTF(env,"I'm comes from 5454552444444to Native Function!");
  }

从c语言中我们可以看出，这个函数是 通过JNI编程规范编写的，必须要满足JNI的编程规范，通过

JNIEXPORT jstring JNICALL Java_logback_ecmapplication_cetcs_com_myapplicationkldsk_JNI_getStringFromC我们可以知道对应该函数的java层对应的
包名是

logback.ecmapplication.cetcs.com.myapplicationkldsk
对应的类名是JNI，对应的函数名是

getStringFromC
所以我们在工程中应该要建立下面的这样一个文件

package logback.ecmapplication.cetcs.com.myapplicationkldsk;

/**
 * Created by wei.yuan on 2017/11/13.
 */

public class JNI {
    public  native  String  getStringFromC();
    static {
        System.loadLibrary("sb_jni");
    }
}

在这个文件中加载so 库进行调用

调用者：

new JNI().getStringFromC()

工程结构如下：

工程项目代码如下所示：

http://pan.baidu.com/s/1nvHuufB