CMakeLists.txt生成.so ndk开发java飘飘如叶-

ndk开发

由于需调用底层代码申请系统内存就开发了调用底层的so

申请内存主要两个

• 申请内存
• 释放内存

创建对应的java调取接口jni

//com.aa.factorylibrary.jni.MemOpJni public class MemOpJni { static {         System.loadLibrary("memory_malloc"); } public static native int malloc(int size); public static native void free(); } 

生成对应的.h文件

• 切换到java目录
  …mainjava> javah -jni com.aa.factorylibrary.jni.MemOpJni
• 在mainjava目录下取出对应的.h (com_aa_factorylibrary_jni_MemOpJni.h)
• 重命名.h , 根据.h文件生成对应的c或者cpp

//memory_malloc.h /* DO NOT EDIT THIS FILE - it is machine generated */ #include <jni.h> /* Header for class com_aa_factorylibrary_jni_MemOpJni */ #ifndef _Included_com_aa_factorylibrary_jni_MemOpJni #define _Included_com_aa_factorylibrary_jni_MemOpJni #ifdef __cplusplus extern "C" { #endif /*  * Class:     com_aa_factorylibrary_jni_MemOpJni  * Method:    malloc  * Signature: (I)I  */ JNIEXPORT jint JNICALL Java_com_aa_factorylibrary_jni_MemOpJni_malloc   (JNIEnv *, jclass, jint); /*  * Class:     com_aa_factorylibrary_jni_MemOpJni  * Method:    free  * Signature: ()I  */ JNIEXPORT void JNICALL Java_com_aa_factorylibrary_jni_MemOpJni_free   (JNIEnv *, jclass); #ifdef __cplusplus } #endif #endif 

// //根据memory_malloc.h生成memory_malloc.cpp // #include "memory_malloc.h" #include "stdlib.h" #include "stdio.h" #include "string.h" #include <unistd.h> #include "android/log.h" #define MEMOP_LOG_TAG "libjnimemory" #define LOGI(...) __android_log_print(ANDROID_LOG_INFO, MEMOP_LOG_TAG, __VA_ARGS__) #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, MEMOP_LOG_TAG, __VA_ARGS__) #define MAX_SIZE 2000 static int *p[MAX_SIZE]; static int count = 0; /*  * Class:     com_aa_factorylibrary_jni_MemOpJni  * Method:    malloc  * Signature: ()I  */ extern "C" JNIEXPORT jint JNICALL Java_com_aa_factorylibrary_jni_MemOpJni_malloc         (JNIEnv *, jclass, jint size) { if (count < MAX_SIZE) {         p[count] = (int *) malloc(256 * 1024 * size * sizeof(int)); memset(p[count], 2, 256 * 1024 * size * sizeof(int));         count++; LOGI("memfill, malloced memory size is %d", size); return size; } else { LOGE("memfill, count is MAX_SIZE"); } return 0; } /*  * Class:     com_aa_factorylibrary_jni_MemOpJni  * Method:    free  * Signature: ()I  */ extern "C" JNIEXPORT void JNICALL Java_com_aa_factorylibrary_jni_MemOpJni_free         (JNIEnv *, jclass) { for (int i = 0; i < MAX_SIZE; i++) { if (NULL != p[i]) { free(p[i]);             p[i] = NULL; } }     count = 0; LOGI("memfree, free memory"); return; } 

由java到c的接口输出完成

• 生成.so文件编译

cmake_minimum_required(VERSION 3.4.1) aux_source_directory(src/main/cpp/memory_malloc DIR_SRCS) add_library( # Sets the name of the library.              memory_malloc               # Sets the library as a shared library.              SHARED               # Provides a relative path to your source file(s).              #src/main/cpp/memory/memory_malloc.cpp )              ${DIR_SRCS} ) 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 ) target_link_libraries( # Specifies the target library.                        memory_malloc                         # Links the target library to the log library                        # included in the NDK.                        ${log-lib} ) 

在build.gradle添加CMakeLists.txt路径即可生成的对应so即可(对应build的目录取出)

apply plugin: 'com.android.library'  android {     compileSdkVersion 29     buildToolsVersion "29.0.2"       defaultConfig {         minSdkVersion 23         targetSdkVersion 29         versionCode 1         versionName "1.0"          testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"         consumerProguardFiles 'consumer-rules.pro'          externalNativeBuild {             cmake { //            apply plugin: 'announce'                 cppFlags "" //生成多个版本的so库 //            abiFilters 'armeabi-v7a', 'arm64-v8a' } } //    ndk { //        abiFilters "armeabi-v7a", "arm64-v8a", "x86", "x86_64" //    } }      externalNativeBuild {         cmake {             path "CMakeLists.txt" } } } ...