NDK开发之三方so包在CMake的引入、文件拆分和合并,以及线程

前言

学过的知识点太容易忘记了,做个记录后续方便查询

正题

主要有三个内容

  • Cmake链接三方so库
  • 文件拆分和合并
  • NDK的线程

Cmake链接三方so库

在平常开发项目的时候常见的是引入三方的so库,然后java调用已经给好的api。如果需要在C++或者C中调用呢,Android的NDK开发,提供了CMake,将三方的so库,动态链接到我们的项目。
这边以一个简单的例子在C++代码调用so的api

项目结构.png

步骤:

  • 将三方so库copy到项目的libs(如果copy到jnilibs下是不需要配置)
    如果将so包复制到module下的libs,需要在build.gradle配置
android{
  .............省略代码............
   sourceSets {
    main {
      jniLibs.srcDirs = ['libs']
      jni.srcDirs = []
    }
  }
}
  • 在CMakeList.txt 配置三方so包,并且链接到当前项目
cmake_minimum_required(VERSION 3.4.1)

#设置so库路径
set(my_lib_path ${CMAKE_SOURCE_DIR}/../../../libs)

#将第三方库作为动态库引用
add_library(myTest
        SHARED
        IMPORTED)

#指定第三方库的绝对路径
set_target_properties(myTest
        PROPERTIES IMPORTED_LOCATION
        ${my_lib_path}/${ANDROID_ABI}/libtest-lib.so)

#设置的本项目生成的so的引用名
add_library( # Sets the name of the library.
             asTest

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             native-lib.cpp )

#引用的是系统的库
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 )

#最后都需要链接到项目中
target_link_libraries( # Specifies the target library.
                       asTest
                       myTest

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )
  • 将三方的api的头文件引入到cpp的目录下


    image.png

    可以看到相关的api

#ifndef SOUSE_MY_TEST_H
#define SOUSE_MY_TEST_H

//申明外部 函数 外部属性
extern int sum(int a, int b);

#endif //SOUSE_MY_TEST_H
  • 在自己的项目中引用
    native-lib.cpp
#include "my-test.h"  //引入头文件

extern "C"
JNIEXPORT jint JNICALL
Java_com_ndk_so_use_MainActivity_doAdd(JNIEnv *env, jobject thiz, jint a, jint b) {
    return sum(a,b);
}
  • java代码调用c++的代码(JNI)
  //native方法的定义
  public native int doAdd(int a, int b);

  //调用
  int result = doAdd(99, 66);
  tv.setText("result = " + result);

文件拆分和合并

文件拆分一般是因为文件比较大需要上传,所以通过拆分成多个文件再进行上传。
关于C++的文件操作的介绍https://www.jianshu.com/p/422b4df24dad之前有整理过。
这边代码后续的native方法是采用动态注册,关于native方法的动态注册可以查看https://www.jianshu.com/p/3aeabe2b5744
:手机读写,6.0以上的机器,需要动态申请权限
撸码

  • native方法的定义:
public class FileUtil {

  public static native int diffFile(String srcPath, String partPath, int count);
  public static native int mergeFile(String mergePath, String partPath, int count);
}
  • 文件拆分
    C++的实现代码:
/**
 * 获取文件大小
 */
long  get_file_size(const char* path) {
    FILE *fp = fopen(path, "rb"); //打开一个文件, 文件必须存在,只运行读
    if(fp == NULL) {
        LOG_I("open file failed...");
        return 0;
    }
    fseek(fp, 0, SEEK_END);
    long ret = ftell(fp);
    fclose(fp);
    return ret;
}

/**
 * 文件拆分
 */
JNIEXPORT jint JNICALL native_diff(JNIEnv *env, jclass jclz, jstring src_path, jstring part_path, jint count)
{
    LOG_I("start begin diff file.");
    //jstring 转 char*
    // 需要拆分的文件路径
    const char* srcPath = env->GetStringUTFChars(src_path, NULL);
    // 拆分后的文件路径格式
    const char* partPath = env->GetStringUTFChars(part_path, NULL);

    char *partPaths[count];
    int i;
    for (i = 0; i < count; ++i) {
        //每个文件名申请地址
        LOG_I("char = %d char * = %d", sizeof(char), sizeof(char *));
        partPaths[i] = (char*)malloc(sizeof(char) * 200);
        // 需要分割的文件 Vibrato.mp4
        // 每个子文件名称 Vibrato_n.mp4
        sprintf(partPaths[i], partPath, i);
        LOG_I("patch path : %s", partPaths[i]);
    }

    int fileSize = get_file_size(srcPath);
    FILE *fpr = fopen(srcPath, "rb");
    if(fpr == NULL) {
        LOG_I("open file failed...");
        return 0;
    }

    //判断文件大小能够被 count 整除
    if(fileSize % count == 0) {
        //能整除就平分,获取每一份的大小
        int part = fileSize / count;
        for (int i = 0; i < count; ++i) {
            FILE *fpw = fopen(partPaths[i], "wb"); //文件已经存在 就删除,只运行写
            for (int j = 0; j < part; ++j) {
                fputc(fgetc(fpr), fpw);
            }
            fclose(fpw);
        }
    } else{
        //不能整除就先分 count -1, 剩下的作为单独一份
        int part = fileSize / (count -1);
        for (int i = 0; i < count - 1; ++i) {
            FILE *fpw = fopen(partPaths[i], "wb");
            for (int j = 0; j < part; ++j) {
                fputc(fgetc(fpr), fpw);
            }
            fclose(fpw);
        }

        FILE *fpw = fopen(partPaths[count - 1], "wb");
        for (int j = 0; j < fileSize % (count - 1); ++j) {
            fputc(fgetc(fpr), fpw);
        }
        fclose(fpw);
    }

    fclose(fpr);

    free(partPaths);
    env->ReleaseStringUTFChars(src_path, srcPath);
    env->ReleaseStringUTFChars(part_path, partPath);
    LOG_I("diff file finish.");
    return 1;
}

java的调用代码:

public void onDiff(View view) {
    (new Thread(){
      @Override
      public void run() {
        String srcPath = SD_CARD_PATH + File.separator + "ZERO.rmvb";
        String partPath = SD_CARD_PATH + File.separator + "ZERO_%d.rmvb";
        final int result = FileUtil.diffFile(srcPath, partPath, 4);
        runOnUiThread(new Runnable() {
          @Override
          public void run() {
            if(result == 1) {
              showToast("拆分成功");
            }else {
              showToast("拆分失败");
            }
          }
        });
      }
    }).start();
  }
  • 文件合并
    C++的实现代码:
/**
 * 文件合并
 */
JNIEXPORT jint JNICALL native_merge(JNIEnv *env, jclass jclz, jstring merge_path, jstring part_path, jint count)
{
    LOG_I("start begin merge file.");
    //获取合并后生成的文件路径
    const char * mergePath = env->GetStringUTFChars(merge_path, NULL);
    //获取拆分文件的格式
    const char * partPath = env->GetStringUTFChars(part_path, NULL);

    char *partPaths[count];

    for (int i = 0; i < count; ++i) {
        partPaths[i] = (char*) malloc(sizeof(char) * 200);

        sprintf(partPaths[i], partPath, i);
        LOG_I("partPaths[%d] = %s", i, partPaths[i]);
    }

    FILE *fpw = fopen(mergePath, "wb");
    if(fpw == NULL) {
        return 0;
    }

    for (int i = 0; i < count; ++i) {
        FILE *fpr = fopen(partPaths[i], "rb");
        int fileSize = get_file_size(partPaths[i]);
        for (int j = 0; j < fileSize; ++j) {
            fputc(fgetc(fpr), fpw);
        }
        fclose(fpr);
    }
    fclose(fpw);
    free(partPaths);
    env->ReleaseStringUTFChars(merge_path, mergePath);
    env->ReleaseStringUTFChars(part_path, partPath);
    LOG_I("file merge finish");
    return 1;
}

java的调用代码:

  public void onMerge(View view) {
    (new Thread(){
      @Override
      public void run() {
        String srcPath = SD_CARD_PATH + File.separator + "ZERO_merge.rmvb";
        String partPath = SD_CARD_PATH + File.separator + "ZERO_%d.rmvb";
        final int result = FileUtil.mergeFile(srcPath, partPath, 4);
        runOnUiThread(new Runnable() {
          @Override
          public void run() {
            if(result == 1) {
              showToast("合并成功");
            }else {
              showToast("合并失败");
            }
          }
        });
      }
    }).start();

  }

线程

在C++中开线程调度java的方法
撸码
java代码native方法的定义:

public class ThreadUtil {


  public native void createThread();

  public native void setJniEnv();

  public native void releaseThread();

  public void jniThreadCallBack() {

  }

  public static void formJni( int i) {
    Log.d("so_use","form jni : " +i);
  };

  public static void formJNIAgain(int i) {
    Log.v("so_use","form_JNI_Again : "+i);
  }
}

C++代码:这边需要使用到新的api,引入pthread的头文件

#include <pthread.h>

JavaVM* g_jvm = NULL;
jobject g_obj = NULL;

//一个进程只有一个jvm
//一个线程一个JniEnv
void* thread_fun(void * args) {

    JNIEnv *env;
    jclass clz;
    jmethodID  mid, mid1;

    if(g_jvm->AttachCurrentThread(&env, NULL) != JNI_OK) {
        LOG_I("%s AttachCurrentThread error failed ",__FUNCTION__);
        return NULL;
    }

    clz = env->GetObjectClass(g_obj);

    if(clz == NULL) {
        LOG_I("load class failed.");
        goto error;
    }

    LOG_I("call back begin");
    mid = env->GetStaticMethodID(clz, "formJni", "(I)V");
    if (mid == NULL) {
        LOG_I("GetStaticMethodID error....");
        goto error;
    }

    env-> CallStaticVoidMethod(clz, mid, args);

    mid1 = env->GetStaticMethodID(clz, "formJNIAgain", "(I)V");
    if (mid1 == NULL) {
        LOG_I("GetStaticMethodID error....");
        goto error;
    }

    env-> CallStaticVoidMethod(clz, mid1, args);

    error:
    if (g_jvm -> DetachCurrentThread() != JNI_OK) {
        LOG_I("%s DetachCurrentThread error failed ",__FUNCTION__);
    }
    pthread_exit(0);
}

JNIEXPORT void JNICALL native_createThread(JNIEnv *env, jobject job)
{
    LOG_I("createThread begin");
    int i;
    pthread_t pt[5];

    for (int i = 0; i < 5; ++i) {
        pthread_create(&pt[i], NULL, &thread_fun, (void*)i);
    }
}

JNIEXPORT void JNICALL native_setJniEnv(JNIEnv *env, jobject job)
{
    LOG_I("native_setJniEnv");
    if(g_jvm != NULL) {
        g_jvm = NULL;
    }

    //保存JVM
    env -> GetJavaVM(&g_jvm);
    //保持actvity对象
    g_obj = env -> NewGlobalRef(job);
}

JNIEXPORT void JNICALL native_releaseThread(JNIEnv *env, jobject job)
{
    LOG_I("native_releaseThread");
    if(g_jvm != NULL) {
        g_jvm = NULL;
    }
    env->DeleteGlobalRef(g_obj);
}

java代码中调用

private ThreadUtil threadUtil;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //创建对象,设置JNI中的全局引用
    threadUtil = new ThreadUtil();
    threadUtil.setJniEnv();
  }

public void onCreateThread(View view) {
    threadUtil.createThread();
}

public void onReleaseThread(View view) {
    threadUtil.releaseThread();
}

以上就是全部的内容
项目的源码:https://github.com/jasonkevin88/SoUse

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