NDK android studio 3.4 和 Eclipse 詳細使用文檔

 

1. Android Studio搭建環境
   • Native c++ 快速生成NDK編譯環境
   • 普通項目使用CMake 手動創建編譯環境
2. Eclipse 搭建環境

         有些公司環境特殊可能因爲某些原因還在繼續使用着Eclipse 。

     3. Android studio 多個c/c++文件配置方式

     4. C/C++調用logcat日誌

      

Android Studio 3.4 NDK搭建環境

在android studio 下對NDK的支持非常的方便，只要在

Studio 3.4.1 進入Android SDK --> SDK Tools 下載 ndk和cmake

Native c++ 一鍵生成NDK編譯環境

 

Android studio 3.3開始創建NewProgr單獨把include c++ support 提取到新的模板。

選擇 Native c++   --->   next下一步

 

選擇Default即可

 

自動生成c++的運行環境 ，直接可以運行在屏幕上顯示 “Hello from c++”說明成功了。

 

Android Studio 利用CMake手動創建NDK 編譯環境

1. 首先還是先進入進入Android SDK --> SDK Tools 下載 ndk和cmake

2. 創建或者導入一個普通的android項目

3. 在項目裏創建一個類並且寫一個native方法

public class MyNative {
    static {
        System.loadLibrary("myLib");
    }
    public static native int add(int number1,int number2);
}

4. 生成 .h 頭文件

進入 Terminal 輸入命令進入java目錄  ：cd app/src/main/java

在java目錄下生成 .h頭文件  ：javah  包名.MyNative

自動生成如下內容

​
/* DO NOT EDIT THIS FILE - it is machine generated */
//需要複製到C/C++文件下
#include <jni.h>
/* Header for class com_laiweifeng_myapplication_MyNative */

#ifndef _Included_com_laiweifeng_myapplication_MyNative
#define _Included_com_laiweifeng_myapplication_MyNative
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_laiweifeng_myapplication_MyNative
 * Method:    add
 * Signature: (II)I
 */
//C/C++文件所需要調用的jni方法
JNIEXPORT jint JNICALL Java_com_laiweifeng_myapplication_MyNative_add
  (JNIEnv *, jclass, jint, jint);

#ifdef __cplusplus
}
#endif
#endif

​

 

5. 在app/src/main下創建jni文件夾，把java目錄下的頭文件和把編寫好的c/c++文件剪切或者複製到jni文件夾下

 

6. 把剛剛生成的 .h 頭文件裏面的方法複製到 .c 文件內,並且改一下變量加上名字和實現方法

#include <jni.h>

JNIEXPORT jint JNICALL Java_com_laiweifeng_myapplication_MyNative_add
  (JNIEnv * env, jclass obj, jint number1, jint number2){
    //加法運算
    return number1+number2;
    
  }

 

7. 右鍵在app目錄下創建File，命名爲“CMakeLists.txt”

 

8 . 把以下的內容複製到CMakeLists.txt下

 

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
             myLib #.so庫名 可自定義

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             src/main/jni/myc.c ) #源文件所在目錄
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
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 )
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
                       myLib #.so庫名 可自定義
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

9. 右鍵 app目錄選擇 “Link C++ project with Gradle”  填寫當前項目下的“CMakeLists.txt” 的絕對路徑後點擊確定自動在app下的build.gradle 生成對應的引入。

 

android {
    
    externalNativeBuild {
        cmake {
            path file('CMakeLists.txt')
        }
    }
}

10 . build -> make project 自動生成so文件說明配置成功,最後調用native方法。

 

Eclipse 搭建NDK開發環境

1. 首先第一部還是下載NDK開發包：https://developer.android.google.cn/ndk/downloads/index.html

我用的是目前最新的 r20 。

2. 解壓android-ndk-r20-windows-x86_64.zip ，並且配置環境變量：我的電腦-> 屬性->高級->環境變量->系統變量->把剛剛解壓的文件路徑添加到path裏。

3. 導入或者新建普通的eclipse項目，創建native本地方法

public class MyNative {
    static {
        System.loadLibrary("myLib");
    }
    public static native int add(int number1,int number2);
}

4. 打開cmd命令窗口，cd 當前工程src目錄下，執行javah 生成頭文件：

   cd  your project/src 

   javah 包名.MyNative

  右鍵刷新一下就可以看到頭文件了。

 

5. 右鍵當前項目創建jni文件夾，並且把頭文件拖到jni文件夾下。

6. 把編寫好的c/c++文件放置在jni目錄下，並把.h生成的方法拷貝到c/c++文件下，實現方法。

#include <jni.h>
JNIEXPORT jint JNICALL Java_com_laiweifeng_jni_MyNative_add
        (JNIEnv * env, jclass obj, jint num1, jint num2){

    return num1+num2;
}

7. 在jni下創建Android.mk 文件，把以下內容拷貝到裏面去。

LOCAL_PATH := $(call my-dir)

# --------------------------------------------------------------
include $(CLEAR_VARS)

LOCAL_MODULE := myLib #自定義so庫名稱
LOCAL_SRC_FILES := myc.c  #調用的c/c++文件
LOCAL_LDLIBS := -llog  #android log日誌聲明使用

include $(BUILD_SHARED_LIBRARY)

8. 在當前工程目錄下執行ndk-build 生成.so庫，右鍵刷新一下就可以看到了。

 

 

 

Android studio 多個c/c++文件配置方式

cmake_minimum_required(VERSION 3.4.1)

add_library( # Sets the name of the library.
             myLib #.so庫名 可自定義

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             src/main/jni/myc.c
             src/main/jni/myc2.c) #多個c文件就在此添加多個
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
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 )
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
                       myLib #.so庫名 可自定義
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

區別只在這裏，其他的調用方式都是一樣的，就不再累述了。

C/C++調用logcat日誌

#include <android/log.h>

#define LOG_TAG "自定義tag名"

#define LOGV(...) __android_log_print(ANDROID_LOG_VERBOSE, LOG_TAG, __VA_ARGS__))

#define  LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__)

#define LOGI(...) __android_log_print(ANDROID_LOG_INFO   , LOG_TAG, __VA_ARGS__))

#define LOGW(...) __android_log_print(ANDROID_LOG_WARN   , LOG_TAG, __VA_ARGS__))

#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR  , LOG_TAG, __VA_ARGS__))

//調用示例
LOGV("我是打印");
LOGV("我是 %s","小明");

打印Log要拼接字符串需要使用佔位符，詳情瀏覽以下鏈接

https://blog.csdn.net/qq_29350001/article/details/52278308