AndroidStudio NDK环境3种搭建方式

AndroidStudio NDK环境3种搭建方式

 

 

转载。 https://blog.csdn.net/zhang_jun_ling/article/details/85621427

一、前言

如今Android开发IDE都是使用的AndroidStudio，之前我写过一篇文章介绍的是如何在Eclipse中搭建NDK环境　Android NDK --初始android NDK
这边博客介绍下在AndroidStudio中搭建NDK环境的三种方式。

二、知识点概述

本片我们将从以下几点初步认识、创建Android NDK：
1.Java加载/调用NDK端的代码；
2.本地 c++代码的编写；
3.编写构建系统文件（android.mk、application.mk）
4.通过构建系统编译c++代码
4.1、通过Gradle搭建NDK环境；
4.2、通过NDKBuild搭建NDK环境（重点介绍）;
4.3、通过CMake搭建NDK环境;

三、知识点详解

(1)Java加载/调用NDK端的代码

1、Java端代码:

public class MainActivity extends AppCompatActivity {

    static {
        System.loadLibrary("helloworld");
    }

    private TextView mDataView;

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

        initView();
    }

    private void initView() {
        mDataView = (TextView) this.findViewById(R.id.tv_data);
        mDataView.setText(getStrFromNative());
    }

    private native String getStrFromNative();
}

2、在AndroidStudio打开命令行界面，cd app/src/main/java 运行

javah com.zhangjunling.ndk_environment_gradle.MainActivity

• 1

这时会自动在目录下生成一个com_zhangjunling_ndk_environment_gradle_MainActivity.h文件，把文件拷贝到 main/jni 目录中。

(２) 本地 c++代码的编写

由于本编只是介绍NDK环境的搭建问题，所以代码越简单越容易把所有的精力都放在环境搭建上，所以ｃ++代码只是简单的 HelloWrold程序；

helloworld.cpp

#include "com_zhangjunling_ndk_environment_gradle_MainActivity.h"

JNIEXPORT jstring JNICALL Java_com_zhangjunling_ndk_1environment_1gradle_MainActivity_getStrFromNative
  (JNIEnv *env, jobject obj){
      return env->NewStringUTF("Hello. I'm form native");
}

(3)编写构建系统文件

在jni目录下创建Android.mk、Application.mk文件内容如下:
Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE    := helloworld
LOCAL_SRC_FILES := helloworld.cpp

include $(BUILD_SHARED_LIBRARY)

Application.mk

APP_STL := gnustl_static
APP_ABI := armeabi

关于构建系统里面的键值对的含义，现在先不关心，下篇文章我会详细介绍；

(4)通过构建系统编译c++代码

通过Gradle搭建NDK环境

Gradle是androidstudio上的编译工具，我们可以通过从项目下的local.properties获取ndk.dir=xxxxxxxx，获取ndk-build路径，然后执行ndk-build便可以编译出需要的动态库文件；gradle的语法这里不在进行讲解，感兴趣的可以从网络上获取资料学习；
build.gradle代码如下：

import org.apache.tools.ant.taskdefs.condition.Os

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.zhangjunling.ndk_environment_gradle"
        minSdkVersion 19
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    sourceSets {
        main {
            jniLibs.srcDir 'src/main/libs'
            jni.srcDirs = []
        }
    }
}

tasks.withType(JavaCompile) {
    compileTask -> compileTask.dependsOn ndkBuild
}

String getNdkBuildPath() {
    Properties properties = new Properties()
    properties.load(project.rootProject.file('local.properties').newDataInputStream())
    def ndkBuildingDir = properties.getProperty("ndk.dir")
    def ndkBuildPath = ndkBuildingDir
    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
        ndkBuildPath = ndkBuildingDir + '/ndk-build.cmd'
    } else {
        ndkBuildPath = ndkBuildingDir + '/ndk-build'
    }
    return ndkBuildPath
}

task ndkBuild(type: Exec, description: 'Compile JNI source via NDK') {
    println('executing ndkBuild')
    def ndkBuildPath = getNdkBuildPath();
    commandLine ndkBuildPath, '-j8', '-C', file('src/main').absolutePath
}

task ndkClean(type: Exec, description: 'clean JNI libraries') {
    println('executing ndkBuild clean')
    def ndkBuildPath = getNdkBuildPath();
    commandLine ndkBuildPath, 'clean', '-C', file('src/main').absolutePath
}
clean.dependsOn 'ndkClean'

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

• 1过工具栏 Build/ReBuild Project，观察到libs目录、obj目录自动产生，没有报错。这可以说明我们的配置没有什么问题；可以运行项目看到：

Hello. I'm form native

通过NDKBuild搭建NDK环境（重点介绍）

通过ndk-build交叉编译c++本地代码是我们重点学习的，后面我会重点介绍通过ndk-build交叉编译出我们需要的动态库。本篇只介绍环境的搭建。
Android.mk构建好了之后，ndk-build环境就比较简单了，步骤：

项目右键－>Link C++ Project　With　Gradle　
路径选择Android.mk　就OK 了。

通过CMake搭建NDK环境

CMake搭建NDK环境有两种方式：
１、与ndk-build相同

项目右键－>Link C++ Project　With　Gradle　
路径选择CMakeList.txt　就OK 了。

2、在Create Android Project的时候底部勾选Include C++ support，项目创建好了之后，自动创建好了NDK环境。我们可以在此基础上开发NDK。

项目路径：AndroidStudio环境搭建源码

 
三种方法 app/build.gradle文件内容如下：

import org.apache.tools.ant.taskdefs.condition.Os
apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.myapplication"
        minSdkVersion 16
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

        ndk {
            moduleName "Test"
            ldLibs "log"
//          abiFilters "armeabi", "armeabi-v7a", "x86" //输出指定三种abi体系结构下的so库，目前可有可无
        }

        // 使用Cmake工具-way1
//start way1
//        externalNativeBuild {
//            cmake {
//                cppFlags ""
//                abiFilters 'arm64-v8a','armeabi-v7a','x86','x86_64'
//            }
//        }
    }

//    // 配置CMakeLists.txt路径-way1
//    externalNativeBuild {
//        cmake {
//            path "CMakeLists.txt"   // 设置所要编写的c源码位置，以及编译后so文件的名字
//        }
// end way2

// 设置按android.mk 进行编译-way2
//start way2
    externalNativeBuild {
        ndkBuild {
            path "src/main/jni/Android.mk"
        }
    }
//end way2
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'

        }
    }

//    sourceSets.main {
//        jni.srcDirs = ['src/main/jni', 'src/main/jni/']
//        jniLibs.srcDirs "src/main/libs"
//    }
    sourceSets {
        main {
            jniLibs.srcDir 'src/main/libs'
            jni.srcDirs = []
        }
    }
    compileOptions {
        sourceCompatibility = '1.8'
        targetCompatibility = '1.8'
    }
    buildToolsVersion = '28.0.3'

}
/*
//begin -- way3
tasks.withType(JavaCompile) {
    compileTask -> compileTask.dependsOn ndkBuild
}

String getNdkBuildPath() {
    Properties properties = new Properties()
    properties.load(project.rootProject.file('local.properties').newDataInputStream())
    def ndkBuildingDir = properties.getProperty("ndk.dir")
    def ndkBuildPath = ndkBuildingDir
    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
        ndkBuildPath = ndkBuildingDir + '/ndk-build.cmd'
    } else {
        ndkBuildPath = ndkBuildingDir + '/ndk-build'
    }
    return ndkBuildPath
}

task ndkBuild(type: Exec, description: 'Compile JNI source via NDK') {
    println('executing ndkBuild')
    def ndkBuildPath = getNdkBuildPath();
    commandLine ndkBuildPath, '-j8', '-C', file('src/main').absolutePath
}

task ndkClean(type: Exec, description: 'clean JNI libraries') {
    println('executing ndkBuild clean')
    def ndkBuildPath = getNdkBuildPath();
    commandLine ndkBuildPath, 'clean', '-C', file('src/main').absolutePath
}
clean.dependsOn 'ndkClean'
//end-way3
*/
dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:2.0.0-alpha4'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

在app/build.gradle同目录下的CMakeLists.txt文件内容如下：

# 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.
#CMakeLists.txt
#指定需要CMake的最小版本
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.
            # 设置so文件名称.
             Test

             # Sets the library as a shared library.
             SHARED
             # 设置这个so文件为共享.

             # Provides a relative path to your source file(s).
             # 设置这个so文件的源码文件.
             src/main/jni/Test.cpp)

# 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.
                       # 制定目标库.
                       Test

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

在jni目录下的Android.mk内容如下：

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := Test
LOCAL_SRC_FILES := Test.cpp

LOCAL_LDLIBS :=  -llog

include $(BUILD_SHARED_LIBRARY)

在jni目录下的Application.mk内容如下：

APP_MODULES := Test
APP_PLATFORM := android-16
APP_ABI := all