android ndk开发

https://developer.android.google.cn/ndk/guides/build.html
ndk-build 和cmake 两种方式
参考 Android Studio 2.2 之 NDK开发

http://www.jianshu.com/p/cb3064450688

ndk-build

image.png

app
build.gradle
需android.mk 文件 目录jni

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.0"
    defaultConfig {
        applicationId "com.example.xin.ndkapplication2"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            /*cmake {
                cppFlags "-std=c++11 -frtti -fexceptions"
            }*/
           /* ndk {
                abiFilters "armeabi", "armeabi-v7a", "arm64-v8a", "x86", "x86_64", "mips", "mips64"
            }*/
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        /*cmake {
            path "CMakeLists.txt"
        }*/
        ndkBuild {
            path file("src/main/jni/Android.mk")
        }
    }
    sourceSets { main { jni.srcDirs = ['src/main/jni', 'src/main/cpp/'] } }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:26.+'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
}

Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE    := native-lib
LOCAL_SRC_FILES    :=   native-lib.cpp
include $(BUILD_SHARED_LIBRARY)
LOCAL_LDLIBS        := -llog

native-lib.cpp

#include <jni.h>
#include <string.h>

extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_xin_ndkapplication2_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
    return env->NewStringUTF("fds");
}

cmake

配置文件CMakeLists.txt。

image.png

build.gradle

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.0"
    defaultConfig {
        applicationId "com.example.xin.myapplication"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ""
            }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"

        }
    }
}

native-lib.cpp

#include <jni.h>
#include <string>

JNIEXPORT jstring JNICALL
Java_com_example_xin_myapplication_MainActivity_getStringForm(JNIEnv *env, jobject instance) {

    // TODO


    return env->NewStringUTF("fdsaf");
}

extern "C"
JNIEXPORT jstring JNICALL
Java_com_example_xin_myapplication_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}

CMakeLists.txt

# 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.
             native-lib

             # Sets the library as a shared library.
             SHARED

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

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