簡(jiǎn)介
項(xiàng)目需要涉及到JNI調(diào)用C++ 代碼所以所以學(xué)習(xí)了一了一下Android Studio 工具下 Cmake方式的 Jni 調(diào)用的一些知識(shí)特此記錄一下
環(huán)境版本
- Android Studio 4.1.3
- Gradle 4.1.3
- Cmake 3.10.2
- ndk 21.1.6352462
- buildToolsVersion 30.0.3
1.項(xiàng)目配置
plugins {
id 'com.android.application'
id 'kotlin-android'
}
android {
compileSdkVersion 31
// 31.0.0 版本有異常不能用
buildToolsVersion "30.0.3"
defaultConfig {
applicationId "com.wkq.cdemo"
minSdkVersion 21
targetSdkVersion 31
versionCode 1
versionName "1.0"
//設(shè)置NDK版本(生成動(dòng)態(tài)so庫(kù)的時(shí)候要用)
ndkVersion "21.1.6352462"
// gradle 執(zhí)行的任務(wù)名字
externalNativeBuild {
cmake {
cppFlags ""
// 過濾生成的庫(kù)類型
// abiFilters 'armeabi-v7a'
// 庫(kù)格式'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
//生成指定版本的 CMakeLists.txt 文件
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
version "3.10.2"
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
}
dependencies {
implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.0'
implementation 'com.google.android.material:material:1.4.0'
}
文件.png
2.CMakeLists 文件介紹
# 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.
#設(shè)置CMake的最低版本
cmake_minimum_required(VERSION 3.10.2)
# Declares and names the project.
project("cdemo")
#這些 native-lib.cpp資源打包設(shè)置成一個(gè)名為hellow 的共享庫(kù)（SHARED 替換為STATIC則設(shè)置為靜態(tài)庫(kù)）
# native-lib.cpp
add_library( # Sets the name of the library.
hellow
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
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.
#（設(shè)置要鏈接的庫(kù)文件的名稱 hellow）
target_link_libraries( # Specifies the target library.
hellow
# Links the target library to the log library
# included in the NDK.
${log-lib} )
3.cpp 文件簡(jiǎn)介
// include 是導(dǎo)包
#include <jni.h>
#include <string>
// extern "C" :C++兼容C代碼的
// JNIEXPORT 類似于public修飾符
// JNICALL 用來表示函數(shù)的調(diào)用規(guī)范
// jstring 返回?cái)?shù)據(jù)類型 這里是String
// Java_<包名>_<類名>_<方法名>
extern "C"
JNIEXPORT jstring JNICALL Java_com_wkq_cdemo_MyJniUtil_stringFromJNI(
JNIEnv* env,
jobject /* this */) {
std::string hello = "1122211";
return env->NewStringUTF(hello.c_str());
}
4. JNI 工具類
package com.wkq.cdemo;
/**
* @author wkq
* @date 2022年06月28日 16:46
* @des
*/
public class MyJniUtil {
//加載 so庫(kù)
static{
System.loadLibrary("hellow");
}
// jni 調(diào)用
public static native String stringFromJNI();
}
5.調(diào)用
String content=MyJniUtil.stringFromJNI();
6.生成動(dòng)態(tài)So庫(kù)
生成動(dòng)態(tài)So庫(kù)有兩種方式
- make project
-
Gradle任務(wù)中執(zhí)行 externalNativeBuildRelease/externalNativeBuildRelease或者externalNativeBuildDebug 任務(wù)
生成方式.png
結(jié)果.png
總結(jié)
簡(jiǎn)單的梳理了C++類型項(xiàng)目中一些配置,然后生成了動(dòng)態(tài)的So庫(kù).
那些打不死我的終將使我強(qiáng)大,繼續(xù)死磕JNI
