2023年12月8日发(作者：)
Androidstudio使用Cmake完成CC++的使用以及生成so文件
Android studio 2.2版本以后对C/C++的支持可以说很方便了，当然官方推荐使用Cmake完成对C/C++的支持
2.2版本以上的同学新建一个项目就知道了，步骤如下：
File -> New -> New Project,如下图：
然后勾选Include C++ support,一直next ，最后Finish以后，项目就出现了，和一般的项目略有不同，其实只要多了几个文件，而已：
1：目录下多了个文件
2：src目录下多了一个cpp目录，里面有个.cpp文件，C++文件都是以.cpp结尾的。
3：就是内容中添加了几行配置
一一解读一下，先来看看 文件里面的内容是什么：# For more information about using CMake with Android Studio, read the
# documentation: /studio/projects/
# 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/ )
# 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} )
这里有设置Cmake版本啊，引用的cpp文件的路径啊等等，如果自己引用的话 其实值需要修改引用的cpp路径即可，
其他的暂时不需要动
看下native_文件内容：
#include
#include
extern "C"
JNIEXPORT jstring JNICALL
Java_com_process_main_myapplication_MainActivity_stringFromJNI(
JNIEnv* env,
jobject /* this */) {
std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());
}
很简单 其实就是输出Hello from C++这段文字：
再看下的配置改变：apply plugin: 'ation'
android {
compileSdkVersion 25
buildToolsVersion "25.0.2"
defaultConfig {
applicationId "ication"
minSdkVersion 22
targetSdkVersion 25
versionCode 1
versionName "1.0"
testInstrumentationRunner "dJUnitRunner"
externalNativeBuild {
cmake {
cppFlags ""
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile(''), ''
}
}
externalNativeBuild {
cmake {
path ""
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('so:espresso-core:2.2.2', {
exclude group: 't', module: 'support-annotations'
})
compile 't:appcompat-v7:25.1.1'
compile 'aint:constraint-layout:1.0.0-beta4'
testCompile 'junit:junit:4.12'
}
主要多了两个地方的改变：
1：defaultConfig中添加：
externalNativeBuild {
cmake {
cppFlags ""
}
}
2：在android{}中添加：
externalNativeBuild {
cmake {
path ""
}
}
其实也就是引用文件。
说到这里，大致知道C++项目的大致结构了。那么原始项目怎么添加C++呢，步骤如下：
1，现在src/main目录下新建cpp目录和java目录同级，然后在cpp目录中新建一个.cpp文件，这里以为例子直接copy进去
2，右键项目（选中项目，然后右键）如下：
选择第二个Link C++ Project with Gradle，出现以下界面：
关于Project Path是选择文件的路径，这里先把之前的文件直接copy过来，然后相应的修改即可：
选择CmakeLists文件然后点击OK按钮。修改文件中的cpp文件引用目录即可(add_library {第三行})。
接下来，在java代码中调用C++代码啦，看下MainActivity中的代码：public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
te(savedInstanceState);
setContentView(ty_main);
// Example of a call to a native method
TextView tv = (TextView) findViewById(_text);
t(stringFromJNI());
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
public native String stringFromJNI();
// Used to load the 'native-lib' library on application startup.
static {
brary("native-lib");
}
}
这里注意brary("native-lib"),加载（native-lib）Library，这里是CmakeLists文件中配置好的Library名字要对应。
然后就是native调用stringFromJNI ()方法啦》
最后编译一下app，Make Project build一下，然后run到手机上就可以运行了。
这里有同学想问那.so文件在哪里找啊 ，如下图：
这里的so文件就可以用到其他项目中啦；
至此一个简单的使用C++项目就完成啦
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