android studio ndk 开发

新建工程, 选中Include C++ Support

一路Next之后, 在最后Finish页面尽量选中图示两项, 这样会给我们包裹一些特定的示例代码, 帮助我们理解和使用

自动生成的代码:

MainActivity.java

public class MainActivity extends AppCompatActivity {    // Used to load the 'native-lib' library on application startup.    static {        System.loadLibrary("native-lib");    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        // Example of a call to a native method        TextView tv = (TextView) findViewById(R.id.sample_text);        tv.setText(stringFromJNI());    }    public native String stringFromJNI();}

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} )

app/main/src/native-lib.cpp

#include <jni.h>#include <string>extern "C"JNIEXPORT jstring JNICALLJava_thereisnospon_ndkdemo_MainActivity_stringFromJNI(        JNIEnv *env,        jobject /* this */) {    std::string hello = "Hello from C++";    return env->NewStringUTF(hello.c_str());}

自己模仿写个 lib : c1

Hello.java

public class Hello {    static {        System.loadLibrary("c1");    }    public static native String getStr();}

app/main/src/c1.cpp

#include<jni.h>#include<string>using namespace std;extern "C"  // 记得加这个。。JNIEXPORT jstring JNICALLJava_thereisnospon_ndkdemo_Hello_getStr(JNIEnv *env, jclass type) {    // TODO    string c="ldsf";    return env->NewStringUTF(c.c_str());}

CMakelists.txt 添加

add_library(             c1             SHARED             src/main/cpp/c1.cpp)