android studio 编译so文件入门（ndk配置及demo)2

上一节简单介绍了ndk的安装及demo运行，这次记录下demo的结构及作用

1 cpp目录及cmakeLists.txt

cp目录，是写c++源码的文件目录，创建demo后，会自带native-lib.cpp,这是一个c++返回字符串的示例

include

include

extern “C”
jstring
Java_com_buybal_www_ndkdemo2_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = “Hello from C++”;
return env->NewStringUTF(hello.c_str());
}
activity 调用c++的方式：
public class MainActivity extends AppCompatActivity {

// Used to load the 'native-lib' library on application startup.static {    System.loadLibrary("native-lib");}@Overrideprotected 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());}/** * A native method that is implemented by the 'native-lib' native library, * which is packaged with this application. */public native String stringFromJNI();

}

这里注意System.loadLibrary(“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》,特别说明的是c++的方法名规则是 Java_包名_方法名

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。

2 cmakeLists.txt
add_library( # Sets the name of the library.
native-lib //生成so文件名
# Sets the library as a shared library.
SHARED

         # Provides a relative path to your source file(s).         # Associated headers in the same location as their source         # file are automatically included.         src/main/cpp/native-lib.cpp //生成so文件的源文件          )

描述的可能有些不详细，多拿demo改改看看效果就能摸清门道了，摸清demo后，入了门，就进入实践阶段了，敬请关注下一集。