AndroidStudio java项目中添加cpp支持_android studio cpp no file

如果在AndroidStudio中创建android项目时未设置c/cpp属性，则需要如下步骤来添加native cpp的支持：

1. 添加cpp目录。添加文件一定要小心，目录不要弄错。注意此目录要放在app/src/main目录下，同时完成添加cpp文件和代码编写等。其余的，比如java代码中调用native函数的语法、cpp中java调用函数的命名规则（注意这些函数不用导出）等编程细节不再赘述。

2. 添加CMakeLists.txt。注意CMakeLists.txt文件要放在app目录下。根据cpp文件的名称，修改CMakeLists.txt中的原文件全路径名称和so模块名称。该文件模板如下：

#CMakeLists.txt 内容如下：
# Sets the minimum version of CMake required to build your native library.
# This ensures that a certain set of CMake features is available to
# your build.

cmake_minimum_required(VERSION 3.4.1)

# Specifies a library name, specifies whether the library is STATIC or
# SHARED, and provides relative paths to the source code. You can
# define multiple libraries by adding multiple add.library() commands,
# and CMake builds them for you. When you build your app, Gradle
# automatically packages shared libraries with your APK.

add_library( # Specifies 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 )
			 
# Specifies a path to native header files.
# include_directories(src/main/cpp/include/)

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3. 修改build.gradle 文件。注意android中有两个gradle文件，要修改的文件在app目录下面的，而不是根目录下的gradle文件。（疑问：为何一个工程需要两个同名文件，此两个同名文件有何区别？）
若工程未添加过cpp文件，则gradle中android字段只需要添加如下字段：

    externalNativeBuild {

        // Encapsulates your CMake build configurations.
        cmake {

            // Provides a relative path to your CMake build script.
            path "CMakeLists.txt"
        }
    }
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如此操作后，将实现android stuidio对native开发的支持。