Your project contains C++ files but it is not using a supported native...

Android Studio配置NDK时出现问题：

Error: Your project contains C++ files but it is not using a supported native build system.
Consider using CMake or ndk-build integration. For more information, go to:
 https://d.android.com/r/studio-ui/add-native-code.html
Alternatively, you can use the experimental plugin:
 https://developer.android.com/r/tools/experimental-plugin.html

原因：

1. 没有创建Android.mk文件进行库文件配置；
2. 没有把Android.mk文件添加到项目中；

解决办法：
切换到Android视图-右键项目-Link C++ Project with Gradle

在Build System中选择ndk-build，并在Project Path添加Android.mk路径

ok了