Android Studio 错误消息：使用未声明的标识符“accept4”

Question

the jni folder not appear in android studio and after build only java folder get build .

as you can see the jni folder appear in explorer but not inside android studio .

EDIT: so after i added this in my build.gradle

externalNativeBuild {
    ndkBuild {

        path 'src/main/jni/Android.mk'

    }
}

the jni folder appered as cpp folder name but when i compile i get this error from SocketServer.cpp :

use of undeclared identifier 'accept4'

This is the code:

bool SocketServer::Accept() {
    if ((acceptfd = accept4(listenfd, nullptr, nullptr, SOCK_CLOEXEC)) < 0) {
        Close();
        return false;
    }
    return true;
}

and headers is already includes :

#include <sys/types.h>
#include <sys/socket.h>

Answer 1

i get pass the error " use of undeclared identifier 'accept4' " by setting these:

from compileSdkVersion 29       to compileSdkVersion 30
from buildToolsVersion "29.0.3" to buildToolsVersion "30.0.3"
from minSdkVersion 21           to minSdkVersion 22
from targetSdkVersion 29        to targetSdkVersion 30