How to properly include C++ support to Android Studio project?

Issue

I have a project in C++ and I want to use it in my android application.

Created new application according to Google's instructions:

1. In the Choose your project section of the wizard, select the Native C++ project type.
2. Click Next.
3. Complete all other fields in the next section of the wizard.
4. Click Next.
5. In the Customize C++ Support section of the wizard, you can customize your project with the C++ Standard field. Use the drop-down list to select which standardization of C++ you want to use. Selecting Toolchain Default uses the default CMake setting.
6. Click Finish.

Here is the project I ended up with: (I didn't change anything so it should be generic)

native-lib.cpp:

#include <jni.h>
#include <string>

extern "C" JNIEXPORT jstring JNICALL 
Java_e_viktor_testinggitapplication_MainActivity_stringFromJNI(JNIEnv *env,

jobject /* this */) {
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}

MainActivity.java:

package e.viktor.testinggitapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

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 = 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();
}

Here I only added cmake's version

Gradle:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "e.viktor.testinggitapplication"
        minSdkVersion 15
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"         

testInstrumentationRunner"android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                version "3.10.2"
                cppFlags ""
            }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'),'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

CMakeLists.txt:

cmake_minimum_required(VERSION 3.4.1)
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)
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)
target_link_libraries( # Specifies the target library.
        native-lib

        # Links the target library to the log library
        # included in the NDK.
        ${log-lib})

As a result - 'Cannot resolve corresponding JNI function' in MainActivity.java

and

'Cannot find field' for all the #include and 'Cannot resolve type' for all the types in cpp file.

An interesting thing is that gradle builds successfully.

Edit:

Added CMakeLists.txt

Solution

I suppose the problem was in missing pieces of NDK, as after updating studio to 3.3 everything solved.

For anyone with a similar situation:
I had this problem even though I manually installed NDK in Tools section and used only autogenerated by Android Studio project.

Answered By - Viktor Scherbakov