JNI

build.gradle.kts

@@ -2,4 +2,5 @@ plugins {
     alias(libs.plugins.androidLibrary).apply(false)
     alias(libs.plugins.kotlinMultiplatform).apply(false)
     alias(libs.plugins.vanniktech.mavenPublish).apply(false)
+    alias(libs.plugins.kotlin.android) apply false
 }

gradle/libs.versions.toml

@@ -8,6 +8,13 @@ mavenPublish = "0.29.0"
 
 #Coroutines
 kotlin-coroutines = "1.9.0"
+kotlinVersion = "1.9.0"
+coreKtx = "1.15.0"
+junit = "4.13.2"
+junitVersion = "1.2.1"
+espressoCore = "3.6.1"
+appcompat = "1.7.0"
+material = "1.12.0"
 
 [libraries]
 kotlin-test = { module = "org.jetbrains.kotlin:kotlin-test", version.ref = "kotlin" }
@@ -16,8 +23,15 @@ nexus-publish = { module = "io.github.gradle-nexus.publish-plugin:io.github.grad
 #Coroutines
 kotlin-coroutines = {module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version.ref = "kotlin-coroutines"}
 kotlin-coroutines-test = { group = "org.jetbrains.kotlinx", name = "kotlinx-coroutines-test", version.ref = "kotlin-coroutines" }
+core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
+junit = { group = "junit", name = "junit", version.ref = "junit" }
+ext-junit = { group = "androidx.test.ext", name = "junit", version.ref = "junitVersion" }
+espresso-core = { group = "androidx.test.espresso", name = "espresso-core", version.ref = "espressoCore" }
+appcompat = { group = "androidx.appcompat", name = "appcompat", version.ref = "appcompat" }
+material = { group = "com.google.android.material", name = "material", version.ref = "material" }
 
 [plugins]
 androidLibrary = { id = "com.android.library", version.ref = "agp" }
 kotlinMultiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
-vanniktech-mavenPublish = {id = "com.vanniktech.maven.publish", version.ref = "mavenPublish"}
+vanniktech-mavenPublish = {id = "com.vanniktech.maven.publish", version.ref = "mavenPublish"}
+kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlinVersion" }

nativelib/.gitignore

@@ -0,0 +1 @@
+/build

nativelib/build.gradle.kts

@@ -0,0 +1,54 @@
+plugins {
+    alias(libs.plugins.androidLibrary)
+    alias(libs.plugins.kotlin.android)
+}
+
+android {
+    namespace = "more.math.nativelib"
+    compileSdk = 35
+
+    defaultConfig {
+        minSdk = 22
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        consumerProguardFiles("consumer-rules.pro")
+        externalNativeBuild {
+            cmake {
+                cppFlags("")
+            }
+        }
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro"
+            )
+        }
+    }
+    externalNativeBuild {
+        cmake {
+            path("src/main/cpp/CMakeLists.txt")
+            version = "3.22.1"
+        }
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_1_8
+        targetCompatibility = JavaVersion.VERSION_1_8
+    }
+    kotlinOptions {
+        jvmTarget = "1.8"
+    }
+}
+
+dependencies {
+
+    implementation(libs.core.ktx)
+    implementation(libs.appcompat)
+    implementation(libs.material)
+    testImplementation(libs.junit)
+    androidTestImplementation(libs.ext.junit)
+    androidTestImplementation(libs.espresso.core)
+}

nativelib/proguard-rules.pro

@@ -0,0 +1,21 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

nativelib/src/androidTest/java/more/math/TestNativeLib.kt

@@ -0,0 +1,15 @@
+package more.math
+
+import more.math.nativelib.NativeLib
+import org.junit.Test
+import org.junit.Assert.*
+
+class TestNativeLib {
+    @Test
+    fun testInitString() {
+        val lib = NativeLib().apply { init() }
+        val expected = "Hello from C++"
+        val actual = lib.stringFromJNI()
+        assertEquals(expected, actual)
+    }
+}

nativelib/src/main/cpp/CMakeLists.txt

@@ -0,0 +1,37 @@
+# For more information about using CMake with Android Studio, read the
+# documentation: https://d.android.com/studio/projects/add-native-code.html.
+# For more examples on how to use CMake, see https://github.com/android/ndk-samples.
+
+# Sets the minimum CMake version required for this project.
+cmake_minimum_required(VERSION 3.22.1)
+
+# Declares the project name. The project name can be accessed via ${ PROJECT_NAME},
+# Since this is the top level CMakeLists.txt, the project name is also accessible
+# with ${CMAKE_PROJECT_NAME} (both CMake variables are in-sync within the top level
+# build script scope).
+project("nativelib")
+
+# Creates and names a library, sets it as either STATIC
+# or SHARED, and provides the relative paths to its source code.
+# You can define multiple libraries, and CMake builds them for you.
+# Gradle automatically packages shared libraries with your APK.
+#
+# In this top level CMakeLists.txt, ${CMAKE_PROJECT_NAME} is used to define
+# the target library name; in the sub-module's CMakeLists.txt, ${PROJECT_NAME}
+# is preferred for the same purpose.
+#
+# In order to load a library into your app from Java/Kotlin, you must call
+# System.loadLibrary() and pass the name of the library defined here;
+# for GameActivity/NativeActivity derived applications, the same library name must be
+# used in the AndroidManifest.xml file.
+add_library(${CMAKE_PROJECT_NAME} SHARED
+        # List C/C++ source files with relative paths to this CMakeLists.txt.
+        nativelib.cpp)
+
+# Specifies libraries CMake should link to your target library. You
+# can link libraries from various origins, such as libraries defined in this
+# build script, prebuilt third-party libraries, or Android system libraries.
+target_link_libraries(${CMAKE_PROJECT_NAME}
+        # List libraries link to the target library
+        android
+        log)

nativelib/src/main/cpp/nativelib.cpp

@@ -0,0 +1,11 @@
+#include <jni.h>
+#include <string>
+
+extern "C"
+JNIEXPORT jstring JNICALL
+Java_more_math_nativelib_NativeLib_stringFromJNI(
+        JNIEnv* env,
+        jobject thiz) {
+    std::string hello = "Hello from C++";
+    return env->NewStringUTF(hello.c_str());
+}

nativelib/src/main/java/more/math/nativelib/NativeLib.kt

@@ -0,0 +1,9 @@
+package more.math.nativelib
+
+class NativeLib {
+    external fun stringFromJNI(): String
+
+    fun init() {
+        System.loadLibrary("nativelib")
+    }
+}

nativelib/src/test/java/more/plumsoftware/nativelib/TestNativeLib.kt

@@ -0,0 +1,15 @@
+package more.plumsoftware.nativelib
+
+import more.math.nativelib.NativeLib
+import org.junit.Test
+import org.junit.Assert.*
+
+class TestNativeLib {
+    @Test
+    fun testInitString() {
+        val lib = NativeLib().apply { init() }
+        val expected = "Hello from C++"
+        val actual = lib.stringFromJNI()
+        assertEquals(expected, actual)
+    }
+}

settings.gradle.kts

@@ -15,3 +15,4 @@ dependencyResolutionManagement {
 
 rootProject.name = "more-math"
 include(":library")
+include(":nativelib")