Adopt jextract JNI callbacks and Compose demo UI

.github/workflows/swift.yml

@@ -7,13 +7,20 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        swift: ['6.2.3', 'nightly-6.3']
+        # Package manifests require swift-tools 6.3.
+        swift: ['6.3.3']
         arch: ['aarch64', 'x86_64', 'armv7']
         sdk: ['28', '29', '31', '33']
     runs-on: macos-15
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v4
+      # Java is required by android-commandlinetools (skip android sdk install)
+      # and by the swift-java jextract plugin.
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '21'
       - name: "Build Swift Package for Android"
         run: |
           brew install skiptools/skip/skip || (brew update && brew install skiptools/skip/skip)

.gitignore

@@ -76,4 +76,10 @@ Package.resolved
 # Android
 *.so
 .gradle
-.idea
+.idea
+# GenerateBluetoothDefinitions plugin artifacts leaked into cwd by --disable-sandbox builds
+*-2.d
+*-2.dia
+*-2.swiftdeps
+*-2.swiftmodule
+.kotlin/

Demo/Package.swift

@@ -10,7 +10,7 @@ let package = Package(
         .library(
             name: "SwiftAndroidApp",
             type: .dynamic,
-            targets: ["SwiftAndroidApp"]
+            targets: ["BluetoothDemoBridge"]
         ),
     ],
     dependencies: [
@@ -21,23 +21,68 @@ let package = Package(
             url: "https://github.com/PureSwift/Android.git",
             branch: "master"
         ),
+        .package(
+            url: "https://github.com/swiftlang/swift-java.git",
+            branch: "main"
+        ),
+        .package(
+            url: "https://github.com/swift-android-sdk/swift-android-native.git",
+            from: "2.1.0"
+        ),
+        .package(
+            url: "https://github.com/PureSwift/GATT.git",
+            from: "4.0.0"
+        ),
+        .package(
+            url: "https://github.com/PureSwift/Bluetooth.git",
+            from: "8.0.0"
+        )
     ],
     targets: [
         .target(
-            name: "SwiftAndroidApp",
+            name: "BluetoothDemoBridge",
             dependencies: [
                 .product(
                     name: "AndroidBluetooth",
                     package: "AndroidBluetooth"
                 ),
+                .product(
+                    name: "AndroidBluetoothBridge",
+                    package: "AndroidBluetooth"
+                ),
+                .product(
+                    name: "GATT",
+                    package: "GATT"
+                ),
+                .product(
+                    name: "Bluetooth",
+                    package: "Bluetooth"
+                ),
+                .product(
+                    name: "SwiftJava",
+                    package: "swift-java"
+                ),
                 .product(
                     name: "AndroidKit",
                     package: "Android"
+                ),
+                .product(
+                    name: "AndroidContext",
+                    package: "swift-android-native"
                 )
             ],
-            path: "./app/src/main/swift",
+            path: "./app/src/main/swift-bridge/BluetoothDemoBridge",
+            exclude: [
+              "swift-java.config"
+            ],
             swiftSettings: [
               .swiftLanguageMode(.v5)
+            ],
+            plugins: [
+              .plugin(
+                name: "JExtractSwiftPlugin",
+                package: "swift-java"
+              )
             ]
         )
     ]

Demo/app/build.gradle.kts

@@ -4,6 +4,111 @@ plugins {
     alias(libs.plugins.kotlin.compose)
 }
 
+// ---------------------------------------------------------------------------
+// swift-java (jextract, JNI mode) integration
+//
+// The Swift package graph (AndroidBluetooth + AndroidBluetoothBridge +
+// BluetoothDemoBridge) is cross-compiled to native `.so`s with the official
+// Swift Android SDK; the `JExtractSwiftPlugin` emits the Java JNI bindings as
+// a side effect of `swift build`. Gradle then adds the generated Java +
+// SwiftKitCore runtime sources to the source set and stages every required
+// `.so` into `jniLibs`.
+// ---------------------------------------------------------------------------
+
+val swiftPackageRoot: File = rootProject.projectDir
+val androidTriple = "aarch64-unknown-linux-android28"
+val swiftAbi = "arm64-v8a"
+val userHome: String = System.getProperty("user.home")
+
+// Configuration the Swift package is cross-compiled with, independent of the
+// Android build type. Override with `-PswiftBuildConfig=release`.
+val swiftBuildConfig: String = (findProperty("swiftBuildConfig") as String?) ?: "debug"
+
+// Locates both the toolchain and the matching Android SDK artifactbundle.
+val swiftToolchainVersion: String = (findProperty("swiftToolchainVersion") as String?) ?: "6.3.3"
+
+// The Android SDK's prebuilt Swift modules require the matching swift.org
+// toolchain. Override with `-PswiftBin=/path/to/swift` if installed elsewhere.
+val swiftBin: String = (findProperty("swiftBin") as String?)
+    ?: "$userHome/Library/Developer/Toolchains/swift-$swiftToolchainVersion-RELEASE.xctoolchain/usr/bin/swift"
+
+// swift-java's `enableJavaCallbacks` feature runs its own internal Gradle
+// sub-build to compile the generated Java callback interfaces, requiring a
+// modern JDK — independent of whatever JDK runs *this* Gradle build.
+// Override with `-PcallbacksJdkHome=/path/to/jdk`.
+val callbacksJdkHome: String = (findProperty("callbacksJdkHome") as String?)
+    ?: "/opt/homebrew/opt/openjdk@25"
+
+// SwiftPM plugin output convention: `outputs/<package-dir-lowercased>/<TargetName>/...`.
+// Both bridge targets generate Java: the AndroidBluetooth library's callback
+// bridge and the demo's UI-facing bridge.
+val generatedLibraryJavaDir = File(swiftPackageRoot, ".build/plugins/outputs/androidbluetooth/AndroidBluetoothBridge/destination/JExtractSwiftPlugin/src/generated/java")
+val generatedDemoJavaDir = File(swiftPackageRoot, ".build/plugins/outputs/demo/BluetoothDemoBridge/destination/JExtractSwiftPlugin/src/generated/java")
+val swiftKitCoreDir = File(swiftPackageRoot, ".build/checkouts/swift-java/SwiftKitCore/src/main/java")
+val swiftBuildDir = File(swiftPackageRoot, ".build/$androidTriple/$swiftBuildConfig")
+val swiftAndroidRuntimeDir = File(
+    (findProperty("swiftAndroidRuntimeDir") as String?)
+        ?: "$userHome/Library/org.swift.swiftpm/swift-sdks/swift-${swiftToolchainVersion}-RELEASE_android.artifactbundle/swift-android/swift-resources/usr/lib/swift-aarch64/android"
+)
+
+// Supplies libc++_shared.so, which every Swift Android binary links against.
+val swiftAndroidSysroot = File(
+    (findProperty("swiftAndroidSysroot") as String?)
+        ?: "$userHome/Library/org.swift.swiftpm/swift-sdks/swift-${swiftToolchainVersion}-RELEASE_android.artifactbundle/swift-android/ndk-sysroot"
+)
+
+// Cross-compile the Swift package + generate the JNI Java bindings.
+val jextract = tasks.register<Exec>("jextract") {
+    workingDir = swiftPackageRoot
+    environment("JAVA_HOME", callbacksJdkHome)
+    commandLine(
+        swiftBin, "build",
+        "--swift-sdk", androidTriple,
+        "-c", swiftBuildConfig,
+        "--disable-sandbox"
+    )
+    outputs.dir(generatedLibraryJavaDir)
+    outputs.dir(generatedDemoJavaDir)
+    outputs.file(File(swiftBuildDir, "libSwiftAndroidApp.so"))
+    // `swift build` is incremental itself; let it decide what is stale.
+    outputs.upToDateWhen { false }
+}
+
+// SwiftKitCore is consumed as source (swift-java is not published to Maven),
+// minus two annotations that pull in `jdk.jfr` (Java Flight Recorder), which
+// is unavailable on Android. `Unsigned` (which the generated bindings DO
+// reference) is replaced by an Android-compatible copy in `src/main/java`.
+val patchedSwiftKitCoreDir = layout.buildDirectory.dir("swiftkitcore-java")
+val stageSwiftKitCore = tasks.register<Sync>("stageSwiftKitCore") {
+    dependsOn(jextract)
+    from(swiftKitCoreDir)
+    exclude(
+        "org/swift/swiftkit/core/annotations/ThreadSafe.java",
+        "org/swift/swiftkit/core/annotations/Unsigned.java"
+    )
+    into(patchedSwiftKitCoreDir)
+}
+
+// Stage the cross-compiled libraries, the swift-java runtime, the Swift
+// Android runtime and libc++_shared into jniLibs so they end up in the APK.
+val stageJniLibs = tasks.register<Copy>("stageJniLibs") {
+    dependsOn(jextract)
+    into(layout.projectDirectory.dir("src/main/jniLibs/$swiftAbi"))
+    from(swiftBuildDir) {
+        // Every dynamic library product built by the package graph — anything
+        // less leaves a dangling `dlopen` at runtime.
+        include("*.so")
+    }
+    from(swiftAndroidRuntimeDir) {
+        include("*.so")
+        // Test-only runtime libraries are not needed by the app.
+        exclude("*Testing*", "libXCTest.so")
+    }
+    from(File(swiftAndroidSysroot, "usr/lib/aarch64-linux-android")) {
+        include("libc++_shared.so")
+    }
+}
+
 android {
     namespace = "com.pureswift.swiftandroid"
     compileSdk = 35
@@ -16,7 +121,7 @@ android {
         versionName = "1.0"
         ndk {
             //noinspection ChromeOsAbiSupport
-            abiFilters += listOf("arm64-v8a")
+            abiFilters += listOf(swiftAbi)
         }
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
@@ -31,15 +136,21 @@ android {
         }
     }
     compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_11
-        targetCompatibility = JavaVersion.VERSION_11
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
     }
     kotlinOptions {
-        jvmTarget = "11"
+        jvmTarget = "17"
     }
     buildFeatures {
         compose = true
     }
+
+    // Generated JNI bindings + the (patched) SwiftKitCore Java runtime.
+    sourceSets["main"].java.srcDir(generatedLibraryJavaDir)
+    sourceSets["main"].java.srcDir(generatedDemoJavaDir)
+    sourceSets["main"].java.srcDir(patchedSwiftKitCoreDir)
+
     packaging {
         resources {
             excludes += listOf("/META-INF/{AL2.0,LGPL2.1}")
@@ -54,16 +165,16 @@ android {
     }
 }
 
-// Compile native Swift code for the demo app with `skip android build`.
-val buildSwift by tasks.registering(Exec::class) {
-    group = "build"
-    description = "Build native Swift sources for Android"
-    workingDir(rootProject.projectDir)
-    commandLine("bash", "build-swift.sh")
+// Ensure Swift is built + bindings generated + libs staged before Java or
+// Kotlin compiles (Kotlin also consumes the generated Java bindings).
+tasks.withType<JavaCompile>().configureEach {
+    dependsOn(jextract, stageSwiftKitCore)
+}
+tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {
+    dependsOn(jextract, stageSwiftKitCore)
 }
-
 tasks.named("preBuild") {
-    dependsOn(buildSwift)
+    dependsOn(stageJniLibs)
 }
 
 dependencies {
@@ -75,8 +186,6 @@ dependencies {
     implementation(libs.androidx.ui)
     implementation(libs.androidx.ui.graphics)
     implementation(libs.androidx.ui.tooling.preview)
-    implementation(libs.androidx.recyclerview)
-    implementation(libs.androidx.navigation.runtime)
     implementation(libs.androidx.material3)
     implementation(libs.material)
     testImplementation(libs.junit)

Demo/app/src/main/java/org/swift/swiftkit/core/annotations/Unsigned.java

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+package org.swift.swiftkit.core.annotations;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.*;
+
+/**
+ * Value is of an unsigned numeric type.
+ * <p>
+ * Android-compatible copy of SwiftKitCore's {@code Unsigned} annotation: the
+ * upstream source carries {@code jdk.jfr} annotations that are unavailable on
+ * Android, so the original is excluded from the source set and replaced by
+ * this one.
+ */
+@Documented
+@Target({TYPE_USE, PARAMETER, FIELD, METHOD})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Unsigned {
+}

Demo/app/src/main/kotlin/com/pureswift/swiftandroid/Application.kt

@@ -1,29 +1,8 @@
 package com.pureswift.swiftandroid
 
-import com.example.swift.HelloSubclass
-
-class Application: android.app.Application() {
+class Application : android.app.Application() {
 
     init {
         NativeLibrary.shared()
     }
-
-    override fun onCreate() {
-        super.onCreate()
-        onCreateSwift()
-    }
-
-    private external fun onCreateSwift()
-
-    override fun onTerminate() {
-        super.onTerminate()
-        onTerminateSwift()
-    }
-
-    private external fun onTerminateSwift()
-
-    fun sayHello() {
-        val result = HelloSubclass("Swift").sayHello(17, 25)
-        println("sayHello(17, 25) = $result")
-    }
-}
+}