@Observable support for Jetpack Compose UI

.gitignore

@@ -25,6 +25,10 @@ BuildLogic/out/
 **/build/
 lib/
 
+# Android local SDK location + native build intermediates
+local.properties
+**/.cxx/
+
 # Ignore JVM crash logs
 **/*.log
 

Samples/SwiftKitAndroidComposeSample/Package.swift

@@ -0,0 +1,41 @@
+// swift-tools-version: 6.2
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import CompilerPluginSupport
+import PackageDescription
+
+let package = Package(
+  name: "SwiftKitAndroidComposeSample",
+  platforms: [
+    .macOS(.v15)
+  ],
+  products: [
+    .library(
+      name: "MySwiftLibrary",
+      type: .dynamic,
+      targets: ["MySwiftLibrary"]
+    ),
+  ],
+  dependencies: [
+    .package(name: "swift-java", path: "../../"),
+    .package(url: "https://github.com/swift-android-sdk/swift-android-native.git", from: "2.0.0")
+  ],
+  targets: [
+    .target(
+      name: "MySwiftLibrary",
+      dependencies: [
+        .product(name: "SwiftJava", package: "swift-java"),
+        .product(name: "AndroidLooper", package: "swift-android-native", condition: .when(platforms: [.android]))
+      ],
+      exclude: [
+        "swift-java.config"
+      ],
+      swiftSettings: [
+        .swiftLanguageMode(.v5)
+      ],
+      plugins: [
+        .plugin(name: "JExtractSwiftPlugin", package: "swift-java")
+      ]
+    ),
+  ]
+)

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/CounterModel.swift

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+import Observation
+
+@Observable
+public class CounterModel {
+  public var count: Int64 = 0
+
+  public init() {}
+
+  public func increment() {
+    count += 1
+  }
+
+  public func reset() {
+    count = 0
+  }
+}

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/DashboardModel.swift

@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+import Observation
+
+/// A view model with **many observable states** of different primitive types.
+/// Each property drives a different Compose control (text, slider, switch,
+/// stepper). Only the property that actually changed should recompose the
+/// widgets that read it.
+@Observable
+public class DashboardModel {
+  public var title: String = "My Dashboard"
+  public var counter: Int64 = 0
+  public var level: Int32 = 1
+  public var temperature: Double = 20.5
+  public var progress: Double = 0.25
+  public var isEnabled: Bool = true
+  public var isFavorite: Bool = false
+
+  public init() {}
+
+  public func increment() { counter += 1 }
+  public func decrement() { counter -= 1 }
+  public func levelUp() { level += 1 }
+  public func warmer() { temperature += 0.5 }
+  public func cooler() { temperature -= 0.5 }
+  public func toggleEnabled() { isEnabled.toggle() }
+  public func toggleFavorite() { isFavorite.toggle() }
+
+  public func reset() {
+    counter = 0
+    level = 1
+    temperature = 20.5
+    progress = 0.25
+    isEnabled = true
+    isFavorite = false
+  }
+}

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/EdgeCasesModel.swift

@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+import Observation
+
+/// Exercises the things that should **NOT** participate in observation:
+///
+/// - `static let` / `static var`: type-level, never tracked per-instance.
+/// - `let`: immutable stored property; `@Observable` does not track it.
+/// - `@ObservationIgnored var`: explicitly opted out of tracking.
+///
+/// Only `visibleCounter` is a normal observed `var`. The UI should recompose
+/// when `visibleCounter` changes, but NOT when `hiddenCounter` changes — even
+/// though `hiddenCounter` really is mutating under the hood (which we can prove
+/// by copying it into `visibleCounter`, forcing a legitimate refresh).
+@Observable
+public class EdgeCasesModel {
+  /// Type-level constant — must not generate any per-instance observation.
+  public static let appName: String = "SwiftJava Observable Sample"
+
+  /// Type-level mutable — also must not be observed per instance.
+  public static var launchCount: Int64 = 0
+
+  /// Immutable stored property — never changes, so must not be observed.
+  public let createdLabel: String = "Created once at init"
+
+  /// Explicitly excluded from observation tracking.
+  @ObservationIgnored public var hiddenCounter: Int64 = 0
+
+  /// The only genuinely observed property.
+  public var visibleCounter: Int64 = 0
+
+  public init() {
+    EdgeCasesModel.launchCount += 1
+  }
+
+  /// Mutates an ignored property — the UI should NOT react to this.
+  public func bumpHidden() { hiddenCounter += 1 }
+
+  /// Mutates an observed property — the UI SHOULD react to this.
+  public func bumpVisible() { visibleCounter += 1 }
+
+  /// Pulls the (silently changed) hidden value into the observed one, so a
+  /// real notification fires and the UI finally reflects the hidden mutations.
+  public func revealHidden() { visibleCounter = hiddenCounter }
+}

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/FormModel.swift

@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import Observation
+
+/// Demonstrates **two-way bindings**: each `var` is read by a Compose
+/// `TextField` and written back from its `onValueChange`. `fullName` is a
+/// read-only computed property that should recompute (and recompose) whenever
+/// `firstName` or `lastName` change.
+@Observable
+public class FormModel {
+  public var firstName: String = ""
+  public var lastName: String = ""
+  public var email: String = ""
+  public var bio: String = ""
+
+  public init() {}
+
+  public var fullName: String {
+    let joined = "\(firstName) \(lastName)"
+    return joined.trimmingCharacters(in: .whitespaces)
+  }
+
+  public var isComplete: Bool {
+    !firstName.isEmpty && !lastName.isEmpty && !email.isEmpty
+  }
+
+  public func clear() {
+    firstName = ""
+    lastName = ""
+    email = ""
+    bio = ""
+  }
+}

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/Library.swift

@@ -0,0 +1,5 @@
+import AndroidLooper
+
+public func setupAndroidMainLooper() {
+  AndroidMainActor.setupMainLooper()
+}

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/ProfileModel.swift

@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+import Observation
+
+/// A child `@Observable` object, nested inside `ProfileModel`.
+@Observable
+public class AddressModel {
+  public var street: String = "1 Infinite Loop"
+  public var city: String = "Cupertino"
+  public var country: String = "USA"
+
+  public init() {}
+
+  public var oneLine: String {
+    "\(street), \(city), \(country)"
+  }
+}
+
+/// Demonstrates **nested observable objects**. `ProfileModel` owns an
+/// `AddressModel`. Mutating a field on the nested object (e.g. `address.city`)
+/// should be observable to a UI that is tracking the nested object.
+///
+/// Note: the parent only directly observes its own `name` and the `address`
+/// *reference*. To react to changes *inside* the nested object, the Compose
+/// layer observes the child as well (see `NestedScreen`).
+@Observable
+public class ProfileModel {
+  public var name: String = "Jane Appleseed"
+  public var address: AddressModel = AddressModel()
+
+  public init() {}
+
+  public func moveToLondon() {
+    address.street = "10 Downing Street"
+    address.city = "London"
+    address.country = "UK"
+  }
+
+  /// Replaces the whole nested object (reference change on the parent).
+  public func replaceAddress() {
+    address = AddressModel()
+  }
+}

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/TodoListModel.swift

@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+import Observation
+
+/// Demonstrates **arrays**. Mutating the `items` array (append/remove) is an
+/// observable change, so a Compose list that reads `items` should recompose.
+@Observable
+public class TodoListModel {
+  public var items: [String] = ["Buy milk", "Walk the dog", "Learn swift-java"]
+
+  public init() {}
+
+  /// Read-only computed property derived from the array.
+  public var count: Int64 {
+    Int64(items.count)
+  }
+
+  public var isEmpty: Bool {
+    items.isEmpty
+  }
+
+  public func add(_ item: String) {
+    items.append(item)
+  }
+
+  public func removeLast() {
+    if !items.isEmpty {
+      items.removeLast()
+    }
+  }
+
+  public func removeAll() {
+    items.removeAll()
+  }
+}

Samples/SwiftKitAndroidComposeSample/Sources/MySwiftLibrary/swift-java.config

@@ -0,0 +1,6 @@
+{
+  "javaPackage": "com.example.swift.compose",
+  "mode": "jni",
+  "observableComposeBridging": true,
+  "memoryManagementMode": "allowGlobalAutomatic"
+}