refactor(kotlin): convert SDK to Android library and move WebViewTransport

ochafik · claude · ochafik · commit b370494d6546 · 2025-12-18T15:46:24.000Z
- Convert Kotlin SDK from pure JVM to Android library to match Swift SDK structure - Move WebViewTransport.kt from example to SDK transport folder - Update package from com.example.mcpappshost to io.modelcontextprotocol.apps.transport - Update Gradle to 8.10.2 and Android Gradle Plugin to 8.7.3 - Add proguard and consumer rules for serialization - Fix lint compatibility issues with Kotlin 2.1 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
diff --git a/examples/basic-host-kotlin/build.gradle.kts b/examples/basic-host-kotlin/build.gradle.kts
@@ -1,5 +1,5 @@
 plugins {
-    id("com.android.application") version "8.2.0"
+    id("com.android.application") version "8.7.3"
     kotlin("android") version "2.1.0"
     kotlin("plugin.serialization") version "2.1.0"
     kotlin("plugin.compose") version "2.1.0"
@@ -30,18 +30,25 @@ android {
     }
 
     compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_17
-        targetCompatibility = JavaVersion.VERSION_17
+        sourceCompatibility = JavaVersion.VERSION_21
+        targetCompatibility = JavaVersion.VERSION_21
     }
 
     kotlinOptions {
-        jvmTarget = "17"
+        jvmTarget = "21"
     }
 
     buildFeatures {
         compose = true
     }
 
+    lint {
+        // Workaround for kotlinx-metadata version mismatch with Kotlin 2.1
+        disable += setOf(
+            "FlowOperatorInvokedInComposition",
+            "StateFlowValueCalledInComposition"
+        )
+    }
 
     packaging {
         resources {
diff --git a/examples/basic-host-kotlin/gradle.properties b/examples/basic-host-kotlin/gradle.properties
@@ -10,6 +10,9 @@
 # The setting is particularly useful for tweaking memory settings.
 org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
 
+# Java home
+org.gradle.java.home=/opt/homebrew/opt/openjdk@21
+
 # When configured, Gradle will run in incubating parallel mode.
 # This option should only be used with decoupled projects. More details, visit
 # http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
diff --git a/examples/basic-host-kotlin/gradle/wrapper/gradle-wrapper.properties b/examples/basic-host-kotlin/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.2.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.10.2-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
diff --git a/examples/basic-host-kotlin/src/main/kotlin/com/example/mcpappshost/MainActivity.kt b/examples/basic-host-kotlin/src/main/kotlin/com/example/mcpappshost/MainActivity.kt
@@ -31,6 +31,7 @@ import androidx.compose.ui.viewinterop.AndroidView
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
 import androidx.lifecycle.viewmodel.compose.viewModel
+import io.modelcontextprotocol.apps.transport.injectBridgeScript
 import kotlinx.serialization.json.jsonArray
 import kotlinx.serialization.json.jsonObject
 import kotlinx.serialization.json.jsonPrimitive
diff --git a/kotlin/build.gradle.kts b/kotlin/build.gradle.kts
@@ -1,25 +1,48 @@
 plugins {
-    kotlin("jvm") version "2.1.0"
+    id("com.android.library") version "8.7.3"
+    kotlin("android") version "2.1.0"
     kotlin("plugin.serialization") version "2.1.0"
     id("maven-publish")
 }
 
 group = "io.modelcontextprotocol"
 version = "0.1.0-SNAPSHOT"
 
-repositories {
-    mavenCentral()
-    google()
-}
+android {
+    namespace = "io.modelcontextprotocol.apps"
+    compileSdk = 34
 
-// Target Java 21 (Kotlin doesn't support 25 yet)
-tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
-    kotlinOptions.jvmTarget = "21"
-}
+    defaultConfig {
+        minSdk = 26  // Android 8.0 - required for WebView features
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        consumerProguardFiles("consumer-rules.pro")
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro"
+            )
+        }
+    }
 
-tasks.withType<JavaCompile> {
-    sourceCompatibility = "21"
-    targetCompatibility = "21"
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_21
+        targetCompatibility = JavaVersion.VERSION_21
+    }
+
+    kotlinOptions {
+        jvmTarget = "21"
+    }
+
+    publishing {
+        singleVariant("release") {
+            withSourcesJar()
+        }
+    }
 }
 
 dependencies {
@@ -31,13 +54,29 @@ dependencies {
 
     // Coroutines
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.9.0")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.9.0")
+
+    // AndroidX Core (for Handler, etc.)
+    implementation("androidx.core:core-ktx:1.12.0")
 
     // Testing
     testImplementation(kotlin("test"))
     testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.9.0")
     testImplementation("org.junit.jupiter:junit-jupiter:5.10.0")
+
+    androidTestImplementation("androidx.test.ext:junit:1.1.5")
+    androidTestImplementation("androidx.test.espresso:espresso-core:3.5.1")
 }
 
-tasks.test {
-    useJUnitPlatform()
+afterEvaluate {
+    publishing {
+        publications {
+            create<MavenPublication>("release") {
+                from(components["release"])
+                groupId = "io.modelcontextprotocol"
+                artifactId = "mcp-apps-kotlin-sdk"
+                version = project.version.toString()
+            }
+        }
+    }
 }
diff --git a/kotlin/consumer-rules.pro b/kotlin/consumer-rules.pro
@@ -0,0 +1,19 @@
+# Keep JSON serialization classes
+-keepattributes *Annotation*, InnerClasses
+-dontnote kotlinx.serialization.AnnotationsKt
+
+-keepclassmembers class kotlinx.serialization.json.** {
+    *** Companion;
+}
+-keepclasseswithmembers class kotlinx.serialization.json.** {
+    kotlinx.serialization.KSerializer serializer(...);
+}
+
+# Keep MCP Apps SDK classes
+-keep,includedescriptorclasses class io.modelcontextprotocol.apps.**$$serializer { *; }
+-keepclassmembers class io.modelcontextprotocol.apps.** {
+    *** Companion;
+}
+-keepclasseswithmembers class io.modelcontextprotocol.apps.** {
+    kotlinx.serialization.KSerializer serializer(...);
+}
diff --git a/kotlin/gradle.properties b/kotlin/gradle.properties
@@ -1,2 +1,4 @@
 kotlin.code.style=official
 kotlin.mpp.stability.nowarn=true
+org.gradle.java.home=/opt/homebrew/opt/openjdk@21
+android.useAndroidX=true
diff --git a/kotlin/gradle/wrapper/gradle-wrapper.properties b/kotlin/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.2.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.10.2-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
diff --git a/kotlin/proguard-rules.pro b/kotlin/proguard-rules.pro
@@ -0,0 +1,2 @@
+# ProGuard rules for MCP Apps SDK
+# Add project specific ProGuard rules here.
diff --git a/kotlin/settings.gradle.kts b/kotlin/settings.gradle.kts
@@ -1 +1,17 @@
+pluginManagement {
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
 rootProject.name = "mcp-apps-sdk"
diff --git a/kotlin/src/main/kotlin/io/modelcontextprotocol/apps/transport/WebViewTransport.kt b/kotlin/src/main/kotlin/io/modelcontextprotocol/apps/transport/WebViewTransport.kt
@@ -1,12 +1,11 @@
-package com.example.mcpappshost
+package io.modelcontextprotocol.apps.transport
 
 import android.os.Handler
 import android.os.Looper
 import android.util.Log
 import android.webkit.JavascriptInterface
 import android.webkit.WebView
 import io.modelcontextprotocol.apps.protocol.JSONRPCMessage
-import io.modelcontextprotocol.apps.transport.McpAppsTransport
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.serialization.json.Json
@@ -15,6 +14,21 @@ private const val TAG = "WebViewTransport"
 
 /**
  * Transport for MCP Apps communication using Android WebView.
+ *
+ * This transport enables bidirectional communication between a Kotlin/Android host
+ * application and a Guest UI running in a WebView.
+ *
+ * ## Usage
+ *
+ * ```kotlin
+ * val webView = WebView(context)
+ * val transport = WebViewTransport(webView)
+ *
+ * val bridge = AppBridge(hostInfo, hostCapabilities)
+ * bridge.connect(transport)
+ *
+ * webView.loadDataWithBaseURL(null, htmlContent, "text/html", "UTF-8", null)
+ * ```
  */
 class WebViewTransport(
     private val webView: WebView,
@@ -76,7 +90,16 @@ class WebViewTransport(
     }
 }
 
-/** Injects bridge script into HTML before loading */
+/**
+ * Injects bridge script into HTML before loading.
+ *
+ * Use this when you need to inject the bridge script into static HTML content
+ * before loading it into a WebView.
+ *
+ * @param html The HTML content to inject the bridge script into
+ * @param handlerName The JavaScript handler name (must match WebViewTransport handlerName)
+ * @return The HTML with the bridge script injected
+ */
 fun injectBridgeScript(html: String, handlerName: String = "mcpBridge"): String {
     val script = """
         <script>

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+# ProGuard rules for MCP Apps SDK`
	`2`	`+# Add project specific ProGuard rules here.`