feat(android): migrate app to Kotlin, Compose, and Gradle Kotlin DSL

Rewrite the demo app in Kotlin with a Material3 Compose UI, convert Gradle
scripts to .kts, raise minSdk to API 30, and remove leftover View-based
scaffolding (XML layouts, placeholder tests, appcompat dependencies).

Author: mallocnew

.github/workflows/android.yml

@@ -36,7 +36,7 @@ jobs:
       - name: Setup Android SDK
         uses: android-actions/setup-android@v3
         with:
-          packages: 'platforms;android-34 build-tools;34.0.0'
+          packages: 'platforms;android-36 build-tools;36.0.0'
 
       # sdkmanager has no bare "ndk" package — must install "ndk;X.Y.Z". Pick the
       # newest side-by-side NDK from the package list.
@@ -79,13 +79,13 @@ jobs:
           python -m tn  --language zh --overwrite_cache --cache_dir "$assets"
           python -m itn --language zh --overwrite_cache --cache_dir "$assets"
 
-      - name: Build APK
+      - name: Build release APK
         working-directory: runtime/android
-        run: ./gradlew :app:assembleDebug -PabiFilters=arm64-v8a --no-daemon
+        run: ./gradlew :app:assembleRelease -PabiFilters=arm64-v8a --no-daemon
 
-      - name: Upload APK
+      - name: Upload release APK
         uses: actions/upload-artifact@v4
         with:
-          name: app-debug-arm64-v8a
-          path: runtime/android/app/build/outputs/apk/debug/app-debug.apk
+          name: app-release-arm64-v8a
+          path: runtime/android/app/build/outputs/apk/release/app-release.apk
           if-no-files-found: error

runtime/CMakePresets.json

@@ -19,7 +19,7 @@
       "generator": "Ninja",
       "cacheVariables": {
         "CMAKE_TOOLCHAIN_FILE": "$env{ANDROID_NDK_HOME}/build/cmake/android.toolchain.cmake",
-        "ANDROID_PLATFORM": "android-21",
+        "ANDROID_PLATFORM": "android-30",
         "CMAKE_BUILD_TYPE": "Release"
       }
     },

runtime/android/.gitignore

@@ -1,5 +1,6 @@
 *.iml
 .gradle
+.kotlin/
 /local.properties
 /.idea/caches
 /.idea/libraries

runtime/android/app/build.gradle

@@ -0,0 +1,75 @@
+plugins {
+    // AGP 9 has built-in Kotlin support (it bundles KGP and enables it by default),
+    // so the org.jetbrains.kotlin.android plugin must NOT be applied here.
+    alias(libs.plugins.android.application)
+    // Compose compiler plugin (required since Kotlin 2.0+).
+    alias(libs.plugins.compose.compiler)
+}
+
+fun nativeAbis(): List<String> =
+    (project.findProperty("abiFilters") as String? ?: "armeabi-v7a,arm64-v8a,x86,x86_64")
+        .split(",").map { it.trim() }.filter { it.isNotEmpty() }
+
+android {
+    namespace = "com.wenet.WeTextProcessing"
+    lint {
+        abortOnError = false
+    }
+    signingConfigs {
+        create("release") {
+            storeFile = file("wenet.keystore")
+            storePassword = "123456"
+            keyAlias = "wenet"
+            keyPassword = "123456"
+        }
+    }
+    compileSdk = 36
+
+    defaultConfig {
+        applicationId = "com.wenet.WeTextProcessing"
+        minSdk = 30
+        targetSdk = 36
+        versionCode = 1
+        versionName = "1.0"
+
+        ndk {
+            abiFilters.addAll(nativeAbis())
+        }
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            signingConfig = signingConfigs.getByName("release")
+            proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
+        }
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+    // Built-in Kotlin defaults jvmTarget to compileOptions.targetCompatibility (17).
+    buildFeatures {
+        compose = true
+    }
+}
+
+dependencies {
+    implementation(platform(libs.androidx.compose.bom))
+
+    implementation(libs.androidx.activity.compose)
+    implementation(libs.androidx.compose.ui)
+    implementation(libs.androidx.compose.ui.graphics)
+    implementation(libs.androidx.compose.ui.tooling.preview)
+    implementation(libs.androidx.compose.material3)
+    debugImplementation(libs.androidx.compose.ui.tooling)
+}
+
+// Native libs are NOT built by Gradle. Build them beforehand with CMake presets
+// (from repo root) so the .so files exist in app/src/main/jniLibs/<abi>/:
+//   export ANDROID_NDK_HOME=$ANDROID_HOME/ndk/<version>
+//   cd runtime
+//   cmake --preset android-arm64-v8a
+//   cmake --build --preset android-arm64-v8a
+//   cmake --install build/aarch64-linux-android --component jni
+// Gradle only packages whatever is already present under jniLibs.

runtime/android/app/build.gradle.kts

@@ -1,13 +1,11 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <application
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
-        tools:replace="android:theme"
         android:theme="@style/Theme.Wenet">
         <activity
             android:name=".MainActivity"

runtime/android/app/src/androidTest/java/com/wenet/WeTextProcessing/ExampleInstrumentedTest.java

@@ -1,6 +1,6 @@
 # Android model assets
 
-The app loads four FST models at runtime (see `MainActivity.java` and
+The app loads four FST models at runtime (see `MainActivity.kt` and
 `wetextprocessing.cc`). They are **not** checked into git and must be placed in
 this directory before building the APK: