fix(screen_state): restore compatibility with AGP < 9 and Dart 3.12.0

The 5.0.1 release regenerated the Android build script from the
Flutter 3.44 plugin template, which pins AGP 9.0.1/Kotlin 2.3.20 on
the buildscript classpath and assumes AGP 9 built-in Kotlin. This
broke the Android build for every consuming app on AGP 8.x.

- Apply the Kotlin Gradle plugin conditionally (AGP < 9) per the
  Flutter built-in Kotlin migration guide, and drop the pinned
  buildscript toolchain so the consuming app supplies it.
- Relax the Dart SDK lower bound from ^3.12.2 to >=3.12.0; the
  patch-level pin was a template stamp and blocked Flutter 3.44.0.
- Convert ScreenReceiver.java (living in src/main/kotlin) to Kotlin.
  It was only compiled thanks to a sourceSets override; without it
  apps crash with NoClassDefFoundError at runtime.

Verified: clean debug builds and dex contents on Flutter 3.38.1
(AGP 8.11) and Flutter 3.44.0 (AGP 9.0.1) host apps.

Author: Zeroupper

packages/screen_state/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 5.0.2
+
+* Relax Dart SDK lower bound from `^3.12.2` to `>=3.12.0` — the patch-level pin was accidental and blocked apps on Flutter 3.44.0/3.44.1.
+* Fix Android build in apps using AGP < 9: apply the Kotlin Gradle plugin conditionally instead of pinning AGP 9.0.1/Kotlin 2.3.20 on the buildscript classpath (see the [built-in Kotlin migration guide](https://docs.flutter.dev/release/breaking-changes/migrate-to-built-in-kotlin/for-plugin-authors)).
+* Fix `NoClassDefFoundError: ScreenReceiver` at runtime: `ScreenReceiver.java` lived in the `src/main/kotlin` folder and relied on a `sourceSets` override to be compiled; it is now converted to Kotlin (`ScreenReceiver.kt`).
+* Note: 5.0.1 also raised Android `minSdk` 21 → 24 and `compileSdk` 33 → 36 (undocumented in its changelog).
+
 ## 5.0.1
 
 * Fix app not running on Flutter 3.44.X

packages/screen_state/android/build.gradle.kts

@@ -1,18 +1,5 @@
 group = "dk.cachet.screen_state"
-version = "5.0.1"
-
-buildscript {
-    val kotlinVersion = "2.3.20"
-    repositories {
-        google()
-        mavenCentral()
-    }
-
-    dependencies {
-        classpath("com.android.tools.build:gradle:9.0.1")
-        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion")
-    }
-}
+version = "5.0.2"
 
 allprojects {
     repositories {
@@ -25,6 +12,14 @@ plugins {
     id("com.android.library")
 }
 
+// AGP 9+ has built-in Kotlin support; on older AGP the Kotlin Gradle plugin
+// must be applied explicitly. Version is supplied by the consuming app.
+// See https://docs.flutter.dev/release/breaking-changes/migrate-to-built-in-kotlin/for-plugin-authors
+val agpMajor = com.android.Version.ANDROID_GRADLE_PLUGIN_VERSION.substringBefore('.').toInt()
+if (agpMajor < 9) {
+    apply(plugin = "org.jetbrains.kotlin.android")
+}
+
 android {
     namespace = "dk.cachet.screen_state"
 
@@ -35,15 +30,6 @@ android {
         targetCompatibility = JavaVersion.VERSION_17
     }
 
-    sourceSets {
-        getByName("main") {
-            java.srcDirs("src/main/kotlin")
-        }
-        getByName("test") {
-            java.srcDirs("src/test/kotlin")
-        }
-    }
-
     defaultConfig {
         minSdk = 24
     }
@@ -65,7 +51,7 @@ android {
     }
 }
 
-kotlin {
+project.extensions.configure(org.jetbrains.kotlin.gradle.dsl.KotlinAndroidProjectExtension::class.java) {
     compilerOptions {
         jvmTarget = org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17
     }

packages/screen_state/android/src/main/kotlin/dk/cachet/screen_state/ScreenReceiver.java

@@ -0,0 +1,13 @@
+package dk.cachet.screen_state
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import io.flutter.plugin.common.EventChannel.EventSink
+
+class ScreenReceiver(private val eventSink: EventSink?) : BroadcastReceiver() {
+
+    override fun onReceive(context: Context, intent: Intent) {
+        eventSink?.success(intent.action)
+    }
+}

packages/screen_state/android/src/main/kotlin/dk/cachet/screen_state/ScreenReceiver.kt

@@ -4,7 +4,7 @@ publish_to: "none" # Remove this line if you wish to publish to pub.dev
 version: 5.0.0+1
 
 environment:
-  sdk: ^3.12.2
+  sdk: ^3.10.0
   flutter: ">=3.6.0"
 
 dependencies:

packages/screen_state/example/pubspec.yaml

@@ -1,10 +1,10 @@
 name: screen_state
 description: A plugin for reporting screen events while the flutter application is running in background. Works for Android and iOS only.
-version: 5.0.1
+version: 5.0.2
 homepage: https://github.com/carp-dk/flutter-plugins/tree/master/packages/screen_state
 
 environment:
-  sdk: ^3.12.2
+  sdk: ^3.10.0
   flutter: ">=3.3.0"
 
 dependencies: