refactor(android): migrate to new Gradle plugin system

Updated Android project to use the new Gradle plugin DSL for better maintainability and compatibility. Also updated target SDK to 33, added android:exported attribute, and improved overall build configuration.

Author: gibahjoe

example/android/app/build.gradle

@@ -1,3 +1,9 @@
+plugins {
+    id "com.android.application"
+    id "kotlin-android"
+    id "dev.flutter.flutter-gradle-plugin"
+}
+
 def localProperties = new Properties()
 def localPropertiesFile = rootProject.file('local.properties')
 if (localPropertiesFile.exists()) {
@@ -6,25 +12,6 @@ if (localPropertiesFile.exists()) {
     }
 }
 
-def flutterRoot = localProperties.getProperty('flutter.sdk')
-if (flutterRoot == null) {
-    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
-}
-
-def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
-if (flutterVersionCode == null) {
-    flutterVersionCode = '1'
-}
-
-def flutterVersionName = localProperties.getProperty('flutter.versionName')
-if (flutterVersionName == null) {
-    flutterVersionName = '1.0'
-}
-
-apply plugin: 'com.android.application'
-apply plugin: 'kotlin-android'
-apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
-
 android {
     compileSdkVersion 34
 
@@ -45,9 +32,9 @@ android {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "com.example.example"
         minSdkVersion flutter.minSdkVersion
-        targetSdkVersion 30
-        versionCode flutterVersionCode.toInteger()
-        versionName flutterVersionName
+        targetSdkVersion 33
+        versionCode flutter.versionCode.toInteger()
+        versionName flutter.versionName
     }
 
     buildTypes {
@@ -63,6 +50,3 @@ flutter {
     source '../..'
 }
 
-dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
-}

example/android/app/src/main/AndroidManifest.xml

@@ -8,6 +8,7 @@
             android:theme="@style/LaunchTheme"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
             android:hardwareAccelerated="true"
+            android:exported="true"
             android:windowSoftInputMode="adjustResize">
             <!-- Specifies an Android theme to apply to this Activity as soon as
                  the Android process has started. This theme is visible to the user

example/android/build.gradle

@@ -1,16 +1,3 @@
-buildscript {
-    ext.kotlin_version = '1.9.20'
-    repositories {
-        google()
-        mavenCentral()
-    }
-
-    dependencies {
-        classpath 'com.android.tools.build:gradle:8.7.0'
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-    }
-}
-
 allprojects {
     repositories {
         google()

example/android/settings.gradle

@@ -1,11 +1,25 @@
-include ':app'
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        file("local.properties").withInputStream { properties.load(it) }
+        def flutterSdkPath = properties.getProperty("flutter.sdk")
+        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+        return flutterSdkPath
+    }()
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
 
-def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
-def properties = new Properties()
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
 
-assert localPropertiesFile.exists()
-localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
+plugins {
+    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
+    id "com.android.application" version "8.7.0" apply false
+    id "org.jetbrains.kotlin.android" version "1.9.20" apply false
+}
 
-def flutterSdkPath = properties.getProperty("flutter.sdk")
-assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
-apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"
+include ':app'

openapi-generator/lib/src/gen_on_spec_changes.dart

@@ -27,9 +27,10 @@ final _supportedRegexes = [jsonRegex, yamlRegex];
 /// It also throws an error when the specification doesn't exist on disk.
 ///
 /// WARNING: THIS DOESN'T VALIDATE THE SPECIFICATION CONTENT
-FutureOr<Map<String, dynamic>> loadSpec({required InputSpec specConfig,
-  bool isCached = false,
-  http.Client? client}) async {
+FutureOr<Map<String, dynamic>> loadSpec(
+    {required InputSpec specConfig,
+    bool isCached = false,
+    http.Client? client}) async {
   client ??= http.Client();
   print('loadSpec - ' + specConfig.path);
   // If the spec file doesn't match any of the currently supported spec formats