Made required changes according to https://docs.flutter.dev/release/breaking-changes/flutter-gradle-plugin-apply

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()) {
@@ -6,11 +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'
@@ -21,11 +22,6 @@ if (flutterVersionName == null) {
     flutterVersionName = '1.0'
 }
 
-apply plugin: 'com.android.application'
-apply plugin: 'kotlin-android'
-apply plugin: 'dev.rikka.tools.refine'
-apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
-
 def keystoreProperties = new Properties()
 def keystorePropertiesFile = rootProject.file('key.properties')
 if (keystorePropertiesFile.exists()) {
@@ -33,7 +29,8 @@ if (keystorePropertiesFile.exists()) {
 }
 
 android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
+    namespace "dev.imranr.obtainium"
+    compileSdk flutter.compileSdkVersion
     ndkVersion flutter.ndkVersion
 
     compileOptions {
@@ -54,7 +51,7 @@ android {
         // You can update the following values to match your application needs.
         // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-build-configuration.
         minSdkVersion 24
-        targetSdkVersion rootProject.ext.targetSdkVersion
+        targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }