Examples: revert to fixed SDK versions in Android build files.

Author: greenrobot-team

objectbox/example/flutter/objectbox_demo/android/app/build.gradle

@@ -26,8 +26,10 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion flutter.compileSdkVersion
-    ndkVersion flutter.ndkVersion
+    // Using explicit versions to build with Flutter 2.2.0 in CI.
+    // compileSdkVersion flutter.compileSdkVersion
+    // ndkVersion flutter.ndkVersion
+    compileSdkVersion 31
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8
@@ -46,8 +48,11 @@ android {
         applicationId "com.example.objectbox_demo"
         // 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 flutter.minSdkVersion
-        targetSdkVersion flutter.targetSdkVersion
+        // minSdkVersion flutter.minSdkVersion
+        // targetSdkVersion flutter.targetSdkVersion
+        // Using explicit versions to build with Flutter 2.2.0 in CI.
+        minSdkVersion 16
+        targetSdkVersion 29
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }

objectbox/example/flutter/objectbox_demo_relations/android/app/build.gradle

@@ -26,8 +26,10 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion flutter.compileSdkVersion
-    ndkVersion flutter.ndkVersion
+    // Using explicit versions to build with Flutter 2.2.0 in CI.
+    // compileSdkVersion flutter.compileSdkVersion
+    // ndkVersion flutter.ndkVersion
+    compileSdkVersion 31
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8
@@ -46,8 +48,11 @@ android {
         applicationId "com.example.objectbox_demo_relations"
         // 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 flutter.minSdkVersion
-        targetSdkVersion flutter.targetSdkVersion
+        // minSdkVersion flutter.minSdkVersion
+        // targetSdkVersion flutter.targetSdkVersion
+        // Using explicit versions to build with Flutter 2.2.0 in CI.
+        minSdkVersion 16
+        targetSdkVersion 29
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }

objectbox/example/flutter/objectbox_demo_sync/android/app/build.gradle

@@ -26,8 +26,10 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion flutter.compileSdkVersion
-    ndkVersion flutter.ndkVersion
+    // Using explicit versions to build with Flutter 2.2.0 in CI.
+    // compileSdkVersion flutter.compileSdkVersion
+    // ndkVersion flutter.ndkVersion
+    compileSdkVersion 31
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8
@@ -47,7 +49,9 @@ 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 21 // ObjectBox Sync requires at least SDK 21 (Android 5.0)
-        targetSdkVersion flutter.targetSdkVersion
+        // targetSdkVersion flutter.targetSdkVersion
+        // Using explicit version to build with Flutter 2.2.0 in CI.
+        targetSdkVersion 29
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }