Updated readme file

README.md

@@ -47,3 +47,20 @@ export ADB_TRACE=info
 In case of any issues try `adb kill-server` and then `adb start-server`. Run `export ADB_TRACE=all` to see verbose output.
 You can also check open 5037 port with `fuser 5037/tcp`. Processes using this port can be killed with `fuser -k 5037/tcp`.
 
+### Targeting Android SDK versions
+
+See `/opt/dev/init/dev-init-android.sh` for default SDK and build tools versions. Use sdkmanager or AVD magager to install other SDKs, emulators and build tools.
+
+Avoid changing `build.gradle` and other config files when flutter variables are used. Edit `android/local.properties` file instead. Example content:
+
+```
+flutter.sdk=/opt/flutter
+flutter.compileSdkVersion = 34
+flutter.targetSdkVersion = 23
+flutter.buildMode=debug
+flutter.versionName=1.0.0
+flutter.versionCode=1
+sdk.dir=/opt/android-sdk
+```
+
+Note that you can use new compile SDK and build tools to target older API.