FlutterActivityLaunchConfigs is not public ;

FlutterActivity.NewEngineIntentBuilder builder = FlutterActivity.withNewEngine();
builder.initialRoute("recorder");
builder.backgroundMode(FlutterActivityLaunchConfigs.BackgroundMode.transparent);

so I can't use it;

flutter doctor -v
[✓] Flutter (Channel dev, v1.12.15, on Mac OS X 10.15.1 19B88, locale zh-Hans-CN)
• Flutter version 1.12.15 at /opt/google/flutter
• Framework revision 459c7fb (33 hours ago), 2019-11-26 17:04:51 +0000
• Engine revision e136d63
• Dart version 2.7.0

[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at /opt/google/android/sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-29, build-tools 28.0.3
• ANDROID_HOME = /opt/google/android/sdk
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.1)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.1, Build version 11A1027
• CocoaPods version 1.8.3

[✓] Android Studio (version 3.5)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 41.1.2
• Dart plugin version 191.8593
• Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)

[!] IntelliJ IDEA Ultimate Edition (version 2018.1)
• IntelliJ at /Applications/IntelliJ IDEA.app
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
• For information about installing plugins, see
https://flutter.dev/intellij-setup/#installing-the-plugins

[✓] Connected device (1 available)
• COL AL10 • VBJDU18725002458 • android-arm64 • Android 9 (API 28)