🙊 문제인식

• flutter의 작동방식 상 시작 시 화면이 매끄럽지 않다는 것을 체감할 수 있다.
• 이를 해결 하기 위해서는 flutter가 화면을 렌더링 하기 전까지 splash screen을 보여주면 된다.

🔑 flutter_native_splash

https://pub.dev/packages/flutter_native_splash

• flutter_native_splash 패키지를 사용하여 이를 쉽게 구현 할 수 있다. 간단한 설정 만으로도 splash 화면을 어떤 플랫폼이든 상관 없이 보여 줄 수 있다!!

　📦 사용법

1. package 다운

flutter_native_splash package를 다운 받는다. 그렇다면 pubspec.yaml 파일에 해당 종속성이 추가 된다.

dependencies:
  flutter_native_splash: ^2.3.1

2. splash screen 설정

pubspec.yaml에 아래 코드를 추가 혹은 lib 디렉토리에 flutter_native_splash.yaml 파일을 만든 후 아래 코드를 추가한다.

flutter_native_splash:
  # This package generates native code to customize Flutter's default white native splash screen
  # with background color and splash image.
  # Customize the parameters below, and run the following command in the terminal:
  # dart run flutter_native_splash:create
  # To restore Flutter's default white splash screen, run the following command in the terminal:
  # dart run flutter_native_splash:remove

  # color or background_image is the only required parameter.  Use color to set the background
  # of your splash screen to a solid color.  Use background_image to set the background of your
  # splash screen to a png image.  This is useful for gradients. The image will be stretch to the
  # size of the app. Only one parameter can be used, color and background_image cannot both be set.
  color: "#42a5f5"
  #background_image: "assets/background.png"

  # Optional parameters are listed below.  To enable a parameter, uncomment the line by removing
  # the leading # character.

  # The image parameter allows you to specify an image used in the splash screen.  It must be a
  # png file and should be sized for 4x pixel density.
  #image: assets/splash.png

  # The branding property allows you to specify an image used as branding in the splash screen.
  # It must be a png file. It is supported for Android, iOS and the Web.  For Android 12,
  # see the Android 12 section below.
  #branding: assets/dart.png

  # To position the branding image at the bottom of the screen you can use bottom, bottomRight,
  # and bottomLeft. The default values is bottom if not specified or specified something else.
  #branding_mode: bottom

  # The color_dark, background_image_dark, image_dark, branding_dark are parameters that set the background
  # and image when the device is in dark mode. If they are not specified, the app will use the
  # parameters from above. If the image_dark parameter is specified, color_dark or
  # background_image_dark must be specified.  color_dark and background_image_dark cannot both be
  # set.
  #color_dark: "#042a49"
  #background_image_dark: "assets/dark-background.png"
  #image_dark: assets/splash-invert.png
  #branding_dark: assets/dart_dark.png

  # Android 12 handles the splash screen differently than previous versions.  Please visit
  # https://developer.android.com/guide/topics/ui/splash-screen
  # Following are Android 12 specific parameter.
  android_12:
    # The image parameter sets the splash screen icon image.  If this parameter is not specified,
    # the app's launcher icon will be used instead.
    # Please note that the splash screen will be clipped to a circle on the center of the screen.
    # App icon with an icon background: This should be 960×960 pixels, and fit within a circle
    # 640 pixels in diameter.
    # App icon without an icon background: This should be 1152×1152 pixels, and fit within a circle
    # 768 pixels in diameter.
    #image: assets/android12splash.png

    # Splash screen background color.
    #color: "#42a5f5"

    # App icon background color.
    #icon_background_color: "#111111"

    # The branding property allows you to specify an image used as branding in the splash screen.
    #branding: assets/dart.png

    # The image_dark, color_dark, icon_background_color_dark, and branding_dark set values that
    # apply when the device is in dark mode. If they are not specified, the app will use the
    # parameters from above.
    #image_dark: assets/android12splash-invert.png
    #color_dark: "#042a49"
    #icon_background_color_dark: "#eeeeee"

  # The android, ios and web parameters can be used to disable generating a splash screen on a given
  # platform.
  #android: false
  #ios: false
  #web: false

  # Platform specific images can be specified with the following parameters, which will override
  # the respective parameter.  You may specify all, selected, or none of these parameters:
  #color_android: "#42a5f5"
  #color_dark_android: "#042a49"
  #color_ios: "#42a5f5"
  #color_dark_ios: "#042a49"
  #color_web: "#42a5f5"
  #color_dark_web: "#042a49"
  #image_android: assets/splash-android.png
  #image_dark_android: assets/splash-invert-android.png
  #image_ios: assets/splash-ios.png
  #image_dark_ios: assets/splash-invert-ios.png
  #image_web: assets/splash-web.gif
  #image_dark_web: assets/splash-invert-web.gif
  #background_image_android: "assets/background-android.png"
  #background_image_dark_android: "assets/dark-background-android.png"
  #background_image_ios: "assets/background-ios.png"
  #background_image_dark_ios: "assets/dark-background-ios.png"
  #background_image_web: "assets/background-web.png"
  #background_image_dark_web: "assets/dark-background-web.png"
  #branding_android: assets/brand-android.png
  #branding_dark_android: assets/dart_dark-android.png
  #branding_ios: assets/brand-ios.gif
  #branding_dark_ios: assets/dart_dark-ios.gif

  # The position of the splash image can be set with android_gravity, ios_content_mode, and
  # web_image_mode parameters.  All default to center.
  #
  # android_gravity can be one of the following Android Gravity (see
  # https://developer.android.com/reference/android/view/Gravity): bottom, center,
  # center_horizontal, center_vertical, clip_horizontal, clip_vertical, end, fill, fill_horizontal,
  # fill_vertical, left, right, start, or top.
  #android_gravity: center
  #
  # ios_content_mode can be one of the following iOS UIView.ContentMode (see
  # https://developer.apple.com/documentation/uikit/uiview/contentmode): scaleToFill,
  # scaleAspectFit, scaleAspectFill, center, top, bottom, left, right, topLeft, topRight,
  # bottomLeft, or bottomRight.
  #ios_content_mode: center
  #
  # web_image_mode can be one of the following modes: center, contain, stretch, and cover.
  #web_image_mode: center

  # The screen orientation can be set in Android with the android_screen_orientation parameter.
  # Valid parameters can be found here:
  # https://developer.android.com/guide/topics/manifest/activity-element#screen
  #android_screen_orientation: sensorLandscape

  # To hide the notification bar, use the fullscreen parameter.  Has no effect in web since web
  # has no notification bar.  Defaults to false.
  # NOTE: Unlike Android, iOS will not automatically show the notification bar when the app loads.
  #       To show the notification bar, add the following code to your Flutter app:
  #       WidgetsFlutterBinding.ensureInitialized();
  #       SystemChrome.setEnabledSystemUIMode(SystemUiMode.manual, overlays: [SystemUiOverlay.bottom, SystemUiOverlay.top], );
  #fullscreen: true

  # If you have changed the name(s) of your info.plist file(s), you can specify the filename(s)
  # with the info_plist_files parameter.  Remove only the # characters in the three lines below,
  # do not remove any spaces:
  #info_plist_files:
  #  - 'ios/Runner/Info-Debug.plist'
  #  - 'ios/Runner/Info-Release.plist'

이때, splash screen에 추가 할 내용이 많지 않다면 새로운 yaml 파일을 만드는 것보다 pubspec.yaml에 바로 추가하는 것이 좋은 선택지 일 수도 있다. 해당 방식에 대해서 조금 더 설명하자면, 아래 코드 처럼 수정해주면 된다.
(이때, 들여쓰기가 상당히 중요하니 유의하자!!)

dev_dependencies:
	flutter_native_splash: ^2.3.1
flutter_native_splash:
	...
    # your splash screen
    # color : "#42a5f5"
    ...
	

3. splash screen 적용

이제 수정한 splash screen을 적용하기 위해서 아래 명령을 터미널에 입력한다.

flutter clean
flutter pub get
flutter pub run flutter_native_splash:create

혹은 파일 경로를 지정하려면 아래 코드를 입력한다.

flutter clean
flutter pub get
flutter pub run flutter_native_splash:create --path=path/to/my/file.yaml

4. splash screen 제어

import 'package:flutter_native_splash/flutter_native_splash.dart';

void main() {
  WidgetsBinding widgetsBinding = WidgetsFlutterBinding.ensureInitialized();
  FlutterNativeSplash.preserve(widgetsBinding: widgetsBinding);
  runApp(const MyApp());
}

// whenever your initialization is completed, remove the splash screen:
    FlutterNativeSplash.remove();

위의 코드는 기본적으로 package에서 제공되는 예시이다.
FlutterNativeSplash.preserve(widgetsBinding: widgetsBinding) 를 사용하면, 첫 프레임을 flutter에서 렌더링 하더라도 splash screen을 없애지 않는다.

앱 시작 전 원하는 행위 (http request)등을 끝낸 후 FlutterNativeSplash.remove();를 사용하여 스플래시 화면을 없앨 수 있다.

💡 유의사항

새로 splash screen을 설정 할 때에는 android/app/main/res 디렉토리에서 drawable 관련 파일들을 모두 삭제하고 다시 screen을 설정 하거나

flutter pub run flutter_native_splash:remove

명령을 터미널에 실행 한 후 재설정 해준다.

또한, 안드로이드 12로 업데이트 되면서 splash 화면이 기본 앱 아이콘으로 고정이 되어 버렸다.. 그래서 이를 native_splash_screen package에서 지원 하니, flutter_native_splash.yaml 파일에서 android 12항목에 추가로 splash screen을 설정해주면 된다.