Flutter APK file is showing only gray screen

Question

My APK file is showing only gray screen but it works well in debug mode.

Flutter Doctor (Edit):

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.8.0, on Microsoft Windows [Version 10.0.19043.1415], locale ko-KR)
[√] Android toolchain - develop for Android devices (Android SDK version 31.0.0)
[√] Chrome - develop for the web
[√] Android Studio (version 2020.3)
[√] VS Code (version 1.63.2)
[√] Connected device (3 available)

• No issues found!

main.dart:

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  await Hive.initFlutter();
  await Hive.openBox("myBox1");
  SystemChrome.setPreferredOrientations(
    [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown]
  ).then((_) => runApp(const MyApp()));
}

AndroidManifest.xml:

<uses-permission android:name="android.permission.INTERNET"/>

What is causing this problem?

Answer 1

did you already try to finish the Android Toochain setup? I mean, it says that you don't have the cmdline-tools component and you didn't accepted the android licenses.

It says that you have the Android Studio Installed, so the only thing that you have to do is to:

• Locate the SdkManager (it depends of your O.S.), then you will run something like this: ./sdkmanager --install "cmdline-tools;latest".
• After that, you just accept the Android licenses, like this: flutter doctor --android-licenses (note, I suggest to to restart the console after the the previous step, and then try this command).

Note: I wanted to add this to the comment section, although I don't have the required reputation.

If that doesn't solve the problem I think that maybe is due to the line with the SystemChrome stuff.

So I would recommend to test it instead of this:

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  await Hive.initFlutter();
  await Hive.openBox("myBox1");
  SystemChrome.setPreferredOrientations(
    [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown]
  ).then((_) => runApp(const MyApp()));
}

With this:

import 'package:flutter/foundation.dart' show kIsWeb;

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  await Hive.initFlutter();
  await Hive.openBox("myBox1");
  if (kIsWeb) {
    // running on the web!
    SystemChrome.setPreferredOrientations(
      [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown]
    ).then((_) => runApp(const MyApp()));
  } else {
    // NOT running on the web! You can check for additional platforms here.
    runApp(const MyApp()));
  }
  
}

There is a global boolean kIsWeb which can tell you whether or not the app was compiled to run on the web.

Documentation: https://api.flutter.dev/flutter/foundation/kIsWeb-constant.html

You can check more about that on this StackOverflow question.

I hope that was helpful .