How to import intl library in Flutter?

Just to double check, you did import intl: ^0.15.7 into pubspec.yaml; triple check that it has four spaces in front of it (no more and no less); and you ran packages get?

Also, put your focus on the tab for main.dart and hit the green arrow to run it. Sometimes you will then see a popup bar at the top of the screen that tells you pubspec.yaml has changed and you need to run it again from that link in order for it to take. (I've seen that in IntelliJ)

Also, if it's showing red lines under publspec.yaml in the project window but everything is working, that's a bug in the analysis. Ignore it but yes, they do know about it and are working on it. It's often there because, for some reason, pubspec.yaml says your assets directory doesn't exist even though you can access the assets without any problem.

Let IDE do this for you :

flutter pub add intl

After running above command, It will resolve the dependency with the latest version available.

OR Manual Process

1) Add package in pubspec.yaml file under dependencies field :

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^1.0.2
  intl: ^0.17.0   // Add this line

2) Execute the following command in terminal :

flutter packages get

3) Import package in your dart file :

import 'package:intl/intl.dart';

When you import any package, example:

import 'package:intl/intl.dart';

You need to also add the package inside the pubspec.yaml file under the dependencies field example:

dependencies:
  intl: ^0.15.7

Then from the terminal you can execute the following command:

flutter packages get

or

From Android Studio/IntelliJ:

Click Packages Get in the action ribbon at the top of pubspec.yaml

more info here:

https://flutter.io/using-packages/