Change app name in pubspec.yaml cause error on imports - flutter

Question

I have created a new flutter project in AS and for some reason the name in pubspec.yaml for my app is just app even when I named it something else when I created new app
name: app
description: My new application.
When I rename it to whatever I need then all my imports error out in my project.
Example:
import 'package:app/main.dart';
So how do you change the name in pubspec.yaml without crashing all imports
UPDATE
After renaming name, AS doesn't show package option with the new name

Answer 1

For example, if the default app name is
name: defaultappname
description: My new application.
and you want to change it to
name: app
description: My new application.
then you have to just do the search and replace operation:

Answer 2

That's because you need to change the imported packages which now has a different source. The usual form for importing packages is like this:
import 'package:ApplicationNameDefinedInPubspec/FolderInLib/SubFolder/DartFileName.dart';.
so for example in your case it should be something like this:
import 'package:NewAppName/main.dart';.
And also to change the app name showing on the devices, the Flutter documentation points out where you can change the display name of your application for both Android and IOS. This may be what you are looking for:
Preparing an Android App for Release
Preparing an iOS App for Release
For Android
In the AndroidManifest.xml as the application entry.
Review the default App Manifest file AndroidManifest.xml located in
/android/app/src/main/ and verify the values are correct,
especially:
application: Edit the application tag to reflect the final name of the
app.
For iOS
See the Review Xcode project settings section:
Navigate to your target’s settings in Xcode:
In Xcode, open Runner.xcworkspace in your app’s ios folder.
To view your app’s settings, select the Runner project in the Xcode project
navigator. Then, in the main view sidebar, select the Runner target.
Select the General tab. Next, you’ll verify the most important
settings:
Display Name: the name of the app to be displayed on the home screen
and elsewhere.