Recent questions tagged Flutter

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flutter - Fluter- Image picker package: show images one after another with delete action

In my Flutter pr project, I am using Image Picker plugin to select images from android mobile gallery or capture images with camera and show them one after another ... ) : new Image.file(file), ); } } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - Getting permission to the external storage (file_provider plugin)

I'm having some problems getting permissions to the external storage on android devices with flutter. When I try to create a directory in my external ... gives the same permission error. Hope to hear! See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - How to know if a widget is visible within a viewport?

I have a view that consists of a Scaffold and a single ListView in its body, each children of the list is a different widget that represents various ... initially visible due to being far down the list). See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - dart advantage of a factory constructor identifier

I've been investigating JSON parsing for my Flutter app and have a question about factory constructors that I can't resolve. I'm trying to understand ... a factory or is using a factory here superfluous? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - Could not find the correct provider above this widget

I have a problem using Flutter Provider... My flow is like this: After login user id is passed to new widget -> from there it preforms save to ... , but could not find anything suitable to my problem. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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911 views

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flutter - Null check operator used on a null value

I am new to Flutter I got this error when I run my simple flutter APP. I could not figure out why this error occurred. Error Null check operator ... found issues in 1 category. Can anyone provide a solution for this? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - Programmatically scrolling to the end of a ListView

I have a scrollable ListView where the number of items can change dynamically. Whenever a new item is added to the end of the list, I would like to ... only a small number of items that fit within the ListView viewport. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - What is Null Safety in Dart?

I have heard of the new Dart null safety language feature (NNBD), currently the "'non-nullable' experiment". It is supposed to introduce non-nullable by default. ... issue here. How does it work and where can I try it? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - How to wait for forEach to complete with asynchronous callbacks?

sample code Map<String,String> gg={'gg':'abc','kk':'kojk'}; Future<void> secondAsync() async { await Future.delayed(const Duration(seconds: 2)); ... then i want to print third expected Output Second! Third! Third! third Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.1k views

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flutter - How to call methods in Dart portion of the app, from the native platform using MethodChannel?

I am writing a native plugin that, in some cases, has to call functions in the Flutter portion of the app, written in Dart. How it's achieved, is ... way of returning a value from the non-native Dart portion of the app? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - How to use Expanded in SingleChildScrollView?

How to use Expanded in SingleChildScrollView? I have a screen with Image.network, ListView.builder and Row (TextFormField and IconButton). I wrapped ListView ... /flutter/issues/new?template=BUG.md I/flutter ( 6816): Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - Scaffold.of() called with a context that does not contain a Scaffold

As you can see, my button is inside the Scaffold's body. But I get this exception: Scaffold.of() called with a context that does ... should be a Stateful widget though. _scaffoldKey.currentState.showSnackBar(snackbar); Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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918 views

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flutter - What is the difference between named and positional parameters in Dart?

Dart supports both named optional parameters and positional optional parameters. What are the differences between the two? Also, how can you tell if an optional parameter was actually specified? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - Navigator operation requested with a context that does not include a Navigator

I'm trying to start a new screen within an onTap but I get the following error: Navigator operation requested with a context that does not include a ... { return new Scaffold( appBar: buildAppBar(context), ); } } Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - How to get height of a Widget?

I don't understand how LayoutBuilder is used to get the height of a Widget. I need to display the list of Widgets and get their height so I can compute ... depend on the size of the child. And that's a weird limitation. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - Dart assigning to variable right away or in constructor?

In Dart, is there a difference in assigning values right away vs in constructor like in Java? class Example { int x = 3; } vs class Example { ... it was not possible with the former method but possible with the latter. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - The argument type 'String' can't be assigned to the parameter type 'Uri'

I am trying to make an HTTP POST request with the flutter plugin HTTP but I am getting an error of the title. Does anyone know the cause ... : appSecret, "code": authorizationCode, "grant_type": "authorization_code" }); Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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3.7k views

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flutter - "The operator can’t be unconditionally invoked because the receiver can be null" error after migrating to Dart null-safety

I'm upgrading a personal package that is based on the Flutter framework. I noticed here in the Flutter Text widget source code that there is a null check ... question was solved on GitHub so I'm posting an answer below. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.1k views

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flutter - What is a NoSuchMethod error and how do I fix it?

I have some code and when I run it produces an error, saying: NoSuchMethod: the method 'XYZ' was called on null What does that mean and how do I fix it? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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950 views

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flutter - How to deal with unwanted widget build?

For various reasons, sometimes the build method of my widgets is called again. I know that it happens because a parent updated. But this causes undesired ... unwanted build? Is there any way to prevent a build call? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - What is a Future and how do I use it?

I get the following error: A value of type 'Future<int>' can't be assigned to a variable of type 'int' It might be another type instead of int, but basically ... I use to display my value when all I have is a Future<T>? Question&Answers:os...

asked Oct 16, 2021 in Technique[技术] by 深蓝 (71.8m points)

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flutter - How to pass data down the tree using flutter_blocs?

I am quite stuck on this thing for the past few days. So my use case here is,? A -> B -> C -> D Update some data in A when there ... from:https://stackoverflow.com/questions/65829588/how-to-pass-data-down-the-tree-using-flutter-blocs...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.3k views

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flutter - Why is ChangeNotifierProvider.value not updating its builder?

I have a lot of data objects. Each with a ChangeNotifier. So I want to update the smallest area possible. What must be changed to ... https://stackoverflow.com/questions/65830117/why-is-changenotifierprovider-value-not-updating-its-builder...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.7k views

1 answer

flutter - StreamProvider not rebuilding the widget tree when AsyncValue updates

I am to listening firebase AuthStateChanges stream and provide the stream with streamProvider to change the view based on the stream value. And ... com/questions/65830274/streamprovider-not-rebuilding-the-widget-tree-when-asyncvalue-updates...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.4k views

1 answer

flutter - How mock a instance of File in Dart

I want mock the method file.writeAsBytes, but I don't know how to make this. note: I do not intend to save the files in the test, just ... question from:https://stackoverflow.com/questions/65830661/how-mock-a-instance-of-file-in-dart...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.0k views

1 answer

flutter - Flutteronic method of scheduling code to run on the next event loop

This is common in other languages. setTimeout(fn, 0) in JavaScript, and DispatchQueue.main.async() {} in Swift. How best to do this in Flutter? ... .com/questions/65831125/flutteronic-method-of-scheduling-code-to-run-on-the-next-event-loop...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.1k views

1 answer

flutter - How to add a list in a list to another list

I have a list called test3 and I want to add this list to another list test0. The problem is that I only want the "noequipment" "sublist" to be added ... ://stackoverflow.com/questions/65831543/how-to-add-a-list-in-a-list-to-another-list...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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895 views

1 answer

flutter - Approach 2 not populating Firstname

About Fetching the current user data from firebase. Approach 1 var currentUser = FirebaseAuth.instance.currentUser; if (currentUser != null) { var ... from:https://stackoverflow.com/questions/65832175/approach-2-not-populating-firstname...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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