ListView animation when item is deleted using Dismissible - dart

I'm using Dismissible to dismiss the items, but when an item is dismissed I get default boring animation. Is there a way to change that animation like Gmail does?
Example:
My own animation (not smooth)
So, in my animation, you can see slight pause when the item is deleted and next item coming up on the screen taking up old item position.

That's the default animation of Dismissible.
List<String> content;
ListView.builder(
itemCount: content.length,
itemBuilder: (context, index) {
return Dismissible(
key: ValueKey(content[index]),
onDismissed: (_) {
setState(() {
content = List.from(content)..removeAt(index);
});
},
background: Container(color: Colors.green),
child: ListTile(
title: Text(content[index]),
),
);
},
)

Thanks to #Rémi Rousselet for his efforts.
Finally I found the reason for that ugly animation. Never use itemExtent when you are planning to use Dismissible. I was mad, I used it.

Related

Error thrown on navigator pop until : "!_debugLocked': is not true."

When popping a screen navigating to other one by clicking on the showBottomSheet, this error is thrown through the following code . I cant get why this is occurring.
class _CheckoutButtonState extends State<_CheckoutButton> {
final GlobalKey<ScaffoldState> _globalKey = GlobalKey();
final DateTime deliveryTime = DateTime.now().add(Duration(minutes: 30));
final double deliveryPrice = 5.00;
#override
Widget build(BuildContext context) {
SubscriptionService subscriptionService =
Provider.of<SubscriptionService>(context);
CheckoutService checkoutService = Provider.of<CheckoutService>(context);
return Container(
height: 48.0,
width: MediaQuery.of(context).size.width * 0.75,
child: StreamBuilder(
stream: subscriptionService.subscription$,
builder: (_, AsyncSnapshot<Subscription> snapshot) {
if (!snapshot.hasData) {
return Text("CHECKOUT");
}
final Subscription subscription = snapshot.data;
final List<Order> orders = subscription.orders;
final Package package = subscription.package;
num discount = _getDiscount(package);
num price = _totalPriceOf(orders, discount);
return StreamBuilder<bool>(
stream: checkoutService.loading$,
initialData: false,
builder: (context, snapshot) {
bool loading = snapshot.data;
return ExtendedFloatingActionButton(
loading: loading,
disabled: loading,
action: () async {
checkoutService.setLoadingStatus(true);
final subscription =
await Provider.of<SubscriptionService>(context)
.subscription$
.first;
try {
await CloudFunctions.instance.call(
functionName: 'createSubscription',
parameters: subscription.toJSON);
final bottomSheet =
_globalKey.currentState.showBottomSheet(
(context) {
return Container(
width: MediaQuery.of(context).size.width,
decoration: BoxDecoration(
gradient: LinearGradient(
begin: Alignment.topCenter,
end: Alignment.bottomCenter,
colors: [
Theme.of(context).scaffoldBackgroundColor,
Theme.of(context).primaryColor,
Theme.of(context).primaryColor,
],
stops: [-1.0, 0.5, 1.0],
),
),
child: Column(
children: <Widget>[
Expanded(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding:
const EdgeInsets.only(bottom: 16.0),
child: Text(
"Thank you for your order",
textAlign: TextAlign.center,
style: Theme.of(context)
.textTheme
.display1,
),
),
SvgPicture.asset(
'assets/images/thumb.svg',
height: 120.0,
width: 100.0,
)
// CircleAvatar(
// radius: 40.0,
// backgroundColor: Colors.transparent,
// child: Icon(
// Icons.check,
// color: Theme.of(context)
// .textTheme
// .display1
// .color,
// size: 80.0,
// ),
// ),
],
),
),
Container(
width:
MediaQuery.of(context).size.width * 0.9,
height: 72.0,
padding: EdgeInsets.only(bottom: 24),
child: ExtendedFloatingActionButton(
text: "ORDER DETAILS",
action: () {
Navigator.of(context).pop();
},
),
),
],
),
);
},
);
bottomSheet.closed.then((v) {
Navigator.of(context)
.popUntil((r) => r.settings.isInitialRoute);
});
} catch (e) {
print(e);
final snackBar =
SnackBar(content: Text('Something went wrong!'));
Scaffold.of(context).showSnackBar(snackBar);
}
},
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
"CHECKOUT ",
style: Theme.of(context)
.textTheme
.display4
.copyWith(color: Colors.white),
),
Text(
"EGP " +
(price + (orders.length * deliveryPrice))
.toStringAsFixed(2),
style: Theme.of(context)
.textTheme
.display4
.copyWith(color: Theme.of(context).primaryColor),
),
],
),
);
});
},
),
);
}
num _totalPriceOf(List<Order> orders, num discount) {
num price = 0;
orders.forEach((Order order) {
List<Product> products = order.products;
products.forEach((Product product) {
price = price + product.price;
});
});
num priceAfterDiscount = price * (1 - (discount / 100));
return priceAfterDiscount;
}
num _getDiscount(Package package) {
if (package == null) {
return 0;
} else {
return package.discount;
}
}
}
Error :
>══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (24830): The following assertion was thrown building Navigator-[GlobalObjectKey<NavigatorState>
I/flutter (24830): _WidgetsAppState#90d1f](dirty, state: NavigatorState#6b2b6(tickers: tracking 1 ticker)):
I/flutter (24830): 'package:flutter/src/widgets/navigator.dart': Failed assertion: line 1995 pos 12: '!_debugLocked':
I/flutter (24830): is not true.
I/flutter (24830): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter (24830): more information in this error message to help you determine and fix the underlying cause.
I/flutter (24830): In either case, please report this assertion by filing a bug on GitHub:
I/flutter (24830): https://github.com/flutter/flutter/issues/new?template=BUG.md
I/flutter (24830): When the exception was thrown, this was the stack:
Instead of giving you a direct answer, I'm going to walk you through how I thought about this when I saw the question, in the hope that it'll help you in the future.
Let's take a look at the assertion. It says Failed assertion: line 1995 pos 12: '!_debugLocked': I/flutter (24830): is not true.. Hmm, interesting. Let's take a look at that line of code.
assert(!_debugLocked);
Well, that doesn't give me much more information, let's look at the variable.
bool _debugLocked = false; // used to prevent re-entrant calls to push, pop, and friends
That's better. It's there to prevent re-entrant calls to push, pop, etc (by that it means that it doesn't want you calling 'push', 'pop', etc from within a call to 'push', 'pop'). So let's trace that back to your code.
This seems like the likely culprit:
bottomSheet.closed.then((v) {
Navigator.of(context)
.popUntil((r) => r.settings.isInitialRoute);
});
I'm going to skip a step here and use deductive reasoning instead - I'm betting that the closed future is finished during a pop. Go ahead and confirm that by reading the code if you feel like it.
So, if the issue is that we're calling pop from within a pop function, we need to figure out a way to defer the call to pop until after the pop has completed.
This becomes quite simple - there's two ways to do this. The simple way is to just use a delayed future with zero delay, which will have dart schedule the call as soon as possible once the current call stack returns to the event loop:
Future.delayed(Duration.zero, () {
Navigator. ...
});
The other more flutter-y way of doing it would be to use the Scheduler to schedule a call for after the current build/render cycle is done:
SchedulerBinding.instance.addPostFrameCallback((_) {
Navigator. ...
});
Either way should eliminate the problem you're having.
Another option is also possible though - in your ExtendedFloatingActionButton where you call pop:
ExtendedFloatingActionButton(
text: "ORDER DETAILS",
action: () {
Navigator.of(context).pop();
},
),
you could instead simply do the call to Navigator.of(context).popUntil.... That would eliminate the need for the doing anything after bottomSheet.closed is called. However, depending on whatever else you might or might not need to do in your logic this may not be ideal (I can definitely see the issue with having the bottom sheet set off a change to the main part of the page and why you've tried to make that happen in the page's logic).
Also, when you're writing your code I'd highly recommend separating it into widgets - for example the bottom sheet should be its own widget. The more you have in a build function, the harder it is to follow and it can actually have an effect on performance as well. You should also avoid using GlobalKey instances wherever possible - you can generally either pass objects (or callbacks) down if it's only through a few layers, use the .of(context) pattern, or use inherited widgets.
For those who are invoking the Navigator as part of the build process. I found that it will intermittently throwing asserting error on the debugLocked
I avoided this issue by wrapping with a addPostFrameCallback:
WidgetsBinding.instance.addPostFrameCallback((_) {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (_) => MyPage()));
});
I had this same issue any answer not worked for me and this error doesn't explain any thing.
After going each line code i found that we cannot launch any state in build method like this
#override
Widget build(BuildContext context) {
var viewmodel = Provider.of<ViewModel>(context);
Navigator.of(context).push(MaterialPageRoute(builder:
(context)=>CreateItemPage(viewmodel.catalogData))); // this is way i was getting error.
return Scaffold();
}
I was getting error in CreateItemPage screen because of that line.
Solution of this issue create button which call this line Navigator.of(context).push(MaterialPageRoute(builder: (context)=>CreateItemPage(viewmodel.catalogData)));
For me, it was coming because I created a cycle of pushes that was causing this error.
For example,
In the Initial route which was /loading the code was pushing /home
class _LoadingState extends State<Loading> {
void getTime() async {
// DO SOME STUFF HERE
Navigator.pushNamed(context, '/home');
}
#override
void initState() {
super.initState();
getTime();
}
And in the /home initState I was pushing /loading creating a cycle.
class _HomeState extends State<Home> {
#override
void initState() {
super.initState();
Navigator.pushNamed(context, '/loading');
}
Add Some Delay Then Try to do this Your Problem will be Solved :
Future.delayed(const Duration(milliseconds: 500), () {
// Here you can write your code
setState(() {
Navigator.of(context).pushAndRemoveUntil(
MaterialPageRoute(builder: (context) => SetCategory()),
(route) => false);
});
});
I had similar error, like a dialog box which had a logout button, which when pressed goes to login screen, but an _debugLocked error occurs, so I used
Navigator.of(context).pushNamedAndRemoveUntil('/screen4', (Route<dynamic> route) => false);
This removes all routes in the stack so that user cannot go back to the previous routes after they have logged out.
Setting (Route<dynamic> route) => false will make sure that all routes before the pushed route are removed.
I don't know if this is the "real" solution but it helped me as a beginner to Flutter.
I've gotten this error due to a typo accidentally calling Navigator.of(context).push during my build():
E/flutter ( 6954): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: 'package:flutter/src/widgets/navigator.dart': Failed assertion: line 2845 pos 18: '!navigator._debugLocked': is not true.
The simulator flashed a more informative error:
setState() or markNeedsBuild() called during build.
This Overlay widget cannot be marked as needing to build because the framework
is already in the process of building widgets. A widget can be marked as needing
to be built during the build phase only if one of its ancestors is currently
building. This exception is allowed because the framework builds parent widgets
before children, which means a dirty descendant will always be built.
Otherwise, the framework might not visit this widget during this build phase The
widget on which setState() or markNeedsBuild() was called was:
Overlay-[LabeledGlobalKey<OverlayState>#de69b]
The widget which was currently being built when the offending call was made was:
FutureBuilder
Basically, you should not be trying to push/pop to a new route in the middle of a build. If you really need to, wait for the build to finish, which is why others are suggesting wrapping it in a SchedulerBinding.instance.addPostFrameCallback to execute after everything is rendered, but you probably should find a better way to do this outside of a build.
In my case, I typed:
onTap: _onTap(context),
when I really meant to type:
onTap: () => _onTap(context),
my _onTap handler was doing the Navigator push. I had forgotten to wrap my handler in a closure that captures the context it needs, and instead actually was executing it instead of passing onTap: my callback.
Dialog solution
For those who encounter this when calling Navigator.push(..) from a Dialog.
You need to do Navigator.pop(context);to programmatically close modal first, then call Navigator.push(..).
For people encountering this issue while using bloc, make sure you are using navigation in a BlocListener (or BlocConsumer's listener). In my case I was using Navigator inside BlocBuilder. I am new to Flutter/Bloc and the accepted answer resolved the problem, but was not the proper solution. Switching my BlocBuilder to a BlocConsumer allowed for me to navigate during specific states.
Example of using BlocConsumer, navigate when state is 'LoginSuccess':
BlocConsumer<LoginBloc, LoginState>(
listener: (BuildContext context, state) {
if (state is LoginSuccess) {
Navigator.of(context).pushReplacement(
// Add your route here
PageRouteBuilder(
pageBuilder: (_, __, ___) => BlocProvider.value(
value: BlocProvider.of<NavigationBloc>(context),
child: HomeScreen(),
),
),
);
}
},
// Only build when the state is not LoginSuccess
buildWhen: (previousState, state) {
return state is! LoginSuccess;
},
// Handle all states other than LoginSuccess here
builder: (BuildContext context, LoginState state) {
if (state is LoginLoading) {
return Center(child: CircularProgressIndicator());
} else .....
In resume, you just need to remove it from your initState.
I would recomend extend the class with AfterLayout and inside the
afterFirstLayout you can redirect it to the page you want. This will garantee that everything is ok before routing.
See bellow the steps:
Add to pubspec: after_layout: ^1.0.7+2
Then, You will extend it to the class you want to use. In my case was a statefull widget named HomePage. So it will looks like:
class HomePage extends StatefulWidget {
#override
HomePageState createState() => HomePageState();
} //no changes here
class HomePageState extends State<HomePage> with AfterLayoutMixin<HomePage> {
//the with AfterLayoutMixin<pageName> is the only thing you need to change.
Now, you need to implement a method called afterlayout, that will be executed after the build is completed.
#override
Future<void> afterFirstLayout(BuildContext context) {
//your code here safetly
}
You can find information here:
https://pub.dev/packages/after_layout
For those that still have the same issue, this help me to solve it.
navigationService.popUntil((_) => true);
navigationService.navigateTo(
'authentication',
);
basically i wait until the navigation finish setting everything and then call the navigateTo.
I got this error because my initialRoute was /login. However, the initialRoute is required to be /.
If the route name starts with a slash, then it is treated as a "deep link", and before this route is pushed, the routes leading to this one are pushed also. For example, if the route was /a/b/c, then the app would start with the four routes /, /a, /a/b, and /a/b/c loaded, in that order.
Here is a link to the docs for reference.
I had the same issue and took me some time to figure out. I was listening to the state on the screen based on which it will navigate to different screen. And then on button click I was changing that state and navigating to different screen which was causing an issue.
I am using flutter version 2.3.3
I also faced this issue when i try to pop back into my home screen from a second screen with command Navigator.pop(context)
I solved this issue by replacing this line of code with Navigator.of(context).pop(context)
It worked fine for me hope it hepls

Select Item effect in a GridView Builder

I have items loaded in GridView.builder from sqflite database. Since the model class of it is not Stateful, ofcourse, I am not able to create Select effect on the items from there.
What i mean by select effect is this:
When users tap on an item, it is selected
GridView.builder(
gridDelegate:.....,
itemBuilder: (BuildContext context, int index) {
bool _selectItem = false;
return InkWell(
onTap: () {},
child: Stack(
children: <Widget>[
itemsList[index]), //====Actual Item=====//
InkWell(onTap: () { //===To create Select Effect====//
setState(() {
if (_selectItem == false) {
_selectItem = true;
print("Item Selected");
} else {
_selectItem = false;
print("Item UnSelected");
}
});
},
child: Opacity(
opacity: _selectItem == true ? 0.5 : 0.0,
child: Icon(Icons.select)
),]); },
itemCount: itemsList.length,
))
I am able to create a select effect, but it selects all items if I tap on any one item. How can create select effect for each individual item.
So how can I create select effect for each individual item?
P.S. I have written only relevant things in the code
Link to the original question: (Flutter) Select Effect on items in Grid View Builder
Okay I would suggest you wrap your stateless item into a GestureDetector
Then you can decide which gesture you want to detect and react to it, here's the doc
Hope it's help
You can try using the Hero widget for a simple animation, but if you're using custom animations you're going to have to change it to a stateful widget.
short video on hero widget: https://www.youtube.com/watch?v=Be9UH1kXFDw

Remove Index wise CustomWidget from List<Widget> in Flutter

I have initially empty list of Widget in Column. Now on Other widget click I am adding new Custom Widget in _contactItems
Column(
children: _contactItems,
)
List<Widget> _contactItems = new List<CustomWidget>();
_contactItems.add(newCustomWidget(value));
Now Suppose I have 6 Records (6 Custom Widgets in Column). I am trying to remove index wise records (Example. I am removing 3rd record then 1st record. Column Widgets (dynamic widgets) should be updated as _contactItems updating in setState())
Now on CustomWidget click I am removing that particular CustomWidget from Column.
setState(() {
_contactItems.removeAt(index);
});
Also tried with
_contactItems.removeWhere((item) {
return item.key == _contactItems[index].key;
});
Try this (assuming that your Column widget keys have this format):
setState(() {
this._contactItems.removeWhere((contact) => contact.key == Key("index_$index"));
});
If this doesn't solve your issue, maybe we'll need more info.
If you want to manipulate a ListView or GridView it is important that you assign a Key to each child Widget of the List/GridView
In short Flutter compares widgets only by Type and not state. Thus when the state is changed of the List represented in the List/GridView, Flutter doesn't know which children should be removed as their Types are still the same and checks out. The only issue Flutter picks up is the number of items, which is why it only removes the last widget in the List/GridView.
Therefore, if you want to manipulate lists in Flutter, assign a Key to the top level widget of each child. A more detailed explanation is available in this article.
This can be achieved be adding
return GridView.count(
shrinkWrap: true,
crossAxisCount: 2,
crossAxisSpacing: 5.0,
mainAxisSpacing: 5.0,
children: List.generate(urls.length, (index) {
//generating tiles with from list
return GestureDetector(
key: UniqueKey(), //This made all the difference for me
onTap: () => {
setState(() {
currentUrls.removeAt(index); // deletes the item from the gridView
})
},
child: FadeInImage( // A custom widget I made to display an Image from
image: NetworkImage(urls[index]),
placeholder: AssetImage('assets/error_loading.png')
),
);
}),
);

Flutter Codelab: Update ListView on different screen

I completed the Flutter NameGenerator code lab and wanted to extend it to remove items directly from the "Saved suggestions list".
To do so, I've added the onTap handler below which removes the pair from the list.
However, the list doesn't update until I navigate back and reopen the screen again.
How do I immediately update the list on the second screen?
void _pushSaved() {
Navigator.of(context).push(MaterialPageRoute<void>(
builder: (BuildContext context) {
final Iterable<ListTile> tiles = _saved.map((WordPair pair) {
return ListTile(
title: Text(
pair.asPascalCase,
style: _biggerFont,
),
onTap: () => setState(() {
_saved.remove(pair);
}),
);
});
final List<Widget> divided = ListTile.divideTiles(
context: context,
tiles: tiles,
).toList();
return Scaffold(
appBar: AppBar(
title: const Text('Saved Suggestions'),
),
body: new ListView(children: divided),
);
}),
);
}
Why your code doesn't work
The reason your list doesn't update is that it's a different screen pushed on the Navigator.
Because your _pushSaved method is inside the original screen, you call setState on that screen and rebuild all the widgets of the original screen.
The pushed screen isn't affected because it's not a child of your original screen.
Rather, the original screen told the Navigator to create a new screen, so it's some subtree of the Navigator of your MaterialApp and not accessible to you.
Solution
Accessing the same live data on different screens is something that's not that easy to do just with StatefulWidgets.
Basically, your project has grown complex enough so that it's time to think about a more sophisticated state management solution.
Here's a video from Google I/O about state management that you could check out for some inspiration.

How to extend PageView to both sides with builder?

Using PageView.builder I can get an infinite list of pages, but only in one direction, i.e. it is finite in the other direction!
The default scrollDirection of a PageView is Axis.horizontal. So what I mean is that in the regular case I can only scroll infinitely to the right, but not to the left.
I want to be able to scroll infinitely in both directions. I have not found a way to do this, especially, because I would expect the itemBuilder to give out negative indices then, which I have never seen. That leads me to wondering whether this is implemented at all, but I am open to custom solutions and will try to come up with something aswell.
There's no official way of having an infinite scroll in both directions.
But you can instead use PageController's initialPage property. Setting it to an absurdly big value. And then use this value as your "index 0".
class MyHomePage extends StatelessWidget {
final PageController pageController = new PageController(initialPage: 4242);
#override
Widget build(BuildContext context) {
return new Scaffold(body: new PageView.builder(
controller: pageController,
itemBuilder: (context, _index) {
final index = _index - 4242;
return new Container(
margin: const EdgeInsets.all(9.0),
color: Colors.red,
child: new Center(
child: new Text(index.toString()),
),
);
},
));
}
}
I solved it pretty straight forward. Honestly, I must have been out of my mind writing the question and issueing the bounty.
// number is irrelevant
final initialPage = (
.161251195141521521142025 // :)
* 1e6,).round();
final itemCount = getSomeItemCount();
PageView.builder(
pageController: PageController(
initialPage: initialPage,
),
itemBuilder: (context, page) {
final index = itemCount - (initialPage - page - 1) % itemCount - 1;
return getPageContent(index);
},
);
I am not sure if I should give credit to Rémi Rousselet because I was using this method before he proposed his answer. I just wanted to mention him because this question is getting undeserved traffic and he helped me to solve my problem :)

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