I need to have some lists collapse by their topics in my project and am wondering if I'll need to implement this from zero or rather use a component from flutter. Does this component exist?
Thanks in advance :)
The Flutter Gallery has two examples that may be relevant for your accordion-like lists.
Expansion Panel Demo & Two-level List Demo
The Expansion Panel demo is probably what you want. If so, take a look at how the demo leverages ExpansionPanel and uses a headerBuilder and body. You can extends this to make the header and bodies as complex as you need. The Gallery demo adds a DemoItem helper class. You can use this pattern or come up with your own design.
Here is a snippet that shows the demo using ExpansionPanelList by passing a callback and the list of DemoItems:
child: new ExpansionPanelList(
expansionCallback: (int index, bool isExpanded) {
setState(() {
_demoItems[index].isExpanded = !isExpanded;
});
},
children: _demoItems.map((DemoItem<dynamic> item) {
return new ExpansionPanel(
isExpanded: item.isExpanded,
headerBuilder: item.headerBuilder,
body: item.build()
);
}).toList()
),
Related
How to boost flutter performance and speed up our application.
As I am working on a larg application and I worried about performance issue, becuase I need a supper fast app.
Here I have a large list of items like a chat application and there is something mentioned below that I am worry about:
1: I need scrolling more than 3000 items smoothly
2: I need to update specific item during chat, like: seen, delived, sent or deleted.
3: and navigation
In react-native there is a lot of way like using PureComponent
or shouldComponentUpdate(nextProps, nextState) function to decrease rendering.
for example in react-native we can split a big list Component into sub Component of items, then we can use shouldComponentUpdate(nextProps, nextState) and prevent any rendering does not depends to the current Item.
This aprroach help us to just render the item we need to update.
and also there is alot of other way we can use for speed up our application.
although One big problem I encounted in react-native is, if we scroll very fast more than 300 items there a blank space appears instaed of list items.
So my question is how to find same tips in FLUTTER, I mean Is there a tips/trick for flutter like I mentioned above in react-native? if yes please help me with a simple examples.
Thank you in befor
Here I have a large list of items like a chat application and there is something mentioned below that I am worry about: 1: I need scrolling more than 3000 items smoothly 2: I need to update specific item during chat, like: seen, delived, sent or deleted. 3: and navigation
Use ListView.builder() widget to create smooth scrollable list without any length without any performance issue.
It's functionality basically corresponds to RecyclerView (Native Android).
The items which are not visible on the screen are not rendered so it doesn't practically matter how many items exist in the list in total.
Flutter handles all those minor things for you so that you can focus on other important aspects of your app. Flutter and RN are similar to some extent but they are not the same.
Working Example:
import 'package:flutter/material.dart';
List<String> litems = ["1","2","Third","4"];
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext ctxt) {
return new MaterialApp(
home: new ListDisplay(),
);
}
}
class ListDisplay extends StatelessWidget {
#override
Widget build (BuildContext ctxt) {
return new Scaffold(
appBar: new AppBar(title: new Text("Dynamic Demo"),),
body: new ListView.builder(
itemCount: litems.length,
itemBuilder: (BuildContext ctxt, int index) {
return new Text(litems[index]);
}
)
),
);
}
}
If you still face the same issue, then try running the app in release mode. That should surely solve your issue for the above example.
If you want some more tips on increasing your app's overall performance head over to the links given below,
https://flutter.dev/docs/testing/best-practices
https://medium.com/flutter-community/improve-your-flutter-app-performance-split-your-widgets-935f97e93f7d
To run your app in release mode execute flutter run --release in your app's terminal to run your app in release mode.
While using the provider for example if have data that you will need only on a specific page and this data will be temporarily viewed avoid adding it to the provider I highly advise you to use multiple providers. so you avoid rebuiding all the screen components when changing the state. also if you have too many stateless widgets in a screen and you have only few widgets that are stateful. you should wrap those with state changeable components (stateful) with consumer so when notifying the UI of a state change only those concerne will be updated. that will help avoiding rebuid entire screen.
Use Stateless widgets instead of Stateful widgets in the cases that you dont have to use it so you dont have always to rebuild your application , and try to not Use setState() methode because it is heavy and expensive and use instead of it StreamBuilder()
Split Larger Widgets into smaller widgets
Use Const keyword , Using the const keyword wherever applicable can be a great way to reduce memory usage , and you can use the Const KeyWord in lot of places like EdgeInsets, Color and Text , and Also in Constructors
const EdgeInsets.fromLTRB(16, 4, 16, 8); const Color lightGray = Color(0xFFFEFEFE); const Text('This is a static text')
Also in the constructors:
Column(children: [
const JDSearchIcon(),
InkWell(....),
const JDSearchIcon(),],),
Render only widgets that are visible on the screen , When you are dealing with a large vertical or horizontal list of widgets, you should avoid using a solution that creates all the widgets visible on the screen at once. Instead, try using ListView.builder to improve the performance of your flutter app.
ListView.builder(
itemCount: dataSource.length,
itemBuilder: (context, index) {
return Tweet(dataSource[index]);
},
)
I've been researching some list sorting libraries like flutter_list_drag_and_drop, reorderable_list, flutter_reorderable_list, dragable_flutter_list, and others, but all work with only one list.
What I'm wanting to do can be understood in the image below, which is exactly what the Trello app has.
Any library suggestions or how to do this?
I've been researching some list sorting libraries like flutter_list_drag_and_drop, reorderable_list, flutter_reorderable_list, dragable_flutter_list and others, but all work with only one list.
Right ! All current available libraries work with only one list.
I got one more plugin called orderable_stack which is based on a "data items" list
Please refer orderable_stack for more details.
Also you can refer this link for more draggable implementations.
Note: Currently orderable_stack is incompatible with Dart 2
Hope this will helps you
I use boardview flutter plugin.
import 'package:boardview/board_item.dart';
import 'package:boardview/board_list.dart';
import 'package:boardview/boardview.dart';
#override
Widget build(BuildContext context) {
List<BoardList> boardList = List<BoardList>();
List<BoardItem> boardItem = List<BoardItem>();
boardItem.add(new BoardItem(
boardList: BoardListState(),
item: boarditem(),
test: '1',
));
boardList.add(BoardList(
index: 1,
items: boardItem,
header: header()
));
Widget header() {
return Row( ... );}
Widget boarditem() {
return Card( ... );}
return BoardView(
lists: boardList,
);
}
Just to complete this old question and for the case someone like me is searching in 2021 here is a package that can manage drag and drop items from one list to another and drag and drop these lists themselves.
Flutter package from pub.dev
Tutorial can be found here: Tutorial by Johannes Milke
If you still haven't found a good solution there's the boardview flutter plugin.
It has the same features as trellos draggable lists.
(P.S. I'm the developer for it I was lazy when creating it so there are no example gifs for it)
Android has PreferenceScreen which provides you the consistent Settings interface and handles a lot of SharedPreferences functionality on its own.
Is there anything similar in Flutter or do I have to create it by my own using custom ListView?
So, there doesn't exist any widget like that, you will have to create it on your own and handle their action in onChanged or onTap events. For example:
CheckBoxPreference
CheckboxListTile(
value: true,
title: Text("This is a CheckBoxPreference"),
onChanged: (value) {},
),
SwitchPreference
SwitchListTile(
value: false,
title: Text("This is a SwitchPreference"),
onChanged: (value) {},
),
ListPreference
ListTile(
title: Text("This is a ListPreference"),
subtitle: Text("Subtitle goes here"),
onTap: (){},
)
In Flutter the easiest way to make a PreferenceScreen page is with a ListView and ListTiles.
ListView(children: <Widget>[
ListTile(
title: Text('Enable Feature'),
trailing: Checkbox(
value: PrefService.getBool('feature_enabled'),
onChanged: (val) {
setState(() {
PrefService.setBool('feature_enabled', val);
});
},
),
onTap: () {
setState(() {
PrefService.setBool(
'feature_enabled', !PrefService.getBool('feature_enabled'));
});
},
)
]),
But you still need to listen for changes and save them.
To make that easier you can use the package preferences. It removes the boilerplate code and manages saving the changes. The example above would look like this with preferences:
PreferencePage([
CheckboxPreference(
'Enable Feature',
'feature_enabled',
)
]),
You can find it under https://pub.dartlang.org/packages/preferences.
For more features like subpages, hiding of preferences or more widgets look at the example.
According to my research now (I checked the https://pub.dartlang.org and other resources), the answer to your question is, no there is no page like that in Flutter (Check the official documentation). There is one plugin to have SharedPreferences which is from Flutter team, but if you check out its source code, you can see that it just does data modification. Other alternatives from other developers doesn't have anything visual too (I will keep checking, if I find one, I will edit my post).
There are some ways to do it, you can do it by calling android bridge and having android specific screen for only android (yeah I know, it doesn't make much sense) when you are with flutter or my real answer would be you can implement it by using list view as you mentioned and assign different child elements according to your needs.
I am learning the Flutter framework and want to ask about the first example app from google tutorials. Namely, I wonder how this code really works.
Widget _buildSuggestions() {
return new ListView.builder(
padding: new EdgeInsets.all(6.0),
itemBuilder: (_, int i) {
if (i.isOdd)
return new Divider(
height: 1.0,
);
final int index = i ~/ 2;
print(index);
print('sug leng ${_suggestions.length}');
if (index >= _suggestions.length) {
_suggestions.addAll(generateWordPairs().take(10));
}
return _buildRow(_suggestions[index]);
});
}
How the words are really generated. Like when I inspect the index and the length of _suggestions it's saying that I've generated 20 words but the index is 14 when I slide down the index is moving up and at some point, the new words are added. How it detects when to add and when to stop counting the index? If someone can briefly explain to me this I would appreciate!! Thanks!
First off, ListView's itemBuilder is called lazily. Which means that ListView only request the widgets it needs.
So when you scroll down, the index requested increases.
Then, the widget that instantiate ListView possess a _suggestions. Which is a list of suggestions.
The thing is, when ListView will try to access an index that is not available inside _suggestions, that code detect it and then insert another 10 suggestions to _suggestions before returning it.
While this code works ; don't use this logic if you want to have an infinite scroll behavior. This only work because it displays mocked data. But it won't work with datas coming from a server.
A more production ready approach would be to pass listview a ScrollController. And then listen that scrollcontroller to know when we reach the end of the current content.
I 've a search form with multiple fields and it's result (a json from an http call) should be listed in a ListView.
Which is the correct pattern in Flutter to show that results? Update the state of the ListView (making it visible) and hide the search form? Or wait for the results in the search form page (search_page.dart) and then send those results to other page (results_page.dart) where the ListView will show it?
Thanks!
You can use the Navigator class to navigate to a new widget:
onPressed: () {
Navigator.push(
context,
new MaterialPageRoute(builder: (context) => new SecondScreen()),
);
}
You can pass arguments into the constructor there. There's a little more info about this here:
https://flutter.io/cookbook/navigation/navigation-basics/