I am building a fitness app (image here: Fitness App example
) where the user can log their sets. I am having an issue when using the dismissible widget inside of my app. The swipe to delete functionality sends the following exception: a dismissed dismissible widget is still part of the tree
When swiping to delete a single set, I still need to retain the information the user has put into the other sets. I believe this is an issue with the key, however I've already tried UniqueKey() (which resets all of the other input fields) and the example below.
How can I remove a single set using dismissible and still retain the rest of the users data for the other sets? Thanks.
late List count = [0];
ListView.builder(
shrinkWrap: true,
itemCount: _count.length,
itemBuilder: (context, index) {
// Create a new variable to display the set
int setNumber = index + 1;
return Dismissible(
key: ValueKey(_count[index]),
background: _swipeStyle(),
onDismissed: (direction) {
// Remove the item from the data source.
setState(() {
_count.removeAt(index);
});
},
child: Row(
children: [
Expanded(flex: 1, child: Text('Set $setNumber')),
Expanded(flex: 2, child: _buildWeight(index)),
const SizedBox(
width: 24.0,
),
Expanded(flex: 2, child: _buildReps(index)),
],
),
);
},
),
Since the Key is based on a list of ints, maybe there are repeated keys? In that case the framework won't know which item was removed and will trigger the error you just found.
A possible solution would be to assign an unique ID to each item, that way you will never have repeated keys.
Try replace key: ValueKey(_count[index]) with UniqueKey()
Related
Goodmorning,
I'm developing an app with flutter but I'm facing some problems with Provider (I think something miss in my knowledge).
My app fetch data from my API and displays them in listview.
In whole app I have different screen which displays different data type in listview and now I want to create filtering logic.
To avoid rewrite same code multiple times I thought to create one screen to reuse for filtering purposes but I'm facing problems with state management.
What I did:
create base model for filter information
`
enum FilterWidget { TEXT_FIELD, DROPDOWN } //to resolve necessary Widget with getWidget() (to implement)
class FilterBaseModel with ChangeNotifier {
String? value= 'Hello';
FilterWidget? widgetType;
FilterBaseModel(this.value, this.widgetType);
onChange() {
value= value== 'Hello' ? 'HelloChange' : 'Hello';
notifyListeners();
}
}
`
One screen for display filters depending on request
List<FilterBaseModel> filters = [];
FilterScreen() {
//Provided from caller. Now here for test purposes
filters.add(FilterBaseModel('Filter1', FilterWidget.TEXT_FIELD));
filters.add(FilterBaseModel('Filter2', FilterWidget.TEXT_FIELD));
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: SafeArea(
minimum: EdgeInsets.symmetric(vertical: 15, horizontal: 15),
child: SingleChildScrollView(
child: Container(
height: 400,
child: Column(
children: filters
.map(
(e) => Consumer<FilterBaseModel>(
builder: (_, filter, child) =>
ChangeNotifierProvider.value(
value: filter,
child: CustomTextField(
`your text` initialText: e.value,
onTap: () {
e.onChange();
filter.onChange();
},
),
),
),
)
.toList(),
))),
),
);
}
`
The problem is in Consumer and ChangeNotifier.value.
Screen works quite well: widget are displayed and callback are called, what is wrong? I need to use onChange method of both instance to update UI otherwhise method was called but widget is not rebuilt.
I know that probably putting consumer there is not right way but I tried also to put outside but doesn't work.
I expect to have one filter screen which receives in input filters list information, display them, handle their state managment and return their value.
P.S: this code now works, but I know is not the right way
Thank you for help!
EDIT
Have same behaviour without ChangeNotifierProvider.value. Therefore I'm more confused than before because still persist the double call to onChange for correct rebuilding.
More bit confused about ChangeNotifierProvider.value using...
There's a way to create a recommended from user ListView using fire base and flutter...
For example I have a list of data in firebase that I am fetching them from firebase as I show them in the data list screen, and I have a list of recommended list view from user for example the clicked data item from user something shows like the below image:
To be more specific how figure if the data was viewed by user or not?
There's a way or docs to do something like this?
In case your intention is to provide some kind of "user likes" functionality.
You can create Provider of ChangeNotifier with Provider package at root (for example) and store Set<YourShopItem> there.
Then expose methods like add(YourShopItem item) and remove(YourShopItem item) on this ChangeNotifier which should add and remove items from your set and call notifyListeners() every time you call this method.
Then when you need to determine if your item is liked just obtain your ChangeNotifier and check if item is in set. Your widgets is gonna be updated every time add or remove methods are called because of their subscription to ChangeNotifier through Provider.
In case your intention is to track visibility of item.
You can use visibility detector package to track whether certain widget is visible. You can subscribe to certain widget and when it's shown, a callback is gonna be fired. So you should wrap every widget of your list into VisibilityDetector widget and save that your item was viewed.
Something like that should do the job:
final List<String> entries = <String>['A', 'B', 'C'];
final List<int> colorCodes = <int>[600, 500, 100];
ListView.builder(
padding: const EdgeInsets.all(8),
itemCount: entries.length,
itemBuilder: (BuildContext context, int index) {
return VisibilityDetector(
onVisibilityChanged: (VisibilityInfo info) {
if (info.visibleFraction == 1) {
ON_YOUR_ITEM_IS_VISIBLE_FUNCTION();
}
},
child: Container(
height: 50,
color: Colors.amber[colorCodes[index]],
child: Center(child: Text('Entry ${entries[index]}')),
),
);
}
);
Also refer to this: https://stackoverflow.com/a/63577928/13737975.
Dears,
it could be just a mistake of mine but ...it's driving me crazy ;)
I have a ListView inside my statefulwidget:
Expanded(
child: ListView.builder(
padding: EdgeInsets.all(10.0),
itemCount: searchableFoodList.length,
itemBuilder: (BuildContext context, int index) {
print('4 - SFL - ${searchableFoodList[index].id} - ${searchableFoodList[index].name}');
return
FoodItem(
id: searchableFoodList[index].id,
baseUnit: searchableFoodList[index].baseUnit,
baseUnitS: searchableFoodList[index].baseUnitS,
baseVal: searchableFoodList[index].baseVal,
baseValCal: searchableFoodList[index].baseValCal,
mediumVal: searchableFoodList[index].mediumVal,
mediumValCal: searchableFoodList[index].mediumValCal,
name: searchableFoodList[index].name,
note: searchableFoodList[index].note
);
},
),
searchableFoodList is modified (according user selection) inside a setState().
Let say that we have a 3 FoodItem(s), so my searchableFoodList is [FoodItem-1, FoodItem-2, FoodItem-3] and everything is working fine.
If I select a single item in my list, let say "FoodItem-2", the searchableFoodList becomes [FoodItem-2] and the list displayed contains (correctly) just one item but it is FoodItem-1.
Note that I inserted a print ...and it prints "FoodItem-2"
I guess that the problem is that it is considered the "original list" and it is changed only the length of the list but the list itself is not re-generated.
I have no more ideas ...any suggestions to solve this problem?
P.S.
FoodItem is stateful widget as well (an animated one). I did something similar with using stateless widget and I didn't have any problem
When I run this code I'm getting an error: Multiple widgets used the same GlobalKey.
So I can fix this issue.
How I can pass dynamically keys to my listview.Builder. is it possible to pass?. Here is simplified version my code:
GlobalKey<AutoCompleteTextFieldState<String>> key0 = new GlobalKey();
#override
Widget build(BuildContext context) {
return M Scaffold(
appBar: appBar,
body: SingleChildScrollView(
child: Container(
child: ListView.builder(
itemCount: 3,
itemBuilder: (context, index) {
return SimpleAutoCompleteTextField(
key: key0,
suggestions: suggestions,
textChanged: (text) => print(text),
clearOnSubmit: false,
textSubmitted: (text) => print(text)
),
}
),
),
),
);
}
Pass index as your value
key: ValueKey(index),
GlobalKey must be unique across the entire application.
You cannot simultaneously include two widgets in the tree with the same global key. Attempting to do so will assert at runtime.
It means that multiple elements can't use the same key. Here's a short video about keys in Flutter and not that short article about using keys, including GlobalKey's.
What you should do in this case is to derive keys of each element from their uniquely defining features such as content or some ID.
Things to note:
1.
Key('AAA') == Key('AAA'); // true
it means that you don't have to create Key objects outside of your build function and can go with just:
return SimpleAutoCompleteTextField(
key: Key(itemId),
or even rather ValueKey(itemData) in your case: ValueKey.
GlobalKey's are relatively expensive and if you don't explicitly need to move them from one place of the app to another, prefer regular Key.
Don't derive keys from indices. It's considered a bad practice because it will lead to misbehavior when you try to reorder existing widgets in the same subtree.
The most amazing part of Flutter is that every widget is an object. But, when I try to make an object from a Row and add a List of widgets to its children, I get this error on runtime:
Cannot add to an unmodifiable list
I'm currently creating my Row like this:
Row rowStar = Row();
rowStar.children.addAll(rowChildren);
Is this wrong? If so, what's the correct way?
1. Why it won't work
If all you want to do is add a list to a Row, you should create the list and then initialize the Row with it. You cannot add the list afterwards because Flutter's widgets typically have final fields/properties, which are not modifiable at runtime.
2. The Flutter Way
However, what you could do to dynamically modify the list is pass a function that builds your list internally at runtime. And that's exactly what the ListView.builder() constructor of ListView does.
For example, this the docs example for dynamically creating a List of Containers based on the the Lists entries and colorCodes.
final List<String> entries = <String>['A', 'B', 'C'];
final List<int> colorCodes = <int>[600, 500, 100];
ListView.builder(
padding: const EdgeInsets.all(8),
itemCount: entries.length,
itemBuilder: (BuildContext context, int index) {
return Container(
height: 50,
color: Colors.amber[colorCodes[index]],
child: Center(child: Text('Entry ${entries[index]}')),
);
}
);
You could add a button to .add, say, the letter D and the colorCode 400, to the respective Lists, and Flutter would render the respective Containers dynamically on the screen.
I'm not sure if I get it right, but what you're trying to do doesn't make sense. If you want to reuse a Row with widgets and information you can just build it once and save the whole thing as widget.
Try it like this:
Build a Row.
Create widgets for your children.
Display them as widgets of the row.
Row(
children: <Widget>[
customWidget1(),
customWidget2(),
customWidget3(),
],
)
Your custom widgets are the content of the Row then.
Hope it helps.
In my case, I can make a Row from a previously created List<Widget>:
Row calculateListOfStars(ranking) {
final List<Widget> rowList = [];
rowList.addAll([
// make my custom widget
]);
final Row rowStars = Row(
children: rowList,
);
return rowStars;
}
Use Listview:
ListView(
children: rowStar((data) {
return ListTile();
}).toList();