How to clear objects in a listviewbuilder in flutter? - flutter

Question

How to control listviewbuilder from outside the listview in flutter?
In a textfield I can use a controller like so: controller: Textcontroller. Can I do something similar in listviewbuilder to clear all the objects in it?
So to be exact. My code looks something like this
Expanded(
child: new ListView.builder(
itemCount: List.length,
itemBuilder: (context,index){
return new Card(
//all stuff with data
),
),
);
},
....
How would I do so that when called from another function it removes all the items in the listview?

Answer 1

You need a Store class that holds this list along with list manipulation methods, then you can use provider for example to access that class and render that list.

Answer 2

You can define a variable in the state of your widget:
var _clear = false;
When this variable is true, the list will be cleared and when it's false, the list will be displayed. You can use setState to toggle this variable. Setting the itemCount of the ListView.builder to 0 clears the list.
Full code:
var _clear = false;
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(30.0),
child: FlatButton(
child: Text('clear'),
color: Colors.pinkAccent,
onPressed: () {
setState(() {
_clear = true;
});
},
),
),
FlatButton(
child: Text('add'),
color: Colors.greenAccent,
onPressed: () {
setState(() {
_clear = false;
});
},
),
Expanded(
child: ListView.builder(
controller: _scrollController,
itemCount: _clear ? 0 : 100,
itemBuilder: (context, index) {
return Container(
height: 300,
child: Card(
child: Center(
child: Text('$index'),
),
),
);
},
),
),
],
),
);
}