I have a GridView created using data from an SQLite database. Since the data comes from a database I have to use FutureBuilder. I need to find the height of the GridView but findRenderObject() always returns an error (findRenderObject() called on null). I tried using an async function and WidgetsBinding.instance.addPostFrameCallback but it still doesn't work. Is there a way to find the height of a widget rendered with a FutureBuilder?
class _example extends State<example> {
Future grid;
GlobalKey _gridKey = GlobalKey();
@override
void initState() {
super.initState();
grid = getGrid('data.db');
WidgetsBinding.instance.addPostFrameCallback((_) => showOverlay(context));
}
void showOverlay(BuildContext context) {
print('grid height from overlay: '+_getGridHeight().toString());//doesn't work
OverlayState overlayState = Overlay.of(context);
entry = OverlayEntry(
builder: (context) => Positioned(
left: 0.0,
top: 500.0,//I NEED GRID HEIGHT TO PLACE OVERLAY AT THE RIGHT SPOT
bottom: 0.0,
width: (MediaQuery.of(context).size.width),
child: QPanel(dbName: widget.xwordnumber),
),
);
overlayState.insert(entry);
}
_getGridHeight(){//changing it to async makes no difference
final RenderBox renderBoxGrid = _gridKey.currentContext.findRenderObject();
final gridHeight = renderBoxGrid.size.height;
final roundedHeight = gridHeight.floorToDouble();
print('roundedHeight: '+roundedHeight.toString());
return roundedHeight;
}
@override
Widget build(BuildContext context) {
return Scaffold(
//key: _gridKey, if the key is here it works but I need GridView height NOT Scaffold height
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: FutureBuilder(
future: grid,
builder: (context, snapshot) {
if (snapshot.hasData) {
return Align(
alignment: Alignment.topCenter,
child: Container(
margin: EdgeInsets.zero,
child: GridView.count(
padding: EdgeInsets.only(left:4.0,top:5.0,right:4.0,bottom: 0.0),
key: _gridKey,//doesn't work
shrinkWrap: true,
crossAxisCount: 15,
mainAxisSpacing: 2,
crossAxisSpacing: 2,
children: List.generate(snapshot.data.length, (index) {
return FocusScope(
node: _node,
child: Container(
decoration: BoxDecoration(
color: snapshot.data[index] == "#" ? Colors.black : Colors.white,
border: Border.all(color: Colors.black)),
child:
snapshot.data[index] == "#"
? Text('#')
: _isTextField(snapshot.data[index], index),
));
}),
),
) );
} else if (snapshot.hasError) {
return Text("${snapshot.error}");
}
return CircularProgressIndicator();
},
),
),
);
}
}
I found this question: Flutter best way to get size/position of widget when it doesn't render which is the same as mine bur it has no answer...
EDIT :
tried this:
_getGridHeight(){
Future.microtask(() {
final RenderBox renderBoxGrid = _gridKey.currentContext.findRenderObject() as RenderBox;
if(renderBoxGrid?.size != null){
print('Grid Height: '+renderBoxGrid.size.height.toString());
return renderBoxGrid?.size ?? Size.zero;
}
});
}
...but it still complains of findRenderObject being called on null...
UPDATE
I cannot believe I got NO ANSWER AT ALL...nobody has ever run into a similar problem? I think an answer to this question may be beneficial to many people but maybe I'm wrong...
