Попробуйте это.
return new StreamBuilder<QuerySnapshot>(
stream: Firestore.instance.collection(PRODUCTS_COLLECTION).snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (!snapshot.hasData) return new Center(child: new CircularProgressIndicator());
return new StaggeredGridView.count(
physics: new BouncingScrollPhysics(),
crossAxisCount: 2,
children: buildGrid(snapshot.data.documents),
staggeredTiles: generateRandomTiles(snapshot.data.documents.length),
);
},
);
List<Widget> buildGrid(List<DocumentSnapshot> documents) {
List<Widget> _gridItems = [];
_products.clear();
for (DocumentSnapshot document in documents) {
_products.add(Product.fromDocument(document));
}
for (Product product in _products) {
_gridItems.add(buildGridItem(product));
}
return _gridItems;
}
Widget buildGridItem(Product product) {
return new GestureDetector(
child: new Card(
elevation: 2.0,
margin: const EdgeInsets.all(5.0),
child: new Stack(
alignment: Alignment.center,
children: <Widget>[
new Hero(
tag: product.name,
child: new Image.network(product.imageUrl, fit: BoxFit.cover),
),
new Align(
child: new Container(
padding: const EdgeInsets.all(6.0),
child: new Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Text('\u20B9 ${product.price}',
style: new TextStyle(
color: Colors.white,
fontWeight: FontWeight.bold,
fontSize: 16.0)),
new Text(product.name,
style: new TextStyle(color: Colors.white)),
],
),
color: Colors.black.withOpacity(0.4),
width: double.infinity,
),
alignment: Alignment.bottomCenter,
),
],
),
),
onTap: () async {
// TODO
},
);
}
List<StaggeredTile> generateRandomTiles(int count) {
Random rnd = new Random();
List<StaggeredTile> _staggeredTiles = [];
for (int i=0; i<count; i++) {
num mainAxisCellCount = 0;
double temp = rnd.nextDouble();
if (temp > 0.6) {
mainAxisCellCount = temp + 0.5;
} else if (temp < 0.3) {
mainAxisCellCount = temp + 0.9;
} else {
mainAxisCellCount = temp + 0.7;
}
_staggeredTiles.add(new StaggeredTile.count(rnd.nextInt(1) + 1, mainAxisCellCount));
}
return _staggeredTiles;
}