Flutter: Future Builder fetch multiple data - dart

Question

I am consulting the news section of my website.
I'm using Future Builder to get the data from the web.
The problem I get is related to the image that I try to show on the screen.
And when there is a lot of news, the data load takes a long time and I do not know if there is a solution for loading faster.
I am consulting the text of the news through a json.
At that moment you get the URL of another JSON where the image is in thumbnail format.
I hope to solve this problem, I appreciate any help.
News.dart - Code
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: searchBar.build(context),
key: _scaffoldKey,
body: new Container(
color: Colors.grey[800],
child: new RefreshIndicator(
child: new ListView(
children: <Widget>[
new FutureBuilder<List<Post>>(
future: fetchPosts(URLWEB),
builder: (context, snapshot) {
if(snapshot.hasData) {
List<Post> posts = snapshot.data;
return new Column(
children: posts.map((post2) => new Column(
children: <Widget>[
new Card(
margin: new EdgeInsets.symmetric(vertical: 20.0, horizontal: 20.0),
color: Colors.white,
child: new GestureDetector(
child: new Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
new FutureBuilder(
future: fetchPostsIMG(post2.imagen),
builder: (context, AsyncSnapshot<PostImg> snapshot2){
return new Container(
height: 200.0,
decoration: new BoxDecoration(
image: new DecorationImage(
image: CachedNetworkImageProvider(snapshot2.data.imagen == null ? new AssetImage('images/logotipo.png') : snapshot2.data.imagen),
fit: BoxFit.fitWidth
)
),
width: MediaQuery.of(context).size.width,
);
},
),
new ListTile(
title: new Text(post2.titulo.replaceAll("‘", "").replaceAll(
"’", "").replaceAll("–", "")
.replaceAll("…", "").replaceAll(
"”", "")
.replaceAll("“", ""),
style: new TextStyle(
color: Colors.black,
fontSize: 18.0,
fontWeight: FontWeight.bold),),
subtitle: new HtmlView(data: post2.informacion),
dense: true,
)
],
),
onTap: () {
//Navigator.of(context).push(new MaterialPageRoute(builder: (BuildContext context)=> new WebView(url: post2.urlweb, titulo: titulo)));
},
)
)
],
)).toList(),
);
}
else if(snapshot.hasError)
{
return new Container();
}
return new Center(
child: new Column(
children: <Widget>[
new Padding(padding: new EdgeInsets.all(50.0)),
new CircularProgressIndicator(),
],
),
);
},
),
],
),
onRefresh: _autoRefresh
),
),
);
}
}

Answer 1

It's because you are trying to access imagen on null object. You can do hasData check like below
CachedNetworkImageProvider(snapshot2.hasData ? snapshot2.data.imagen : new AssetImage('images/logotipo.png')),