How to query in a Flutter/FirebaseAnimatedList usi

问题:

I have a this Scaffold with body:

body: new Column(
        children: <Widget>[
          new Flexible(
            child: new FirebaseAnimatedList(
              query: FirebaseDatabase.instance
                  .reference()
                  .child('products')
                  .orderByChild('order'),
              padding: new EdgeInsets.all(8.0),
              reverse: false,
              itemBuilder: (_, DataSnapshot snapshot,
                  Animation<double> animation, int x) {
                return new ProductItem(
                    snapshot: snapshot, animation: animation);
              },
            ),
          ),
        ],
      ),

but I need to add a simple query: 'Active' = true

Is it possible? How? Any example/tutorial?

Thanks.

回答1:

If I am getting your question correctly, you are trying to query some data where ("Active" = true), then see the following example.

I have added a screenshot from my db to have more context on the way my data is structured and hopefully it will put you into perspective to implement something similar on your end.

In the previous example, I am doing the following query to only obtain contact of email set to "[e-mail]" while neglecting the others.

 @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(title: new Text("Firebase Example"),),
      body: new Column(
        children: <Widget>[
          new Flexible(
            child: new FirebaseAnimatedList(
                query: FirebaseDatabase.instance
                    .reference().child("contacts")
                    .orderByChild("email")
                    .startAt("[e-mail]").endAt("[e-mail]"),
                padding: new EdgeInsets.all(8.0),
                reverse: false,
                itemBuilder: (_, DataSnapshot snapshot,
                    Animation<double> animation, int x) {
                  return new ListTile(
                    subtitle: new Text(snapshot.value.toString()),
                  );
                }
            ),
          ),
        ],
      ),
    );
  }

Hope it helped.

P.S: As Chenna Reddy pointed out, you can replace startAt("[e-mail]").endAt("[e-mail]") by equalTo("[e-mail]")

startAt and endAt are useful when you need to limit your query to a certain range.

For more information.

回答2:

Ok, following your guide (@ChennaReddy and @aziza), this is the way I fix my code:

body: new Column(
        children: <Widget>[
          new Flexible(
            child: new FirebaseAnimatedList(
              query: FirebaseDatabase.instance
                  .reference()
                  .child('products')
                  .orderByChild('Active')           // line changed
                  .equalTo(true),                   // line added
              padding: new EdgeInsets.all(8.0),
              reverse: false,
              itemBuilder: (_, DataSnapshot snapshot,
                  Animation<double> animation, int x) {
                return new ProductItem(
                    snapshot: snapshot, animation: animation);
              },
            ),
          ),
        ],
      ),

However, I need the resulting query order by 'order' which is a integer field (or attribute) that some admin users can change (update). So final users can see data ordered by 'order' (but only 'Active'=true as you help me to solve).