在 Flutter 中构建动态列表的最有效方法是什么？

Question

So, I am currently attempting to build a list dynamically in my app by using listview.builder. I was originally planning on sending an http request to load only a few items at a time, but I had a lot of trouble with using both futurebuilder and listview builder. The idea was that if the user scrolled to the bottom then more items were loaded. Now I'm using a streambuilder and the backend sends all items at once, which I believe is inefficient, but because I am inexperienced with building lists from streams I can't tell for sure. Anyhow, I would like some recommendations for building long lists dynamically.

Answer 1

The best way to do this should be by using ListView.builder. To use ListView.builder, you have to create an instance of it by calling its constructor using new, it takes multiple parameters. Assume that we have a global list like this in our application

List<String> litems = ["1","2","Third","4"];

Using LIstView.builder, the code for the same shall look like this

body: new ListView.builder
  (
    itemCount: litems.length,
    itemBuilder: (BuildContext ctxt, int index) {
     return new Text(litems[index]);
    }
  )

In here, the in-place callback function shall be called 4 times and each call will generate a Text Widget which shall be displayed in the body.

You can also write a separate function which can be called from itemBuilder as

// A Separate Function called from itemBuilder
Widget buildBody(BuildContext ctxt, int index) {
  return new Text(litems[index]);
}
body: new ListView.builder
(
  itemCount: litems.length,
  itemBuilder: (BuildContext ctxt, int index) => 
buildBody(ctxt, index)
),

In both cases, the output will look the same. You can also use ListView.builder(..) in Stateless Widgets if you want to display dynamic (different) contents every time the widget is loaded within an application. With Stateful widgets, it can change the contents of the screen dynamically. I hope this helps