更新的解决方案:
随着Flutter的新版本发布,旧的解决方案已经过时。现在addListener
需要一个ImageStreamListener
。
import 'dart:ui' as ui;
Widget build(BuildContext context) {
Image image = Image.network('https://istack.dev59.com/lkd0a.webp');
Completer<ui.Image> completer = Completer<ui.Image>();
image.image
.resolve(ImageConfiguration())
.addListener(
ImageStreamListener(
(ImageInfo info, bool _) => completer.complete(info.image)));
...
...
如果您已经拥有一个
Image
小部件,您可以通过调用其
ImageProvider
上的
resolve
方法来读取其中的
ImageStream
。
![screenshot](https://istack.dev59.com/HnVmB.webp)
import 'dart:ui' as ui;
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() {
runApp(new MaterialApp(
home: new MyHomePage(),
));
}
class MyHomePage extends StatelessWidget {
Widget build(BuildContext context) {
Image image = new Image.network('https://istack.dev59.com/lkd0a.webp');
Completer<ui.Image> completer = new Completer<ui.Image>();
image.image
.resolve(new ImageConfiguration())
.addListener((ImageInfo info, bool _) => completer.complete(info.image));
return new Scaffold(
appBar: new AppBar(
title: new Text("Image Dimensions Example"),
),
body: new ListView(
children: [
new FutureBuilder<ui.Image>(
future: completer.future,
builder: (BuildContext context, AsyncSnapshot<ui.Image> snapshot) {
if (snapshot.hasData) {
return new Text(
'${snapshot.data.width}x${snapshot.data.height}',
style: Theme.of(context).textTheme.display3,
);
} else {
return new Text('Loading...');
}
},
),
image,
],
),
);
}
}