使用颤振，我带有MemoryImage的CircleAvatar每次重新加载ListView时都会闪烁

Question

我在 CircleAvatar 的背景图像属性中使用 MemoryImage 渲染 base64 图像，并每隔一段时间重新加载 ListView，每次 ListView 重新加载时，图像中都会出现非常明显的闪烁，从蓝色圆圈开始，然后变成适当的图像。我想知道如何摆脱闪烁。

下面是一个完整的示例：

import 'dart:async';
import 'dart:convert';
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Image Flickering Example',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Image Flickering Example'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String img = "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";
Widget body = Text("...");
void _updateListView() {
Widget listView = ListView.builder(
itemCount: 1,
itemBuilder: (BuildContext context, int index){
return Card(
child: CircleAvatar(
backgroundImage: MemoryImage(base64Decode(img)),
),
);
},
);
setState(() {
body = listView;
});
}
Timer listRefreshTimer;
void listRefresher(){
const oneSec = const Duration(seconds: 1);
listRefreshTimer = new Timer.periodic(oneSec,(Timer t){
_updateListView();
});
}
@override
void initState() {
// TODO: implement initState
super.initState();
listRefresher();
}

@override
Widget build(BuildContext context) {
return Scaffold(
body:body
);
}
}

Answer 1

将解码结果移动到变量中，这样它就不会在每次状态更新时重新运行：

class _MyHomePageState extends State<MyHomePage> {
final img = base64Decode("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");
Widget body = Text("...");
void _updateListView() {
Widget listView = ListView.builder(
itemCount: 1,
itemBuilder: (BuildContext context, int index) {
return Card(
child: CircleAvatar(
maxRadius: 40,
backgroundImage: MemoryImage(img),

Answer 2

不要使用CircleAvatar.改为切换到普通Image小部件，并将gaplessPlayback设置为true。

Image.memory(
thumbData,
gaplessPlayback: true,
)