ErrorHint( 'Instead of performing asynchronous work inside a call to setState(), first ' 'execute the work (without updating the widget state), and then synchronously ' 'update the state inside a call to setState().' ), ]); } // We ignore other types of return values so that you ...
Flutter: setState not updating UIAsk Question Asked 4 years, 4 months ago Modified 4 years, 4 months ago Viewed 7k times 4 onTap it prints value but setState doesnt makes any difference in UI and im using it in a stateful widget and inside build too, i couldnt get where im making ...
import 'dart:async'; import 'package:flutter/material.dart'; void main() => runApp(new MaterialApp(home: new Scaffold(body: new MainWidget())); class MainWidget extends StatefulWidget { @override State createState() => new MainWidgetState(); } class MainWidgetState extends State<MainWidget...
实际上是「Stateful Widget」对应的「Stateful Element」被添加到 Element Tree 时,伴随「Stateful Element」的初始化,createState方法被调用。从后文可知一个 Widget 实例可以对应多个 Element 实例 (也就是同一份配置信息 (Widget) 可以在 Element Tree 上不同位置配置多个 Element 节点),因此,createState方法在「Sta...
2.尽可能使用const Widget,为 Widget 提供const构造方法; 3.可以将「Stateless Widget」重构成「Stateful Widget」,以便可以使用「Stateful Widget」中一些特定的优化手法,如:缓存「sub trees」的公共部分,并在改变树结构时使用GlobalKey; 4.尽量减小 rebuilt 范围,如:某个 Widget 因使用了「Inherited Widget」,导致频...
5.2.1Flutter引擎不会直接渲染widget树,因为widget是特别不稳定的,会频繁的调用build方法,widget又相互依赖,一旦调用build,后面的widget都会重新创建,直接去解析widget的话会非常消耗性能,布局需要重新计算。由此引出了Element,RenderObject的概念,Flutter引擎解析的是RenderObject树,并非widget。
;}StatefulElement?_element; 由上面的源码可以得出_element其实就是State的bulid方法中的context 3.Flutter渲染原理 实际上,Flutter的UI绘制包含了三个元素,Widget,Element和RenderObject。这三个元素分别组成了三棵树:Widget树,Element树和RenderObject树,在Flutter渲染的流程中Flutter引擎渲染是针对Render树中的对象进行...
// This widget is the home page of your application. It is stateful, meaning // that it has a State object (defined below) that contains fields that affect // how it looks. // This class is the configuration for the state. It holds the values (in this // case the title) provided...
Hi, I stumbled upon what it seems to be a bug. I'm using a StreamBuilder in order to build a ListView with messages. If I use a stateless widget than everything works as expected; when adding new items to the database, they are updated i...
Widget 是 Flutter 功能的抽象描述,是视图的配置信息,同样也是数据的映射,是 Flutter 开发框架中最基本的概念。 两个比较重要的Widget:StatelessWidget和StatefulWidget。 5.2 渲染过程 5.2.1Flutter引擎不会直接渲染widget树,因为widget是特别不稳定的,会频繁的调用build方法,widget又相互依赖,一旦调用build,后面的widget都...