[RenderObjectToWidgetElement<T>element]){if(element==null){owner.lockState((){element=createElement();assert(element!=null);element.assignOwner(owner);});owner.buildScope(element,(){element.mount(null,null);});}else{element._newWidget=this...
];if(func==null){returnnull;}returnfunc(settings,uniqueId??"");}WidgetappBuilder(Widget home){returnMaterialApp(home:home,debugShowCheckedModeBanner:true,///必须加上builder参数,否则showDialog等会出问题builder:(_,__){returnhome;},);}// This widget is the root of your application...
Widget buildButton() { return RaisedButton( onPressed: () { // 按钮点击事件处理逻辑 }, child: Text('Click Me'), ); } 在其他地方,我们可以直接调用buildButton方法来获取该按钮Widget,并将其添加到应用程序的用户界面中: 代码语言:txt 复制 Widget build(BuildContext context) { return Scaffold( app...
... Normal element mounting (178 frames) #222 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3971:16) #223 MultiChildRenderObjectElement.inflateWidget (package:flutter/src/widgets/framework.dart:6570:36) #224 Element.updateChild (package:flutter/src/widgets/framework.dart:3708:18)...
return null; } }, ) ], ), ); } } widget 组织 将widget 拆分为不同的widget ,而不是同一个文件。 在widget 中使用const 当在一个State上调用setState()时,所有子孙widget都会重新构建。因此,将widget拆分为小的widget,这样setState()调用只会重新构建那些实际需要改变UI的子树的部分。
const Widget({ this.key }); final Key key; @protected Element createElement(); @override String toStringShort() { return key == null ? '$runtimeType' : '$runtimeType-$key'; } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { ...
Future<String> fetchData() async { await Future.delayed(Duration(seconds: 2)); return 'Hello, World!'; } class MyWidget extends StatelessWidget { @override Widget build(BuildContext context) { return FutureBuilder<String>( future: fetchData(), builder: (BuildContext context, AsyncSnapshot<Strin...
Widget build(BuildContext context) { return Scaffold<List<Train>>(body:FutureBuilder( future:TrainClient.getName() , builder: (BuildContext context, AsyncSnapshot snapshot){ if(snapshot.hasError){ print(snapshot) } else if(snapshot.hasData){ print(snapshot.data); return buildDataTable(trains...
I am trying to do some Gesture motion logic based on the size of a widget. To get the size, I am calling the following code in the build method... final RenderBox renderBox = context.findRenderObject(); This is sometimes returning null? What is causing this to return null? Is there...
Widget第一次被加载(Widget 第一次被加入到 Widget Tree 中 ,更准确地说是其对应的 Element 被加入到 Element Tree 时,即 Element 被挂载(mount)时) Parent Widget 修改了其配置信息; 该Widget 依赖的Inherited Widget发生变化时。 当Parent Widget或 依赖的Inherited Widget频繁变化时,build方法也会频繁被调用。