1 Assign Future typed result from function to a variable in Flutter Widget 0 How to return this Future<Widget> as Widget inside Streambuilder 0 unable to get future value into Widget widget 3 Flutter - How to pass a future to a widget without executing it? 0 How to return a widget...
@protected Element createElement(); // Widget的字符串描述 @override String toStringShort() { final String type = objectRuntimeType(this, 'Widget'); return key == null ? type : '$type-$key'; } // 覆写父类的方法,主要是设置诊断树的一些特性 @override void debugFillProperties(DiagnosticPrope...
returnScaffold(appBar:AppBar(title:Text('InheritedWidget Counter')),body:Center(child:Column(mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[Text('Counter Value: $counter',style:TextStyle(fontSize:30)),SizedBox(height:20),ElevatedButton(onPressed: increment,child:Text('Increment'), ),...
让Element调用下面的build函数returnTestElement(this);}/// 这个context其实就是ElementWidgetbuild(BuildContext context){print("TestWidget build");returnText("TestWidget");}}classTestElementextendsElement{Element _child;TestElement(Widget widget):super(widget);@overrideboolgetdebugDoingBuild=>throwUnimplement...
final MediaQuery query = context.inheritFromWidgetOfExactType(MediaQuery); if (query != null) return query.data; if (nullOk) return null; throw new FlutterError( 'MediaQuery.of() called with a context that does not contain a MediaQuery.\n' ...
Widget build(BuildContext context) { ///使用Timer每间隔2s去修改texts的值 return Container( alignment: Alignment.center, child: Text(this.texts), ); } 这样每次渲染的Widget就只有文本这个组件本身,如下图所示: 2.3 减少组件重绘的次数 开发过程中,很容易触发界面的重新渲染,大多数时候都是没有控制好组件...
// Doesn't return var age = 0; showModalBottomSheet<void>( context: context, builder: (BuildContext context) { return StatefulBuilder( builder: (BuildContext context, StateSetter setState) { return Wrap( children: [ Column( children: <Widget>[ Slider( value: age.toDouble(), min: 0...
validator: (value) { // bad if (value!.isEmpty) { return 'Please enter'; } else { 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...
Widget build(BuildContext context) {//我们想使用 material 风格的应用,所以这里用 MaterialAppreturnMaterialApp(//移动设备使用这个 title 来表示我们的应用。具体一点说,在 Android 设备里,我们点击//recent 按钮打开最近应用列表的时候,显示的就是这个 title。title: 'Welcome to Flutter',//应用的“主页”home:...
Widget build(BuildContext context) {returnnewMaterialApp( debugShowCheckedModeBanner:false, title:'From表单Demo', home:newScaffold( appBar:newAppBar( title:newText('Form表单Demo'), leading: Icon(Icons.menu,size:30,), actions:<Widget>[