Widgetbuild(BuildContext context){returnnewScaffold(appBar:newAppBar(title:newText('First Screen'),),body:newCenter(child:newRaisedButton(child:newText('Launch new screen'),onPressed:(){// Navigate to second screen when tapped!},),),);}}classSecondScreenextendsStatelessWidget{@override Widgetbuil...
=0;voidgoToPreviousPage(){ref.read(pageIndexProvider.notifier).update((state)=>state-1);}returnElevatedButton(onPressed:canGoToPreviousPage?null:goToPreviousPage,child:constText('previous'),);}} 这段代码的问题是,每当我们改变当前页面时,"上一页 "按钮就会重新Build。在理想的世界里,我们希望这个按钮...
lib/flutter_plugin_add_method_channel.dart @override Future<bool?> startCounting() async { final val = await methodChannel.invokeMethod<bool>('startCounting'); return val; } 插件调用类 lib/flutter_plugin_add.dart // 类型定义 - 接收函数typedef TypeOnRecvData = void Function(int value); //...
publicclassFlutterNetworkPluginimplementsMethodChannel.MethodCallHandler{privatestaticfinalString CHANNEL_NAME ="com.sankuai.waimai/network";@OverridepublicvoidonMethodCall(MethodCall methodCall,finalMethodChannel.Result result){switch(methodCall.method) {case"post": RetrofitManager.performRequest(post((String) me...
Future<Map<String, dynamic>> post(String path, [Map<String, dynamic> form]) async { return _channel.invokeMethod("post", {'path': path, 'body': form}).then((result) { return new Map<String, dynamic>.from(result); }).catchError((_) => null); ...
第一个参数表示method,方法名称,原生端会解析此参数。 第二个参数表示参数,类型任意,多个参数通常使用Map。 返回Future,原生端返回的数据。 完整代码: classMethodChannelDemoextendsStatefulWidget{@override_MethodChannelDemoState createState() => _MethodChannelDemoState(); ...
return weight_in_kg / (height_in_meter * height_in_meter); } //named parametrs double calculateBMI({int? weight_in_kg, int? height_in_meter}) { return weight_in_kg / (height_in_meter * height_in_meter); } 应该遵循适当有意义的命名规范。
at java.lang.reflect.Method.invoke (Native method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:578) at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1103) Flutter Doctor output Doctor output ...
build 方法直接返回了一个 widget 的 builder。 那我们继续,打开官网看官方Demo怎么写的: 1. `FutureBuilder<String>(` 2. `future: _calculation, // a previously-obtained Future<String> or null` 3. `builder: (BuildContext context, AsyncSnapshot<String> snapshot) {` ...
(dart:async/zone.dart:997:7) #22 _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1037:23) #23 _microtaskLoop (dart:async/schedule_microtask.dart:41:21) #24 _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5) #25 _runPendingImmediateCallback (dart:...