Flutter:集团，如何显示警报对话框

本文介绍了Flutter:集团，如何显示警报对话框的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我是集团模式和流媒体方面的新手.我想在按下按钮时显示一个警报对话框，但是找不到解决方法.其实我的代码是:

I´m new in the bloc pattern and stream stuff. I want to show up an alert dialog when I press a button, but I can´t find a way to do it. Actually my code is:

Widget button() { return RaisedButton( child: Text('Show alert'), color: Colors.blue[700], textColor: Colors.white, onPressed: () { bloc.submit(); }); } return Scaffold( appBar: AppBar( title: Text("Title"), ), body: StreamBuilder( stream: bloc.getAlert, builder: (context, snapshot) { if (snapshot.hasData) { return Text("I have Dataaaaaa ${snapshot.data}"); } else return ListView( children: <Widget>[ Container( button() ) ...

还有BLoC:

final _submissionController = StreamController(); Stream get submissionStream=> _submissionController.stream; Sink get submissionSink=> _submissionController.sink;

我试图做类似的事情:

Widget button() { return StreamBuilder( stream: submissionStream builder: (context, snapshot){ if (snapshot.hasData){ return showDialog(...) }else return RaisedButton( child: Text('Show alert'), color: Colors.blue[700], textColor: Colors.white, onPressed: () { bloc.submit(); }); }

但是，当然，它没有用.

But, of course, it didn´t work.

推荐答案

构建工作时无法显示对话框.当您有新数据时，就可以创建一个新的小部件.在这种情况下，可能不使用流可能会更好，但是如果需要，您应该使用

You can't show a dialog when build working. When you have new data, then you create a new widget. Probably better for you will be not using the stream in this case, but if it necessary you should use

WidgetsBinding.instance.addPostFrameCallback((_)=> yourFunction(context));

WidgetsBinding.instance.addPostFrameCallback((_) => yourFunction(context));

或

Future.microtask(()=> showDialogFunction(context));

Future.microtask(() => showDialogFunction(context));

在您的情况下

if(snapshot.hasData){WidgetsBinding.instance.addPostFrameCallback((_)=> showDialogFunction(context));}

此代码将在构建方法后启动，因此将立即显示对话框.

This code will be launched after build method, so dialog will show immediately.

Bloc函数始终返回小部件，因此在流中有数据时始终返回button()或其他wiget

Bloc function always return widget, so always return button() or different wiget when stream has data