扑setState到另一个类？ [英] Flutter setState to another class?

问题描述

我有一个根类 RootPage ，它是一个始终在视图中的 StatefulWidget 。我想更改 RootPage 中的 body ，该内容由 RootPage的currentPage小部件来自不同类，例如我的 FeedPage 类和我制作的任何其他类？

示例代码

  import'package：flutter / material.dart'; 
 
类RootPage扩展了StatefulWidget {
 @override 
 _RootPageState createState（）=>新的_RootPageState（）; 
} 
类_RootPageState扩展了State< RootPage> {
 FeedPage feedPage; 
 
小部件currentPage; 
 
 @override 
 void initState（）{
 super.initState（）; 
 feedPage = FeedPage（）; 
 
 currentPage = feedPage; 
} 
 
 @override 
小部件build（BuildContext context）{
 return new Scaffold（
 //当前页面是否也要从其他类更改？ 
正文：currentPage 
）; 
} 
} 
 
 
 
类FeedPage扩展了StatefulWidget {
 @override 
 _feedPageState createState（）=>新的_feedPageState（）; 
} 
类_feedPageState扩展了State< FeedPage> {
 
 @override 
 Widget build（BuildContext context）{
 return new FlatButton（
 onPressed：（）{
 setState（（）{
 //更改RootPage中的currentPage，以便将FeedPage切换开，并得到一个新类，我将使它成为
}）; 
}，
子级：new Text（'Go to a新页面，但保持root用户身份，只需替换此供稿部分'），
）; 
} 
} 
  

我敢肯定有一个明显的答案，但我可以似乎并没有弄清楚如何有效地做到这一点，因此可以很容易地集成将来的类并使我的Root始终处于可见状态。

解决方案

您可以使用回调函数实现此目的。请参考以下代码。

  import‘package：flutter / material.dart’; 
 
类RootPage扩展了StatefulWidget {
 @override 
 _RootPageState createState（）=>新的_RootPageState（）; 
} 
类_RootPageState扩展了State< RootPage> {
 FeedPage feedPage; 
 
小部件currentPage; 
 
 @override 
 void initState（）{
 super.initState（）; 
 feedPage = FeedPage（this.callback）; 
 
 currentPage = feedPage; 
} 
 
 void callback（Widget nextPage）{
 setState（（）{
 this.currentPage = nextPage; 
}）; 
} 
 
 @override 
小部件build（BuildContext context）{
 return new Scaffold（
 //当前页面是否也要从其他类更改？ 
正文：currentPage 
）; 
} 
} 
 
 
 
类FeedPage扩展了StatefulWidget {
函数回调； 
 
 FeedPage（this.callback）; 
 
 @override 
 _feedPageState createState（）=>新的_feedPageState（）; 
} 
类_feedPageState扩展了State< FeedPage> {
 
 @override 
 Widget build（BuildContext context）{
 return new FlatButton（
 onPressed：（）{
 this.widget.callback（new NextPage（））; 
 // setState（（）{
 // //更改RootPage中的currentPage，以便将FeedPage移开并得到一个新的类，我将使
 // }）; 
}，
子级：new Text（'转到新页面但保留根目录，只需替换此提要部分'），
）; 
} 
} 
  

这与问题，您可以在我的回答中提及第三点。 p>

I have a root class RootPage which is a StatefulWidget which is always in view. I would like to change the body in RootPage which is controlled by RootPage's currentPage Widget from different classes such as my FeedPage class and any other class that I make?

Example code

import 'package:flutter/material.dart';

class RootPage extends StatefulWidget {
  @override
  _RootPageState createState() => new _RootPageState();
}
class _RootPageState extends State<RootPage> {
  FeedPage feedPage;

  Widget currentPage;

  @override
  void initState() {
    super.initState();
    feedPage = FeedPage();

    currentPage = feedPage;
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      //Current page to be changed from other classes too?
      body: currentPage
    );
  }
}



class FeedPage extends StatefulWidget {
  @override
  _feedPageState createState() => new _feedPageState();
}
class _feedPageState extends State<FeedPage> {

  @override
  Widget build(BuildContext context) {
    return new FlatButton(
      onPressed: () {
        setState(() {
          //change the currentPage in RootPage so it switches FeedPage away and gets a new class that I'll make
        });
      },
      child: new Text('Go to a new page but keep root, just replace this feed part'),
    );
  }
}

I'm sure there's an obvious answer but I can't seem to figure out how to do it efficiently so it'll be easy to integrate future classes and keep my Root always in view.

解决方案

You can use callbacks functions to achieve this. Please refer to the below code.

import 'package:flutter/material.dart';

class RootPage extends StatefulWidget {
  @override
  _RootPageState createState() => new _RootPageState();
}
class _RootPageState extends State<RootPage> {
  FeedPage feedPage;

  Widget currentPage;

  @override
  void initState() {
    super.initState();
    feedPage = FeedPage(this.callback);

    currentPage = feedPage;
  }

  void callback(Widget nextPage) {
    setState(() {
      this.currentPage = nextPage;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      //Current page to be changed from other classes too?
        body: currentPage
    );
  }
}



class FeedPage extends StatefulWidget {
  Function callback;

  FeedPage(this.callback);

  @override
  _feedPageState createState() => new _feedPageState();
}
class _feedPageState extends State<FeedPage> {

  @override
  Widget build(BuildContext context) {
    return new FlatButton(
      onPressed: () {
        this.widget.callback(new NextPage());
//        setState(() {
//          //change the currentPage in RootPage so it switches FeedPage away and gets a new class that I'll make
//        });
      },
      child: new Text('Go to a new page but keep root, just replace this feed part'),
    );
  }
}

This is very similar to this problem and you could refer 3rd point in my answer.

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