Flutter - 单击时渲染新的小部件

Question

标题基本上都说明了一切.一个非常高兴的问题......我有这个基本代码来创建我的应用程序的初始状态:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Some title'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {

    return new Scaffold(
      appBar: new AppBar(title: new Text(config.title)),
      body: new Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          new InputWidget(),
        ]
      ),
    );
  }
}

现在,当用户点击按钮时,如何呈现新的Widget？假设我想实例化另一个InputWidget.

谢谢

Answer 1

我希望我能正确理解你的问题......

我认为主要的一点是你不应该想到"另一个"小部件 - 如果你改变了MyHomePage第一个孩子的内容,然后是两个你没有真正保留第一个孩子,然后再添加另一个孩子.你只是先说"我想要一个孩子"然后你改变主意并说"我想要两个孩子".

在你的代码中,你可以通过调用setState内部来完成_MyHomePageState.Flutter负责保留第一个并添加第二个孩子.

import 'dart:core';
import 'package:flutter/material.dart';

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Some title'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  int count = 1;

  @override
  Widget build(BuildContext context) {
    List<Widget> children = new List.generate(count, (int i) => new InputWidget(i));

    return new Scaffold(
        appBar: new AppBar(title: new Text(widget.title)),
        body: new Column(
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: children
        ),
        floatingActionButton: new FloatingActionButton(
          child: new Icon(Icons.add),
          onPressed: () {
            setState(() {
              count = count + 1;
            });
          },
        )
    );
  }
}

class InputWidget extends StatelessWidget {

  final int index;

  InputWidget(this.index);

  @override
  Widget build(BuildContext context) {
    return new Text("InputWidget: " + index.toString());
  }
}

这是你的意思吗？