在Flutter中动态生成小部件 [英] Dynamically generate widgets in Flutter

问题描述

我正在尝试根据特定条件动态生成一组小部件.在这种情况下，我试图生成RadioTiles列表

I am trying to dynamically generate a set of widgets based on a particular condition. In this case I am trying to generate a list of RadioTiles

这就是我尝试生成的方式

This is how I am trying to generate

  List _listings = new List();

  Widget _getListings() {
    // TODO this will accept json objects in order to display the data
    List listings = new List();
    int i = 0;
    for (i = 0; i < 5; i++) {
      listings.add(
        new RadioListTile<SingingCharacter>(
          title: const Text('Lafayette'),
          value: SingingCharacter.lafayette,
          groupValue: _character,
          onChanged: (SingingCharacter value) {
            setState(() {
              _character = value;
            });
          },
        ),
      );
    }
//     return listings;
  }

并且我试图在这样的有状态小部件中显示此内容:

and I am trying to display this within a stateful widget like this :

 return new SafeArea(
        child: Column(children: <Widget>[
      new Padding(
        padding: const EdgeInsets.all(20.0),
        child: new Text(
          "Verify and Select a Single Listing?",
          style: _textStyle,
        ),
      ),
      ListView(
        shrinkWrap: true,
        padding: const EdgeInsets.all(20.0),
        children: <Widget>[
          _getListings(),
        ],
      ),
    ]));

问题在于，由于我无法在屏幕上显示任何小部件，所以列表的值为空.

The issue is that the value of listings is null due to which I am unable to display any widgets on the screen.

任何见解都是有用的.

谢谢

如果我确实尝试返回列表，这就是我看到的内容:

If I do try to return a list this is what I see:

我不确定这是否是动态创建窗口小部件的最佳方法.

I am not sure if this is the best way to dynamically create widgets.

推荐答案

以下是您代码的一些更新:

Here are some updates to your code:

      Widget build(BuildContext context) {

    return Scaffold(body: SafeArea(
        child: Container(child: Column(children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(20.0),
            child: Text("Verify and Select a Single Listing?",),
          ),
          Expanded(child:  ListView(
            padding: const EdgeInsets.all(20.0),
            children: _getListings(), // <<<<< Note this change for the return type
          ),
          )
        ])
        )));
  }

  List _listings = new List();

  List<Widget> _getListings() { // <<<<< Note this change for the return type
    List listings = List<Widget>();
    int i = 0;
    for (i = 0; i < 5; i++) {
      listings.add(
        RadioListTile<String>(
          title: const Text('Lafayette'),
          value: "c",
          groupValue: "x",
          onChanged: (_) {

          },
        ),
      );
    }
     return listings;
  }

上面要考虑的一些事情:

Some things to consider above:

为了进行编译并用于此答案，我已经进行了一些更改，使代码得以实现.

I've made changes to make the code in order to compile and be used for this answer.

• 添加了针对重大更改的评论
• 列表 _listings 未使用
• 您还可以在创建新对象时删除 new 关键字(新版本的dart可以处理此问题)

• added comments for notable changes
• List _listings is unused
• you can also drop the new keyword when creating new objects (the new version of dart is able to handle this)

结果:

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