Need to access a single value when the item is selected in the list. When the item is clicked, it prints the whole list of objects, instead the value of the selected object. For example, when user selects Sp,flutter"/>

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Need to access a single value when the item is selected in the list. When the item is clicked, it prints the whole list of objects, instead the value of the selected object. For example, when user selects Sp

flutter - 如何从 Map 访问特定值 flutter

Need to access a single value when the item is selected in the list. When the item is clicked, it prints the whole list of objects, instead the value of the selected object. For example, when user selects Sp

问题描述

Need to access a single value when the item is selected in the list. When the item is clicked, it prints the whole list of objects, instead the value of the selected object. For example, when user selects Spanish, should print SP instead of the list of objects. I have a class and a list for the languages, but for this question is not relevant.

This is what I have achieved so far:

 List <Object> Dictionary = [
{'Spanish': 'SP'},
{'Italian': 'IT'},
{'German': 'DE'},
{'Arab': 'AR'},
{'Greek': 'GR'},
{'Thai': 'TH'},
{'Chinese': 'CH'},
{'French': 'FR'}

];

  List<Language> newDataList;
  final finalList = dictionary.values.toList();

  onItemChanged(String value) {
    setState(() {
      newDataList = languages.where((lang) => lang.title.toLowerCase().contains(value.toLowerCase())).toList();
    });
  }

  @override
  initState() {
    super.initState();
    newDataList = [...languages];
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(12.0),
            child: TextField(
              controller: _textController,
              decoration: InputDecoration(
                icon: Icon(Icons.search),
                hintText: 'Type languages',
              ),
              onChanged: onItemChanged,
            ),
          ),
          Expanded(
            child: ListView(
              padding: EdgeInsets.all(12.0),
              children: newDataList.map((data) {
                return Ink(
                  color: data.selected ? TheBaseColors.lightGreen : Colors.transparent,
                  child: ListTile(
                      title: Text(data.title),
                      onTap: () {
                        setState(() {
                          data.selected = !data.selected;

                          print("${data.title} is now ${data.selected ? "selected" : "not selected"}");
                          print(Dictionary);

                        });
                      }),
                );
              }).toList(),
            ),
          ),
          Expanded(
              child: Column(children: [
            Text('Selected languages :'),
            Expanded(
                child: ListView(
                    children: newDataList.where((l) => l.selected).map((l) => Padding(child: Text(l.title), padding: EdgeInsets.only(right: 10))).toList()))
          ]))
        ],
      ),
    );
  }
}

Tried dictionary.value, dictionary[value]

The issue with your style is that the nested styles are defined in its Resources. These can only be accessed in the scope of this style. Consequently, the button cannot, because it has a different scope.

I do not think that it is possible to nest styles this way, but you could alternatively create a DataTemplate for the Content of the button and nest the styles there. Assign a key to them and reference them from your TextBlocks. In your mainButton style, you can add a setter to set the ContentTemplate to this template. You could also set the ContentTemplate on your button explicitly (but this would mean you have to move the data template out of the style). I hope this is the kind of nesting or encapsulation that you wanted to achive.

<Style x:Key="mainButton" TargetType="Button">
   <Style.Resources>
      <DataTemplate x:Key="MyButtoDataTemplate">
         <DataTemplate.Resources>
            <Style x:Key="ImageStyle" TargetType="{x:Type TextBlock}">
               <Setter Property="FontFamily" Value="/Genesis_desktop;component/tools/fontawesome-free-5.15.1-desktop/otfs/#Font Awesome 5 Free Solid"/>
               <Setter Property="FontSize"  Value="14"/>
               <Setter Property="VerticalAlignment" Value="Center"/>
               <Setter Property="HorizontalAlignment" Value="Center"/>
               <Setter Property="Foreground" Value="orange"/>
            </Style>
            <Style x:Key="LabelStyle" TargetType="{x:Type TextBlock}">
               <Setter Property="FontSize"  Value="14"/>
               <Setter Property="VerticalAlignment" Value="Center"/>
               <Setter Property="HorizontalAlignment" Value="Left"/>
            </Style>
         </DataTemplate.Resources>
         <Grid>
            <Grid.ColumnDefinitions>
               <ColumnDefinition Width="40"/>
               <ColumnDefinition Width="200"/>
            </Grid.ColumnDefinitions>

            <TextBlock x:Name="Image" Grid.Column="0" Style="{StaticResource ImageStyle}">cogs</TextBlock>
            <TextBlock x:Name="Label" Grid.Column="1" Style="{StaticResource LabelStyle}" Text="SETTINGS" />
         </Grid>
      </DataTemplate>
   </Style.Resources>
   <Setter Property="Background" Value="White"/>
   <Setter Property="Foreground" Value="DarkSlateGray"/>
   <Setter Property="FontSize"  Value="14"/>
   <Setter Property="BorderThickness" Value="0"/>
   <Setter Property="Cursor" Value="Hand"/>
   <Setter Property="ContentTemplate" Value="{StaticResource MyButtoDataTemplate}"/>
   <Style.Triggers>
      <Trigger Property="IsMouseOver" Value="True">
         <Setter Property="Foreground" Value="DodgerBlue"/>
      </Trigger>
   </Style.Triggers>
</Style>

Your Button definition is simplified to this, as the style already defines everything:

<Button  Grid.Column="1"
         Grid.Row="5"
         Grid.ColumnSpan="2"
         HorizontalAlignment="Stretch"
         Style="{DynamicResource mainButton}"
         Template="{DynamicResource mainButtonTemplate}"/>

标签： flutter

解决方案

而不是List<Object>你想用Map<String, String>这个。

 Map<String, String> dictionary = {
  'Spanish': 'SP',
  'Italian': 'IT',
  'German': 'DE',
  'Arab': 'AR',
  'Greek': 'GR',
  'Thai': 'TH',
  'Chinese': 'CH',
  'French': 'FR'
};

如果您使用它，您可以轻松完成dictionary['Spanish']并接收“SP”作为价值。

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