CollectionView将不会定位在中心

分类：编程问答

如何解决CollectionView将不会定位在中心

我已经在这个编程问题上停留了一段时间了。我已经在Xamarin.Forms应用程序中设计了this屏幕。我卡住的部分将CollectionView居中放置，这是屏幕中堆叠月份的部分。我已经尝试过使用Margin，但这并不是最好的解决方案，因为它在每个屏幕上都会显示不同的内容。我试过弄乱StackLayout并将其Horizo​​ntalOptions设置为Center / Expand无效。即使直接将CollectionView设置为Center / Expand，CollectionView的内容仍将位于屏幕的“开始”对齐位置。我在这里很笨，不知道我在做什么错。请注意，此控件堆叠在主Grid的Grid.Row内部。

XAML粘贴在这里

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:converters="clr-namespace:Covid19Tracker.Converters;assembly=Covid19Tracker"
             xmlns:i18n="clr-namespace:Covid19Tracker.Common;assembly=Covid19Tracker"
             xmlns:chart1="clr-namespace:Telerik.XamarinForms.Chart;assembly=Telerik.XamarinForms.Chart"
             mc:Ignorable="d"
             FlowDirection="{x:Static Device.FlowDirection}"
             BackgroundColor="#0c0e28"
             NavigationPage.HasNavigationBar="False"
             x:Class="Covid19Tracker.Views.MainView">
    <ContentPage.Resources>
        <ResourceDictionary>
            <converters:FlowDirectionConverter x:Key="FlowDirectionConverter"/>
            <converters:ListMarginConverter x:Key="MarginConverter"/>
        </ResourceDictionary>
    </ContentPage.Resources>
    <ContentPage.Content>

        <RefreshView IsRefreshing="{Binding IsBusy,Mode=OneWay}" Command="{Binding RefreshCommand}">
            <ScrollView>
                <Grid>

                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>

                    <!--Topbar-->
                    <Grid Padding="30">

                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto"/>
                            <ColumnDefinition Width="Auto"/>
                            <ColumnDefinition Width="*"/>
                        </Grid.ColumnDefinitions>

                        <Image Grid.Column="0" HeightRequest="22" WidthRequest="22" Source="menu.png"/>

                        <Label Grid.Column="1" Margin="30,0" FontSize="24" Text="{i18n:Translate TopbarLabel}"/>

                        <StackLayout Grid.Column="2" Orientation="Horizontal" HorizontalOptions="EndAndExpand">
                            <Image HeightRequest="22" WidthRequest="22" Source="search.png"/>
                            <Image Margin="20,0" HeightRequest="22" WidthRequest="22" Source="options.png"/>
                        </StackLayout>
                    </Grid>
                    <!--Topbar-->

                    <!--Graph-->
                    <chart1:RadCartesianChart Grid.Row="1" HeightRequest="150" BackgroundColor="Transparent">
                        <chart1:RadCartesianChart.HorizontalAxis>
                            <chart1:CategoricalAxis MajorTickBackgroundColor="Transparent" 
                                                    LabelTextColor="Transparent" 
                                                    LineColor="Transparent" 
                                                    LabelFitMode="MultiLine"
                                                    PlotMode="OnTicks" />
                        </chart1:RadCartesianChart.HorizontalAxis>
                        <chart1:RadCartesianChart.VerticalAxis>
                            <chart1:NumericalAxis MajorTickBackgroundColor="Transparent" 
                                                  LineColor="Transparent"
                                                  LabelTextColor="Transparent"/>
                        </chart1:RadCartesianChart.VerticalAxis>
                        <chart1:RadCartesianChart.Series>
                            <chart1:SplineSeries 
                                Stroke="#e32049"
                                ValueBinding="Value"
                                ItemsSource="{Binding InfectionHistory}"/>
                            <chart1:SplineSeries 
                                Stroke="#2979ff"
                                ValueBinding="Value"
                                ItemsSource="{Binding RecoveredHistory}"/>
                        </chart1:RadCartesianChart.Series>
                    </chart1:RadCartesianChart>
                    <!--Graph-->

                    <!--Statistics-->
                    <Grid Grid.Row="2" Margin="15" HorizontalOptions="CenterAndExpand">

                        <Grid.ColumnDefinitions>
                            <ColumnDefinition/>
                            <ColumnDefinition/>
                        </Grid.ColumnDefinitions>

                        <Grid Grid.Column="0">

                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto"/>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>

                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*"/>
                            </Grid.ColumnDefinitions>

                            <StackLayout Grid.Row="0" Margin="20,0">
                                <Label HorizontalTextAlignment="{Binding Converter={StaticResource FlowDirectionConverter}}" FontSize="Large" Text="{Binding Recovered,StringFormat='{}{0:0,0}'}"/>
                                <Label FontSize="Medium" Text="{i18n:Translate txtRecovering}" TextColor="#2979ff"/>
                            </StackLayout>

                            <BoxView Grid.Row="1" Grid.Column="0" Margin="0,15,0" Color="#2979ff" HeightRequest="1" WidthRequest="180"/>
                        </Grid>

                        <Grid Grid.Column="1">

                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto"/>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>

                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*"/>
                            </Grid.ColumnDefinitions>

                            <StackLayout Grid.Row="0" Margin="20,0">
                                <Label HorizontalTextAlignment="{Binding Converter={StaticResource FlowDirectionConverter}}" FontSize="Large" Text="{Binding Infected,0}'}"/>
                                <Label FontSize="Medium" Text="{i18n:Translate txtInfections}" TextColor="#e32049"/>
                            </StackLayout>

                            <BoxView Grid.Row="1" Grid.Column="0" Margin="0,0" Color="#e32049" HeightRequest="1" WidthRequest="180" />
                        </Grid>

                    </Grid>
                    <!--Statistics-->

                    <!--Extended details-->
                    <CollectionView  
                        x:Name="CollectionView"
                        Grid.Row="3" 
                        SelectionMode="Single"
                        SelectionChangedCommand="{Binding SelectionChangedCommand}"  
                        SelectionChangedCommandParameter="{Binding SelectedItem,Source={x:Reference CollectionView}}"
                        Margin="0,10,30"
                        ItemsSource="{Binding MonthModels}" 
                        HeightRequest="30">
                        <CollectionView.ItemsLayout>
                            <LinearItemsLayout Orientation="Horizontal" ItemSpacing="70"/>
                        </CollectionView.ItemsLayout>
                        <CollectionView.ItemTemplate>
                            <DataTemplate>
                                <Grid>
                                    <VisualStateManager.VisualStateGroups>
                                        <VisualStateGroup Name="CommonStates">
                                            <VisualState Name="Selected">
                                                <VisualState.Setters>
                                                    <Setter Property="BackgroundColor" Value="#0c0e28" />
                                                </VisualState.Setters>
                                            </VisualState>
                                        </VisualStateGroup>
                                    </VisualStateManager.VisualStateGroups>

                                    <Label FontSize="Large" Text="{Binding MonthLabel}">
                                        <VisualStateManager.VisualStateGroups>
                                            <VisualStateGroup Name="CommonStates">
                                                <VisualState Name="Normal">
                                                    <VisualState.Setters>
                                                        <Setter Property="TextColor" Value="#4f516e"></Setter>
                                                    </VisualState.Setters>
                                                </VisualState>
                                                <VisualState Name="Selected">
                                                    <VisualState.Setters>
                                                        <Setter Property="TextColor" Value="White" />
                                                    </VisualState.Setters>
                                                </VisualState>
                                            </VisualStateGroup>
                                        </VisualStateManager.VisualStateGroups>
                                    </Label>
                                </Grid>
                            </DataTemplate>
                        </CollectionView.ItemTemplate>
                    </CollectionView>

                    <ListView
                            Grid.Row="4"
                            SeparatorVisibility="Default"
                            SeparatorColor="#232539"
                            HasUnevenRows="True"
                            HeightRequest="350"
                            VerticalOptions="FillAndExpand"
                            HorizontalOptions="FillAndExpand"
                            x:Name="ListView"
                            x:FieldModifier="public"
                            ItemsSource="{Binding ListViewItems}">
                        <ListView.ItemTemplate>
                            <DataTemplate>
                                <ViewCell>
                                    <Grid Padding="20">
                                        <Grid.ColumnDefinitions>
                                            <ColumnDefinition Width="2*"/>
                                            <ColumnDefinition/>
                                            <ColumnDefinition/>
                                        </Grid.ColumnDefinitions>

                                        <Label TextColor="White" Margin="{Binding Converter={StaticResource MarginConverter}}" Text="{Binding date,StringFormat='{}{0:MMMM dd}'}" />

                                        <StackLayout Orientation="Horizontal" Grid.Column="1">
                                            <Image Margin="0,6,0" WidthRequest="6" HeightRequest="6" Source="BluePoly.png"/>
                                            <Label TextColor="#2774f5" Text="{Binding recovered,0}'}" />
                                        </StackLayout>

                                        <StackLayout Orientation="Horizontal" Grid.Column="2">
                                            <Image Margin="0,0" WidthRequest="6" HeightRequest="6" Source="RedPoly.png"/>
                                            <Label TextColor="#e32049" Text="{Binding infected,0}'}" />
                                        </StackLayout>
                                    </Grid>
                                </ViewCell>
                            </DataTemplate>
                        </ListView.ItemTemplate>
                    </ListView>
                    <!--Extended details-->

                </Grid>

            </ScrollView>
        </RefreshView>
    </ContentPage.Content>
</ContentPage>

我希望我正确提出了这个问题，以便获得认真的帮助，而不是“阅读FAQ”

解决方法

您可以在标签的左侧和右侧添加一个额外的列。

<DataTemplate>
  <Grid>

     <Grid.ColumnDefinitions>

        <ColumnDefinition Width="0.1*" />
        <ColumnDefinition Width="0.8*" />  
        <ColumnDefinition Width="0.1*" />

    </Grid.ColumnDefinitions>

<Label Grid.Column="1" FontSize="Large" Text="{Binding MonthLabel}" HorizontalTextAlignment="Center" >

现在标签将显示在屏幕中央

enter image description here

更新

您还可以将整个CollectionView放在第二个

 <Grid>

            <Grid.ColumnDefinitions>

                <ColumnDefinition Width="0.1*" />
                <ColumnDefinition Width="0.8*" />
                <ColumnDefinition Width="0.1*" />

            </Grid.ColumnDefinitions>



            <!--Extended details-->
            <CollectionView 
                Grid.Column="1"
                        //...>
                
                  //...
            </CollectionView>
</Grid>
,

这就是我解决集合居中的方法。你会在这里找到它：

How to centre CollectionView items?

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