对象引用未设置为...在 COLLECTIONVIEW 中的命令中

Question

我有一个 collectionview，command.The 问题是当我将对象读取到命令时，由于某种原因它为零，抱歉，请帮助解决错误

XAML

              <CollectionView ItemsSource="{Binding MyPins}"  x:Name="ListPlaces"    
                   SelectionMode="None">

        <CollectionView.ItemsLayout>
            <LinearItemsLayout Orientation="Vertical" ItemSpacing="10"/>
        </CollectionView.ItemsLayout>
        <CollectionView.ItemTemplate>
            <DataTemplate>
                           <Frame HasShadow="True" HorizontalOptions="FillAndExpand"  BorderColor="#E5E5E5" CornerRadius="10"  VerticalOptions="Start">
                        <StackLayout  Orientation="Vertical">
                                    <StackLayout.GestureRecognizers>
                                        <TapGestureRecognizer     Command="{Binding BindingContext.CallPlace, Source={x:Reference ListPlaces}}"  ></TapGestureRecognizer>
                                    </StackLayout.GestureRecognizers>
                            <Label x:Name="NameOfPlace" Text="{Binding Name}" TextColor="#2D78FD" FontSize="14" FontFamily="Robobo"/>
                            <Label x:Name="AdressOfPlace" Text="{Binding Address}"  TextColor="#616161" FontSize="12" FontFamily="Robobo"/>
                            <StackLayout Orientation="Horizontal">
                                <Label x:Name="TimeWork" VerticalOptions="Center" Text="Open until  -  "  TextColor="#616161" FontSize="12" FontFamily="Robobo"/>
                                            <Label x:Name="TimeWork1" VerticalOptions="Center" Text="{Binding Opened}"  TextColor="#616161" FontSize="12" FontFamily="Robobo"/>
                                            <Image Source="openIcon" VerticalOptions="Center" />
                                <Button HeightRequest="24" VerticalOptions="Center" Padding="0,-3,0,0" WidthRequest="92" HorizontalOptions="EndAndExpand" FontSize="14" CornerRadius="45" BackgroundColor="#2D78FD" TextColor="White" Text="Call up"/>
                            </StackLayout>

                        </StackLayout>
                    </Frame>
               
            </DataTemplate>
        </CollectionView.ItemTemplate>
    </CollectionView>

代码隐藏

public PlacesList()
        {
            InitializeComponent();
            BindingContext =  this;
            CallPlace = new Command<CustomPin>((key) =>
            {
             var currentPlace = key as CustomPin;
             MapPage.PlacesHandler(currentPlace);
             
            });

        }

Answer 1

使用命令参数将数据传递到命令中属性

 <TapGestureRecognizer   CommandParameter={Binding .}  Command="{Binding BindingContext.CallPlace, Source={x:Reference ListPlaces}}"  />

假设 CustomPin 是您要绑定到此 CollectionView 的列表对象的类型。

此外，使用免费的 XAML 样式器和扩展，它使您的 XAML 非常漂亮每次保存文件

https://marketplace.visualstudio.com/items?itemName=TeamXavalon.XAMLStyler

对象引用未设置为...在 COLLECTIONVIEW 中的命令中

Object reference not set to... IN COMMAND IN COLLECTIONVIEW

c#

xaml

xamarin.android

xamarin

xamarin.forms