Question

我跟随以下带有listview的轮播示例，当我去打开Navigation.PushAsync时，列表视图中的项目仅被调用第一项，在所有项目上只点击了他的名字第一项，位置错误？

    void Handle_ItemSelected(object sender, SelectedItemChangedEventArgs e)
   {
        var monkey = ((ListView)sender).SelectedItem as Monkey;

        if (monkey == null)
            return;

        Navigation.PushAsync(new DetailsPage(monkey));
    }

https://blog.xamarin.com/flip-through-items-with-xamarin-forms-carouselview/

修改

MonkeysPage.xaml

    <?xml version="1.0" encoding="UTF-8"?>
    <ContentPage
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Class="Monkeys.Views.MonkeysPage"
    xmlns:design="clr-namespace:Monkeys;assembly=Monkeys"
    xmlns:controls="clr-namespace:ImageCircle.Forms.Plugin.Abstractions;assembly=ImageCircle.Forms.Plugin.Abstractions"
    xmlns:cv="clr-namespace:Xamarin.Forms;assembly=Xamarin.Forms.CarouselView"
        BindingContext="{x:Static design:ViewModelLocator.MonkeysViewModel}"
    x:Name="MonkeysPage"
    Title="Traditional Monkeys">
<ContentPage.Content>
  <ListView ItemsSource="{Binding MonkeysGrouped}"
            ItemSelected="Handle_ItemSelected"
            HasUnevenRows="true"
            GroupShortNameBinding = "{Binding Key}"
            IsGroupingEnabled = "true"
            GroupDisplayBinding = "{Binding Key}">
     <ListView.Header>
      <cv:CarouselView x:Name="CarouselZoos" ItemsSource="{Binding Path=BindingContext.Zoos, Source={x:Reference MonkeysPage}}" HeightRequest="200">
        <cv:CarouselView.ItemTemplate>
          <DataTemplate>
            <Grid>
              <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
                <RowDefinition Height="Auto"/>
              </Grid.RowDefinitions>
              <Image Grid.RowSpan="2" Aspect="AspectFill" Source="{Binding ImageUrl}"/>
              <StackLayout Grid.Row="1" BackgroundColor="#80000000" Padding="12">
                  <Label TextColor="White" Text="{Binding Name}" FontSize="16" HorizontalOptions="Center" VerticalOptions="CenterAndExpand"/>
              </StackLayout>
            </Grid>
          </DataTemplate>
        </cv:CarouselView.ItemTemplate>
      </cv:CarouselView>
    </ListView.Header>
    <ListView.ItemTemplate>
      <DataTemplate>
        <ViewCell>
          <Grid Padding="10" RowSpacing="10" ColumnSpacing="10">
            <Grid.RowDefinitions>
              <RowDefinition Height="Auto"/>
              <RowDefinition Height="*"/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
              <ColumnDefinition Width="Auto"/>
              <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <controls:CircleImage
                   BorderColor="Aqua"
                   BorderThickness="3"
                   HeightRequest="66"
                   HorizontalOptions="CenterAndExpand"
                   VerticalOptions="CenterAndExpand"
                   Aspect="AspectFill"
                   WidthRequest="66"
                   Grid.RowSpan="2"
                   Source="{Binding Image}"/>
            <Label Grid.Column="1"
                   Text="{Binding Name}"
                   VerticalOptions="End"/>
            <Label Grid.Column="1"
                   Grid.Row="1"
                   VerticalOptions="Start"
                   Text="{Binding Location}"/>
          </Grid>
        </ViewCell>
      </DataTemplate>
    </ListView.ItemTemplate>
  </ListView>

MonkeysPage.xaml.cs

  public MonkeysPage()
    {
        InitializeComponent();
        BindingContext = new MonkeysViewModel();
    }


    async void Handle_ItemSelected(object sender, SelectedItemChangedEventArgs e)
    {
        var monkey = e.SelectedItem as Monkey;

        if (monkey == null)
            return;

        await Navigation.PushAsync(new DetailsPage(monkey)); // always await Navigations
        ((ListView)sender).SelectedItem = null;
    }

DetailsPage.xaml

<?xml version="1.0" encoding="UTF-8"?>
  <ContentPage 
    xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    x:Class="Monkeys.Views.DetailsPage"
    xmlns:design="clr-namespace:Monkeys;assembly=Monkeys"
    xmlns:controls="clr-namespace:ImageCircle.Forms.Plugin.Abstractions;assembly=ImageCircle.Forms.Plugin.Abstractions"
    BindingContext="{x:Static design:ViewModelLocator.DetailsViewModel}"
    Title="{Binding Monkey.Name}">
<ContentPage.Content>
    <ScrollView>
        <StackLayout Padding="10">
            <controls:CircleImage 
                    BorderColor="Aqua"
                    BorderThickness="3"
                    HeightRequest="200"
                    WidthRequest="200"
                    HorizontalOptions="CenterAndExpand"
                    Aspect="AspectFill"
                    Source="{Binding Monkey.Image}"/>
            <Label Text="{Binding Monkey.Name}" FontAttributes="Bold"/>
            <Label Text="{Binding Monkey.Location}" FontSize="Micro"/>
            <Label Text="{Binding Monkey.Details}" FontSize="Large"/>
        </StackLayout>
    </ScrollView>
</ContentPage.Content>

DetailsPage

  public partial class DetailsPage : ContentPage
{
    public DetailsPage(Monkey monkey)
    {
        InitializeComponent();

    }
}

Answer 1

除了忘记将SelectedItem重置为null之外，您已做好一切，这就是为什么您总是会点击第一个列表项。

您的代码应如下所示：

async void Handle_ItemSelected(object sender, SelectedItemChangedEventArgs e)
{
     var monkey = e.SelectedItem as Monkey;

     if (monkey == null)
        return;

     await Navigation.PushAsync(new DetailsPage(monkey)); // always await Navigations
     ((ListView)sender).SelectedItem = null;
}

P.S。使您的方法异步，这样您就不会导致UI线程阻止

修改

尝试从SelectedItemChangedEventArgs中获取所选项目。

var monkey = e.SelectedItem as Monkey;

<强>更新

好的，SelectedItem正在成功更新，但是＆＃39; Monkey Item＆＃39;在DetailsPage后面的ViewModel上没有！

所以在DetailsPage上添加以下行：

public partial class DetailsPage : ContentPage { public DetailsPage(Monkey monkey) { InitializeComponent(); BindingContext = new DetailsViewModel(monkey); // Update the BindingContext } }

并删除DetailsPage.xaml上的这一行：

BindingContext="{x:Static design:ViewModelLocator.DetailsViewModel}"

导航中出错。 PushAsync（新的DetailsPage（猴子））

1 个答案: