c# - Parallax 工作，但 PARALLAX 中的 ListView 不起作用 - Xamarin Forms

Question

我个人在我的应用程序中创建了视差效果，但在效果 (PARALLAX) 中，我有一个显示我的内容的 LISTVIEW！只有当效果结束时，ListView SCROLL 不起作用，不会加载所有内容！

我的代码

视差控制.cs

 public class ParallaxControl : ScrollView
{
    public ParallaxControl()
    {
        Scrolled += (sender, e) => Parallax();
    }

    public static readonly BindableProperty ParallaxViewProperty =
        BindableProperty.Create(nameof(ParallaxControl), typeof(View), typeof(ParallaxControl), null);

    public View ParallaxView
    {
        get { return (View)GetValue(ParallaxViewProperty); }
        set { SetValue(ParallaxViewProperty, value); }
    }

    double height;

    public void Parallax()
    {

        if (ParallaxView == null || Device.RuntimePlatform == "Windows" || Device.RuntimePlatform == "WinPhone")
            return;

        if (height <= 0)
            height = ParallaxView.Height;
        ParallaxView.IsEnabled = false;

        var y = -(int)((float)ScrollY / 2.5f);

        if (y < 0)
        {

            //Move a imagem no eixo Y em uma fração da posição Y do ScrollView.

            ParallaxView.Scale = 1;

            ParallaxView.TranslationY = y;

        }

        else if (Device.RuntimePlatform == "iOS")
        {

            //Calcula uma escala que iguala a altura x scroll.

            double newHeight = height + (ScrollY * -1);

            ParallaxView.Scale = newHeight / height;

            ParallaxView.TranslationY = -(ScrollY / 2);

        }
        else
        {

            ParallaxView.Scale = 1;

            ParallaxView.TranslationY = 0;

        }
    }
}

菜单.XAML

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"            
         xmlns:local="clr-namespace:DeLivre.Controls"
         xmlns:cardView="clr-namespace:DeLivre"          
         xmlns:local1="clr-namespace:DeLivre.Controls"
         xmlns:controls="clr-namespace:ImageCircle.Forms.Plugin.Abstractions;assembly=ImageCircle.Forms.Plugin"
         x:Class="DeLivre.Views.Cardapio_Menu">
<ContentPage.ToolbarItems>
    <ToolbarItem Name="MenuItem1" Order="Primary" Icon="ic_Carrinho" Clicked="MenuItem1_Clicked" Text="Carrinho" Priority="0" />
</ContentPage.ToolbarItems>


<Grid>

    <Grid.RowDefinitions>
        <RowDefinition Height="200" x:Name="Row1Header"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

    <Grid RowSpacing="0" ColumnSpacing="0" x:Name="HeaderView">          

        <StackLayout Padding="5,5,5,0" BackgroundColor="White" Orientation="Vertical">
            <SearchBar x:Name="CardapioPesquisa" Placeholder="Pesquise por um lanche!" HeightRequest="40" BackgroundColor="White" TextChanged="CardapioPesquisa_TextChanged" />
            <cardView:CardView x:Name="CardEstabelecimento" BackgroundColor="White" CardViewHasShadow="True" HeightRequest="220">
                <cardView:CardView.CardViewContent>
                    <StackLayout x:Name="Stack"
                             Padding="2"
                             HorizontalOptions="Center"
                             Spacing="2"
                             VerticalOptions="Center">
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="80"/>
                                <ColumnDefinition Width="*"/>
                                <ColumnDefinition Width="80"/>
                            </Grid.ColumnDefinitions>
                            <controls:CircleImage x:Name="ImagemEstab"
                                              Grid.Column="1"
                                              BorderColor="#EF5350" 
                                              BorderThickness="2" 
                                              Margin="1,0,1,0" 
                                              WidthRequest="100" 
                                              HeightRequest="100"                                                 
                                              Aspect="AspectFit"/>

                            <Label x:Name="lblEntrega"                                              
                               Grid.Column="0"
                                   Text="ENTREGA"
                               TextColor="{StaticResource asphaltPrimary}"                              
                               FontSize="16" FontAttributes="Bold"/>

                            <Label x:Name="EstabLocal"                                              
                               Grid.Column="0"
                               Margin="0,20"
                               TextColor="{StaticResource asphaltPrimary}"                              
                               FontSize="13"/>

                            <Label x:Name="EstabEntrega"                              
                               Grid.Column="0"
                               TextColor="{StaticResource asphaltPrimary}"
                                            Margin="-15,35,0,0"
                                            FontSize="13"
                                            HorizontalTextAlignment="End"/>


                            <Label x:Name="EstabFuncionamento"                                             
                               TextColor="{StaticResource asphaltPrimary}"
                               Grid.Column="2"                                              
                               FontSize="13"/>

                            <Label x:Name="EstabFrete"                                            
                               Grid.Column="2"
                               TextColor="{StaticResource asphaltPrimary}"
                               Margin="0,15,0,0"
                               FontSize="13" />

                        </Grid>

                        <Label x:Name="Descricao"      
                               Text="Teste"
                               HorizontalTextAlignment="Center"
                               TextColor="{StaticResource asphaltPrimary}"
                               Margin="0,15,0,0"
                               FontSize="13" />
                    </StackLayout>
                </cardView:CardView.CardViewContent>
            </cardView:CardView>
        </StackLayout>
    </Grid>

    <local:ParallaxControl x:Name="MainScroll" Grid.RowSpan="2">

        <Grid RowSpacing="0" ColumnSpacing="0" >
            <Grid.RowDefinitions>
                <RowDefinition Height="200"/>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>


            <StackLayout Grid.Row="1">

                <ListView x:Name="ListaCardapio"                  
                  BackgroundColor="White"                    
                  SeparatorColor="{StaticResource grayPrimary}"
                  VerticalOptions="FillAndExpand"                      
                  HasUnevenRows="true"                                      
                  ItemSelected="ListaCardapio_ItemSelected"
                  ItemsSource="{Binding Cardapios}"
                  CachingStrategy="RecycleElement">

                    <ListView.ItemTemplate>
                        <DataTemplate>
                            <ViewCell>

                                    <StackLayout >
                                        <StackLayout Orientation="Horizontal">
                                            <controls:CircleImage x:Name="ImagemEstab"
                                              Grid.Column="1"
                                              Source="{Binding Icon_Lanche}"
                                              BorderColor="#EF5350" 
                                              BorderThickness="2" 
                                              Margin="1,0,1,0" 
                                              WidthRequest="100" 
                                              HeightRequest="100"                                                 
                                              Aspect="AspectFit"/>

                                            <Label x:Name="NomeLanche" Text="{Binding Tipo}" 
                                       FontSize="13"                                         
                                       Margin="-5,7"
                                       TextColor="{StaticResource asphaltPrimary}" />

                                        </StackLayout>
                                    </StackLayout>

                            </ViewCell>
                        </DataTemplate>
                    </ListView.ItemTemplate>
                </ListView>
            </StackLayout>
        </Grid>
    </local:ParallaxControl>
</Grid>

菜单.XAML.CS

  public Cardapio_Menu()
    {
        InitializeComponent ();

        MainScroll.ParallaxView = HeaderView;
    }

效果有效，问题是当效果结束时，Listview滚动不起作用，不显示我的其余数据！

请帮忙

标签： c#listviewmobilexamarin.formsparallax

Answer 1

你可以做的是Xamarin.Forms ListView用RepeaterView

RepeaterView是一个从 stacklayout 继承的控件，它的工作方式与 ListView 非常相似，但没有自己的滚动条，因为您已经有了一个滚动条，它应该非常适合您。

public class RepeaterView<T> : StackLayout where T : class
{
    public static readonly BindableProperty HeaderTemplateProperty = BindableProperty.Create(nameof(HeaderTemplate), typeof(DataTemplate), typeof(RepeaterView<T>), default(DataTemplate));

    public static readonly BindableProperty ItemTemplateProperty = BindableProperty.Create(nameof(ItemTemplate), typeof(DataTemplate), typeof(RepeaterView<T>), default(DataTemplate));

    public static readonly BindableProperty ItemsSourceProperty = BindableProperty.Create(nameof(ItemsSource), typeof(IEnumerable<T>), typeof(RepeaterView<T>), null, defaultBindingMode: BindingMode.OneWay, propertyChanged: ItemsChanged);

    public RepeaterView()
    {
        Spacing = 0;
    }

    public IEnumerable<T> ItemsSource
    {
        get { return (IEnumerable<T>)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }

    public DataTemplate ItemTemplate
    {
        get { return (DataTemplate)GetValue(ItemTemplateProperty); }
        set { SetValue(ItemTemplateProperty, value); }
    }

    public DataTemplate HeaderTemplate
    {
        get { return (DataTemplate)GetValue(HeaderTemplateProperty); }
        set { SetValue(HeaderTemplateProperty, value); }
    }

    protected virtual View ViewFor(T item)
    {
        View view = null;
        if (ItemTemplate != null)
        {
            var content = ItemTemplate.CreateContent();
            view = (content is View) ? content as View : ((ViewCell)content).View;

            view.BindingContext = item;
        }

        return view;
    }

    protected View HeaderView()
    {
        View view = null;

        if (HeaderTemplate != null)
        {
            var content = HeaderTemplate.CreateContent();
            view = (content is View) ? content as View : ((ViewCell)content).View;
            view.BindingContext = this.BindingContext;
        }

        return view;
    }

    private static void ItemsChanged(BindableObject bindable, object oldValue, object newValue)
    {
        var control = bindable as RepeaterView<T>;
        if (control == null)
            return;

        control.Children.Clear();

        IEnumerable<T> items = (IEnumerable<T>)newValue;
        if (items.Any())
        {
            var header = control.HeaderView();
            if (header != null)
                control.Children.Add(header);

            foreach (var item in items)
                control.Children.Add(control.ViewFor(item));
        }
    }
}

为了更好地了解此控件的工作原理，您可以在此处查看指南

如果您有疑问，请随时回复