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首页 > 解决方案 > 如何将 ContentView 中的 CommandParameter 绑定到 Xamarin Forms 中父 ContentPage 中的元素

xaml - 如何将 ContentView 中的 CommandParameter 绑定到 Xamarin Forms 中父 ContentPage 中的元素

问题描述

我有一个父 ContentPage，其中有几个 ContentView 在单独的文件中。我试图将父 ContentView 中的元素作为引用传递给其中一个视图中的 CommandParameter，下面是我到目前为止的代码。

这是父 ContentPage

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
x:Class="Acies.NitroT.Views.Shop.RefillPage"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:base="clr-namespace:Acies.NitroT.ViewModels.Base;assembly=Acies.NitroT.Mobile.Shared"
xmlns:behaviors="clr-namespace:Acies.NitroT.Behaviors;assembly=Acies.NitroT.Mobile.Shared"
xmlns:control="clr-namespace:Acies.NitroT.Controls"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:homeViews="clr-namespace:Acies.NitroT.Views.Home"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:tab="clr-namespace:Syncfusion.XForms.TabView;assembly=Syncfusion.SfTabView.XForms"
xmlns:transViews="clr-namespace:Acies.NitroT.Views.Transaction"
Title="Gas Refill"
Padding="0"
base:ViewManager.AutoWireViewModel="true"
BackgroundColor="{DynamicResource Gray-White}"
NavigationPage.HasNavigationBar="False"
Visual="Material"
mc:Ignorable="d">
<ContentPage.Content>
    <RelativeLayout Padding="0">
        <RelativeLayout.Margin>
            <OnPlatform x:TypeArguments="Thickness">
                <On Platform="iOS" Value="0, 40, 0, 0" />
            </OnPlatform>
        </RelativeLayout.Margin>
        <Grid
            Padding="0"
            RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent,
                                                                   Property=Height,
                                                                   Factor=1}"
            RowSpacing="0"
            VerticalOptions="FillAndExpand">
            <Grid.RowDefinitions>
                <RowDefinition Height="auto" />
                <RowDefinition Height="*" />
                <RowDefinition Height="auto" />
            </Grid.RowDefinitions>

            <!--#region Google Map [Row:0] Pins="{Binding Pins}"-->
            <control:GoogleMapView
                x:Name="Map"
                Grid.Row="0"
                Grid.RowSpan="2"
                Margin="0"
                Padding="0"
                HorizontalOptions="FillAndExpand"
                VerticalOptions="FillAndExpand" />
            <!--#endregion-->

            <!--#region Search Control [Row:1]-->
            <Grid
                Grid.Row="1"
                Margin="20"
                VerticalOptions="Start">

                <Grid.RowDefinitions>
                    <RowDefinition Height="*" />
                    <RowDefinition Height="auto" />
                    <RowDefinition Height="auto" />
                </Grid.RowDefinitions>

                <!--#region Search Bar-->
                <homeViews:SearchBarView Grid.Row="0" Padding="0" />
                <!--#endregion-->

                <!--#region Chip Group-->
                <homeViews:AddressChipView Grid.Row="1" />
                <!--#endregion-->

                <!--#region Search Results View-->
                <homeViews:SearchResultsView Grid.Row="2" Padding="0" />
                <!--#endregion-->
            </Grid>
            <!--#endregion-->

            <!--#region Bottom Control [Row:2]-->
            
            <homeViews:CommandButtonsView
                Grid.Row="1"
                Margin="0,0,0,10"
                VerticalOptions="End" />
            <!--#endregion-->
        </Grid>
    </RelativeLayout>
</ContentPage.Content>

这是我尝试将control:GoogleMapViewwithx:Name="Map"作为传递的 ContentPageCommandParameter

<?xml version="1.0" encoding="UTF-8" ?>
<ContentView
x:Class="Acies.NitroT.Views.Home.AddressChipView"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:behaviors="clr-namespace:Acies.NitroT.Behaviors"
xmlns:buttons="clr-namespace:Syncfusion.XForms.Buttons;assembly=Syncfusion.Buttons.XForms"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:controls="clr-namespace:Acies.NitroT.Controls;assembly=Acies.NitroT.Mobile.Shared"
mc:Ignorable="d">

<ContentView.Content>
    <!--#region Chip Group-->
    
    <StackLayout Grid.Row="1">
        <ScrollView
            Margin="{StaticResource ChipMargin}"
            HorizontalScrollBarVisibility="Never"
            Orientation="Horizontal">
            <buttons:SfChipGroup
                ChipPadding="2,0,0,0"
                Command="{Binding SelectedAddressCommand}"
                DisplayMemberPath="Nickname"
                ItemsSource="{Binding AddressItems}"
                SelectedChipBackgroundColor="{StaticResource BlueDark}"
                SelectedItem="{Binding SelectedAddress}"
                ShowIcon="True"
                Type="Choice">
                <buttons:SfChipGroup.Behaviors>
                    <behaviors:EventToCommandBehavior
                        Command="{Binding AddressSelectionChangedCommand}"
                        CommandParameter="{Binding Source={x:RelativeSource Mode=FindAncestor, AncestorType={x:Type controls:GoogleMapView}}, Path=.}"
                        EventName="SelectionChanged" />
                </buttons:SfChipGroup.Behaviors>
            </buttons:SfChipGroup>
        </ScrollView>
    </StackLayout>
    <!--#endregion-->
</ContentView.Content>

上面的代码给了我以下错误：

09-29 10:52:19.447 I/MonoDroid(25814): UNHANDLED EXCEPTION:
09-29 10:52:19.449 I/MonoDroid(25814): System.InvalidOperationException: Operation is not valid due to the current state of the object.
09-29 10:52:19.449 I/MonoDroid(25814):   at Xamarin.Forms.Binding.ApplyRelativeSourceBinding (Xamarin.Forms.BindableObject targetObject, Xamarin.Forms.BindableProperty targetProperty) [0x00041] in D:\a\1\s\Xamarin.Forms.Core\Binding.cs:153 
09-29 10:52:19.449 I/MonoDroid(25814):   at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__7_0 (System.Object state) [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1021 
09-29 10:52:19.449 I/MonoDroid(25814):   at Android.App.SyncContext+<>c__DisplayClass2_0.<Post>b__0 () [0x00000] in <7d2292394f8c488b97f5bc2a0ac0240d>:0 
09-29 10:52:19.449 I/MonoDroid(25814):   at Java.Lang.Thread+RunnableImplementor.Run () [0x00008] in <7d2292394f8c488b97f5bc2a0ac0240d>:0 
09-29 10:52:19.449 I/MonoDroid(25814):   at Java.Lang.IRunnableInvoker.n_Run (System.IntPtr jnienv, System.IntPtr native__this) [0x00008] in <7d2292394f8c488b97f5bc2a0ac0240d>:0 
09-29 10:52:19.449 I/MonoDroid(25814):   at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.1(intptr,intptr)

我怎样才能达到预期的结果。

标签： xamlxamarin.forms

解决方案

您可以检查以下代码

在 AddressChipView.xaml

由于您使用过 Custom ContentView ，因此您需要使用可绑定属性来绑定ContentView和Parent ContentPage中的元素之间的值

<?xml version="1.0" encoding="UTF-8" ?>
<ContentView
x:Class="Acies.NitroT.Views.Home.AddressChipView"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:behaviors="clr-namespace:Acies.NitroT.Behaviors"
xmlns:buttons="clr-namespace:Syncfusion.XForms.Buttons;assembly=Syncfusion.Buttons.XForms"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:controls="clr-namespace:Acies.NitroT.Controls;assembly=Acies.NitroT.Mobile.Shared"
mc:Ignorable="d"

x:Name="ChipView" // set the name of AddressChipView

>

<buttons:SfChipGroup
                ChipPadding="2,0,0,0"
                Command="{Binding Source={x:Reference ChipView}, Path=SelectedAddressCommand}"
                //...
                SelectedItem="{Binding Source={x:Reference ChipView}, Path=SelectedAddress}"
                ShowIcon="True"
                Type="Choice">
                <buttons:SfChipGroup.Behaviors>
                    <behaviors:EventToCommandBehavior
                        Command="{Binding Source={x:Reference ChipView}, Path=AddressSelectionChangedCommand}"
                        CommandParameter="{Binding Source={x:Reference ChipView}, Path=CurrentMapView}"
                        EventName="SelectionChanged" />
                </buttons:SfChipGroup.Behaviors>
            </buttons:SfChipGroup>

在 AddressChipView.xaml.cs

public static readonly BindableProperty AddressSelectionChangedCommandProperty =
            BindableProperty.Create(nameof(AddressSelectionChangedCommand), typeof(ICommand), typeof(AddressChipView));

        public ICommand AddressSelectionChangedCommand
        {
            get => (ICommand)GetValue(AddressSelectionChangedCommandProperty );
            set => SetValue(AddressSelectionChangedCommandProperty , value);
        }

        public static BindableProperty CurrentMapViewProperty =
            BindableProperty.Create(nameof(CurrentMapView), typeof(object), typeof(AddressChipView));

        public object CurrentMapView
        {
            get => (object)GetValue(CurrentMapViewProperty );
            set => SetValue(CurrentMapViewProperty , value);
        }

        //... other bindable property

现在您可以在 ContentPage 中绑定它

<homeViews:AddressChipView Grid.Row="1"  AddressSelectionChangedCommand={Binding xxxCommand}  CurrentMapView = {Binding Source={x:Reference Map}, Path=.} />

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