Windows Phone 8.1 ListView元素在绑定后执行代码

Question

I have a ListView defined in a XAML interface which is bound to a collection.

The list view's DataTemplate features a WebView. I need this WebView to size to its contents, which means that after the ListView is bound, and elements are created, and those elements are bound, I need to execute a fragment of code on each WebView.

I've already taken care of getting the WebView to bind, and I have the code which will size a WebView. I simply need to know how to execute it; where to put it; how to get the WebViews and when to try to get them.

EDIT:

Here's my list view.

        <ListView Opacity="{Binding IsRefreshing, Mode=OneWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource BooleanToGhost}}" Grid.Row="0" Name="listView" ItemsSource="{Binding Messages}"  IsItemClickEnabled="False" SelectionMode="Single">
            <ListView.ItemContainerStyle>
                <Style TargetType="ListViewItem">
                    <Setter Property="HorizontalContentAlignment" Value="Stretch" />
                </Style>
            </ListView.ItemContainerStyle>
            <ListView.ItemTemplate>
                <DataTemplate>
                    <Grid Margin="8">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="*" />
                            <RowDefinition Height="*" />
                        </Grid.RowDefinitions>
                        <Rectangle Grid.ColumnSpan="2" Grid.RowSpan="2" Fill="White" RadiusX="12" RadiusY="12" />
                        <TextBlock Foreground="#FFAAAAAA" Grid.Row="0" Grid.Column="0" Margin="8" Text="You" HorizontalAlignment="Left" FontSize="11" Visibility="{Binding IsFromStaff, Mode=OneTime,Converter={StaticResource BooleanToInvisibility}}" />
                        <TextBlock Foreground="#FFAAAAAA" Grid.Row="0" Grid.Column="0" Margin="8" Text="Staff" HorizontalAlignment="Left" FontSize="11" Visibility="{Binding IsFromStaff, Mode=OneTime,Converter={StaticResource BooleanToVisibility}}" />
                        <TextBlock Foreground="#FFAAAAAA" Grid.Row="0" Grid.Column="1" Margin="8" Text="{Binding Timestamp, Mode=OneTime}" HorizontalAlignment="Right" FontSize="11" />
                        <WebView local:MyProperties.HtmlString="{Binding Body}" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" Margin="8" ScrollViewer.VerticalScrollBarVisibility="Disabled" />
                    </Grid>
                </DataTemplate>
            </ListView.ItemTemplate>
            <interactivity:Interaction.Behaviors>
                <core:EventTriggerBehavior EventName="SelectionChanged">
                    <core:InvokeCommandAction Command="{Binding ShowCaseCommand, Mode=OneWay}" CommandParameter="{Binding ElementName=listView, Path=SelectedItem}" />
                </core:EventTriggerBehavior>
            </interactivity:Interaction.Behaviors>
        </ListView>

Answer 1

The solution is something called "Behaviors".

We see in the code snippet that the DataTemplate contains a WebView , which is the item I want to affect. So I add a Behavior to the WebView, which is a class with code. The class looks like so:

public class WebViewSizeBehavior : DependencyObject, IBehavior
{
    public DependencyObject AssociatedObject { get; private set; }

    public void Attach(DependencyObject associatedObject)
    {
        var control = associatedObject as WebView;
        if (control == null)
            throw new ArgumentException(
                "WebViewSizeBehavior can be attached only to WebView.");
        AssociatedObject = associatedObject;
        control.LoadCompleted += Control_LoadCompleted;
    }

    private void Control_LoadCompleted(object sender, Windows.UI.Xaml.Navigation.NavigationEventArgs e)
    {
        var control = (WebView) AssociatedObject;

        var resizeTask = control.ResizeToContent();
    }

    public void Detach()
    {
        var control = (WebView) AssociatedObject;
        control.LoadCompleted -= Control_LoadCompleted;
        AssociatedObject = null;
    }
}

My namespaces and XAML are rigged up such that this class is reachable only the local namespace. How this is done is beyond the scope of this answer. So, given that, I can amend the XAML like so:

<ListView.ItemTemplate>
    <DataTemplate>
        …
        <WebView …>
            <interactivity:Interaction.Behaviors>
                <local:WebViewSizeBehavior />
            </interactivity:Interaction.Behaviors>
        </WebView>
    </DataTemplate>
</ListView.ItemTemplate>

I've left out content which is beyond the scope of this thread. Information about fitting a WebView to its content, as well as namespaces and XML namespaces, is available elsewhere.