监听GridView中控件，修改控件属性

Question

我新建了一个Gridview网格应用程序，没做任何修改，就用系统默认的GridView x:Name="itemGridView" 然后再cpp里面用这个方法，int i = VisualTreeHelper::GetChildrenCount(itemGridView);得到i = 0;

GroupedItemsPage.xaml:

<!-- 在大多数视图状态中使用的水平滚动网格-->
        <GridView
            x:Name="itemGridView"
            AutomationProperties.AutomationId="ItemGridView"
            AutomationProperties.Name="Grouped Items"
            Grid.RowSpan="2"
            Padding="116,137,40,46"
            ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}"
            ItemTemplate="{StaticResource Standard250x250ItemTemplate}"
            SelectionMode="None"
            IsSwipeEnabled="false"
            IsItemClickEnabled="True"
            ItemClick="ItemView_ItemClick">
            <GridView.ItemsPanel>
                <ItemsPanelTemplate>                        
                    <VirtualizingStackPanel Orientation="Horizontal"/>
                </ItemsPanelTemplate>
            </GridView.ItemsPanel>
            <GridView.GroupStyle>
                <GroupStyle>
                    <GroupStyle.HeaderTemplate>
                        <DataTemplate>
                            <Grid Margin="1,0,0,6">
                                <Button
                                    AutomationProperties.Name="Group Title"
                                    Click="Header_Click"
                                    Style="{StaticResource TextPrimaryButtonStyle}" >
                                    <StackPanel Orientation="Horizontal">
                                        <TextBlock Text="{Binding Title}" Margin="3,-7,10,10" Style="{StaticResource GroupHeaderTextStyle}" />
                                        <TextBlock Text="{StaticResource ChevronGlyph}" FontFamily="Segoe UI Symbol" Margin="0,-7,0,10" Style="{StaticResource GroupHeaderTextStyle}"/>
                                    </StackPanel>
                                </Button>
                            </Grid>
                        </DataTemplate>
                    </GroupStyle.HeaderTemplate>
                    <GroupStyle.Panel>
                        <ItemsPanelTemplate>
                            <VariableSizedWrapGrid Orientation="Vertical" Margin="0,0,80,0"/>
                        </ItemsPanelTemplate>
                    </GroupStyle.Panel>
                </GroupStyle>
            </GridView.GroupStyle>
        </GridView>

StandardStyles.xaml:

 <!-- GroupedItemsPage 和 ItemsPage 中显示的适合网格的 250 像素平方的项模板-->
    <DataTemplate x:Key="Standard250x250ItemTemplate">
        <Grid HorizontalAlignment="Left" Width="250" Height="250">
            <Border Background="{StaticResource ListViewItemPlaceholderBackgroundThemeBrush}">
                <Image Source="{Binding Image}" Stretch="UniformToFill" AutomationProperties.Name="{Binding Title}"/>
            </Border>
            <StackPanel VerticalAlignment="Bottom" Background="{StaticResource ListViewItemOverlayBackgroundThemeBrush}">
                <TextBlock Text="{Binding Title}" Foreground="{StaticResource ListViewItemOverlayForegroundThemeBrush}" Style="{StaticResource TitleTextStyle}" Height="60" Margin="15,0,15,0"/>
                <TextBlock Text="{Binding Subtitle}" Foreground="{StaticResource ListViewItemOverlaySecondaryForegroundThemeBrush}" Style="{StaticResource CaptionTextStyle}" TextWrapping="NoWrap" Margin="15,0,15,10"/>
            </StackPanel>
        </Grid>
    </DataTemplate>

GroupedItemsPage.xaml.cpp:

void GroupedItemsPage::LoadState(Object^ navigationParameter, IMap<String^, Object^>^ pageState)
{
	// TODO: 创建适用于问题域的合适数据模型以替换示例数据
	auto sampleDataGroups = Data::SampleDataSource::GetGroups(safe_cast<String^>(navigationParameter));
	DefaultViewModel->Insert("Groups", sampleDataGroups);
	int i = VisualTreeHelper::GetChildrenCount(itemGridView);
}

Debug 的结果：

Answer 1

Hi,

VisualTreeHelper不能够放到LoadState中，原因是在LoadState的时候可视树还没有构建完成，你要等可视树构建完成才能够调用，比如你放到Page的Loaded中就比较好。

---

Aaron
MSDN Community Support | Feedback to us
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Answer 2

哦，谢谢哈~