如何在 Xamarin Forms 中的其他项目之上显示 ListView？

I have a ListView that displays recent Search items. I have added it in the Stack Layout of my Main page. I want to show ListView over the other UI elements just like this: How can it be done.

我目前使用新页面只是为了SearchBar and ListView。在主页上我只有一个搜索按钮，当我单击该按钮时，应用程序将导航到包含的新页面SearchBar and ListView。但我希望它在同一页面上完成。当点击搜索按钮时，SearchBar and ListViewshow 在其他 UI 元素上变得可见。

这是我的代码：

在 MainPage.xaml 上

<Button Text="Search" Clicked="SearchButtonPressed" />

C# Code

void SearchButtonPressed(object sender, EventArgs e)
{
    Navigation.PushAsync(new SearchPage());
}

SearchPage.xaml 代码

<StackLayout>
    <SearchBar x:Name="SearchBar"
                TextChanged="Handle_SearchButtonPressed"
                Placeholder="Search places..."
                CancelButtonColor="Red" />

    <ListView x:Name="ListView" ItemsSource="{Binding Source=list}" RowHeight="50" IsVisible="True">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell Tapped="ViewCell_Tapped">
                    <Label Text="{Binding}" TextColor="Black" VerticalOptions="Center" />
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</StackLayout>

你可以用网格来做到这一点：

<Grid>

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


    <Entry Grid.Row="0"
           Placeholder="SearchItem"
           TextChanged="Entry_TextChanged"/>
    <Image Grid.Row="1"
           Aspect="Fill"
           Source="testImage.png"/>

        <ListView x:Name="ListView"
                  Grid.Row="1"
                  VerticalOptions="Start"
                  HorizontalOptions="Fill"
                  IsVisible="False"
                  HeightRequest="300"
                  BackgroundColor="White"
                  Opacity="0.8">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextCell Text="{Binding}"/>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

</Grid>

如果搜索条目的文本发生更改，则显示列表视图：

private void Entry_TextChanged(object sender, TextChangedEventArgs e)
    { 
        ListView.IsVisible =  e.NewTextValue.Length > 0; 
    }