xamarin - Xamarin.Forms-如何以编程方式将ActivityIndi​​cator叠加在StackLayout的中间

Question

我想将我的ActivityIndi​​cator覆盖在表单中间，但是我不确定我该怎么做，我想我需要将堆栈布局包装在相对布局中吗？

我正在代码中执行此操作，而我发现的最接近的示例是使用XAML，该XAML使用如下所示的网格:

 <ScrollView BackgroundColor="#d3d6db">
    <RelativeLayout
        VerticalOptions="FillAndExpand"
        HorizontalOptions="FillAndExpand">
        <StackLayout Orientation="Vertical"
                     VerticalOptions="FillAndExpand"
                     Padding="10"
                     RelativeLayout.XConstraint="{ConstraintExpression Type=Constant, Constant=0}"
                     RelativeLayout.YConstraint="{ConstraintExpression Type=Constant, Constant=0}">

            <Grid x:Name="SegmentGrid"
                  RowSpacing="10"
                  ColumnSpacing="10">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
            </Grid>
            <WebView BackgroundColor="White" VerticalOptions="FillAndExpand" Source="{Binding DescriptionHtml}" />
        </StackLayout>

        <ActivityIndicator IsVisible="{Binding IsBusy}"
                           IsRunning="{Binding IsBusy}"
                           Color="Black"
                           VerticalOptions="CenterAndExpand"
                           HorizontalOptions="CenterAndExpand"
                           RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent,
                                    Property=Height,
                                    Factor=0.33}"
                           RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent,
                                    Property=Height,
                                    Factor=0.33}" />
    </RelativeLayout>
</ScrollView>

Answer 1

如果您在RelativeLayout上遇到问题，也可以使用在类似上下文中工作的AbsoluteLayout。下面的示例代码:

var overlay = new AbsoluteLayout();
var content = new StackLayout();
var loadingIndicator = new ActivityIndicator();
AbsoluteLayout.SetLayoutFlags(content, AbsoluteLayoutFlags.PositionProportional);
AbsoluteLayout.SetLayoutBounds(content, new Rectangle(0f, 0f, AbsoluteLayout.AutoSize, AbsoluteLayout.AutoSize));
AbsoluteLayout.SetLayoutFlags(loadingIndicator, AbsoluteLayoutFlags.PositionProportional);
AbsoluteLayout.SetLayoutBounds(loadingIndicator, new Rectangle(0.5, 0.5, AbsoluteLayout.AutoSize, AbsoluteLayout.AutoSize));
overlay.Children.Add(content);
overlay.Children.Add(loadingIndicator);

如果您想要一个完整的工作示例，请给我一个@ https://github.com/teamtam/xamarin-forms-timesheet