WPF - 请求等待动画--Loading

仅作参考
XAML页面
Loading.XAML
这里创建的是Window窗体，并不是用户控件。
可以将背景设置为透明色，需要给Window标签写入AllowsTransparency=“True” background=“Transparent”
以上两句，或自行设置其它颜色。

    <Grid Width="65" Height="90" HorizontalAlignment="Center" VerticalAlignment="Center"  Loaded="Grid_Loaded">
        <Grid.Resources>
            <DrawingBrush x:Key="brush" Stretch="None" AlignmentX="Center" AlignmentY="Top">
                <DrawingBrush.Drawing>
                    <GeometryDrawing Brush="Black">
                        <GeometryDrawing.Geometry>
                            <EllipseGeometry RadiusX="8" RadiusY="8"/>
                        </GeometryDrawing.Geometry>
                    </GeometryDrawing>
                </DrawingBrush.Drawing>
            </DrawingBrush>
        </Grid.Resources>

        <Rectangle x:Name="r01" Fill="{StaticResource brush}" Opacity="0.4" RenderTransformOrigin="0.5,0.5">
            <Rectangle.RenderTransform>
                <RotateTransform Angle="0"/>
            </Rectangle.RenderTransform>
        </Rectangle>
        <Rectangle x:Name="r02" Fill="{StaticResource brush}" Opacity="0.4" RenderTransformOrigin="0.5,0.5">
            <Rectangle.RenderTransform>
                <RotateTransform Angle="30"/>
            </Rectangle.RenderTransform>
        </Rectangle>
        <Rectangle x:Name="r03" Fill="{StaticResource brush}" Opacity="0.4" RenderTransformOrigin="0.5,0.5">
            <Rectangle.RenderTransform>
                <RotateTransform Angle="60"/>
            </Rectangle.RenderTransform>
        </R