WPF Popup UI showing black

I am using a WPF Popup control, and it is showing the background as black. I put a StackPanel inside it with Background="Transparent", but that does not help.

<Popup PlacementTarget="{Binding ElementName=parentStackPanel}" Placement="Center"
        IsOpen="False" Name="m_popWaitNotifier" PopupAnimation="None" 
        AllowsTransparency="False">
    <StackPanel Orientation="Vertical" Background="Transparent">
        <uc:CircularProgressBar x:Name="CB" StartupDelay="0"
                  开发者_StackOverflow中文版                          RotationsPerMinute="20"
                                            Height="25" Foreground="White"
                                            Margin="12"/>
    </StackPanel>
</Popup>

How does one make the background on Popup transparent (or any color)?

You need to set the AllowsTransparency="True" Popup Property to True

Here is an example:

<Grid>
    <StackPanel>
    <Button Click="Button_Click" Width="100" Height="20" Content="Click" />
        <Popup x:Name="popup" Width="100" Height="100" AllowsTransparency="True">
            <Grid Background="Transparent">
                <TextBlock Text="Some Text" />
            </Grid>
        </Popup>
    </StackPanel>
</Grid>

and the click handler

private void Button_Click(object sender, RoutedEventArgs e)
{
    popup.Visibility = System.Windows.Visibility.Visible;
    popup.IsOpen = true;
}

The base color of a Popup, or a Window for that matter, is black. You rarely see it for a Window because Window has a Background property and it defaults to a solid color, but if you set Window.Background to Transparent it will also be black. But Popup doesn't have a Background property and so, pardon the pun, this problem "pops up".

If you want the Popup to be transparent, you need to set AllowsTransparency="True". However, if you want the Popup to be a solid color, the simplest approach is to make the child of the Popup a Panel that supports the Background property and set that property to the color you desire and then set the child of the Panel to be the content you intended for the Popup in the first place. I suggest Grid as it won't affect the layout of your Popup. It's only effect will be to give you the background color you desire.

Make sure that the allow transparency is set to true, vertical and horizontal alignments are centered, and the height and width are set to Auto.

For example:

<Popup Name="popup1" Placement="Top" PlacementTarget="{Binding ElementName=button2}" AllowsTransparency="True" Height="Auto" Width="Auto" Panel.ZIndex="1" HorizontalOffset="-5" HorizontalAlignment="Center" VerticalAlignment="Center">

<StackPanel Height="92" HorizontalAlignment="Left" Margin="93,522,0,0" Name="stackPanelPop" VerticalAlignment="Top" Width="147">
</StackPanel>

</Popup>

Another possible cause:

• using IsOpen="True" in markup before AllowTransparency="True"

Switching the order fixes it.

My guess is that the CircularProgressBar is actually causing the Black background. The only other way that this could happen is if there was a Style or something set on one of the controls (Popup or StackPanel or...).

Here is a quick-n-dirty example that shows a TextBlock in a popup when a checkbox is checked. The colors chosen are just to make sure things stand out visually:

<StackPanel x:Name="stackPanelLayout">
    <StackPanel.Background>
        <RadialGradientBrush Center="0.75, 0.75"
                             SpreadMethod="Reflect">
            <GradientStop Color="LightBlue" Offset="0" />
            <GradientStop Color="SeaGreen" Offset="0.5" />
            <GradientStop Color="MidnightBlue" Offset="0.75" />
        </RadialGradientBrush>
    </StackPanel.Background>


    <CheckBox x:Name="chkShowPopup"
              FontSize="20"
              Foreground="White"
              Content="Show Popup" />

    <Popup PlacementTarget="{Binding ElementName=stackPanelLayout}" 
           Placement="Center" 
           IsOpen="{Binding ElementName=chkShowPopup, Path=IsChecked}" 
           Name="m_popWaitNotifier" 
           PopupAnimation="Slide"
           AllowsTransparency="True">
        <StackPanel Orientation="Vertical" Background="Transparent">
            <TextBlock Foreground="White" FontSize="30" FontWeight="Bold" Text="PopUp" />
        </StackPanel>
    </Popup>
</StackPanel>

So, two tests you can do to determine what is happening:

1. Replace the CircularProgressBar with a simple TextBlock or other control that you don't have a Style applied to.
2. Put the CircularProgressBar as a standalone control somewhere on your window, or on an otherwise blank test Window.

As per this article Why is my WPF Popup black and how do I get it positioned properly? :
You need to set the AllowsTransparency property on the Popup to True, and set the PlacementTarget and Placement properties to control the position the Popup opens in.

As per the code in question:

<Popup PlacementTarget="{Binding ElementName=parentStackPanel}" Placement="Center" IsOpen="False" Name="m_popWaitNotifier" PopupAnimation="None" AllowsTransparency="False">
    <StackPanel Orientation="Vertical" Background="Transparent">
       <uc:CircularProgressBar x:Name="CB" StartupDelay="0" RotationsPerMinute="20" Height="25" Foreground="White" Margin="12"/>
    </StackPanel>
</Popup>

the PlacementTarget is set to parentStackPanel, whereas the questioner has mentioned:

Hi Svetlozar: I tried this but it does not work. For me though I do not have a StackPanel outside the Popup, but I have a StackPanel within the Popup that holds a couple of control on it

The problem could be that Popup could not find the PlacementTarget 'parentStackPanel' because it does not exist.

The problem is that the grid is not orientation places it outside of the popup. Remove VerticalAlignment and horizontalAlignment from all the controls inside the popup, and it will work correctly

Quite old, but may help someone: Add InitializeComponent(); in the constructor, it solved my problem:

class MyPopupClass : Popup {
    /*
    ...
    */
    public MyPopupClass () {
        InitializeComponent();
        /*
        ...
        */
    }
    /*
    ...
    */
}