CommandBar

The CommandBar in Uno is designed to be used the same way you would use the CommandBar on WinUI. In most cases, you should refer to the official CommandBar documentation.

This document exists to highlight some of the differences you might encounter when working with the native mode of CommandBar on either iOS or Android.

Modes

The CommandBar supports 2 different modes:

Mode	Style
Windows	XamlDefaultCommandBar
Native	NativeDefaultCommandBar

Windows

This mode replicates WinUI's CommandBar. It is templatable and supports a template that's almost identical to WinUI's default CommandBar.

Usage Example

<Style TargetType="CommandBar" BasedOn="{StaticResource XamlDefaultCommandBar}" />

Remarks

• This mode hasn't been extensively tested.
• We usually avoid using this mode, and prefer to use the Native one instead.

Native

This mode is the preferred one and is enabled by default. It uses platform-specific controls to ensure a more native user experience.

Platform	Native control	Benefits
Android	Toolbar	Native pressed states (ripple), native overflow menu.
iOS	UINavigationBar	Transitions when navigating between pages.

The rest of this document will exclusively cover this mode.

Usage Example

<Style TargetType="CommandBar" BasedOn="{StaticResource NativeDefaultCommandBar}" />

Remarks

In this mode, the CommandBar can't be fully customized like other templatable controls would. Additionally, you can't customize the visual states of either the CommandBar or its AppBarButtons.

Padding

You must use VisibleBoundsPadding.PaddingMask="Top" on CommandBar to properly support the notch or punch-holes on iOS and Android.

Back button

An important difference with this mode is the presence of a back button. Whenever the CommandBar is part of a Page whose Frame has a non-empty back stack, the back button will be displayed.

On Android, tapping the back button triggers SystemNavigationManager.BackRequested. It's the responsibility of the application's navigation controller to eventually call Frame.GoBack().

On iOS, tapping the back button automatically triggers a back navigation on the native UINavigationController (which is part of the native Frame implementation). The Frame will raise the Navigated event, and its state will automatically be updated to reflect the navigation. The navigation can't be intercepted or canceled. To intercept back navigation, you must replace the native back button with your own custom button using NavigationCommand (see below).

Properties

Property	Windows	iOS	Android	Comments
Background	x	x	x
Content	x	x	x
Foreground	x	x	x
Height	x	-	-	iOS and Android: Fixed and can't be changed.
HorizontalAlignment	x	-	x	iOS: Always use HorizontalAlignment.Stretch.
Opacity	x	x	x
Padding	x	x	x	iOS and Android: Please refer to the Padding section.
PrimaryCommands	x	x	x
SecondaryCommands	x	-	x	iOS: Not supported.
VerticalAlignment	x	-	x	iOS: Always use VerticalAlignment.Top.
Visibility	x	x	x
Width	x	-	x	iOS: Always use double.NaN.
HorizontalContentAlignment	x	-	x	Android: Stretch and Left are supported. Windows: Set IsDynamicOverflowEnabled="False" for proper behavior.
VerticalContentAlignment	x	-	-	Only supported on Windows. Android: Alignment needs to be done through the content itself.

If it's not listed, assume it's not supported.

Background

Gets or sets a brush that describes the background of a control.

Remarks

• Only supports SolidColorBrush.
• Changing the opacity through SolidColorBrush.Opacity is supported.

Content

Gets or sets the content of a ContentControl.

Remarks

The Content is processed differently whether it's of type string or FrameworkElement.

When Content is a string, it's displayed using the platform's default font family, font size, font style and text alignment. Only the foreground color can be changed, using Foreground.

Platform	FontFamily	FontSize	HorizontalAlignment
iOS	San Francisco	17	Center
Android	Roboto	20	Left

When Content is a FrameworkElement, it's displayed within the available area:

Platform	Available height
iOS	30px
Android	48px

Please note that:

• HorizontalContentAlignment and VerticalContentAlignment are ignored.
• On iOS, the Content is automatically centered horizontally unless HorizontalAlignment.Stretch is used.

Foreground

Gets or sets a brush that describes the foreground color.

Remarks

• This is typically used to change the Content`'s text color.
• Only supports SolidColorBrush.
• Setting this property will not affect any of the CommandBar's AppBarButton tint Color. If you need to change the AppBarButton tint, this is possible by setting the ShowAsMonochrome property to true as well as setting the ForegroundSolidColorBrushon theBitmapIcon.
• OnAndroid, you can also enable a feature that will allow that theSolidColorBrushset on your CommandBar Foreground to update yourAppBarButtons Tint. To enable this, set on your App.xml.cs the FeatureConfiguration.AppBarButton.EnableBitmapIconTint to true.

PrimaryCommands

Gets the collection of primary command elements for the CommandBar.

Remarks

• Only supports AppBarButton. AppBarToggleButton and AppBarSeparator are not supported.
• Refer to the AppBarButton section for details.

SecondaryCommands

Gets the collection of secondary command elements for the CommandBar.

Remarks

• Only supported on Android.

Height

Gets or sets the suggested height of a FrameworkElement.

Remarks

The height is fixed and cannot be changed.

Platform	Form factor	Portrait	Landscape
iOS	Phone	44pt	44pt
iOS	Tablet	44pt	44pt
Android	Phone	48dp	56dp
Android	Tablet	64dp	64dp

Source (Android)

Extensions

Extensions are attached properties that extend the UWP APIs to provide platform-specific features.

They can be found in the Uno.UI.Toolkit namespace.

Extensions to extend the functionality of CommandBar can be found in the CommandBarExtensions class.

Attached Property	Windows	iOS	Android	Comments
BackButtonForeground	-	x	x
BackButtonIcon	-	x	x
BackButtonTitle	-	x	x
NavigationCommand	-	x	x
Subtitle	-	-	x

BackButtonForeground

Gets or sets the back button foreground for the CommandBar.

Remarks

• Only supports SolidColorBrush.

BackButtonIcon

Gets or sets the back button icon for the CommandBar.

Remarks

• Only supports BitmapIcon.

BackButtonTitle

Gets or sets the back button title for the CommandBar.

Remarks

Only supported on iOS.

On iOS, the back button displays the title of the previous page (which we usually set as string on Content). When the title of the previous page is too long (over 140px wide on iPhone 5) or isn't set (for example, if we set FrameworkElement instead of string on Content), "Back" will be displayed instead.

To explicitly provide a value to be used by the back button of the next page, use BackButtonTitle.

To remove the back button title from all pages (and only leave the back arrow), set BackButtonTitle to "" in the default CommandBar style.

WARNING: The name of this property can be misleading, and doesn't actually let you change the title of the back button displayed on the given CommandBar. Read above for recommended usage.

Elevation

Gets or sets the elevation of the UIElement.

Remarks

• This is usually only used on Android.
• According to Google's Material Design Guidelines, the recommended elevation for CommandBar is 8.

NavigationCommand

Gets or sets the navigation command for the CommandBar.

Remarks

Unlike the PrimaryCommands or SecondaryCommands, which appear to the right of the CommandBar, the NavigationCommand appears to the left of the CommandBar.

This is typically used for burger menus.

On iOS, the back gesture can be enabled or disabled using this property.

• When a CommandBar (visible or collapsed) is in the visual tree, the back gesture is enabled.
• When a CommandBar has a NavigationCommand, the back gesture is disabled.

On Android, only icons are supported (AppBarButton.Icon). This is due to a platform limitation, which can be explained by the fact that CommandBar.Content is left-aligned.

Subtitle (Android)

Gets or sets the subtitle for the CommandBar.

Remarks

• The subtitle is displayed below the native title (Content of type string).
• The color of the subtitle currently can't be changed.

Placement

On iOS, the same UINavigationBar instance is shared throughout all pages. When navigating between two pages, you can see that the UINavigationBar doesn't move, and only its content and the pages have a transition. To get the same effect while still letting you use CommandBar as you would on UWP (as part of the Page), we have to do some magic. Namely, the CommandBar you define inside your Page is never actually rendered there, and only serves as a placeholder from which to read the information we need to pass to the shared UINavigationBar instance.

To ensure everything works properly, you must follow a few rules:

• The CommandBar must stretch horizontally and be aligned with the top of your Page.
• The CommandBar can't move (i.e., don't put it inside a ScrollViewer)
• The CommandBar must be accessible as soon as the page is being navigated to (i.e., don't put it inside a DataTemplate or an AsyncValuePresenter).
• There can only be one CommandBar per page.

Extensibility

The CommandBar it automatically managed by the Frame control, however you can still use the "native" mode of the CommandBar with your own navigation mechanism.

On iOS a CommandBarHelper is available for this purpose, you only have to invoke each of the provided method in your own UIViewController implementation.

AppBarButton

The AppBarButton in Uno is designed to be used the same way you would use the AppBarButton on UWP. In most cases, you should refer to the official CommandBar documentation.

When AppBarButton is used within a native CommandBar, its control template is completely ignored and can't be customized.

Events

Event	Windows	iOS	Android	Comments
Clicked	x	x	x

Properties

Property	Windows	iOS	Android	Comments
Command	x	x	x
Content	x	x*	x*	Supports string and FrameworkElement.
Foreground	x	x	x*	Android: See details below.
Icon	x	x*	x*	Only supports BitmapIcon.
IsEnabled	x	x	x*	Android: Not supported with Content.
Label	x	x*	x*	See details below.
Opacity	x	x	x
Visibility	x	x	x

If it's not listed, assume it's not supported.

Foreground

Gets or sets a brush that describes the foreground color.

Remarks

• This changes the color of the Content (text) or Icon.
• Only supports SolidColorBrush.
• On Android, this only affects the color of Icon, not Content (text).
• On iOS, the default value is blue.

Content

Gets or sets the content of a ContentControl.

Remarks

• When given a string, its text will be displayed instead of the icon.
• When given a FrameworkElement:
  • it will be displayed instead of the icon
  • the native pressed state and tooltip (Android only) won't work
• Make sure to set Icon to null, as it takes priority over Content.

Icon

Gets or sets the graphic content of the app bar button.

Remarks

• Only supports BitmapIcon (with PNG).

Recommended icon sizes (by scale)

Platform	100%	150%	200%	300%	400%
iOS	25x25	-	50x50	75x75	-
Android	24x24	36x36	48x48	72x72	96x96
Windows	32x32	48x48	64x64	96x96	128x128

Label

Gets or sets the text description displayed on the app bar button.

Remarks

Unlike on UWP, the Label will not be displayed below the Icon.

It is only displayed on Android when the AppBarButton is displayed from the overflow (when part of SecondaryCommands)

It is highly recommended to set and localize Label on all AppBarButtons, if only for accessibility.

IsEnabled

Gets or sets a value indicating whether the user can interact with the control.

Remarks

• When set to false, buttons are disabled and grayed out (semi-transparent).
• You can't customize the disabled visual state of buttons.
• On Android, the disabled visual state only works with Icon and not with Content (text).

Known issues

iOS

• Can't have multiple CommandBars in the same page (e.g., Master/Details, bottom CommandBar).
• Can't change the title of the back button if the previous page doesn't have a CommandBar.
• You must define the title of the back button of the current page's CommandBar in the CommandBar of the previous page.
• Can't have a smooth transition between pages with different CommandBar backgrounds.
• Can't have a smooth transition between pages with and without a CommandBar.
• Can't change the position and size of the CommandBar (always top-aligned, horizontally-stretched, height of 44).
• Can't remove the 1px underline/shadow without making the CommandBar's background transparent.
• Can't change the height of the CommandBar.
• Can't use the back gesture on pages without a CommandBar.
• Can't disable the back gesture without using workarounds (fake back buttons).
• Can't change the Visibility of a CommandBar.
• Can't change the Opacity of a CommandBar.
• Can't superpose views over a CommandBar.
• Can't animate/translate the CommandBar (i.e., when hiding/showing it based on scroll offset).
• Can't put your CommandBar inside a ScrollViewer and make it scroll.
• Can't put your CommandBar inside templates (i.e., AVP).
• Can't cancel a back navigation using BackRequestedEventArgs.Handled.

FAQ: CommandBar

• Why is my content underneath the CommandBar for iOS and the CommandBar underneath the StatusBar/Notch for Android ?

  You must use VisibleBoundsPadding.PaddingMask="Top" on CommandBar to properly support the notch or punch-holes on iOS and Android.

  xmlns:toolkit="using:Uno.UI.Toolkit"
  ...
  <Style Target="CommandBar">
      <Setter Property="toolkit:VisibleBoundsPadding.PaddingMask"
              Value="Top" />
  </Style>
  

• How can I remove the back button title from all pages on iOS?

  xmlns:toolkit="using:Uno.UI.Toolkit"
  ...
  <Style Target="CommandBar">
      <Setter Property="toolkit:CommandBarExtensions.BackButtonTitle"
              Value="" />
  </Style>
  

• How can I change the back button icon/arrow/chevron in my app?

  xmlns:toolkit="using:Uno.UI.Toolkit"
  ...
  <Style Target="CommandBar">
      <Setter Property="toolkit:CommandBarExtensions.BackButtonIcon">
          <Setter.Value>
              <BitmapIcon UriSource="ms-appx://Assets/back.png" />
          </Setter.Value>
      </Setter>
  </Style>
  

• How can I change the color of the back button?

  xmlns:toolkit="using:Uno.UI.Toolkit"
  ...
  <CommandBar toolkit:CommandBarExtensions.BackButtonForeground="Red" />
  

• Why does my back button display "Back" on iOS?

  The back button will display "Back" if:

  • The previous page doesn't have a CommandBar.
  • The previous page's CommandBar doesn't have a Content of type string.
  • The previous page's CommandBar doesn't have a CommandBarExtensions.BackButtonTitle.
  • The previous page's CommandBar has a title that's too long (more than 140pt).

• Why can't I overlap content over the CommandBar on iOS?

  The CommandBar is not actually part of the Page on iOS, and you can't overlap content over it like you would on UWP or Android. Please refer to the Placement section for details.

• Why doesn't my CommandBar show a back button?

  For a CommandBar to show a back button, it must first be resolved by Frame as soon as it navigates to a Page. To ensure that CommandBar is available as soon as the navigation starts, make sure it's directly part of a page, and not part of a DataTemplate or ControlTemplate.

• Why don't my AppBarButton visual states work?

  You can't customize the ControlTemplate of AppBarButton when using CommandBar in native mode.

• How can I change the foreground of the CommandBarExtensions.Subtitle on Android?

  You can't currently customize the foreground of the CommandBarExtensions.Subtitle on Android.

• Why doesn't CommandBarExtensions.Subtitle work on iOS?

  CommandBarExtensions.Subtitle is not currently implemented on iOS.

  You can replicate the same effect by setting a custom Content on CommandBar:

  <CommandBar>
      <CommandBar.Content>
          <StackPanel HorizontalAlignment="Center">
              <TextBlock Text="Title"
                         HorizontalAlignment="Center"
                         FontSize="15" />
              <TextBlock Text="Subtitle"
                         HorizontalAlignment="Center"
                         FontSize="12"
                         Opacity="0.5" />
          </StackPanel>
      </CommandBar.Content>
  </CommandBar>
  

• How can I add a badge to an AppBarButton?

  You can implement your own badge by setting a custom content on AppBarButton:

  <AppBarButton>
      <AppBarButton.Content>
          <Grid Height="48"
                Width="48">
              <Image Source="ms-appx:///Assets/Icons/cart.png"
                     VerticalAlignment="Center"
                     HorizontalAlignment="Center" />
              <Border x:Name="Badge"
                      VerticalAlignment="Top"
                      HorizontalAlignment="Right"
                      Background="Red"
                      Margin="8,4"
                      Padding="4,0"
                      MinWidth="16"
                      Height="16"
                      CornerRadius="8">
                  <TextBlock x:Name="Count"
                             HorizontalAlignment="Center"
                             VerticalAlignment="Center"
                             Foreground="White"
                             FontSize="8"
                             Text="0" />
              </Border>
          </Grid>
      </AppBarButton.Content>
  </AppBarButton>
  

• How can I set custom content to an AppBarButton?

  You can set a custom content to an AppBarButton like this:

  <AppBarButton>
      <AppBarButton.Content>
          <TextBlock Text="Custom content goes here" />
      </AppBarButton.Content>
  </AppBarButton>
  

• Why does my CommandBar always appear at the top of the page on iOS?

  You can't place your CommandBar anywhere other than at the top of the Page on iOS. See the Placement section for details.

• How can I change the height of my CommandBar?

  You can't currently change the height of the CommandBar.

• How can I remove the 1px line displayed below the CommandBar on iOS?

  To hide the native 1px shadow that's displayed below the CommandBar on iOS, make its background transparent:

  <CommandBar Background="Transparent" />
  

• How can I add an elevation shadow to the CommandBar on Android?

  xmlns:toolkit="using:Uno.UI.Toolkit"
  ...
  <CommandBar toolkit:UIElementExtensions.Elevation="4" />
  

• How can I use a Path for the AppBarButton Icon?

  AppBarButton doesn't currently support PathIcon. Only BitmapIcon with PNGs is supported. Please refer to the Icon section.

• Why doesn't CommandBarExtensions.BackButtonTitle change the title of my back button?

  CommandBarExtensions.BackButtonTitle must be set on the page to which the back button navigates to. Please refer to the BackButtonTitle section.

• Why doesn't my CommandBarExtensions.NavigationCommand display anything on Android?

  CommandBarExtensions.NavigationCommand only supports AppBarButton with Icon (not Content). Please refer to the NavigationCommand section.

• How can I localize CommandBarExtensions.BackButtonTitle?

  For attached properties, you need a special syntax in the Name column of a .resw file. Ref: Microsoft documentation.

  More specifically :

  
  <CommandBar x:Uid="MyCommandBar"
              toolkit:CommandBarExtensions.BackButtonTitle="My Page Title">
          ...
  </CommandBar>
  

  And in the .resw file, the name would be: MyCommandBar.[using:Uno.UI.Toolkit]CommandBarExtensions.BackButtonTitle

• How can I put a ComboBox in my CommandBar?

  <CommandBar>
      <CommandBar.Content>
          <ComboBox />
      </CommandBar.Content>
  </CommandBar>
  

• How can I customize the pressed/disabled visual states of my AppBarButton?

  You can't currently customize the visual states of AppBarButton when using CommandBar in native mode.

• Why doesn't the disabled state work on my AppBarButton on Android?

  AppBarButton doesn't currently support the disabled state when used with Content (of string) on Android. You can use an Icon instead.

• How can I disable the back swipe/gesture on iOS?

  To disable the back swipe/gesture on iOS, you must remove the CommandBar or replace the back button with a custom one:

  <CommandBar>
      <toolkit:CommandBarExtensions.NavigationCommand>
          <AppBarButton Command="{Binding GoBack}">
              <AppBarButton.Icon>
                  <BitmapIcon UriSource="ms-appx:///Assets/Icons/back.png" />
              </AppBarButton.Icon>
          </AppBarButton>
      </toolkit:CommandBarExtensions.NavigationCommand>
  </CommandBar>
  

• How can I display two CommandBars side by side on iOS (i.e., master-detail)

  Page only supports a single CommandBar at a time. To display two CommandBars side by side (i.e., master-detail), you should place two Frames side by side and put a CommandBar in the Page of each Frame.

• How can I add a burger menu to the left of my CommandBar?

  <CommandBar>
      <toolkit:CommandBarExtensions.NavigationCommand>
          <AppBarButton Command="{Binding ToggleMenu}">
              <AppBarButton.Icon>
                  <BitmapIcon UriSource="ms-appx:///Assets/Icons/menu.png" />
              </AppBarButton.Icon>
          </AppBarButton>
      </toolkit:CommandBarExtensions.NavigationCommand>
  </CommandBar>
  

• Why doesn't Flyout work on my AppBarButton?

  AppBarButton doesn't currently support Flyout when using CommandBar in native mode. You can use MenuFlyout instead.

• Why can't I change the Foreground of my AppBarButton on Android?

  AppBarButton doesn't currently support Foreground when displaying text (using Content of string).

  However, you can change the color of all textual AppBarButtons globally using Android styles:

  Colors.xml

  <color name="red">#FFFF0000</color>
  

  Styles.xml

  <item name="android:actionMenuTextColor">@color/red</item>
  <item name="actionMenuTextColor">@color/red</item>
  

  If you need the button to display a different color to reflect being in a disabled state, you can add a selector in its own file, under res/color, like so:

  PrimaryTextColorSelector.xml

  <?xml version="1.0" encoding="utf-8"?>
  <selector xmlns:android="http://schemas.android.com/apk/res/android" >
      <item android:state_enabled="false" android:color="#88888888"/>
      <item android:color="#FF00FFFF"/>
  </selector>
  

  Styles.xml

  <item name="android:actionMenuTextColor">@color/PrimaryTextColorSelector</item>
  <item name="actionMenuTextColor">@color/PrimaryTextColorSelector</item>
  

• How can I customize the font of the CommandBar title/content?

  You can't currently customize the font of the native CommandBar title (set with a string on Content). Only the color can be changed, using the Foreground property.

  To customize the font of the CommandBar's title, you must set a custom FrameworkElement as the Content of your CommandBar:

  <CommandBar>
      <CommandBar.Content>
          <TextBlock Text="Title"
                     FontStyle="Italic"
                     FontWeight="Bold"
                     FontSize="30" />
      </CommandBar.Content>
  </CommandBar>
  

• Why doesn't my CommandBar scroll when placed inside a ScrollViewer on iOS?

  CommandBar can't be placed inside a ScrollViewer. It must be anchored to the top of your Page at all time. Please refer to the Placement section for details.

• How can I change the color of the ripple effect when pressing on AppBarButtons on Android?

  You can change the color of the ripple effect globally using Android styles:

  Colors.xml

  <!-- https://android.googlesource.com/platform/frameworks/support/+/415f740/v7/appcompat/res/values/colors_material.xml -->
  <color name="ripple_material_light">#20444444</color>
  <color name="ripple_material_dark">#20ffffff</color>
  

  Styles.xml

  <item name="colorControlHighlight">@color/ripple_material_dark</item>
  

• Why doesn't my AppBarToggleButton work?

  AppBarToggleButton is not currently supported.

  To implement a similar effect, you can bind your AppBarButton's icon to a state using a converter:

  <CommandBar>
      <AppBarButton Command="{Binding ToggleIsFavorite}">
          <AppBarButton.Icon>
              <BitmapIcon UriSource="{Binding IsFavorite, Converter={StaticResource IsFavoriteToStarIcon}}" />
          </AppBarButton.Icon>
      </AppBarButton>
  </CommandBar>
  

• How can I show an image under my CommandBar?

  You can show an image under a CommandBar by making its background transparent and superposing it over an Image:

  <Grid>
      <Image Source="http://www.example.com/image.png">
      <CommandBar Background="Transparent"
                  VerticalAlignment="Top" />
  </Grid>
  

  

• What size should my AppBarButton icons be?

  Please refer to the Icon section for details.

• Why does my back button icon change when swiping back on iOS?

  This can happen when navigating between two pages with CommandBars using different CommandBarExtensions.BackButtonIcons.

  To avoid this issue, please make sure that all CommandBars use the same CommandBarExtensions.BackButtonIcon by using a style:

  <Style Target="CommandBar">
      <Setter Property="toolkit:CommandBarExtensions.BackButtonIcon">
          <Setter.Value>
              <BitmapIcon UriSource="ms-appx:///Assets/Icons/back.png" />
          </Setter.Value>
      </Setter>
  </Style>
  

  If the issue still occurs, make sure that both pages have a CommandBar. If you don't want your page to display a CommandBar, you can simply collapse it:

  <CommandBar Visibility="Collapsed" />