Menu
The Menu control adds a top-level menu to an application. A Menu is usually placed in a DockPanel in a Window, docked to the top of the window:
<Window xmlns="https://github.com/avaloniaui"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<DockPanel>
<Menu DockPanel.Dock="Top">
<MenuItem Header="_File">
<MenuItem Header="_Open..."/>
<Separator/>
<MenuItem Header="_Exit"/>
</MenuItem>
<MenuItem Header="_Edit">
<MenuItem Header="Copy"/>
<MenuItem Header="Paste"/>
</MenuItem>
</Menu>
</DockPanel>
</Window>
A menu will usually contain a set of nested MenuItems. The first level of MenuItems represent the items that will be displayed horizontally along the menu. The second level of MenuItems represent the menu items that will be dropped down from the top-level and subsequent nested MenuItems represent sub-menus.
The text of the MenuItem is displayed by the Header property; the inner content of the MenuItem is where the sub-items are placed.
Separators are added by including a Separator control or a MenuItem with a header of "-".
Accelerator Keys
An accelerator key is a key on your keyboard that you can press to quickly access a menu. It is also sometimes called a hot key, access key or mnemonic.
If you will press Alt with the example above you will see that some letters are underlined. You can use a combination of Alt + underlined letter to navigate within a menu. In Avalonia to identify the accelerator key, you will need to use _ next character to this character would be an accelerator key.
Menu Commands
Like Button, commands can be bound to MenuItems. The command will be executed when the menu item is clicked or selected with the keyboard:
<Menu>
<MenuItem Header="_File">
<MenuItem Header="_Open..." Command="{Binding OpenCommand}"/>
</MenuItem>
</Menu>
See the Binding to Commands section for more information on binding to commands.
Menu Icons
A menu icon can be displayed by placing an Image in the Icon property:
<MenuItem Header="_Open...">
<MenuItem.Icon>
<Image Source="resm:MyApp.Assets.Open.png"/>
</MenuItem.Icon>
</MenuItem>
Checkboxes
Similarly, a CheckBox can be displayed in the Icon property to make the MenuItem checkable:
<MenuItem Header="_Open...">
<MenuItem.Icon>
<CheckBox BorderThickness="0"
IsHitTestVisible="False"
Command="{Binding ToggleCommand}">
Toggle _Me
</CheckBox>
</MenuItem.Icon>
</MenuItem>
Dynamically Creating Menus
Menus can also be dynamically created using bindings and DataTemplates. To do this, you will usually create a view model to represent your Window with a set of commands relating to the menu commands:
public class MainWindowViewModel
{
public MainWindowViewModel()
{
OpenCommand = ReactiveCommand.CreateFromTask(Open);
SaveCommand = ReactiveCommand.Create(Save);
OpenRecentCommand = ReactiveCommand.Create<string>(OpenRecent);
}
public IReadOnlyList<MenuItemViewModel> MenuItems { get; set; }
public ReactiveCommand<Unit, Unit> OpenCommand { get; }
public ReactiveCommand<Unit, Unit> SaveCommand { get; }
public ReactiveCommand<string, Unit> OpenRecentCommand { get; }
public async Task Open()
{
var dialog = new OpenFileDialog();
var result = await dialog.ShowAsync();
if (result != null)
{
foreach (var path in result)
{
System.Diagnostics.Debug.WriteLine($"Opened: {path}");
}
}
}
public void Save()
{
System.Diagnostics.Debug.WriteLine("Save");
}
public void OpenRecent(string path)
{
System.Diagnostics.Debug.WriteLine($"Open recent: {path}");
}
}
And a view model for the menu items
public class MenuItemViewModel
{
public string Header { get; set; }
public ICommand Command { get; set; }
public object CommandParameter { get; set; }
public IList<MenuItemViewModel> Items { get; set; }
}
Next, you can create your menu structure using the view models. The following code when placed in a Window constructor will create a basic menu structure and assign it to the Window's DataContext.
public MainWindow()
{
InitializeComponent();
var vm = new MainWindowViewModel();
vm.MenuItems = new[]
{
new MenuItemViewModel
{
Header = "_File",
Items = new[]
{
new MenuItemViewModel { Header = "_Open...", Command = vm.OpenCommand },
new MenuItemViewModel { Header = "Save", Command = vm.SaveCommand },
new MenuItemViewModel { Header = "-" },
new MenuItemViewModel
{
Header = "Recent",
Items = new[]
{
new MenuItemViewModel
{
Header = "File1.txt",
Command = vm.OpenRecentCommand,
CommandParameter = @"c:\foo\File1.txt"
},
new MenuItemViewModel
{
Header = "File2.txt",
Command = vm.OpenRecentCommand,
CommandParameter = @"c:\foo\File2.txt"
},
}
},
}
},
new MenuItemViewModel
{
Header = "_Edit",
Items = new[]
{
new MenuItemViewModel { Header = "_Copy" },
new MenuItemViewModel { Header = "_Paste" },
}
}
};
DataContext = vm;
}
Finally assign the bindings to the view model in a Style within the menu:
<Menu Items="{Binding MenuItems}">
<Menu.Styles>
<Style Selector="MenuItem">
<Setter Property="Header" Value="{Binding Header}"/>
<Setter Property="Items" Value="{Binding Items}"/>
<Setter Property="Command" Value="{Binding Command}"/>
<Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
</Style>
</Menu.Styles>
</Menu>