Xamarin.forms: [Spec] ContextMenu

[samhouts]

Related to CollectionView

ContextItem

ContextItem provides a way to specify a contextual interaction, often displayed as part of a context menu.

public class ContextItem
{
    public static readonly BindableProperty TextProperty;
    public string Text { get; set; }

    public static readonly BindableProperty CommandProperty;
    public ICommand Command { get; set; }

    public static readonly BindableProperty CommandParameterProperty;
    public object CommandParameter { get; set; }

    public static readonly BindableProperty IsEnabledProperty;
    public bool IsEnabled { get; set; }

    public static readonly BindableProperty IconProperty;
    public ImageSource Icon { get; set; }

    public event EventHandler Invoked;
}

Properties

| API | Description |
| ------------- | ------------- |
| Text | Gets or sets the text description displayed on the item. |
| Command | Gets or sets the command to execute when this item is invoked. |
| CommandParameter | |
| IsEnabled | Gets or sets a value indicating whether the user can interact with the context item. |
| Icon | Gets or sets the graphic content of the item. |

Events

| API | Description |
| ------------- | ------------- |
| Invoked | Occurs when user interaction indicates that the command represented by this item should execute. |

ContextMenu

Provides a way to specify a set of interactions to be displayed in a context menu. A ContextMenu can be provided for any VisualElement, and is activated/displayed according to the native platform conventions.

public static class ContextMenu
{
    public static readonly BindableProperty MenuItemsProperty =
            BindableProperty.CreateAttached("MenuItems", typeof(ContextMenuItems), typeof(VisualElement));
}


public class ContextMenuItems : IList<ContextItem>
{
}

[powerdude]

could IsVisible be added to the spec?

[samhouts]

@powerdude On ContextItem, right?

[powerdude]

@samhouts yes, sorry for missing that detail. I think wherever there is IsEnabled, there should also be an IsVisible.

[samhouts]

@hartez Any reason we shouldn't include IsVisible?

[hartez]

@powerdude Could you elaborate on that? What's a situation where you would want to have an invisible context item?

[powerdude]

@hartez in general, need the flexibility to hide a menu item in the case a user gains/loses access to feature while the app is running without having to rebuild the context menu. Same philosophy that would be used for toolbar items. From a view model, I should be able to hide an item so a user never sees it until the right conditions are met and also change the enabled stated based on a different set of conditions. Visibility is normally used for authorization scenarios and the enabled state is used to control command process.

[hartez]

@powerdude @samhouts That seems pretty reasonable. At the moment I can't see any reason not to include IsVisible.

[adrianknight89]

@samhouts @hartez Is there a specific reason why we are creating a new class ContextMenuItems instead of directly using IList<ContextItem> in the bindable property type for MenuItemsProperty?

[adrianknight89]

Also, have you thought about nested context menus, inline menus, and destructive context items?

[Bosch-Eli-Black]

As @adrianknight89 mentioned, I wonder if we wouldn't be better off reusing an existing class, such as MenuItem, for this? Maybe not; I'm not super familiar with the Xamarin.Forms internals.

Also, I agree with @powerdude that it would be nice to have an IsVisible property. I'm guessing that if the context menu is already open and a context menu item's IsVisible property changes, then that item probably wouldn't be hidden/shown until after the user right clicked again, which I think is fine :)