Question

我的内容页面中有一个工具栏，其中有一个名为add的项目，点击添加后我想打开DisplayActionSheet

我在ContentPage中创建了Toolbar xaml，并在视图模型中将ICommand附加到DisplayActionSheet。现在<ContentPage.ToolbarItems> <ToolbarItem Name="" Icon="ic_add.png" Order="Primary" Priority="0" Command="{Binding OnAddContactCommand}"/> <ToolbarItem Name="" Icon="ic_search.png" Order="Primary" Priority="1" Command="{Binding OnContactSearchCommand}" /> </ContentPage.ToolbarItems>只能在View中访问，因此我不确定如何访问它并从视图模型中呈现它。

xaml文件

public ICommand OnContactSearchCommand => new Command(OnContactSearch);
public ICommand OnAddContactCommand => new Command(OnAddContactSearch);

查看模型

private async void OnAddContactSearch()
{   
   //var action = await DisplayActionSheet(AppResources.select_contact_source, AppResources.cancel, null, AppResources.manual, AppResources.phonebook);
}

private void OnContactSearch()
{
   Debug.WriteLine("OnContactSearch");
}

活动

$html->find("tr[class='zzz'], tr[class='sss']"); 
foreach($items as $post) {
  echo $post->children(1)->children(0)->src;
}

Answer 1

尝试

Application.Current.MainPage.DisplayActionSheet();

Answer 2

与@Alessandro一样，Application.Current.MainPage也适用于行动表和警报。为了隐藏视图模型中的视图特定内容，我创建了一个IMessageBoxService，它被注入到需要它的视图模型的构造器中。请注意，我使用的是Autofac IoC container。对于Xamarin的DependencyService，您可以更改构造函数并在代码中查找服务。

<强> IMessageBoxService.cs

public interface IMessageBoxService
{
    void ShowAlert(string title, string message, Action onClosed = null);
    // ...
    Task<string> ShowActionSheet(string title, string cancel, string destruction, string[] buttons = null);
}

<强> MessageBoxService.cs

public class MessageBoxService : IMessageBoxService
{
    private static Page CurrentMainPage { get { return Application.Current.MainPage; } }

    public async void ShowAlert(string title, string message, Action onClosed = null)
    {
        await CurrentMainPage.DisplayAlert(title, message, TextResources.ButtonOK);
        onClosed?.Invoke();
    }

    public async Task<string> ShowActionSheet(string title, string cancel, string destruction = null, string[] buttons = null)
    {
        var displayButtons = buttons ?? new string[] { };
        var action = await CurrentMainPage.DisplayActionSheet(title, cancel, destruction, displayButtons);
        return action;
    }
}

<强> AppSetup.cs

    protected void RegisterDependencies(ContainerBuilder cb)
    {
        // ...
        cb.RegisterType<MessageBoxService>().As<IMessageBoxService>().SingleInstance();
    }

<强>用法

public class EditProductViewModel : AddProductViewModel
{
    private IMessageBoxService _messageBoxService;

    public ICommand DeleteCommand { get; set; }

    public EditProductViewModel(IPageNavigator navigator, IMessenger messenger,
        IMessageBoxService messageBoxService, TagDataStore tagDataStore) : base(navigator, messenger, tagDataStore)
    {
        _messageBoxService = messageBoxService;
        DeleteCommand = new Command(DeleteItem);
    }

...

    private async void DeleteItem()
    {
        var action = await _messageBoxService.ShowActionSheet(TextResources.MenuTitleDeleteProduct,
            TextResources.ButtonCancel, TextResources.ButtonDelete);
        if (action == TextResources.ButtonDelete)
        { } // delete

如果您正在进行viewmodel首次导航（s。Xamarin或Jonathan Yates' blog），您可以选择将此部分作为导航器服务。这是一个品味问题

从视图模型访问并打开DisplayActionSheet

2 个答案: