如何使ViewCell的Tapped事件向通用函数发送一个参数,然后为该ViewCell元素打开一个选择器？

Question

更新: 提醒一下,如果有人可以告诉我如何在不使用手势的情况下实现此功能,那么就有500点奖金>

我正在使用ViewCell和手势识别器打开一个带有以下代码的选择器.ViewCell左侧有一个标签,右侧有一个标签区域,最初在应用程序启动时填充,稍后在单击ViewCell时使用选择器填充.

XAML

<ViewCell x:Name="ati" Tapped="OpenPickerCommand">
   <Grid VerticalOptions="CenterAndExpand" Padding="20, 0">
      <Grid.GestureRecognizers>
         <TapGestureRecognizer 
             Command="{Binding OpenPickerCommand}" 
             CommandParameter="{x:Reference atiPicker}" NumberOfTapsRequired="1" />
      </Grid.GestureRecognizers>
      <local:LabelBodyRendererClass Text="Answer Time Interval" HorizontalOptions="StartAndExpand" />
      <Picker x:Name="atiPicker" IsVisible="false" HorizontalOptions="End" SelectedIndexChanged="atiPickerSelectedIndexChanged" ItemsSource="{Binding Times}"></Picker>
      <local:LabelBodyRendererClass x:Name="atiLabel" HorizontalOptions="End"/>
   </Grid>
</ViewCell>

<ViewCell x:Name="pti" Tapped="OpenPickerCommand">
   <Grid VerticalOptions="CenterAndExpand" Padding="20, 0">
      <Grid.GestureRecognizers>
         <TapGestureRecognizer 
             Command="{Binding OpenPickerCommand}" 
             CommandParameter="{x:Reference ptiPicker}" NumberOfTapsRequired="1" />
      </Grid.GestureRecognizers>
      <local:LabelBodyRendererClass Text="Phrase Time Interval" HorizontalOptions="StartAndExpand" />
      <Picker x:Name="ptiPicker" IsVisible="false" HorizontalOptions="End" SelectedIndexChanged="ptiPickerSelectedIndexChanged" ItemsSource="{Binding Times}"></Picker>
      <local:LabelBodyRendererClass x:Name="ptiLabel" HorizontalOptions="End"/>
   </Grid>
</ViewCell>

C#这适用于使用CommandParameter的不同选择器(ati,bti,pti等)

public SettingsPage()
{
   InitializeComponent();
   BindingContext = new CommandViewModel();
}

void atiPickerSelectedIndexChanged(object sender, EventArgs e)
    {
        var picker = (Picker)sender;
        int selectedIndex = picker.SelectedIndex;
        if (selectedIndex != -1)
        {
            App.DB.UpdateIntSetting(Settings.Ati, selectedIndex);
            atiLabel.Text = AS.ati.Text();
        }
    }

void ptiPickerSelectedIndexChanged(object sender, EventArgs e)
    {
        var picker = (Picker)sender;
        int selectedIndex = picker.SelectedIndex;
        if (selectedIndex != -1)
        {
            App.DB.UpdateIntSetting(Settings.Pti, selectedIndex);
            ptiLabel.Text = AS.pti.Text();
        }
    }


public class CommandViewModel: ObservableProperty
{
    public ICommand openPickerCommand;

    public CommandViewModel()
    {
        openPickerCommand = new Command<Picker>(PickerFocus);
        //openPickerCommand = new Command(tapped);
    }

    public ICommand OpenPickerCommand
    {
        get { return openPickerCommand; }
    }

    void PickerFocus(Picker param)
    {
        param.Focus();
    }
}

我想删除TapGestureRecognizers的使用,但我仍然希望保留功能和布局.

有人向我建议,如果我像这样使用ViewCell的Tapped事件会更好:

 Tapped="OnTapped"

有人可以详细解释我如何用C#连接它.我是否最好在CommandViewModel以及C#支持代码中编写代码.视图模型还有一个方法可以使用参数,因此它可以用来打开不同的选择器吗？

我非常感谢我如何做到这一点的一个例子.请注意,如果有一种方法可以通过.cs支持代码进行编码,我并不特别需要使用CommandViewModel.

Answer 1

（抱歉英语不好）

尽管不是最佳实践，我想你可以做这样的事情，忽略视图模型：

XAML：

<ViewCell x:Name="ati" Tapped="OpenPickerCommand">
   <Grid VerticalOptions="CenterAndExpand" Padding="20, 0">
      <local:LabelBodyRendererClass Text="Answer Time Interval" HorizontalOptions="StartAndExpand" />
      <Picker x:Name="atiPicker" 
              IsVisible="false" 
              HorizontalOptions="End" 
              SelectedIndexChanged="atiPickerSelectedIndexChanged" 
              ItemsSource="{Binding Times}">
      </Picker>
      <local:LabelBodyRendererClass x:Name="atiLabel" HorizontalOptions="End"/>
   </Grid>
</ViewCell>

<ViewCell x:Name="pti" Tapped="OpenPickerCommand">
   <Grid VerticalOptions="CenterAndExpand" Padding="20, 0">
      <local:LabelBodyRendererClass Text="Phrase Time Interval" HorizontalOptions="StartAndExpand" />
      <Picker x:Name="ptiPicker" IsVisible="false" HorizontalOptions="End" SelectedIndexChanged="ptiPickerSelectedIndexChanged" ItemsSource="{Binding Times}"></Picker>
      <local:LabelBodyRendererClass x:Name="ptiLabel" HorizontalOptions="End"/>
   </Grid>
</ViewCell>

C＃：

private void OpenPickerCommand(object sender, System.EventArgs e)
{
    if (sender != null)
    {
        Picker pkr = sender == ati ? atiPicker : ptiPicker;
        pkr.Focus();
    }
}

回答您的问题“视图模型可以有一个接受参数的方法吗？”，这正是您已经使用“OpenPickerCommand”方法所做的事情。问题是，使用 ViewCell 的公共事件“Tapped”，您无法为委托处理程序设置参数。

让我知道它是否适合您或者您是否需要更多信息。

我希望它有帮助。