将ViewCell条目集中在ListView项目选择上 [英] Focus ViewCell Entry on ListView item selection

问题描述

我有一个带有自定义ViewCell的Xamarin.Forms ListView，该ViewCell包含带有Entry和Label的StackLayout.我希望Entry能够在选择ViewCell的任何时候得到关注.

I have a Xamarin.Forms ListView with a custom ViewCell that contains a StackLayout with an Entry and Label. I'd like the Entry to get focus any time that the ViewCell is selected.

ItemSelected 提供选定的项目，但不提供ViewCell.我可以为ViewCell创建一个自定义类，但看不到如何知道它何时被选中.

ItemSelected provides the item that is selected, but not the ViewCell. I can create a custom class for the ViewCell, but I don't see how it can know when it is selected.

如何将条目集中在ListView项的选择上?

How can I focus the Entry upon ListView item selection?

推荐答案

将条目移动到视图模型中，然后将该条目绑定到ViewCell中的 ContentView .现在，在 ListView.ItemSelected 事件处理程序中， SelectedItem 包含条目，您可以在其上调用 Focus .

Move the Entry into the view model, and bind the Entry to a ContentView in the ViewCell. In the ListView.ItemSelected event handler, SelectedItem now contains the Entry, on which you can call Focus.

XAML看起来像这样:(在此示例中，条目包含一个数量.)

The XAML looks like this: (In this example, the Entry holds a quantity.)

<ViewCell>
    <StackLayout Orientation="Horizontal">
        <ContentView Content="{Binding QuantityView}" />
        <Label ... />
    </StackLayout>
</ViewCell>

视图模型如下:

public class MyViewModel {
    public string Quantity {get; set;}
    public Entry QuantityView { get; } = new Entry {...};

    public MyViewModel() {
        QuantityView.SetBinding(Entry.TextProperty, nameof(Quantity));
    }
}

ItemSelected 事件处理程序如下:

void FocusQuantity(object sender, SelectedItemChangedEventArgs e) {
    if (e.SelectedItem == null) return;
    ((MyViewModel)e.SelectedItem).QuantityView.Focus();
}

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