LongListSelector 更改 ItemTemplate [英] LongListSelector change ItemTemplate

问题描述

我想动态更改 LongListSelector 的 ItemTemplate.我通过将它绑定到我的 ViewModel 中的一个属性来做到这一点:

I want to dynamically change the ItemTemplate of a LongListSelector. I do this by Binding it to a property in my ViewModel:

  <toolkit:LongListSelector ItemTemplate="{Binding ItemTemplate}" ItemsSource="{Binding Items}" />

到目前为止，这有效.问题是，如果我在 ViewModel 中更改模板的属性，则 LongListSelector 不会应用更改后的模板.

This works so far. The problem is that if I change the property for the template in my ViewModel then the LongListSelector doesn't apply the changed template.

我查看了调试器，每当我使用它的 setter 更改属性时，getter 都会依次调用，因此 LongListSelector 读取新模板(但不应用它).

I looked in the debugger, whenever I change the property by using it's setter, then the getter gets called in turn, so the LongListSelector reads the new template (but doesn't apply it).

这是一个错误，还是无法通过绑定更改ItemTemplate?

Is this a bug, or is it not possible to change the ItemTemplate via a binding?

推荐答案

LongListSelector 忽略对其 ItemTemplate 的更改.LongListSelector 中的 DependencyProperty 定义如下所示:

The LongListSelector ignores changes to its ItemTemplate. The DependencyProperty definition in LongListSelector looks like this:

public static readonly DependencyProperty ItemsTemplateProperty =
        DependencyProperty.Register("ItemTemplate", typeof(DataTemplate), 
                                     typeof(LongListSelector), 
                                     new PropertyMetadata(null));

如果你想让它注意到变化，你可以像这样获取源代码并重建它:

If you want it to notice changes, you can fetch the source and rebuild it like this:

    public static readonly DependencyProperty ItemsTemplateProperty =
        DependencyProperty.Register("ItemTemplate", typeof(DataTemplate), 
                                     typeof(LongListSelector), 
                                     new PropertyMetadata(null, 
                                                          OnItemsTemplateChanged));

    private static void OnItemsTemplateChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        ((LongListSelector)obj).OnItemsTemplateChanged();
    }

    private void OnItemsTemplateChanged()
    {
        _flattenedItems = null;
        if (_isLoaded)
        {
            EnsureData();
        }
    }

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