ContentControl不会更改内容-从未调用过的函数 [英] ContentControl does not change the content - function never called

问题描述

我想通过以下代码动态地从AppBar更改内容：

I want to change my content off an AppBar dynamicly whith this code:

<Page.Resources>
    <local:AppBarSelector x:Key="myAppBarSelector"/>
</Page.Resources>

<Page.BottomAppBar>
    <AppBar>
        <ContentControl Content="{Binding SelectedItem, ElementName=listBox}" ContentTemplateSelector="{StaticResource myAppBarSelector}">
            <ContentControl.Resources>
                <DataTemplate x:Key="1">
                    <TextBlock Text="Hallo Welt 1" Foreground="White" />
                </DataTemplate>

                <DataTemplate x:Key="2">
                    <TextBlock Text="Hallo Welt 2" Foreground="White" />
                </DataTemplate>
            </ContentControl.Resources>
        </ContentControl>
    </AppBar>
</Page.BottomAppBar>

这是我后面的代码：

public class AppBarSelector : DataTemplateSelector
{
    protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
    {
        Debug.WriteLine((string)item);
        if (item == null) return base.SelectTemplateCore(item, container);

        var contentControl = (ContentControl)container;
        var templateKey = (string)item;

        return (DataTemplate)contentControl.Resources[templateKey];
    }
}

但是这种方法被称为神经病。 c $ c> Debug.WriteLine 函数。我的错误在哪里？

But this method is nerver called.Even the Debug.WriteLine function. Where is my mistake?

推荐答案

在这里发表一些评论之后...

（注意：这是有点笼统，但是我无法更具体地使用一些代码来反映问题）

Just after some comments here...
(note: this is a bit general but I can't be more specific w/o some more code to reflect the issues)

这应该按原样进行-我看不到会产生此问题的任何问题（我快速检查了相似的示例，并且它与 .ItemsSource = new List< string> {...} 一起很好地工作。

This should work 'as is' - I don't see any problems that would produce that (I check with similar example fast and it works well with .ItemsSource = new List<string>{...}.

所以这不是罪魁祸首-但这并没有伤害我的建议-对属性进行适当的MVVM绑定，使列表 ObservableCollection<> -并且始终建议使用更高级别的 对象（而不只是 string ）作为您的商品（在很多情况下有助于解决类似的问题-该对象实现 INotifyPropertyChanged 等-并在那里绑定属性，而不是整个对象）。

So that's not the culprit - but it doesn't hurt what I suggested - make a proper MVVM binding to properties, make the list ObservableCollection<> - and also it's always recommended to have a more higher-level objects (instead of just string) as your items (helps in many cases with binding with similar issues - that object implements INotifyPropertyChanged etc. - and you bind to a 'property' there, not the entire object).

另一个错误也暗示了一些问题。

The other error suggests some issues as well.

最后将两个contentControl绑定在一起-您通常不需要此类事件。您可以直接从样式或XAML中使用 Triggers -但大多数情况下，只需将两者都绑定到视图模型中的一个属性，并处理该属性中的更改 设定者。

And lastly to bind two contentControls together - you don't normally need events as such. You can use Triggers from the style or XAML directly - but most of the time just bind both to a property in the view-model - and handle the 'change' in your property 'setter'.

您应该放一个重复的小引物-谁知道它可以帮助您意识到自己在做错什么。

You should put up a small primer that repeats this - who knows it might help you realize what you're doing wrong.

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