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ContentControl 与 ViewModel (二)

上文说到 可以使用DataTemplateSelector。

其实等于是用 DataTemplateSelector + 动态创建DataTemplate来实现。

using System;using System.Collections.Generic;using System.Windows;using System.Windows.Controls;using System.Windows.Markup;namespace ContentDemo{    class ContentDataTemplateSelector : DataTemplateSelector    {        //用来标示一下已经创建过的类型        private readonly static Queue<Type> ViewModelQueue = new Queue<Type>();        public override DataTemplate SelectTemplate(object item, DependencyObject container)        {            do            {                if (item == null                    || item is UIElement)                {                    break;                }                // item 就是你的ViewModel的类型,在这主要就是找到ViewModel对应的View                // 好多框架中会在启动时构建自己的Map,来对应ViewModel                // 比如 Caliburn.Micro 框架中默认 是以名称对应的 XXXViewModel 和 XXXView,来构建Map的                //      MvvmCross 框架中不仅提供了 名称,还提供了 Attribute的对应方式                // 在这为了演示方便,我就直接反射对应名称的 View了。                var viewModelType = item.GetType();                if (ViewModelQueue.Contains(viewModelType))                {                    break;                }                var viewModelName = viewModelType.Name;                string name = null;                var index = viewModelName.LastIndexOf("ViewModel", StringComparison.OrdinalIgnoreCase);                if (index > 0)                {                    name = viewModelName.Substring(0, index);                }                if (string.IsNullOrEmpty(name))                {                    break;                }                var viewName = string.Format("{0}.{1}{2}", viewModelType.Namespace, name, "View");                var view = viewModelType.Assembly.GetType(viewName, false, true);                if (view != null)                {                    var dataTemplate = CreateDataTemplate(view, viewModelType);                    var dtkey = dataTemplate.DataTemplateKey;                    if (dtkey != null)                    {                        Application.Current.Resources.Add(dtkey, dataTemplate);                        ViewModelQueue.Enqueue(viewModelType);                    }                    return dataTemplate;                }            } while (false);            return base.SelectTemplate(item, container);        }        /// <summary>        /// 创建DataTemplate        /// </summary>        /// <param name="viewType"></param>        /// <param name="viewModelType"></param>        /// <returns></returns>        private DataTemplate CreateDataTemplate(Type viewType, Type viewModelType)        {            const string xamlTemplate = "<DataTemplate DataType=\"{{x:Type vm:{0}}}\"><v:{1} /></DataTemplate>";            var xaml = String.Format(xamlTemplate, viewModelType.Name, viewType.Name);            var context = new ParserContext();            context.XamlTypeMapper = new XamlTypeMapper(new string[0]);            context.XamlTypeMapper.AddMappingProcessingInstruction("vm", viewModelType.Namespace, viewModelType.Assembly.FullName);            context.XamlTypeMapper.AddMappingProcessingInstruction("v", viewType.Namespace, viewType.Assembly.FullName);            context.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");            context.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");            context.XmlnsDictionary.Add("vm", "vm");            context.XmlnsDictionary.Add("v", "v");            var template = (DataTemplate)XamlReader.Parse(xaml, context);            return template;        }    }}

 

WPF有一个好处就是他的DataType,所以 你也不一定非要在选择器中处理,你可以在任意你想要的时机时,把DataTemplate加到资源里就可以了。

但是WinRT中,的DataTemplate,就没有DataType,就得通过 选择器来,返回对应的DataTemplate.

还有 WinRT中 不支持 ParserContext,就只能拼字符串构造了。

Xaml:

<Window x:Class="ContentDemo.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        xmlns:local="clr-namespace:ContentDemo"        Title="MainWindow" Height="350" Width="525">    <Window.Resources>        <local:MainViewModel x:Key="MainViewModel" />        <!--<DataTemplate DataType="{x:Type local:FirstViewModel}">            <local:FirstView />        </DataTemplate>        <DataTemplate DataType="{x:Type local:SecondViewModel}">            <local:SecondView />        </DataTemplate>-->        <local:ContentDataTemplateSelector x:Key="ContentDataTemplateSelector" />    </Window.Resources>    <Grid DataContext="{StaticResource MainViewModel}">        <Grid.RowDefinitions>            <RowDefinition />            <RowDefinition Height="Auto"/>        </Grid.RowDefinitions>        <Grid.ColumnDefinitions>            <ColumnDefinition />            <ColumnDefinition />        </Grid.ColumnDefinitions>        <ContentControl Grid.ColumnSpan="2" Content="{Binding Path=ViewModel}" ContentTemplateSelector="{StaticResource ContentDataTemplateSelector}" />        <Button Grid.Row="1" Grid.Column="0" Content="ViewModel  1" Command="{Binding Path=FirstCommand}"/>        <Button Grid.Row="1" Grid.Column="1" Content="ViewModel  2" Command="{Binding Path=SecondCommand}"/>    </Grid></Window>    

其实要是,用了很多的 ContentControl ,每一个 都去绑定 Selector,还是很烦人的一件事。

这时候,我们可以加一个 ContentControl 的 默认样式,让他默认就使用这个Selector.

<Application x:Class="ContentDemo.App"             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"             xmlns:local="clr-namespace:ContentDemo"             StartupUri="MainWindow.xaml">    <Application.Resources>        <local:ContentDataTemplateSelector x:Key="ContentDataTemplateSelector" />                <Style TargetType="{x:Type ContentControl}">            <Setter Property="ContentTemplateSelector"                     Value="{StaticResource ContentDataTemplateSelector}"/>        </Style>    </Application.Resources></Application>
<Window x:Class="ContentDemo.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        xmlns:local="clr-namespace:ContentDemo"        Title="MainWindow" Height="350" Width="525">    <Window.Resources>        <local:MainViewModel x:Key="MainViewModel" />        <!--<DataTemplate DataType="{x:Type local:FirstViewModel}">            <local:FirstView />        </DataTemplate>        <DataTemplate DataType="{x:Type local:SecondViewModel}">            <local:SecondView />        </DataTemplate>-->        <!--<local:ContentDataTemplateSelector x:Key="ContentDataTemplateSelector" />-->    </Window.Resources>    <Grid DataContext="{StaticResource MainViewModel}">        <Grid.RowDefinitions>            <RowDefinition />            <RowDefinition Height="Auto"/>        </Grid.RowDefinitions>        <Grid.ColumnDefinitions>            <ColumnDefinition />            <ColumnDefinition />        </Grid.ColumnDefinitions>        <ContentControl Grid.ColumnSpan="2" Content="{Binding Path=ViewModel}" />        <Button Grid.Row="1" Grid.Column="0" Content="ViewModel  1" Command="{Binding Path=FirstCommand}"/>        <Button Grid.Row="1" Grid.Column="1" Content="ViewModel  2" Command="{Binding Path=SecondCommand}"/>    </Grid></Window>    

源码:Code

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ContentControl 与 ViewModel (二)