值不在预期范围内- Windows 8.1应用程序
本文关键字：Windows 应用程序 范围内 | 更新日期: 2023-09-27 18:04:35
放置在我得到异常的代码中:
EventHandler(this, new ObservableDictionaryChangedEventArgs(change, key));
namespace TestGridApp
{
public sealed partial class ItemDetailPage : Page
{
private NavigationHelper navigationHelper;
private ObservableDictionary defaultViewModel = new ObservableDictionary();
public NavigationHelper NavigationHelper
{
get { return this.navigationHelper; }
}
public ObservableDictionary DefaultViewModel
{
get { return this.defaultViewModel; }
}
public ItemDetailPage()
{
this.InitializeComponent();
this.navigationHelper = new NavigationHelper(this);
this.navigationHelper.LoadState += navigationHelper_LoadState;
}
private async void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
// TODO: Create an appropriate data model for your problem domain to replace the sample data
var mitem = await MovieDataSource.GetItemAsync((String)e.NavigationParameter);
//this.DefaultViewModel["Item"] = mitem;
ItemDetailGridView.ItemsSource = mitem;
}
#region NavigationHelper registration
protected override void OnNavigatedTo(NavigationEventArgs e)
{
navigationHelper.OnNavigatedTo(e);
}
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
navigationHelper.OnNavigatedFrom(e);
}
#endregion
}
}
<Page
x:Name="pageRoot"
x:Class="TestGridApp.ItemDetailPage"
DataContext="{Binding DefaultViewModel, RelativeSource={RelativeSource Self}}"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:TestGridApp"
xmlns:data="using:TestGridApp.Data"
xmlns:common="using:TestGridApp.Common"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<!--
This grid acts as a root panel for the page that defines two rows:
* Row 0 contains the back button and page title
* Row 1 contains the rest of the page layout
-->
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Grid.ChildrenTransitions>
<TransitionCollection>
<EntranceThemeTransition/>
</TransitionCollection>
</Grid.ChildrenTransitions>
<Grid.RowDefinitions>
<RowDefinition Height="140"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<!--
TODO: Content should be placed within the following grid
to show details for the current item
-->
<Grid Grid.Row="1" x:Name="contentRegion">
<GridView FlowDirection="LeftToRight" ItemsSource="{Binding Item}" x:Name="ItemDetailGridView">
<GridView.ItemTemplate>
<DataTemplate>
<Grid Height="110" Width="480" Margin="10">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="1" VerticalAlignment="Top" Margin="10,0,0,0" Orientation="Vertical">
<TextBlock Text="{Binding OverView}" Style="{StaticResource TitleTextBlockStyle}" TextWrapping="NoWrap"/>
<StackPanel>
<TextBlock Text="{Binding CreatedBy}" Style="{StaticResource BodyTextBlockStyle}" TextWrapping="NoWrap"/>
<TextBlock Text="{Binding EpisodeRunTime}" Style="{StaticResource BodyTextBlockStyle}" TextWrapping="NoWrap"/>
<TextBlock Text="{Binding homepage}" Style="{StaticResource BodyTextBlockStyle}" TextWrapping="NoWrap"/>
</StackPanel>
</StackPanel>
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
<GridView.Header>
<StackPanel Width="600" Margin="40,4,14,0">
<TextBlock Text="{Binding Title}" Margin="0,0,0,20" Style="{StaticResource SubheaderTextBlockStyle}" MaxHeight="60"/>
<Image Source="{Binding ImagePath}" Height="420" Margin="0,0,0,20" Stretch="UniformToFill"/>
<TextBlock Text="{Binding Airdate}" Margin="0,0,0,0" Style="{StaticResource BodyTextBlockStyle}"/>
</StackPanel>
</GridView.Header>
</GridView>
</Grid>
<!-- Back button and page title -->
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="120"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Button x:Name="backButton" Margin="39,59,39,0" Command="{Binding NavigationHelper.GoBackCommand, ElementName=pageRoot}"
Style="{StaticResource NavigationBackButtonNormalStyle}"
VerticalAlignment="Top"
AutomationProperties.Name="Back"
AutomationProperties.AutomationId="BackButton"
AutomationProperties.ItemType="Navigation Button"/>
<TextBlock x:Name="pageTitle" Text="{Binding UniqueId}" Style="{StaticResource HeaderTextBlockStyle}" Grid.Column="1"
IsHitTestVisible="false" TextWrapping="NoWrap" VerticalAlignment="Bottom" Margin="0,0,30,40"/>
</Grid>
</Grid>
</Page>
我不知道为什么这不起作用，但我已经在谷歌上搜索了5个多小时。
在您的示例中没有一个好的MVVM系统。在xaml中，您将GridView绑定到名为Item的属性:
<GridView FlowDirection="LeftToRight" ItemsSource="{Binding Item}" x:Name="ItemDetailGridView">
Item必须是您的ViewModel类属性之一或ItemDetailPage类属性之一，但我没有在您的代码中看到这一点!然后你试图用代码后面的集合填充ItemsSource…
我建议你尝试为你的项目制作一个正确的MVVM系统。您可以根据以下步骤进行设置:
1)从Item Entity创建一个Model类。例如:
public Class MyItemModel{
public string OverView {get; set;}
public string CreatedBy {get; set;}
public string Homepage {get; set;}
}
2)创建继承INotifyPropertyChanged接口的ViewModel类。例如:
public class MyItemViewModel: INotifyPropertyChanged
{
private ObservableCollection<MyItemModel> _myItems;
private string _createdBy;
private string _homepage;
public ObservableCollection<MyItemModel> MyItems
{
get { return _myItems; }
set
{
_myItems = value;
OnPropertyChanged("MyItems");
}
}
public string CreatedBy
{
get { return _createdBy; }
set
{
_createdBy = value;
OnPropertyChanged("CreatedBy");
}
}
public string Homepage
{
get { return _homepage; }
set
{
_homepage = value;
OnPropertyChanged("Homepage");
}
}
//-----------------------------------------------------------------------
public MyItemViewModel()
{
this.navigationHelper = new NavigationHelper(this);
this.navigationHelper.LoadState += navigationHelper_LoadState;
}
private async void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
var mitem = await MovieDataSource.GetItemAsync((String)e.NavigationParameter);
// You must have data inside mitem if you put a breakpint at the below line
MyItems = mitem;
}
//-----------------------------------------------------------------------
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
3)现在将ViewModel类绑定到DataContext页，并将ViewModel的MyItems属性绑定到Element的ItemsSource。它可以在Xaml或code-behind中执行。我推荐Xaml。例如:
<Page.DataContext>
<vm:MyItemViewModel/>
</Page.DataContext>
.
<GridView FlowDirection="LeftToRight" ItemsSource="{Binding MyItems}" x:Name="ItemDetailGridView">
<!--.....Your other Xaml codes.....-->
注意:你也可以在你的Model类中实现INotifyPropertyChanged