![](/img/trans.png)
[英]How to highlight a selected item in the LongListSelector on WP8?
[英]How to unselect selected row in LongListSelector in WP8
我必须说,我真的不喜欢WP8中的LongListSelector,并且非常喜欢工具箱版本。
首先,它与MVVM不兼容,因此我找到了此代码。
public class LongListSelector : Microsoft.Phone.Controls.LongListSelector
{
public LongListSelector()
{
SelectionChanged += LongListSelector_SelectionChanged;
}
void LongListSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
SelectedItem = base.SelectedItem;
}
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.Register(
"SelectedItem",
typeof(object),
typeof(LongListSelector),
new PropertyMetadata(null, OnSelectedItemChanged)
);
private static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var selector = (LongListSelector)d;
selector.SelectedItem = e.NewValue;
}
public new object SelectedItem
{
get { return GetValue(SelectedItemProperty); }
set { SetValue(SelectedItemProperty, value); }
}
}
然后我使用mvvm light制作了一个视图模型
public class MainViewModel : ViewModelBase
{
public MainViewModel()
{
MyList = new ObservableCollection<Test>
{
new Test
{
Name = "test 1"
},
new Test
{
Name = "test 2"
}
};
ButtonCmd = new RelayCommand(() => Hit());
}
private void Hit()
{
SelectedItem = null;
}
public ObservableCollection<Test> MyList { get; set; }
/// <summary>
/// The <see cref="SelectedItem" /> property's name.
/// </summary>
public const string SelectedItemPropertyName = "SelectedItem";
private Test selectedItem = null;
/// <summary>
/// Sets and gets the SelectedItem property.
/// Changes to that property's value raise the PropertyChanged event.
/// </summary>
public Test SelectedItem
{
get
{
return selectedItem;
}
set
{
if (value != null)
{
MessageBox.Show(value.Name);
}
if (selectedItem == value)
{
return;
}
RaisePropertyChanging(() => SelectedItem);
selectedItem = value;
RaisePropertyChanged(() => SelectedItem);
}
}
public RelayCommand ButtonCmd
{
get;
private set;
}
然后我做了一个模特
public class Test : ObservableObject
{
public string Name { get; set; }
}
然后我做了xaml
<phone:PhoneApplicationPage
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:ignore="http://www.ignore.com"
xmlns:local="clr-namespace:MvvmLight2" x:Class="MvvmLight2.MainPage"
mc:Ignorable="d ignore"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait"
Orientation="Portrait"
shell:SystemTray.IsVisible="True"
DataContext="{Binding Main, Source={StaticResource Locator}}">
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot"
Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<local:LongListSelector ItemsSource="{Binding MyList}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}">
<local:LongListSelector.Resources>
<DataTemplate x:Key="ItemTemplate">
<Grid>
<TextBlock Text="{Binding Name}" HorizontalAlignment="Left" VerticalAlignment="Top" FontSize="48"/>
</Grid>
</DataTemplate>
</local:LongListSelector.Resources>
<local:LongListSelector.ItemTemplate>
<StaticResource ResourceKey="ItemTemplate"/>
</local:LongListSelector.ItemTemplate>
</local:LongListSelector>
<Button Content="Unselect" HorizontalAlignment="Left" Margin="142,81,0,0" Grid.Row="1" VerticalAlignment="Top" Command="{Binding ButtonCmd, Mode=OneWay}"/>
</Grid>
</phone:PhoneApplicationPage>
当我单击列表中的第一项时,将显示消息框,如果再次单击它,则什么也没有发生。 然后,我按下我的按钮,该按钮使selectedItem为空(在旧工具箱版本中就足够了),然后重试,没有任何反应。
我可以选择第一行的唯一方法是选择第二行,如果说该列表在任何给定时间仅包含一项,那确实很糟糕。
奇怪的是,一个简单的字符串集合甚至不需要我将SelectItem设置为null,因为它似乎总是被取消选择,但是当涉及复杂类型时,这是不可行的。
我使用了相同的代码,遇到了同样的问题。 原因是您的SelectedItem属性使base.SelectedItem属性蒙上了阴影。 将其设置为新值时,不仅要设置SelectedItem属性,还要设置基础属性:
public new object SelectedItem
{
get { return GetValue(SelectedItemProperty); }
set
{
SetValue(SelectedItemProperty, value);
base.SelectedItem = value;
}
}
然后,您将获得具有MVVM功能的代码,并且还可以在ViewModel中重置SelectedItem(通过将其设置为null)。
您可以通过selectionchanged事件轻松实现
void LongListSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if((sender as LongListSelector).SelectedItem == null){
return;
}
SelectedItem = base.SelectedItem;
(sender as LongListSelector).SelectedItem = null;
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.