Question

我遇到了listpicker的问题。我有一个设置页面，其中有一个名为“Decimals”的选项，您可以在其中切换“Toggleswitch”，如果打开切换按钮，则会启用listpicker。现在，当您单击listpicker时，您可以选择1到5作为小数位数。如果您在listpicker中选择数字“3”，它将被保存到具有值3的隔离存储上的密钥，如果您转到MainPage，它将检查Isolatedstorage并且它是否包含值“3”，它将设置一个文本块使用3位小数。如果我再次转到我的“设置”页面，应用程序崩溃并显示消息“SelectedIndex必须始终设置为有效值”。它应该显示在listpicker

中选择的正确值

以下是我使用的代码：

Settings.XAML：

<phone:PhoneApplicationPage
xmlns:local="clr-namespace:Vaterpas"
x:Class="Vaterpas.Settings"
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:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait" Orientation="Portrait"
mc:Ignorable="d"
shell:SystemTray.IsVisible="True">

<phone:PhoneApplicationPage.Resources>
    <local:Decimals x:Key="Decimals"/>
    <DataTemplate x:Name="lpkFullItemTemplate">
        <TextBlock FontSize="36" Text="{Binding}" />
    </DataTemplate>
</phone:PhoneApplicationPage.Resources>

<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="100"/>
        <RowDefinition Height="120"/>
        <RowDefinition Height="100"/>
        <RowDefinition Height="100"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="285">
        </ColumnDefinition>
        <ColumnDefinition>
        </ColumnDefinition>
    </Grid.ColumnDefinitions>

    <!--TitlePanel contains the name of the application and page title-->
    <StackPanel Grid.ColumnSpan="2" Grid.Row="0" Margin="12,17,0,28">
        <TextBlock Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}"/>
        <TextBlock Text="Indstillinger" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
    </StackPanel>

    <Grid Grid.Column="2" Grid.Row="2">
        <toolkit:ToggleSwitch Click="tglDecimals_Click" VerticalAlignment="Top" Height="90" Name="tglDecimals" Content="" Margin="0,10,10,0"></toolkit:ToggleSwitch>
        <Grid DataContext="{StaticResource Decimals}">
            <toolkit:ListPicker x:Name="lpkDecimals" ItemsSource="{Binding decimals}" FullModeHeader="Antal decimaler" FullModeItemTemplate="{StaticResource lpkFullItemTemplate}" ExpansionMode="FullScreenOnly" IsEnabled="False" Margin="130,60,20,0" SelectionChanged="lpkDecimals_SelectionChanged"></toolkit:ListPicker>
        </Grid>
</Grid>

Settings.cs

命名空间Vaterpas { public partial class设置：PhoneApplicationPage {

    protected IsolatedStorageSettings m_Settings = IsolatedStorageSettings.ApplicationSettings;

    protected const string TOGGLE_DECIMALS_SETTING_KEY = "ToggleDecimals";
    protected const string DECIMALS_SETTING_KEY = "Decimals";

    public Settings()
    {
        InitializeComponent();
    }

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {

        if (m_Settings.Contains(TOGGLE_DECIMALS_SETTING_KEY))
        {
            string decimalsToggleValue = (string)m_Settings[TOGGLE_DECIMALS_SETTING_KEY];
            string decimalsValue = (string)m_Settings[DECIMALS_SETTING_KEY];

            if (decimalsToggleValue == "On") 
            {
                lpkDecimals.IsEnabled = true;
                tglDecimals.IsChecked = true;
                tblDecimals.Text = "On";

                if (decimalsValue == "1") 
                {
                    lpkDecimals.SelectedIndex = 0; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "2")
                {
                    lpkDecimals.SelectedIndex = 1; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "3")
                {
                    lpkDecimals.SelectedIndex = 2; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "4")
                {
                    lpkDecimals.SelectedIndex = 3; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "5")
                {
                    lpkDecimals.SelectedIndex = 4; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
            }
            else
            {
                tglDecimals.IsChecked = false;
                tblDecimals.Text = "Off";
                lpkDecimals.IsEnabled = false;
            }
        }
        else
        {
            tglDecimals.IsChecked = false;
            tblDecimals.Text = "Off";
        }
        base.OnNavigatedTo(e);
    }

    private void tglDecimals_Click(object sender, RoutedEventArgs e)
    {
        if (tglDecimals.IsChecked == true)
        {
            lpkDecimals.IsEnabled = true;
            tblDecimals.Text = "On";
            m_Settings[TOGGLE_DECIMALS_SETTING_KEY] = "On";
            lpkDecimals.SelectedIndex = 0;
            m_Settings[DECIMALS_SETTING_KEY] = "1";

        }
        else
        {
            lpkDecimals.IsEnabled = false;
            tblDecimals.Text = "Off";
            m_Settings[TOGGLE_DECIMALS_SETTING_KEY] = "Off";
            m_Settings[DECIMALS_SETTING_KEY] = "0";    
        }
    }

    private void lpkDecimals_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        // Make sure we don't handle the event during initiation.
        if (e.RemovedItems != null && e.RemovedItems.Count > 0)
        {
            if (this.lpkDecimals.SelectedItem != null)
            {
                m_Settings[DECIMALS_SETTING_KEY] = lpkDecimals.SelectedItem.ToString();
            }
        } 

    }
}

public class Decimals
{
    public IEnumerable<string> decimals { get { return "1,2,3,4,5".Split(','); } }


}

}

错误：必须始终将SelectedIndex设置为有效值。

我真的希望有人可以帮我解决这个问题。

Answer 1

我认为ItemSource需要时间来分配给listpicker，因为它是在xaml中分配的，OnNavigatedTo有时会在InitializeComponent（）之前运行;加载xaml的方法，并且在OnNavigatedTo中分配了Selected Index属性，这是导致错误的原因。

从.xaml中删除itemsource的赋值，并在所有编码内容之前尝试在OnNavigatedTo中自行分配。

像这样： -

protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        tglDecimals.ItemSource=Your List;
        if (m_Settings.Contains(TOGGLE_DECIMALS_SETTING_KEY))
        {
            string decimalsToggleValue = (string)m_Settings[TOGGLE_DECIMALS_SETTING_KEY];
            string decimalsValue = (string)m_Settings[DECIMALS_SETTING_KEY];

            if (decimalsToggleValue == "On") 
            {
                lpkDecimals.IsEnabled = true;
                tglDecimals.IsChecked = true;
                tblDecimals.Text = "On";

                if (decimalsValue == "1") 
                {
                    lpkDecimals.SelectedIndex = 0; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "2")
                {
                    lpkDecimals.SelectedIndex = 1; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "3")
                {
                    lpkDecimals.SelectedIndex = 2; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "4")
                {
                    lpkDecimals.SelectedIndex = 3; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
                else if (decimalsValue == "5")
                {
                    lpkDecimals.SelectedIndex = 4; // HERE IT CRASHES, WITH THE ERROR (SelectedIndex must always be set to a valid value.") 
                }
            }
            else
            {
                tglDecimals.IsChecked = false;
                tblDecimals.Text = "Off";
                lpkDecimals.IsEnabled = false;
            }
        }
        else
        {
            tglDecimals.IsChecked = false;
            tblDecimals.Text = "Off";
        }
        base.OnNavigatedTo(e);
    }

这会有帮助

Answer 2

首先有一个选定索引的属性，只是为了这样检查 -

int lpkSelectedIndex=0;
public int LpkSelectedIndex
{
    get
    {
        return this.lpkSelectedIndex;
    }
    set
    {
        this.lpkSelectedIndex= value;
    }
}

之后在xaml中将此属性绑定为this.And记住在Itemsource属性之后绑定它并尝试它。

<toolkit:ListPicker x:Name="lpkDecimals" ItemsSource="{Binding decimals}" FullModeHeader="Antal decimaler" FullModeItemTemplate="{StaticResource lpkFullItemTemplate}" ExpansionMode="FullScreenOnly" IsEnabled="False" Margin="130,60,20,0" SelectionChanged="lpkDecimals_SelectionChanged" SelectedIndex="{Binding LpkSelectedIndex, Mode=TwoWay}"></toolkit:ListPicker>

Windows phone listpicker设置selectedIndex

2 个答案: