Question

我使用Visual Studio 2017创建了一个跨平台的Xamarin.Forms应用程序，该应用程序包含一个带有两个ListView的TabPage容器。它工作得很好，直到我尝试添加Picker控件。当我尝试使用添加的选择器进行构建时，我收到以下错误：

“序列不包含元素”

这是我正在添加的Xaml：

    <Picker x:Name="thePicker">
        <Picker.Items>
            <x:String>Make Call</x:String>
            <x:String>Send Text</x:String>
        </Picker.Items>
    </Picker>

感谢您提供的任何帮助。

Answer 1

我认为您的Picker不属于任何类型的Layout。

同样使用新的Picker可绑定API，您的项目列表将变为：

<ContentPage.Content>
  <StackLayout>
    <Label Text="StackOverflow"/>
    <Picker x:Name="thePicker">
        <Picker.ItemsSource>
            <x:Array Type="{x:Type x:String}">
                <x:String>Make Call</x:String>
                <x:String>Send Text</x:String>
            </x:Array>
        </Picker.ItemsSource>
    </Picker>
  </StackLayout>
</ContentPage.Content>

Answer 2

通过您的输入，我找到了一个可行的解决方案。使用的XAML：

    <ContentPage.Content>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <StackLayout Grid.Row="0" Grid.Column="0" Padding="20">
            <Picker x:Name="actionPicker" IsEnabled="False" IsVisible="False" SelectedIndexChanged="cellPhoneSelected" Unfocused="actionPicker_Unfocused" HeightRequest="200">
                <Picker.Items>
                    <x:String>Make Call</x:String>
                    <x:String>Send Text</x:String>
                </Picker.Items>
            </Picker>
        </StackLayout>
        <StackLayout Grid.Row="0" Grid.Column="0">
            <ListView x:Name="listView" ItemSelected="OnItemSelected" HasUnevenRows="True" ItemTemplate="{StaticResource employeeDataTemplateSelector}" IsGroupingEnabled="True" IsPullToRefreshEnabled="True" Refreshing="employee_Refreshing">
                <ListView.GroupHeaderTemplate>
                    <DataTemplate>
                        <ViewCell Height="40">
                            <Grid Padding="4" BackgroundColor="LightGray" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*"  />
                                </Grid.ColumnDefinitions>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto" />
                                </Grid.RowDefinitions>
                                <Label Text="{Binding LongName}" Margin="0,8,0,0" FontAttributes="Bold" Grid.Column="0" Grid.Row="0" VerticalOptions="FillAndExpand" />
                            </Grid>
                        </ViewCell>
                    </DataTemplate>
                </ListView.GroupHeaderTemplate>
            </ListView>
        </StackLayout>
    </Grid>
</ContentPage.Content>

使用的代码：

        void cellPhoneSelected(object sender, EventArgs e)
    {
        var picker = (Picker)sender;
        int selectedIndex = picker.SelectedIndex;

        switch (selectedIndex)
        {
            case 0:
                Device.OpenUri(new Uri(String.Format("tel:{0}", phone)));
                break;
            case 1:
                Device.OpenUri(new Uri(String.Format("sms:{0}", phone)));
                break;
        }

        actionPicker.IsEnabled = false;
        actionPicker.IsVisible = false;
    }

    void phoneSelected(object sender, EventArgs args) {
        phone = ((Label)sender).Text;
        switch (phone.Substring(0, 1))
        {
            case "W":
                phone = phone.Replace("W: ", "").Replace("-", "").Replace("(", "").Replace(")", "").Replace(".", "").Replace(" ", "");
                if (phone.Length == 7)
                {
                    phone = "405" + phone;
                }
                Device.OpenUri(new Uri(String.Format("tel:{0}", phone)));
                break;
            case "C":
                phone = phone.Replace("C: ", "").Replace("-", "").Replace("(", "").Replace(")", "").Replace(".", "").Replace(" ", "");
                if (phone.Length == 7)
                {
                    phone = "405" + phone;
                }
                actionPicker.SelectedIndex = -1;
                actionPicker.IsEnabled = true;
                actionPicker.IsVisible = true;
                actionPicker.Focus();
                break;
            case "H":
                phone = phone.Replace("H: ", "").Replace("-", "").Replace("(", "").Replace(")", "").Replace(".", "").Replace(" ", "");
                if (phone.Length == 7)
                {
                    phone = "405" + phone;
                }
                Device.OpenUri(new Uri(String.Format("tel:{0}", phone)));
                break;
            case "P":
                for (var i = 0; i < employees.Count; i++)
                {
                    for (var c = 0; c < employees[i].Count; c++)
                    {
                        if (employees[i][c].Pager == phone)
                        {
                            if (employees[i][c].Pager2 != null)
                            {
                                phone = employees[i][c].Pager2;
                                Device.OpenUri(new Uri(String.Format("mailto:{0}", phone)));
                            }
                            break;
                        }
                        else
                        {
                            if (employees[i][c].CellPhone == phone)
                            {
                                if (employees[i][c].Pager2 != null)
                                {
                                    phone = employees[i][c].Pager2;
                                    Device.OpenUri(new Uri(String.Format("mailto:{0}", phone)));
                                }
                                break;
                            }
                        }
                    }
                }
                break;
        }
    }

    private void actionPicker_Unfocused(object sender, FocusEventArgs e)
    {
        actionPicker.IsEnabled = false;
        actionPicker.IsVisible = false;
    }

“Unfocused”方法用于在选择器上单击“取消”按钮时隐藏选择器。

再次感谢您的协助！

添加Xamarin.Forms选择器导致“序列包含无元素”错误

2 个答案: