單擊一行時將動態值傳遞給事件處理程序

Question

請參見下面的代碼：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:App1"
             x:Class="App1.MainPage">

    <ContentPage.BindingContext>
        <local:PersonViewModel />
    </ContentPage.BindingContext>

    <StackLayout>
        <ListView x:Name="listView" ItemsSource="{Binding People}">
            <ListView.Header>
                <Grid>
                    <Grid.BindingContext>
                        <local:PersonViewModel />
                    </Grid.BindingContext>


                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*"  />
                        <ColumnDefinition Width="*"  />
                        <ColumnDefinition Width="*"  />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>

                    <Label Grid.Column="1" Text="Id" />
                    <Label Grid.Column="2" Text="First Name" />
                    <Label Grid.Column="3" Text="Surname" />
                    <Label Grid.Column="4" Text="Date Of Birth" />
                </Grid>
            </ListView.Header>

        <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="*"  />
                                <ColumnDefinition Width="*"  />
                                <ColumnDefinition Width="*"  />
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto" />
                            </Grid.RowDefinitions>
                            <Label Grid.Column="1" Text="{Binding Id}" />
                            <Label Grid.Column="2" Text="{Binding FirstName}" />
                            <Label Grid.Column="3" Text="{Binding Surname}" />
                            <Label Grid.Column="4" Text="{Binding Age}" />
                        </Grid>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage>

和下面的視圖模型：

public class PersonViewModel
    {
        private ObservableCollection<Person> _people = new ObservableCollection<Person>();

        public ObservableCollection<Person> People
        {
            get { return _people; }
        }

        public PersonViewModel()
        {
            _people.Add(new Person { Id = Guid.NewGuid().ToString(), Age = 36, FirstName = "Andrew", Surname = "Smith" });
            _people.Add(new Person { Id = Guid.NewGuid().ToString(), Age = 65, FirstName = "David", Surname = "White" });
            _people.Add(new Person { Id = Guid.NewGuid().ToString(), Age = 39, FirstName = "Bert", Surname = "Edwards" });
        }
    }

它按預期工作，即將網格添加到頁面。 如果用戶單擊其中一行； 我希望將該行的ID傳遞給事件處理程序。 我該怎么做呢。 我花了最后三個小時來研究這個問題，但是沒有找到答案。 我找到的最接近的是： https : //forums.xamarin.com/discussion/23002/how-do-you-detect-a-grid-click-tap 。 但是，在這種情況下，傳遞的是靜態值，而不是動態值。

Answer 1

我假設您要的是對象的ID，而不是行的ID（因為那不是相關的恕我直言）

因此，Listview有一個ItemTapped事件：

<ListView x:Name="listView" 
        ItemTapped="TappedListView"
        ItemsSource="{Binding People}">

並且，在您的Page.xaml.cs中

private void TappedListView(object sender, ItemTappedEventArgs e)
{
     var yourItem = e.Item as Person;
         var id = yourItem.Id;
}

您可以在官方文檔中閱讀有關Listview Interactivity的更多信息。

Answer 2

如Jason所說，ListView中有selecteditem屬性，類型是Person模型，您可以在PersonViewmodel中創建Person模型，綁定到ListView SelectedItem並實現INotifyPropertyChanged，以在單擊ListView Item時進行更新。

 <ListView
            x:Name="listView"
            ItemsSource="{Binding peoples}"
            SelectedItem="{Binding selecteditem}">
            <ListView.Header>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>

                    <Label Grid.Column="0" Text="Id" />
                    <Label Grid.Column="1" Text="First Name" />
                    <Label Grid.Column="2" Text="Surname" />
                    <Label Grid.Column="3" Text="Date Of Birth" />
                </Grid>
            </ListView.Header>

            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="*" />
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto" />
                            </Grid.RowDefinitions>
                            <Label Grid.Column="0" Text="{Binding Id}" />
                            <Label Grid.Column="1" Text="{Binding FirstName}" />
                            <Label Grid.Column="2" Text="{Binding Surname}" />
                            <Label Grid.Column="3" Text="{Binding Age}" />
                        </Grid>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

public class PersonViewModel:ViewModelBase
{
    public ObservableCollection<personmodel> peoples { get; set; }

    private personmodel _selecteditem;
    public personmodel selecteditem
    {
        get { return _selecteditem; }
        set
        {
            _selecteditem = value;
            RaisePropertyChanged("selecteditem");
        }
    }     
    public PersonViewModel()
    {
        peoples = new ObservableCollection<personmodel>();
        peoples.Add(new personmodel { Id = Guid.NewGuid().ToString(), Age = 36, FirstName = "Andrew", Surname = "Smith" });
        peoples.Add(new personmodel { Id = Guid.NewGuid().ToString(), Age = 65, FirstName = "David", Surname = "White" });
        peoples.Add(new personmodel { Id = Guid.NewGuid().ToString(), Age = 39, FirstName = "Bert", Surname = "Edwards" });
        selecteditem = peoples[0];
    }
}


public class ViewModelBase: INotifyPropertyChanged
{

    public event PropertyChangedEventHandler PropertyChanged;


    public void RaisePropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

因此，如果您要將點擊的行ID傳遞給事件處理程序，則只需傳遞

selecteditem.Id