Question

我有一个带有ViewCell的Listview，在这个ViewCell中有3个图像和3个标签。为了处理点击事件，我为每个控件编写了一个GestureRecognizers。

<ListView HasUnevenRows="True"
            SeparatorColor="White"
            ItemsSource="{Binding List}"
            SelectedItem="{Binding SelectedItem, Mode=TwoWay}"
            ItemSelected="Handle_ItemSelected"
            ItemTapped="ListView_ItemTapped">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <StackLayout Spacing="0">
                            <StackLayout Orientation="Horizontal" Padding="16,8,16,4">
                                <Image Source="{Binding IconImageSource}" HeightRequest="36" WidthRequest="36"/>
                                <StackLayout HorizontalOptions="StartAndExpand" Padding="8,0,0,0" Spacing="0">
                                    <Label Text="{Binding LocalizedText}" TextColor="White"/>
                                    <Label Text="{Binding Value}" TextColor="Gray" FontSize="Small"/>
                                </StackLayout>
                            </StackLayout>
                            <BoxView Color="WhiteSmoke" HeightRequest="1" HorizontalOptions="FillAndExpand" Opacity="0,5" />
                            <RelativeLayout Padding="0,4,0,4" >
                                <Image Source="ic_ecu_eye"
                                       RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.25}"
                                       RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0, Constant=4}"
                                       />
                                <Label Text="{Binding ViewedCount}" 
                                       RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.25, Constant=20}" />
                                <Image Source="ic_ecu_favorite" 
                                       RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.5}"
                                       RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0, Constant=4}"/>
                                <Label Text="{Binding FavoriteCount}" 
                                       RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.5, Constant=20}" />
                                <Image Source="ic_ecu_comment"  
                                       RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.75}"
                                       RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0, Constant=4}">

                                    <Image.GestureRecognizers>
                                        <TapGestureRecognizer Tapped="TapGestureRecognizer_Tapped"   NumberOfTapsRequired="1"/>
                                    </Image.GestureRecognizers>
                                </Image>
                                <Label Text="{Binding CommentsCount}" 
                                       RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.75, Constant=20}">
                                     <Label.GestureRecognizers>
                                        <TapGestureRecognizer Tapped="TapGestureRecognizer_Tapped"  NumberOfTapsRequired="1"/>
                                    </Label.GestureRecognizers> 
                                </Label>
                            </RelativeLayout>
                        </StackLayout>


                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

代码隐藏

async private void TapGestureRecognizer_Tapped(object sender, System.EventArgs e)
    { 
        // want to get listview item
    }

ListView_ItemTapped用于处理listview点击事件

async private void ListView_ItemTapped(object sender, ItemTappedEventArgs e)
    { // easily get the tapped item via e.Item   }

与listview点击事件不同，TapGestureRecognizer_Tapped无法轻松获取我需要处理某些逻辑的抽头项目。所以这就是我的问题，如果我在GestureRecognizer事件方法中点击Listview中的控件，我怎样才能得到被点击的项目

async private void TapGestureRecognizer_Tapped(object sender, System.EventArgs e)
    { 
        // TODO:
    }

Answer 1

虽然您可以使用某个事件执行此操作，但我认为最好使用Command中的TapGestureRecognizer属性。我已经为您创建了一个示例项目来演示这一点。你可以找到它here。

删除Tapped属性并开始使用Command，就像这样。

<Label.GestureRecognizers>
    <TapGestureRecognizer Command="{Binding Path=BindingContext.TapCommand, Source={x:Reference Name=ThaPage}" CommandParameter="{Binding .}" />
</Label.GestureRecognizers>

您会注意到Command需要一些工作。这是因为BindingContext的{{1}}将是单元格绑定的项目。您希望命令位于页面的ListView上。这样做将从＆＃39; ThaPage＆＃39;的BindingContext中读取BindingContext。别忘了给你的页面Command属性。你可能会想到一个更好的名字。

其次，有x:Name="ThaPage"。通过向其插入CommandParameter Cell`。

现在在{Binding .} here. You bind the actual object of the item bound to that中，定义BindingContext，如下所示：

Command

在尖括号之间，您可以指定您期望的对象类型。你可以把它留下来。然后只需传递一个public Command TapCommand => new Command<Foo>((fooObject) => Tapped(fooObject)); private void Tapped(Foo fooObject) { DisplayAlert("Tapped!", fooObject.Bar, "Gotcha"); }，你需要进行投射。

然后在处理object的方法中，您可以使用已点击的对象。我的案例中的对象是Command，仅用于此示例。

Answer 2

杰拉德回答是答案。

BTW我想你可以试试

async private void TapGestureRecognizer_Tapped(object sender, System.EventArgs e)
{ 
    // want to get listview item
    await Application.Current.MainPage.DisplayAlert("Article", ((YourModel)this.BindingContext).YourField, "Ok");

}

我尝试使用Code创建ViewCell，但它确实有效。我不知道你是否在使用XAML创建ViewCell时遇到了问题。

这是我的ViewCell的完整代码

class ListViewTemplateGrid : ViewCell
{
    public ListViewTemplateGrid(){

        TapGestureRecognizer tgr = new TapGestureRecognizer();
        tgr.Tapped += async (object sender, EventArgs e) => {

            try {

                await Application.Current.MainPage.DisplayAlert("Article", ((ListViewModel)this.BindingContext).Description, "Ok");

            }
            catch(Exception ex){

                await Application.Current.MainPage.DisplayAlert("Error", ex.Message, "Ok");
            }

        };

        Label labelDescription = new Label() {VerticalOptions = LayoutOptions.Center};
        labelDescription.SetBinding(Label.TextProperty, "Description");
        labelDescription.GestureRecognizers.Add(tgr);

        Label labelQty = new Label() { VerticalOptions = LayoutOptions.Center, HorizontalOptions = LayoutOptions.Center };
        labelQty.SetBinding(Label.TextProperty, "Qty");

        Label labelOrdered = new Label() { VerticalOptions = LayoutOptions.Center, HorizontalOptions = LayoutOptions.Center };
        labelOrdered.SetBinding(Label.TextProperty, "Ordered");

        // Add controls to the grid
        Grid grid = CreateGrid();
        grid.Children.Add(labelDescription, 0,1,0,1);
        grid.Children.Add(SeparatorV(), 1, 2, 0, 1);
        grid.Children.Add(labelQty, 2, 3, 0, 1);
        grid.Children.Add(SeparatorV(), 3, 4, 0, 1);
        grid.Children.Add(labelOrdered, 4, 5, 0, 1);

        grid.Children.Add(SeparatorH(), 0, 5, 1, 2);

        this.View = grid;

    }
}

如何在ListView（Xamarin）中处理特定控件的事件

2 个答案: