如何动态地在xamarin表单中创建标签上的click事件

Question

我正在开发跨平台xamarin应用程序,我想为"忘记密码？"创建超链接标签.在登录页面上.我使用以下代码来创建标签,但我不知道如何在其上创建onclick事件.

 MainPage = new ContentPage
            {
                BackgroundImage = "background.png",
                Content = new StackLayout
                {
                    VerticalOptions = LayoutOptions.CenterAndExpand,
                    HorizontalOptions = LayoutOptions.CenterAndExpand,
                    Spacing = 50,
                    Children = {

                        new Label {
                            HorizontalTextAlignment = TextAlignment.Center,
                            Text = "Welcome, Please Sign in!",
                            FontSize=50,
                            TextColor=Color.Gray,
                        },


                         new Entry
                        {
                             Placeholder="Username",
                            VerticalOptions = LayoutOptions.Center,
                            Keyboard = Keyboard.Text,
                            HorizontalOptions = LayoutOptions.Center,
                             WidthRequest = 350,
                             HeightRequest = 50,
                             FontSize=20,
                             TextColor=Color.Gray,
                             PlaceholderColor=Color.Gray,
                        },

                          new Entry
                        {
                             Placeholder="Password",
                            VerticalOptions = LayoutOptions.Center,

                            Keyboard = Keyboard.Text,
                            HorizontalOptions = LayoutOptions.Center,
                             WidthRequest = 350,
                             HeightRequest = 50,
                             FontSize=25,
                             TextColor=Color.Gray,
                             IsPassword=true,
                              PlaceholderColor =Color.Gray,
                        },
                        new Button
                        {
                            Text="Login",
                            FontSize=Device.GetNamedSize(NamedSize.Large,typeof(Button)),
                            HorizontalOptions=LayoutOptions.Center,
                            VerticalOptions=LayoutOptions.Fill,
                            WidthRequest=350,
                            TextColor=Color.Silver,
                            BackgroundColor=Color.Red,
                            BorderColor=Color.Red,
                        },
                       new Label //for this label I want to create click event to open new page
                        {
                            Text="Forgot Password?",
                            FontSize=20,
                            TextColor=Color.Blue,
                            HorizontalOptions=LayoutOptions.Center,

                        },
                    } 
        }
            };

Answer 1

对于喜欢使用XAML并希望将Command直接绑定到ViewModel的用户,可以使用以下命令:

<Label HorizontalOptions="Center"
       TextColor="Blue"
       FontSize="20"
       Text="Forgot Password?">
    <Label.GestureRecognizers>
        <TapGestureRecognizer Command="{Binding ForgotPasswordCommand}" />
    </Label.GestureRecognizers>
</Label>

Answer 2

试试这个 :

        var forgetPasswordLabel = new Label   // Your Forget Password Label
        {
            Text = "Forgot Password?",
            FontSize = 20,
            TextColor = Color.Blue,
            HorizontalOptions = LayoutOptions.Center,
        };


        // Your label tap event
        var forgetPassword_tap = new TapGestureRecognizer();   
        forgetPassword_tap.Tapped += (s,e) =>
        {
            //
            //  Do your work here.
            //
        };
        forgetPasswordLabel.GestureRecognizers.Add(forgetPassword_tap);

样品:

        var forgetPasswordLabel = new Label   // Your Forget Password Label
        {
            Text = "Forgot Password?",
            FontSize = 20,
            TextColor = Color.Blue,
            HorizontalOptions = LayoutOptions.Center,
        };

        MainPage = new ContentPage
        {
            BackgroundImage = "background.png",
            Content = new StackLayout
            {
                VerticalOptions = LayoutOptions.CenterAndExpand,
                HorizontalOptions = LayoutOptions.CenterAndExpand,
                Spacing = 50,
                Children = {

                    new Label {
                        //HorizontalTextAlignment = TextAlignment.Center,
                        Text = "Welcome, Please Sign in!",
                        FontSize=50,
                        TextColor=Color.Gray,
                    },


                    new Entry
                    {
                        Placeholder="Username",
                        VerticalOptions = LayoutOptions.Center,
                        Keyboard = Keyboard.Text,
                        HorizontalOptions = LayoutOptions.Center,
                        WidthRequest = 350,
                        HeightRequest = 50,
                        FontSize=20,
                        TextColor=Color.Gray,
                        PlaceholderColor=Color.Gray,
                    },

                    new Entry
                    {
                        Placeholder="Password",
                        VerticalOptions = LayoutOptions.Center,

                        Keyboard = Keyboard.Text,
                        HorizontalOptions = LayoutOptions.Center,
                        WidthRequest = 350,
                        HeightRequest = 50,
                        FontSize=25,
                        TextColor=Color.Gray,
                        IsPassword=true,
                        PlaceholderColor =Color.Gray,
                    },
                    new Button
                    {
                        Text="Login",
                        FontSize=Device.GetNamedSize(NamedSize.Large,typeof(Button)),
                        HorizontalOptions=LayoutOptions.Center,
                        VerticalOptions=LayoutOptions.Fill,
                        WidthRequest=350,
                        TextColor=Color.Silver,
                        BackgroundColor=Color.Red,
                        BorderColor=Color.Red,
                    },
                    forgetPasswordLabel
                }
            }
        };

        var forgetPassword_tap = new TapGestureRecognizer();
        forgetPassword_tap.Tapped += (s,e) =>
        {
            //
            //  Do your work here.
            //
        };
        forgetPasswordLabel.GestureRecognizers.Add(forgetPassword_tap);

Answer 3

如果有多个带有可点击标签的地方，创建一个继承自 Xamarin.Forms 标签的控件是有意义的，并且不要在需要标签的任何地方放置 TapGestureRecognizer。

public class ExtendedLabel : Label
{
    private event EventHandler click;

    public string Name
    {
        get; set;
    }

    public void DoClick()
    {
        click?.Invoke(this, null);
    }

    public event EventHandler Clicked
    {
        add
        {
            lock (this)
            {
                click += value;

                var g = new TapGestureRecognizer();

                g.Tapped += (s, e) => click?.Invoke(s, e);

                GestureRecognizers.Add(g);
            }
        }
        remove
        {
            lock (this)
            {
                click -= value;

                GestureRecognizers.Clear();
            }
        }
    }
}    

在您的 XAML 文件中，您导入定义控件的命名空间，例如

<ContentPage xmlns:ctrl="clr-namespace:UICore.Controls" ...

并将其用作普通控件：

<ctrl:ExtendedLabel x:Name="quitButton" Clicked="OnQuit">