根据@anand所说的内容，制作了一个快速示例。
创建名为 CustomLabel 的自定义控件。
CustomLabel.xaml
<ContentView
x:Class="BlankApp3.Controls.CustomLabel"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:prism="http://prismlibrary.com"
mc:Ignorable="d">
<ContentView.Content>
<StackLayout HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
<Label x:Name="customLabel" />
<Label
x:Name="lblReadMore"
FontSize="18"
TextColor="#1a0fa9">
<Label.GestureRecognizers>
<TapGestureRecognizer Tapped="TapGestureRecognizer_Tapped" />
</Label.GestureRecognizers>
</Label>
</StackLayout>
</ContentView.Content>
</ContentView>
代码后台。
using System;
using System.Diagnostics;
using System.Linq;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace BlankApp3.Controls
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class CustomLabel : ContentView
{
public CustomLabel()
{
InitializeComponent();
}
#region Bindable Property
public static readonly BindableProperty TextProperty = BindableProperty.Create(
propertyName: nameof(TextProperty),
returnType: typeof(string),
declaringType: typeof(CustomLabel),
defaultBindingMode: BindingMode.TwoWay,
propertyChanged: TextPropertyChanged
);
public string Text
{
get { return (string)base.GetValue(TextProperty); }
set { base.SetValue(TextProperty, value); }
}
private static void TextPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var control = (CustomLabel)bindable;
if (newValue != null)
{
control.customLabel.Text = (string)newValue;
var ss = control.customLabel.Text.Split().Length;
if (control.customLabel.Text.Split().Length >= 30)
{
control.ShortTextVisible = true;
control.ReadMoreLabel = true;
}
}
}
#endregion Bindable Property
public bool ReadMoreLabel { get; set; }
private bool _shortTextVisible;
public bool ShortTextVisible
{
get => _shortTextVisible;
set { _shortTextVisible = value; ShortTextPropertyChanged(); }
}
private void ShortTextPropertyChanged()
{
if (Text != null && Text.Split().Length >= 30)
{
if (ShortTextVisible)
{
if (customLabel != null && !string.IsNullOrWhiteSpace(customLabel.Text) && customLabel.Text.Split().Length < 100)
{
Debug.WriteLine("");
}
customLabel.Text = string.Join(" ", Text.Split().Take(30));
lblReadMore.Text = "See more";
lblReadMore.IsVisible = true;
}
else
{
customLabel.Text = Text;
lblReadMore.Text = "See less";
}
}
}
private void TapGestureRecognizer_Tapped(object sender, EventArgs e)
{
ShortTextVisible = !ShortTextVisible;
}
}
}
MainPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
x:Class="BlankApp3.Views.MainPage"
xmlns="http:
xmlns:x="http:
xmlns:local="clr-namespace:BlankApp3.Controls"
Title=""
BackgroundColor="#ffffff">
<CollectionView ItemsSource="">
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout>
<StackLayout Padding="10" Orientation="Horizontal">
<Image
HeightRequest="80"
Source="https:
VerticalOptions="Start" />
<StackLayout HorizontalOptions="FillAndExpand">
<Frame
Margin="10,0,10,0"
BackgroundColor="#f9f9f9"
CornerRadius="10"
HasShadow="False">
<StackLayout>
<Label FontAttributes="Bold" Text="Dr. Gracy David" />
<local:CustomLabel Text="" />
</StackLayout>
</Frame>
<StackLayout Margin="10,0,10,0" Orientation="Horizontal">
<Label Text="12 April,2020" />
<Label Text="3.20pm" />
</StackLayout>
</StackLayout>
</StackLayout>
</StackLayout>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</ContentPage>
MainPageViewModal.cs
using Prism.Navigation;
using System.Collections.ObjectModel;
namespace BlankApp3.ViewModels
{
public class MainPageViewModel : ViewModelBase
{
public ObservableCollection<string> Monkeys { get; set; }
public MainPageViewModel(INavigationService navigationService)
: base(navigationService)
{
Title = "Main Page";
Monkeys = new ObservableCollection<string>();
}
public async override void OnNavigatedTo(INavigationParameters parameters)
{
Monkeys = new ObservableCollection<string>()
{
"Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.",
"Simple",
"Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum."
};
}
}
}
