编辑：哎呀，我看错了，以为您想要更改新项目的文本颜色。更新了以下内容，以便在新添加项目时更改项目背景颜色，如果自上次刷新后发生更改，则更改值的文本颜色。
您可能希望将 Label 的 TextColor 属性绑定到一个布尔值，以指示该值是否已更改，并且您需要使用 ValueConverter 将布尔值转换为颜色。
这是一个简单的例子（下面的大部分代码是模拟添加和更新列表中的项目，兴趣点是值转换器以及如何使用它们将绑定的布尔值转换为颜色）：
MainPage.xaml.cs：（包括转换器和项目视图模型）
using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Timers;
using Xamarin.Forms;
namespace ChangeTextColorForNewItemsInListView
{
// Learn more about making custom code visible in the Xamarin.Forms previewer
// by visiting https://aka.ms/xamarinforms-previewer
[DesignTimeVisible(false)]
public partial class MainPage : ContentPage
{
public ObservableCollection<ItemViewModel> Items { get; set; } = new ObservableCollection<ItemViewModel>();
Timer _timer;
int itemNumber = 0;
Random randomNumber = new Random(DateTime.Now.Millisecond);
public MainPage()
{
InitializeComponent();
BindingContext = this;
}
protected override void OnAppearing()
{
base.OnAppearing();
for (int i = 0; i < 10; i++)
{
Items.Add(new ItemViewModel
{
ValueA = $"ValueA {++itemNumber}",
ValueB = $"ValueB {itemNumber}",
ValueC = $"ValueC {itemNumber}",
IsNew = true
});
}
_timer = new Timer(2000);
_timer.AutoReset = true;
_timer.Elapsed += Timer_Elapsed;
_timer.Start();
}
private void Timer_Elapsed(object sender, ElapsedEventArgs e)
{
foreach (var item in Items)
{
item.IsNew = false;
item.ValueA = item.ValueA.Replace(" new", "");
item.ValueB = item.ValueB.Replace(" new", "");
item.ValueC = item.ValueC.Replace(" new", "");
item.ValueAChanged = false;
item.ValueBChanged = false;
item.ValueCChanged = false;
int changeValue = randomNumber.Next(0, 15);
switch (changeValue)
{
case 0:
item.ValueA = item.ValueA.Replace(" new","") + " new";
break;
case 1:
item.ValueB = item.ValueB.Replace(" new", "") + " new";
break;
case 2:
item.ValueC = item.ValueC.Replace(" new", "") + " new";
break;
default:
break;
}
}
for (int i = 0; i < randomNumber.Next(1,5); i++)
{
Items.Insert(randomNumber.Next(1, Items.Count -1) ,new ItemViewModel
{
ValueA = $"ValueA {++itemNumber}",
ValueB = $"ValueB {itemNumber}",
ValueC = $"ValueC {itemNumber}",
IsNew = true
});
}
}
}
public class ItemViewModel : INotifyPropertyChanged
{
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public event PropertyChangedEventHandler PropertyChanged;
bool _isNew;
public bool IsNew
{
get => _isNew;
set
{
if (_isNew != value)
{
_isNew = value;
OnPropertyChanged();
}
}
}
bool _valueAChanged;
public bool ValueAChanged
{
get => _valueAChanged;
set
{
if (_valueAChanged != value)
{
_valueAChanged = value;
OnPropertyChanged();
}
}
}
string _valueA;
public string ValueA
{
get => _valueA;
set
{
if (_valueA != value)
{
_valueA = value;
ValueAChanged = true;
OnPropertyChanged();
}
}
}
bool _valueBChanged;
public bool ValueBChanged
{
get => _valueBChanged;
set
{
if (_valueBChanged != value)
{
_valueBChanged = value;
OnPropertyChanged();
}
}
}
string _valueB;
public string ValueB
{
get => _valueB;
set
{
if (_valueB != value)
{
_valueB = value;
ValueBChanged = true;
OnPropertyChanged();
}
}
}
bool _valueCChanged;
public bool ValueCChanged
{
get => _valueCChanged;
set
{
if (_valueCChanged != value)
{
_valueCChanged = value;
OnPropertyChanged();
}
}
}
string _valueC;
public string ValueC
{
get => _valueC;
set
{
if (_valueC != value)
{
_valueC = value;
ValueCChanged = true;
OnPropertyChanged();
}
}
}
}
public class BoolToColorConverterNewItem : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return (bool)value ? Color.Yellow : Color.White;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException("No need to convert from color to bool");
}
}
public class BoolToColorConverterChangedValue : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return (bool)value ? Color.Red : Color.Black;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException("No need to convert from color to bool");
}
}
}
MainPage.xaml：
<?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:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="using:ChangeTextColorForNewItemsInListView"
mc:Ignorable="d"
x:Class="ChangeTextColorForNewItemsInListView.MainPage"
>
<ContentPage.Resources>
<ResourceDictionary>
<local:BoolToColorConverterChangedValue x:Key="boolToColorCV" />
<local:BoolToColorConverterNewItem x:Key="boolToColorNI" />
</ResourceDictionary>
</ContentPage.Resources>
<StackLayout Margin="0,50,0,0">
<!-- Place new controls here -->
<ListView HasUnevenRows="True" ItemsSource="{Binding Items}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Grid BackgroundColor="{Binding IsNew, Converter={StaticResource boolToColorNI}}">
<Label
Grid.Column="0"
Text="{Binding ValueA}"
TextColor="{Binding ValueAChanged, Converter={StaticResource boolToColorCV}}" />
<Label
Grid.Column="1"
Text="{Binding ValueB}"
TextColor="{Binding ValueBChanged, Converter={StaticResource boolToColorCV}}" />
<Label
Grid.Column="2"
Text="{Binding ValueC}"
TextColor="{Binding ValueCChanged, Converter={StaticResource boolToColorCV}}" />
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
</ContentPage>