maui中实现加载更多 RefreshView跟ListView（2）

一个类似商品例表的下拉效果：

代码

新增个类为商品商体类

    public class ProductItem{public string ImageSource { get; set; }public string ProductName { get; set; }public string Price { get; set; }}

界面代码：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"xmlns:d="http://schemas.microsoft.com/dotnet/2021/maui/design"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"mc:Ignorable="d"BackgroundColor="{DynamicResource PageBackgroundColor}"x:Class="fenye.MainPage"><RefreshView IsRefreshing="{Binding IsRefreshing}"  Command="{Binding RefreshCommand}"><StackLayout Margin="10"><ListView ItemsSource="{Binding Items}" ItemAppearing="OnItemAppearing"  RowHeight="70" Margin="20"><ListView.ItemTemplate><DataTemplate><ViewCell><Grid><Grid.ColumnDefinitions><ColumnDefinition Width="Auto" /><!-- 第一列宽度自适应 --><ColumnDefinition Width="*" /><!-- 第二列宽度填充剩余空间 --></Grid.ColumnDefinitions><!-- 左侧图片 --><Image Source="{Binding ImageSource}" Aspect="AspectFit"WidthRequest="150"HeightRequest="150"  Grid.Column="0" /><!-- 右侧商品名和价格 --><StackLayout Grid.Column="1" Margin="10"><Label Text="{Binding ProductName}" FontAttributes="Bold"FontSize="18"/><Label Text="{Binding Price}" FontSize="16" TextColor="Green"/></StackLayout></Grid></ViewCell></DataTemplate></ListView.ItemTemplate></ListView></StackLayout></RefreshView>
</ContentPage>

后端代码：

using System;
using System.Collections.ObjectModel;
using System.Threading.Tasks;
using Microsoft.Maui.Controls;
using Microsoft.Maui.Controls.Xaml;
using System.ComponentModel;
using System.Runtime.CompilerServices;namespace fenye
{public class ProductItem{public string ImageSource { get; set; }public string ProductName { get; set; }public string Price { get; set; }}// 标记 XAML 编译选项[XamlCompilation(XamlCompilationOptions.Compile)]public partial class MainPage : ContentPage{// 数据源，用于存储列表项的集合private ObservableCollection<ProductItem> _items;// 是否正在刷新的标志private bool _isRefreshing;public ObservableCollection<ProductItem> Items => _items;// 随机数生成器private Random _random = new Random();// 各类水果数组private string[] fruits = { "苹果", "香蕉", "橙子", "葡萄", "草莓", "梨", "桃子", "西瓜", "蓝莓", "樱桃" };// 构造函数，初始化页面public MainPage(){InitializeComponent();BindingContext = this;// 初始化数据源并填充一些初始数据_items = new ObservableCollection<ProductItem>();for (int i = 0; i < 20; i++){AddNewItem();}// 通知界面数据源已更新OnPropertyChanged(nameof(Items));}// 数据源的公共属性// 是否正在刷新的属性，并使用 SetProperty 方法实现属性更改通知public bool IsRefreshing{get => _isRefreshing;set => SetProperty(ref _isRefreshing, value);}// 刷新命令，绑定到下拉刷新控件public Command RefreshCommand => new Command(async () => await OnRefresh());// 下拉刷新事件处理方法private async Task OnRefresh(){// 开始刷新IsRefreshing = true;// 模拟异步操作（例如，从网络加载数据）await Task.Delay(2000);// 在主线程上更新 UIawait MainThread.InvokeOnMainThreadAsync(() =>{// 添加新的列表项for (int i = 0; i < 10; i++){AddNewItem();}// 结束刷新IsRefreshing = false;});}// 列表项即将可见事件处理方法private async void OnItemAppearing(object sender, ItemVisibilityEventArgs e){// 检查是否即将显示最后一个列表项，触发加载更多if (e.Item == _items[_items.Count - 1]){await LoadMoreItems();}}// 加载更多的方法private async Task LoadMoreItems(){// 模拟加载更多数据的异步操作await Task.Delay(2000);// 在主线程上更新 UIawait MainThread.InvokeOnMainThreadAsync(() =>{// 添加更多新的列表项for (int i = 0; i < 10; i++){AddNewItem();}IsRefreshing = false;});}private void AddNewItem(){string randomFruit = fruits[_random.Next(fruits.Length)];_items.Add(new ProductItem{ImageSource = "dotnet_bot.png", // 替换为实际的图片路径ProductName = $"{randomFruit}： {_items.Count}",Price = $"价格: {_random.NextDouble() * 100:F2} 元"});}// 通用方法，用于设置属性并触发属性更改通知protected bool SetProperty<T>(ref T backingStore, T value,[CallerMemberName] string propertyName = "",Action onChanged = null){if (EqualityComparer<T>.Default.Equals(backingStore, value))return false;backingStore = value;onChanged?.Invoke();OnPropertyChanged(propertyName);return true;}}
}