WPF 【十月的寒流】学习笔记(3):DataGrid分页

前言

我们这次详细了解一下列表通知的底层是怎么实现的

相关链接

十月的寒流

WPF 中如何制作 DataGrid 的分页功能

代码仓库

我为了方便展示源代码，我将代码提交到了代码仓库里面

B站【十月的寒流】对应课程的代码 Github仓库

项目配置（省略）

想要看的话看我前面的文章就可以了

项目初始配置

和我之前的代码差不多，详细的就看我的源码好了，我会用TabItem来简单说明的。这就是初始配置的代码了

xaml

<UserControl x:Class="DataGrid_Pagination.Views.Demo1View"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:DataGrid_Pagination.Views"
             mc:Ignorable="d" 
             xmlns:hc="https://handyorg.github.io/handycontrol"
             xmlns:viewModels="clr-namespace:DataGrid_Pagination.ViewModels"
             d:DesignHeight="450" d:DesignWidth="800">
    <UserControl.DataContext>
        <viewModels:Demo1ViewModel  x:Name="ViewModel"/>
    </UserControl.DataContext>
    <DockPanel>
        <hc:Pagination MaxPageCount="10"
                       DockPanel.Dock="Bottom"
                       Margin="4 7"
                       PageIndex="5"
                       IsJumpEnabled="True" />
        <DataGrid ItemsSource="{Binding CollectionData.Data}">
            
        </DataGrid>
        
    </DockPanel>
</UserControl>

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viewModel

namespace DataGrid_Pagination.ViewModels
{
    public partial class Demo1ViewModel : ObservableObject
    {

        public Demo1View Demo1View { get; set; }

        [ObservableProperty]
        private CollectionData<Student> collectionData = new CollectionData<Student>();

        public Demo1ViewModel()
        {
            CollectionData = new CollectionData<Student>() {
                Data = new Student().FakeMany(10)
            };
            CollectionData.Init();
            CollectionData.CollectionView.Refresh();
        }
    }
}
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Filter过滤

详细代码

<UserControl x:Class="DataGrid_Pagination.Views.Demo2View"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:DataGrid_Pagination.Views"
             mc:Ignorable="d" 
             xmlns:hc="https://handyorg.github.io/handycontrol"
             xmlns:viewModels="clr-namespace:DataGrid_Pagination.ViewModels"
             d:DesignHeight="450" d:DesignWidth="800">
    <UserControl.DataContext>
        <viewModels:Demo2ViewModel  x:Name="ViewModel"/>
    </UserControl.DataContext>
    <DockPanel>
        <hc:Pagination MaxPageCount="{Binding PageCount}"
                       DockPanel.Dock="Bottom"
                       Margin="4 7"
                       PageIndex="{Binding PageIndex,Mode=TwoWay}"
                       IsJumpEnabled="True" />
        <DataGrid ItemsSource="{Binding CollectionData.Data}">
            
        </DataGrid>
        
    </DockPanel>
</UserControl>

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namespace DataGrid_Pagination.ViewModels
{
    public partial class Demo2ViewModel : ObservableObject
    {

        public Demo2View View { get; set; }

        [ObservableProperty]
        private CollectionData<Student> collectionData = new CollectionData<Student>();



        private int pageIndex = 1;
        public int PageIndex
        {
            get => pageIndex;
            set {
                SetProperty(ref pageIndex, value);
                CollectionData.CollectionView.Refresh();
            }
        }

        public readonly int PageSize = 10;


        [ObservableProperty]
        private int pageCount = 1;




        public Demo2ViewModel()
        {
            CollectionData = new CollectionData<Student>()
            {
                Data = new Student().FakeMany(150)
            };
            CollectionData.Binding();
            CollectionData.CollectionView.CollectionChanged += (s, e) =>
            {
                var count = CollectionData.Data.ToList().Count;
                PageCount = (int)Math.Ceiling((decimal)(count / PageSize));
            };
            CollectionData.CollectionView.Filter = (item) =>
            {
                if (!(item is Student))
                {
                    throw new Exception("属性类型不为Student");
                }
                var index = CollectionData.Data.ToList().IndexOf((Student)item);
                return PageIndex == index / PageSize + 1;

            };
            CollectionData.CollectionView.Refresh();
        }

    }
}
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展示结果

问题

小数据量没问题，但是大数据会出问题。因为主要的计算是indexOf和每个项的Filter。o(n)*o(n)=o(n^2)，复杂度太高了。

Linq过滤

Linq过滤就是我们每次都更新CollectionView绑定的对象，触发更新

CollectionData

    public partial class CollectionData<T>:ObservableObject where T : class
    {
        [ObservableProperty]
        private IEnumerable<T> data = new List<T>();

        public ICollectionView CollectionView { get; set; }
        public CollectionData() { }

        

        public void Binding()
        {
            CollectionView = CollectionViewSource.GetDefaultView(Data);
        }


    }
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xaml

<UserControl x:Class="DataGrid_Pagination.Views.Demo3View"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:local="clr-namespace:DataGrid_Pagination.Views"
             mc:Ignorable="d"
             xmlns:hc="https://handyorg.github.io/handycontrol"
             xmlns:viewModels="clr-namespace:DataGrid_Pagination.ViewModels"
             d:DesignHeight="450"
             d:DesignWidth="800">
    <UserControl.DataContext>
        <viewModels:Demo3ViewModel  x:Name="ViewModel" />
    </UserControl.DataContext>
    <DockPanel>
        <hc:Pagination MaxPageCount="{Binding PageCount}"
                       DockPanel.Dock="Bottom"
                       Margin="4 7"
                       PageIndex="{Binding PageIndex,Mode=TwoWay}"
                       IsJumpEnabled="True" />
        <DataGrid ItemsSource="{Binding CollectionData.Data}">

        </DataGrid>

    </DockPanel>
</UserControl>

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viewModel

namespace DataGrid_Pagination.ViewModels
{
    public partial class Demo3ViewModel : ObservableObject
    {
        public Demo3View View { get; set; }

        [ObservableProperty]
        private CollectionData<Student> collectionData = new CollectionData<Student>();

        private int pageIndex = 1;
        public int PageIndex
        {
            get => pageIndex;
            set
            {
                SetProperty(ref pageIndex, value);
                CollectionData.CollectionView.Refresh();
            }
        }

        public readonly int PageSize = 10;


        [ObservableProperty]
        private int pageCount = 1;

        public readonly List<Student> Students = new Student().FakeMany(150).ToList();


        public Demo3ViewModel()
        {
            CollectionData = new CollectionData<Student>()
            {
                Data = Students.Take(PageSize),
            };
            CollectionData.Binding();
            CollectionData.CollectionView.CollectionChanged += (s, e) =>
            {
                var count = Students.Count;
                PageCount = (int)Math.Ceiling((decimal)(count / PageSize));
                CollectionData.Data = Students.Skip((PageIndex - 1) * PageSize).Take(PageSize);
            };


        }
    }
}
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sql，这里用到数据库，就不展开了

总结

分页是我们最常用的功能，这次简单实现了分页的效果。HandyControl没有提供主动的分页，需要我们组合一下。详细代码可以看我的Github仓库。三种过滤我都写了。