c# - 在 C# 和 WinForms 中将筛选框添加到 ListView 的列标题

Question

在 Windows 资源管理器中(至少在 Win7 中)，当您将鼠标悬停在列标题上时，会出现一个带箭头的筛选框，您可以通过它筛选 ListView 中的结果，例如，您只能显示以“A"或文件 > 128 MB。是否可以在 C# 中的基本 ListView 控件中启用此功能，而无需子类化或修改 ListView？

Answer 1

这里有一些代码可以玩。向您的项目添加一个新类并粘贴如下所示的代码。编译。将工具箱顶部的新 ListViewEx 控件拖放到窗体上。在窗体构造函数中，调用 SetHeaderDropdown() 方法以启用按钮。实现 HeaderDropdown 事件以返回要显示的控件。例如:

public partial class Form1 : Form {
    public Form1() {
        InitializeComponent();
        listViewEx1.SetHeaderDropdown(0, true);
        listViewEx1.HeaderDropdown += listViewEx1_HeaderDropdown;
    }

    void listViewEx1_HeaderDropdown(object sender, ListViewEx.HeaderDropdownArgs e) {
        e.Control = new UserControl1();
    }
}

下面的代码有一个缺陷，弹出窗口显示在一个表单中。它不能太小，并且会把焦点从主要形式上移开。检查this answer on 提示如何实现可以显示为顶层窗口而不需要窗体的控件。代码:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;

class ListViewEx : ListView {
    public class HeaderDropdownArgs : EventArgs {
        public int Column { get; set; }
        public Control Control { get; set; }
    }
    public event EventHandler<HeaderDropdownArgs> HeaderDropdown;

    public void SetHeaderDropdown(int column, bool enable) {
        if (column < 0 || column >= this.Columns.Count) throw new ArgumentOutOfRangeException("column");
        while (HeaderDropdowns.Count < this.Columns.Count) HeaderDropdowns.Add(false);
        HeaderDropdowns[column] = enable;
        if (this.IsHandleCreated) SetDropdown(column, enable);
    }
    protected void OnHeaderDropdown(int column) {
        var handler = HeaderDropdown;
        if (handler == null) return;
        var args = new HeaderDropdownArgs() { Column = column };
        handler(this, args);
        if (args.Control == null) return;
        var frm = new Form();
        frm.FormBorderStyle = FormBorderStyle.FixedSingle;
        frm.ShowInTaskbar = false;
        frm.ControlBox = false;
        args.Control.Location = Point.Empty;
        frm.Controls.Add(args.Control);
        frm.Load += delegate { frm.MinimumSize = new Size(1, 1);  frm.Size = frm.Controls[0].Size; };
        frm.Deactivate += delegate { frm.Dispose(); };
        frm.StartPosition = FormStartPosition.Manual;
        var rc = GetHeaderRect(column);
        frm.Location = this.PointToScreen(new Point(rc.Right - SystemInformation.MenuButtonSize.Width, rc.Bottom));
        frm.Show(this.FindForm());
    }

    protected override void OnHandleCreated(EventArgs e) {
        base.OnHandleCreated(e);
        if (this.Columns.Count == 0 || Environment.OSVersion.Version.Major < 6 || HeaderDropdowns == null) return;
        for (int col = 0; col < HeaderDropdowns.Count; ++col) {
            if (HeaderDropdowns[col]) SetDropdown(col, true);
        }
    }

    private Rectangle GetHeaderRect(int column) {
        IntPtr hHeader = SendMessage(this.Handle, LVM_GETHEADER, IntPtr.Zero, IntPtr.Zero);
        RECT rc;
        SendMessage(hHeader, HDM_GETITEMRECT, (IntPtr)column, out rc);
        return new Rectangle(rc.left, rc.top, rc.right - rc.left, rc.bottom - rc.top);
    }

    private void SetDropdown(int column, bool enable) {
        LVCOLUMN lvc = new LVCOLUMN();
        lvc.mask = LVCF_FMT;
        lvc.fmt = enable ? LVCFMT_SPLITBUTTON : 0;
        IntPtr res = SendMessage(this.Handle, LVM_SETCOLUMN, (IntPtr)column, ref lvc);
    }

    protected override void WndProc(ref Message m) {
        Console.WriteLine(m);
        if (m.Msg == WM_NOTIFY) {
            var hdr = (NMHDR)Marshal.PtrToStructure(m.LParam, typeof(NMHDR));
            if (hdr.code == LVN_COLUMNDROPDOWN) {
                var info = (NMLISTVIEW)Marshal.PtrToStructure(m.LParam, typeof(NMLISTVIEW));
                OnHeaderDropdown(info.iSubItem);
                return;
            }
        }
        base.WndProc(ref m);
    }

    private List<bool> HeaderDropdowns = new List<bool>();

    // Pinvoke
    [DllImport("user32.dll")]
    private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);
    [DllImport("user32.dll")]
    private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, ref LVCOLUMN lvc);
    [DllImport("user32.dll")]
    private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, out RECT rc);
    [DllImport("user32.dll")]
    private static extern IntPtr SetParent(IntPtr hWnd, IntPtr hParent);

    private const int LVM_SETCOLUMN = 0x1000 + 96;
    private const int LVCF_FMT = 1;
    private const int LVCFMT_SPLITBUTTON = 0x1000000;
    private const int WM_NOTIFY = 0x204e;
    private const int LVN_COLUMNDROPDOWN = -100 - 64;
    private const int LVM_GETHEADER = 0x1000 + 31;
    private const int HDM_GETITEMRECT = 0x1200 + 7;


    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct LVCOLUMN {
        public uint mask;
        public int fmt;
        public int cx;
        public string pszText;
        public int cchTextMax;
        public int iSubItem;
        public int iImage;
        public int iOrder;
        public int cxMin;
        public int cxDefault;
        public int cxIdeal;
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct POINT {
        public int x, y;
    }
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct RECT {
        public int left, top, right, bottom; 
    }
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct NMHDR {
        public IntPtr hwndFrom;
        public IntPtr idFrom;
        public int code;
    }
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct NMLISTVIEW {
        public NMHDR hdr;
        public int iItem;
        public int iSubItem;
        public uint uNewState;
        public uint uOldState;
        public uint uChanged;
        public POINT ptAction;
        public IntPtr lParam;
    }
}