Question

我正在研究Delphi 10.2 Tokyo。

在SortArrow On ListView的帮助下，我可以为列表视图组件添加排序箭头（在colclick上添加了排序箭头逻辑），当我执行列调整大小排序箭头时消失。

如何在调整列大小时保持排序箭头（类似于Windows资源管理器）？

以下是我的组件代码：

unit uMyListView1;


interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ComCtrls, Menus, DB, ExtCtrls, Buttons, ADODB,Commctrl;

const ARROW_SIZE = 10;

type

  TMyListView = class(TListView)
  private
    FDataSet:                   TCustomADODataSet;

    FPressedColumn:             integer; //column index
    FLastPressedColumn:         integer; //last column to be pressed
    FSortDir:                   integer; //-1 = desc, 1 = asc
    FSortOrder:                 integer;

    procedure SetListViewColumns;
  protected
    procedure ColClick(Column: TListColumn); override;
  public
    constructor Create(AOwner: TComponent); override;
    destructor  Destroy; override;
    function    BuildListView: boolean;
  published
    property DataSet: TCustomADODataSet read FDataSet write FDataSet;
  end;

implementation

procedure TMyListView.ColClick(Column: TListColumn);
var DC: HDC;
    Pos: TPoint;
  Header: HWND;
  Item: THDItem;
begin
  inherited;
  FLastPressedColumn := -1;
  FPressedColumn := Column.Index;

  FSortDir := 1;

//implement sorting

  Header := ListView_GetHeader(Self.Handle);
  ZeroMemory(@Item, SizeOf(Item));
  Item.Mask := HDI_FORMAT;

  //remove arrow old cloumn
  if FLastPressedColumn <> -1 then
  begin
    Header_GetItem(Header,  FLastPressedColumn, Item);
    Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN);//remove both flags
    Header_SetItem(Header, FLastPressedColumn, Item);
  end;


  Header_GetItem(Header,  Column.Index, Item);
  Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN);//remove both flags

  if (FSortDir = 1) then
    Item.fmt := Item.fmt or HDF_SORTUP//include the sort ascending flag
  else if (FSortDir = -1) then
    Item.fmt := Item.fmt or HDF_SORTDOWN;


  Header_SetItem(Header, Column.Index, Item);
end;

constructor TMYListView.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FPressedColumn     := -1;
  FLastPressedColumn := -1;
  FSortOrder         := 0;
end;

destructor TMYListView.Destroy;
begin
  inherited Destroy;
end;

procedure TMYListView.SetListViewColumns;
var
  NewColumn:        TListColumn;
  i:                integer;
begin
  if FDataSet <> nil then with FDataSet, Self.Columns do
  begin
    Clear;  //clears any columns
    for i := 0 to FieldCount - 1 do
      if Fields[i].Visible then
      begin
        NewColumn          := Add;
        NewColumn.Caption  := Fields[i].DisplayLabel;
        NewColumn.Width    := Fields[i].DisplayWidth * 10;
        NewColumn.Alignment := Fields[i].Alignment;
      end;
  end;
end;

function TMYListView.BuildListView: boolean;
var NewListItem:     TListItem;
    i:               integer;
begin
  Result := FALSE;

  FPressedColumn     := -1;
  FLastPressedColumn := -1;

  Items.Clear;

  if FDataSet = NIL then
  begin
    MessageDlg('The Dataset is NIL', mtError, [mbOK], 0);
    Exit;
  end;
  try
    FDataset.Open;
    SetListViewColumns;

    with FDataSet do
    Begin
      Items.BeginUpdate;
      if not EOF then while not EOF do
      begin
        NewListItem := Items.Add;
        for i := 0 to FieldCount - 1 do
        begin
          if Fields[i].Visible then
          begin
            if i = 0 then NewListItem.Caption := Fields[0].DisplayText
            else if Fields[i].Visible then NewListItem.SubItems.Add(Fields[i].DisplayText);

          end;
        end;
        Next;
        Application.ProcessMessages;
      end;
    end;

    Result := TRUE;
  finally
    FDataSet.Close;
    Items.EndUpdate;
  end;

end;

end.

Answer 1

不确定为什么你的箭会消失。更糟糕的情况是，您可能需要从标题处获取ListView处理HDN_TRACK通知以重置当前箭头（如果有）。

但是，您的代码中还存在与管理箭头有关的其他问题。

您的ColClick()方法在之前将FLastPressedColumn重置为-1 ，使用它来清除现有箭头：

begin inherited; //FLastPressedColumn := -1; // <-- REMOVE THIS! ... //remove arrow old cloumn if FLastPressedColumn <> -1 then begin ... FLastPressedColumn := -1; // <-- MOVED DOWN HERE INSTEAD! end; ... end;

事实上，您根本不需要FLastPressedColumn，FPressedColumn就足够了：

procedure TMyListView.ColClick(Column: TListColumn); var LNewColumn: Integer; Item: THDItem; begin inherited; if Column <> nil then LNewColumn := Column.Index else LNewColumn := -1; if FPressedColumn <> LNewColumn then begin FSortDir := 1; //implement sorting Header := ListView_GetHeader(Self.Handle); ZeroMemory(@Item, SizeOf(Item)); Item.Mask := HDI_FORMAT; //remove arrow old cloumn if FPressedColumn <> -1 then begin Header_GetItem(Header, FPressedColumn, Item); Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN);//remove both flags Header_SetItem(Header, FPressedColumn, Item); end; FPressedColumn := LNewColumn; if FPressedColumn <> -1 then begin Header_GetItem(Header, FPressedColumn, Item); Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN);//remove both flags if (FSortDir = 1) then Item.fmt := Item.fmt or HDF_SORTUP//include the sort ascending flag else if (FSortDir = -1) then Item.fmt := Item.fmt or HDF_SORTDOWN; Header_SetItem(Header, FPressedColumn, Item); end; end; end;

此外，您的组件根本不处理窗口娱乐。如果重新创建ListView的HWND（在此过程的生命周期中可以和发生），则需要恢复当前的排序箭头（如果有）。如果CreateWnd()不是-1，您可以覆盖虚拟CreateWindowHandle()或Header_SetItem()方法来调用FPressedColumn：

type TMyListView = class(TListView) ... protected ... procedure CreateWnd; override; ... end; ... procedure TMyListView.CreateWnd; var Header: HWND; Item: THDItem; begin inherited; if FPressedColumn <> -1 then begin Header := ListView_GetHeader(Self.Handle); ZeroMemory(@Item, SizeOf(Item)); Item.Mask := HDI_FORMAT; Header_GetItem(Header, FPressedColumn, Item); Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN);//remove both flags if (FSortDir = 1) then Item.fmt := Item.fmt or HDF_SORTUP//include the sort ascending flag else if (FSortDir = -1) then Item.fmt := Item.fmt or HDF_SORTDOWN; Header_SetItem(Header, FPressedColumn, Item); end; end;

TListView排序箭头在列调整大小时消失

1 个答案: