TListView中的排序箭頭處理問題

在 Delphi 11 Alexandria 的 Windows 10 中的 32 位 VCL 應用程式中，我有TListView兩列，客戶端與表單對齊。我正在使用此代碼來處理 ListView Header 中的排序箭頭：

procedure TformMain.ListView1ColumnClick(Sender: TObject; Column: TListColumn);
begin
  FSortedColumn := Column.Index; 
  case FSortedColumn of
    0: FColumn0SortedUp := not FColumn0SortedUp;
    1: FColumn1SortedUp := not FColumn1SortedUp;
  end;
  SetListHeaderSortArrow(FSortedColumn);
end;

procedure TformMain.SetListHeaderSortArrow(const aColumnIndex: Integer);
begin
  var Header: HWND;
  var Item: Winapi.CommCtrl.THDItem;
  case aColumnIndex of
    0:
      begin
        Header := Winapi.CommCtrl.ListView_GetHeader(ListView1.Handle);
        Winapi.Windows.ZeroMemory(@Item, SizeOf(Item));
        Item.Mask := Winapi.CommCtrl.HDI_FORMAT;
        Winapi.CommCtrl.Header_GetItem(Header, 0, Item);
        Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN); // remove both flags

        if FColumn0SortedUp then
          Item.fmt := Item.fmt or HDF_SORTUP // include the sort ascending flag
        else
          Item.fmt := Item.fmt or HDF_SORTDOWN; // include the sort descending flag

        Header_SetItem(Header, 0, Item);
      end;
    1:
      begin
        Header := Winapi.CommCtrl.ListView_GetHeader(ListView1.Handle);
        Winapi.Windows.ZeroMemory(@Item, SizeOf(Item));
        Item.Mask := Winapi.CommCtrl.HDI_FORMAT;
        Winapi.CommCtrl.Header_GetItem(Header, 1, Item);
        Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN); // remove both flags

        if FColumn1SortedUp then
          Item.fmt := Item.fmt or HDF_SORTUP // include the sort ascending flag
        else
          Item.fmt := Item.fmt or HDF_SORTDOWN; // include the sort descending flag

        Header_SetItem(Header, 1, Item);
      end;
  end;
end;

procedure TformMain.ListView1Resize(Sender: TObject);
begin
  // This gets inexplicably automatically executed 3 times at program start!!
  // This must be in OnResize, otherwise the sort-arrows get hidden when resizing the ListView:
  SetListHeaderSortArrow(FSortedColumn);
end;

當我點擊 SECOND 列的列標題時，出現了第二列的排序箭頭，但第一列的排序箭頭并沒有消失！只有當我調整 ListView 的大小（通過調整表單的大小）時，第一列上的排序箭頭才會消失。那么如何在單擊第二列標題時使第一列上的排序箭頭立即消失？

uj5u.com熱心網友回復：

更改標志時，在將標志添加到新列之前，您不會從先前選定的列中洗掉標志。

嘗試更多類似的東西：

private:
  FColumnSortedUp: array[0..1] of Boolean;
  FSortedColumn: Integer;

...

procedure TformMain.FormCreate(Sender: TObject);
begin
  FSortedColumn := -1;
end;

procedure TformMain.ListView1ColumnClick(Sender: TObject; Column: TListColumn);
begin
  if FSortedColumn <> -1 then
    SetListHeaderSortArrow(FSortedColumn, False);

  if FSortedColumn = Column.Index then
    FColumnSortedUp[FSortedColumn] := not FColumnSortedUp[FSortedColumn];
  else
    FSortedColumn := Column.Index;

  SetListHeaderSortArrow(FSortedColumn, True);

  // sort ListView items as needed...
end;

procedure TformMain.SetListHeaderSortArrow(const aColumnIndex: Integer;
  const aEnabled: Boolean);
var
  Header: HWND;
  Item: THDItem;
begin
  Header := ListView_GetHeader(ListView1.Handle);
  ZeroMemory(@Item, SizeOf(Item));
  Item.Mask := HDI_FORMAT;
  Header_GetItem(Header, aColumnIndex, Item);
  Item.fmt := Item.fmt and not (HDF_SORTUP or HDF_SORTDOWN); // remove both flags

  if aEnabled then
  begin
    if FColumnSortedUp[aColumnIndex] then
      Item.fmt := Item.fmt or HDF_SORTUP // include the sort ascending flag
    else
      Item.fmt := Item.fmt or HDF_SORTDOWN; // include the sort descending flag
  end;

  Header_SetItem(Header, aColumnIndex, Item);
end;

另請注意，在調整ListView大小時排序箭頭不會消失，而是在調整列大小時。因此，您必須掛鉤 ListView 來處理HDN_ENDTRACK通知，以檢測每列何時調整大小，例如：

private
  ...
  OldWndProc: TWndMethod;
  procedure ListViewWndProc(var Message: TMessage);

...

uses
  ..., Winapi.Messages, Winapi.CommCtrl;

procedure TformMain.FormCreate(Sender: TObject);
begin
  ...
  OldWndProc := ListView1.WindowProc;
  ListView1.WindowProc := ListViewWndProc;
end;

procedure TformMain.ListViewWndProc(var Message: TMessage);
begin
  OldWndProc(Message);
  if Message.Msg = WM_NOTIFY then
  begin
    if TWMNotify(Message).NMHdr.code = HDN_ENDTRACK then
    begin
      if PHDNotify(TWMNotify(Message).NMHdr).Item = FSortedColumn then
        SetListHeaderSortArrow(FSortedColumn, True);
    end;
  end;
end;

uj5u.com熱心網友回復：

我找到了解決問題的解決方法：

procedure PALockWinControl(const WC: Vcl.Controls.TWinControl; ALock: Boolean);
begin
  if (not Assigned(WC)) or (WC.Handle = 0) then EXIT;

  if ALock then
    WC.Perform(WM_SETREDRAW, 0, 0)
  else
  begin
    WC.Perform(WM_SETREDRAW, 1, 0);
    RedrawWindow(WC.Handle, nil, 0, RDW_ERASE or RDW_FRAME or RDW_INVALIDATE or RDW_ALLCHILDREN);
  end;
end;

procedure MyRedrawWorkaround;
begin
  with formMain do
  begin
    PALockWinControl(ListView1, True);
    try
      ListView1.Align := alNone;
      ListView1.Width := lvMRUProjects.Width - 1;
      ListView1.Align := alClient;
    finally
      PALockWinControl(ListView1, False);
    end;
  end;
end;

procedure TformMain.ListView1ColumnClick(Sender: TObject; Column: TListColumn);
begin
  FSortedColumn := Column.Index;
  case FSortedColumn of
    0: FColumn0SortedUp := not FColumn0SortedUp;
    1: FColumn1SortedUp := not FColumn1SortedUp;
  end;
  SetListHeaderSortArrow(FSortedColumn);

  MyRedrawWorkaround;
end;

標籤：

上一篇：如何在UTF8編碼RadStudio/Delphi中將JSONObject保存到json檔案

下一篇：決議JSON中的字串陣列