因此，iamjoosy 的答案的问题是——即使它有效——只要你用绘制的按钮/图像/无论如何滚动浏览这棵树，应该再次离开树的那些仍然存在，正在被绘制在您离开它们的最低/最高位置。根据您刚刚滚动的数量，它会在该列中留下更小或更大的按钮混乱。 AfterCellPaint 不再移动它们，因为不再绘制底部下方/顶部上方的那个现在不可见节点的单元格。
您可以做的是遍历所有树节点（如果您有很多节点，可能会非常昂贵）并检查它们是否真的在树的可见区域并隐藏面板（您可能需要面板内的按钮来用你的按钮/相应的东西画在树的顶部而不是后面）：
procedure TMyTree.MyTreeAfterCellPaint(Sender: TBaseVirtualTree;
TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
CellRect: TRect);
var
InitialIndex: Integer;
// onInitNode I AddOrSetValue a "DataIndexList" TDictionary<PVirtualNode, LongInt>
// to preserve an original index "InitialIndex" (violating the virtual paradigm),
// because I need it for something else anyways
Data: PMyData;
ANode: PVirtualNode;
begin
if Node <> nil then
begin
if Column = 2 then
begin
ANode := MyTree.GetFirst;
while Assigned(ANode) do
begin
DataIndexList.TryGetValue(ANode, InitialIndex);
if not ( CheckVisibility(Sender.GetDisplayRect(ANode, Column, False)) ) then
begin
MyBtnArray[InitialIndex].Visible := False;
MyPanelArray[InitialIndex].Visible := False;
end
else
begin
MyBtnArray[InitialIndex].Visible := True;
MyPanelArray[InitialIndex].Visible := True;
end;
ANode := MyTree.GetNext(ANode);
end;
DataIndexList.TryGetValue(Node, InitialIndex);
Data := MyTree.GetNodeData(Node);
MyPanelArray[InitialIndex].BoundsRect := Sender.GetDisplayRect(Node, Column, False);
end;
end;
end;
function TMyTree.CheckVisibility(R: TRect): Boolean;
begin
// in my case these checks are the way to go, because
// MyTree is touching the top border of the TForm. You will have
// to adjust accordingly if your placement is different
if (R.Bottom < MyTree.Top) or (R.Bottom > MyTree.Top + MyTree.Height) then
Result := False
else
Result := True;
end;
不用说，您可以在许多其他 OnEvents 中成功地使用 visibilityCheck 进行遍历。它不必在 AfterCellPaint 中；也许另一个事件在性能方面可能要好得多。
要创建一个原始 Panel+Button 的 RunTime 副本，放置在 ButtonArray 或您使用的任何结构中，您还必须复制它们的 RTTI。这个过程取自http://www.blong.com/Conferences/BorConUK98/DelphiRTTI/CB140.zip（更多RTTI信息http://www.blong.com/Conferences/BorConUK98/DelphiRTTI/CB140.htm）和“使用TypInfo”：
procedure CopyObject(ObjFrom, ObjTo: TObject);
var
PropInfos: PPropList;
PropInfo: PPropInfo;
Count, Loop: Integer;
OrdVal: Longint;
StrVal: String;
FloatVal: Extended;
MethodVal: TMethod;
begin
{ Iterate thru all published fields and properties of source }
{ copying them to target }
{ Find out how many properties we'll be considering }
Count := GetPropList(ObjFrom.ClassInfo, tkAny, nil);
{ Allocate memory to hold their RTTI data }
GetMem(PropInfos, Count * SizeOf(PPropInfo));
try
{ Get hold of the property list in our new buffer }
GetPropList(ObjFrom.ClassInfo, tkAny, PropInfos);
{ Loop through all the selected properties }
for Loop := 0 to Count - 1 do
begin
PropInfo := GetPropInfo(ObjTo.ClassInfo, PropInfos^[Loop]^.Name);
{ Check the general type of the property }
{ and read/write it in an appropriate way }
case PropInfos^[Loop]^.PropType^.Kind of
tkInteger, tkChar, tkEnumeration,
tkSet, tkClass{$ifdef Win32}, tkWChar{$endif}:
begin
OrdVal := GetOrdProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) then
SetOrdProp(ObjTo, PropInfo, OrdVal);
end;
tkFloat:
begin
FloatVal := GetFloatProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) then
SetFloatProp(ObjTo, PropInfo, FloatVal);
end;
{$ifndef DelphiLessThan3}
tkWString,
{$endif}
{$ifdef Win32}
tkLString,
{$endif}
tkString:
begin
{ Avoid copying 'Name' - components must have unique names }
if UpperCase(PropInfos^[Loop]^.Name) = 'NAME' then
Continue;
StrVal := GetStrProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) then
SetStrProp(ObjTo, PropInfo, StrVal);
end;
tkMethod:
begin
MethodVal := GetMethodProp(ObjFrom, PropInfos^[Loop]);
if Assigned(PropInfo) then
SetMethodProp(ObjTo, PropInfo, MethodVal);
end
end
end
finally
FreeMem(PropInfos, Count * SizeOf(PPropInfo));
end;
end;
稍后看到我的这个旧答案，我现在为 VisibilityCheck 运行了一个不同的解决方案，它更可靠、更容易：
function TFoo.IsNodeVisibleInClientRect(Node: PVirtualNode; Column: TColumnIndex = NoColumn): Boolean;
begin
Result := VST.IsVisible[Node] and
VST.GetDisplayRect(Node, Column, False).IntersectsWith(VST.ClientRect);
end;