问题
In a Delphi VCL project, I have created a simple TVirtualStringTree
with two columns. The first column will contain text identifying the Name
of the data being represented. The data record also contains a status field. The second column is intended to represent the status of the record using an image (16x16 pixel) w/o text.
I have searched demos, but have not mastered the full process for how VTV displays a node, and have not been successful in getting an icon to display in the node of a specified column.
So I have three related questions:
I see how the text is assigned in the
OnGetText
event, but where should I assign or change the image to reflect the current status in my record?How do I get the image to actually display in the column?
Am I limited in size for the images, or can they be larger than icons? If so, do I need to change any settings to adjust the height of each row (if possible)?
回答1:
You need to assign (16x16 in your case) TImageList
to the TVirtualStringTree.Images
property, then handle the event OnGetImageIndex
e.g.:
procedure TForm1.VirtualStringTree1GetImageIndex(Sender: TBaseVirtualTree;
Node: PVirtualNode; Kind: TVTImageKind; Column: TColumnIndex;
var Ghosted: Boolean; var ImageIndex: Integer);
var
NodeRec: PNodeRec;
begin
NodeRec := Sender.GetNodeData(Node);
if Assigned(NodeRec) then
begin
if (Column = 1) then
begin
if Kind in [ikNormal, ikSelected] then
begin
case NodeRec.Status of // check the needed status(es)
1: ImageIndex := 1; // whichever image you need
2: ImageIndex := 2; // whichever image you need
// ...
end;
end;
end;
end;
end;
Am I limited in size for the images, or can they be larger than icons? If so, do I need to change any settings to adjust the height of each row (if possible)
Not sure what you meant by that, because you stated you need a 16x16 images. You could use OnGetImageIndexEx
if you need different image lists with possibly different dimensions. for variable height you could set toVariableNodeHeight
in the TreeOptions.MiscOptions
and handle the OnMeasureItem
event. another way to draw graphics into the VTV canvas is to handle the OnBeforeItemPaint
/OnAfterItemPaint
for example.
回答2:
Create an image list 16x16 (Images) and use code like:
procedure TMyTreeView.OnDrawTextEx(Sender: TBaseVirtualTree;
TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
const Text: string; const CellRect: TRect; var DefaultDraw: Boolean);
var i: integer;
begin
if (Node <> nil) then
begin
case Column of
cStatusColumn:
begin
DefaultDraw := false;
i := 0; // assign the image index from Images list here
if (i <> -1) then
begin
Images.Draw(TargetCanvas, CellRect.Left +
((CellRect.Width - Images.Width) div 2), CellRect.Top, i);
end;
end
else
begin
DefaultDraw := true;
end;
end;
end
else
begin
DefaultDraw := true;
end;
end;
来源:https://stackoverflow.com/questions/43858775/how-to-display-an-icon-or-image-in-a-column-of-tvirtualstringtree