问题
here my simple code to add filename and their associated icon to virtualtreeview
PFileInfoRec = ^TFileInfoRec;
TFileInfoRec = record
strict private
vFullPath: string;
vFileName: string;
vFileIcon: hIcon;
public
constructor Create(const FullPath: string);
property FullPath: string read vFullPath;
property FileNam : string read vFileName;
property FileIcon: hIcon read vFileIcon;
end;
after i got the icon handle using shGetFileInfo Api
procedure TMainFrm.VSTGetImageIndex(Sender: TBaseVirtualTree;
Node: PVirtualNode; Kind: TVTImageKind; Column: TColumnIndex;
var Ghosted: Boolean; var ImageIndex: Integer);
var
FileInfo: PFileInfoRec;
Icon: TIcon;
begin
FileInfo := Sender.GetNodeData(Node);
Icon := TIcon.Create;
try
Icon.Handle := FileInfo.FileIcon;
if Kind in [ikNormal , ikSelected] then
begin
if Column = 1 then ImageIndex := ImageList.AddIcon(Icon);
end;
finally
Icon.Free; //here the probelme
end;
end;
what confuse me whene remove Icon.Free; the code work fine File added with icons but when free TIcon Object the addition of the icon fail!! any one explain to me What's wrong with this code ??
Thanks for the help in advance...
回答1:
First of all, you must stop calling ImageList.AddIcon
in OnGetImageIndex
. I won't repeat the advice in detail but simply refer you to your previous question.
As for what's happening here, this is what is occurring:
- You create an icon handle,
vFileIcon
. - You then pass ownership of that icon to the
TIcon
instance. - You free the icon instance which in turn deletes the icon handle.
- The next time you call
OnGetImageIndex
, the icon handlevFileIcon
refers to a handle that has been destroyed and so naturally your attempts to use that icon fail.
The easiest way to add this icon to the image list is in fact to use ImageList_AddIcon and not bother creating a TIcon
instance.
FileInfo := Sender.GetNodeData(Node);
ImageList_AddIcon(ImageList.Handle, FileInfo.FileIcon);
It is possible to use a TIcon
and not have the handle destroyed when the TIcon
instance is destroyed. Call ReleaseHandle to tell the TIcon
instance that it no longer owns the icon handle.
Icon := TIcon.Create;
try
Icon.Handle := SomeIconHandle;
SomeImageIndex := ImageList.AddIcon(Icon);
Icon.ReleaseHandle;
finally
//because ReleaseHandle was called, this no longer destroys the icon handle
Icon.Free;
end;
来源:https://stackoverflow.com/questions/11170316/virtualtreeview-add-icon-fail