Lazarus

Announcements => Third party => Topic started by: a5607593 on August 05, 2018, 11:48:32 pm

Title: Why dont add nodes in VirtualTree?
Post by: a5607593 on August 05, 2018, 11:48:32 pm

Hello,

help me, pls. I can't add nodes in vstOrders.

type
TMyRecord = record
Active: Boolean;
ID : Longint;
(здесь десяток полей)
NodePointer: PVirtualNode;
end;

rTreeData = record
IndexInMyData: integer;
end;

...

Procedure TForm1.LoadOrders;
var
Node: PVirtualNode;
Data: ^rTreeData;
i,Idx: integer;
Timer: cardinal;
begin
vstOrders.BeginUpdate;

Idx := length(MyArrayData);
SetLength(MyArrayData, length(MyArrayData)+frmDB.dbfOrders.RecordCount );

frmDB.dbfOrders.First;
repeat
Node := vstOrders.AddChild(nil);
Data := vstOrders.GetNodeData(Node);
Data.IndexInMyData := Idx; //а вот здесь возникает ошибка access violation. Node при этом содержит nil

with MyArrayData[Data.IndexInMyData] do begin
Active :=true;
ID :=frmDB.dbfOrders.FieldByName('ID' ).AsInteger;
(и здесь поля)
NodePointer:= Node; //Create link into your data record to VST node
end;
inc(Idx);
frmDB.dbfOrders.Next;
until frmDB.dbfOrders.EOF;
vstOrders.EndUpdate;

End;

Variable Node contains nil. I think, is not correct. May be i must initialize it, but where?

Title: Re: Why dont add nodes in VirtualTree?
Post by: wp on August 06, 2018, 12:07:52 am

Did you somewhere define the size of the tree data record? Event OnGetNodeDataSize or property NodeDatasize.

Code: Pascal  [Select][+][-]

1.  vstOrders.NodeDataSize := SizeOf(rTreeData);

Title: Re: Why dont add nodes in VirtualTree?
Post by: taazz on August 06, 2018, 03:44:49 am

Quote from: a5607593 on August 05, 2018, 11:48:32 pm

Hello,

help me, pls. I can't add nodes in vstOrders.

Code: Pascal  [Select][+][-]

1. type
2. TMyRecord = record
3. Active: Boolean;
4. ID : Longint;
5. (здесь десяток полей)
6. NodePointer: PVirtualNode;
7. end;
8.  
9. rTreeData = record
10. IndexInMyData: integer;
11. end;
12.  
13. ...
14.  
15. Procedure TForm1.LoadOrders;
16. var
17. Node: PVirtualNode;
18. Data: ^rTreeData;
19. i,Idx: integer;
20. Timer: cardinal;
21. begin
22. vstOrders.BeginUpdate;
23.  
24. Idx := length(MyArrayData);
25. SetLength(MyArrayData, length(MyArrayData)+frmDB.dbfOrders.RecordCount );
26.  
27. frmDB.dbfOrders.First;
28. repeat
29. Node := vstOrders.AddChild(nil);
30. Data := vstOrders.GetNodeData(Node);
31. Data.IndexInMyData := Idx; //а вот здесь возникает ошибка access violation. Node при этом содержит nil
32.  
33. with MyArrayData[Data.IndexInMyData] do begin
34. Active :=true;
35. ID :=frmDB.dbfOrders.FieldByName('ID' ).AsInteger;
36. (и здесь поля)
37. NodePointer:= Node; //Create link into your data record to VST node
38. end;
39. inc(Idx);
40. frmDB.dbfOrders.Next;
41. until frmDB.dbfOrders.EOF;
42. vstOrders.EndUpdate;
43.  
44. End;
45.  

Variable Node contains nil. I think, is not correct. May be i must initialize it, but where?

virtual tree has a different model instead of pushing the data to the tree, it request the data. You only inform it on how many rows of data you have, ee you call rootnodecount = length(myArrayData); and use the events oninitnode and oninitchildren to set the nodes data and children respectively.

Title: Re: Why dont add nodes in VirtualTree?
Post by: eny on August 06, 2018, 04:49:59 pm

Quote from: taazz on August 06, 2018, 03:44:49 am

virtual tree has a different model instead of pushing the data to the tree, it request the data. You only inform it on how many rows of data you have, ee you call rootnodecount = length(myArrayData); and use the events oninitnode and oninitchildren to set the nodes data and children respectively.

Although that is true, sequentially adding nodes should still work.
Hence wp's remark might be a nudge in the right direction.
A complete listing of the program will reveal the actual problem.