BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Filling Tree View          BorlandTalk.com Forum Index -> Delphi VCL Components Writing View previous topic :: View next topic   Author Message Ricardo Oliveira Guest Posted: Tue Nov 11, 2003 10:46 am    Post subject: Filling Tree View Hi! Is there anyway to fill a treeview realy fast? I'm filing a treeview with items that are copied from a table (nr. fields * nr. records). The problem is it gets very slow. Anyway of doing this faster? Hope I made my self clear. Ricardo Oliveira Back to top John Leavey Guest Posted: Tue Nov 11, 2003 10:58 am    Post subject: Re: Filling Tree View On Tue, 11 Nov 2003 10:46:37 -0000, "Ricardo Oliveira" <ricardooliveira(removethis)@jpmabreu.pt> wrote: Quote: Hi! Is there anyway to fill a treeview realy fast? I'm filing a treeview with items that are copied from a table (nr. fields * nr. records). The problem is it gets very slow. Anyway of doing this faster? 1) Make sure that the code that populates the tree view is enclosed in TV.Items.BeginUpdate; try ... finally TV.Items.EndUpdate; end; 2) If this is still not fast enough for you, try using Mike Lischke's Virtual Tree View - www.delphi-gems.com, although this requires a slightly different mindset in relation to data handling than a standard tree view. John Leavey Back to top Ricardo Oliveira Guest Posted: Tue Nov 11, 2003 12:02 pm    Post subject: Re: Filling Tree View Hi John! Thanks for your sugestion. I've tested BeginUpdate and it works but it is not fast enough. I have also seen Mike Lischke's Virtual Tree View but I was expecting something less complicated. Any chance of using load(Stream, File, etc.) to load the items? Other Sugestions? :) Thanks again. Ricardo Oliveira. "John Leavey" <johnl (AT) NO_SPAM (DOT) compufile.co.uk> escreveu na mensagem news:41g1rvg645lqgrcmgjues3jphvpve7qtu5 (AT) 4ax (DOT) com... Quote: On Tue, 11 Nov 2003 10:46:37 -0000, "Ricardo Oliveira" ricardooliveira(removethis)@jpmabreu.pt> wrote: Hi! Is there anyway to fill a treeview realy fast? I'm filing a treeview with items that are copied from a table (nr. fields * nr. records). The problem is it gets very slow. Anyway of doing this faster? 1) Make sure that the code that populates the tree view is enclosed in TV.Items.BeginUpdate; try ... finally TV.Items.EndUpdate; end; 2) If this is still not fast enough for you, try using Mike Lischke's Virtual Tree View - www.delphi-gems.com, although this requires a slightly different mindset in relation to data handling than a standard tree view. John Leavey Back to top Constantine Yannakopoulos Guest Posted: Tue Nov 11, 2003 1:24 pm    Post subject: Re: Filling Tree View Author := "Ricardo Oliveira"; Quote: I've tested BeginUpdate and it works but it is not fast enough. I have also seen Mike Lischke's Virtual Tree View but I was expecting something less complicated. Any chance of using load(Stream, File, etc.) to load the items? Other Sugestions? Yes, load the nodes incrementally. <g> I assume that you have only two levels of nodes: records and then field values per record. Start by loading the records in the treeview and put a [+] sign to them without adding any child nodes by setting HasChildren to True. Then write an OnExpanding event handler that loads the child nodes (fields) of a record if they are not already loaded (the test for "not already loaded" is: if Node.HasChildren and not Assigned(Node.getFirstChild) then ...) This way at the time you populate the treeview you do a single loop instead of a double one. Also you do not load fields for a record in the treeview unless the user explicitly requests you to by clicking the [+] sign. HTH -- Constantine Back to top Ricardo Oliveira Guest Posted: Tue Nov 11, 2003 4:01 pm    Post subject: Re: Filling Tree View Hi Constantine! Thanks for your help. I've tried your sugestion but i'm having trouble handling the OnExpanding event. Thanks for your help Ricardo Oliveira. "Constantine Yannakopoulos" <kyan (AT) deltasingular (DOT) remove.this.gr> escreveu na mensagem news:3fb0f134$1 (AT) newsgroups (DOT) borland.com... Quote: Author := "Ricardo Oliveira"; | I've tested BeginUpdate and it works but it is not fast enough. | I have also seen Mike Lischke's Virtual Tree View but I was expecting | something less complicated. | Any chance of using load(Stream, File, etc.) to load the items? | Other Sugestions? :) Yes, load the nodes incrementally. I assume that you have only two levels of nodes: records and then field values per record. Start by loading the records in the treeview and put a [+] sign to them without adding any child nodes by setting HasChildren to True. Then write an OnExpanding event handler that loads the child nodes (fields) of a record if they are not already loaded (the test for "not already loaded" is: if Node.HasChildren and not Assigned(Node.getFirstChild) then ...) This way at the time you populate the treeview you do a single loop instead of a double one. Also you do not load fields for a record in the treeview unless the user explicitly requests you to by clicking the [+] sign. HTH -- Constantine Back to top Ricardo Oliveira Guest Posted: Tue Nov 11, 2003 5:33 pm    Post subject: Re: Filling Tree View Could someone help me please?! Ricardo Oliveira "Ricardo Oliveira" <ricardooliveira(removethis)@jpmabreu.pt> escreveu na mensagem news:3fb10710$1 (AT) newsgroups (DOT) borland.com... Quote: Hi Constantine! Thanks for your help. I've tried your sugestion but i'm having trouble handling the OnExpanding event. Thanks for your help Ricardo Oliveira. "Constantine Yannakopoulos" <kyan (AT) deltasingular (DOT) remove.this.gr> escreveu na mensagem news:3fb0f134$1 (AT) newsgroups (DOT) borland.com... Author := "Ricardo Oliveira"; | I've tested BeginUpdate and it works but it is not fast enough. | I have also seen Mike Lischke's Virtual Tree View but I was expecting | something less complicated. | Any chance of using load(Stream, File, etc.) to load the items? | Other Sugestions? :) Yes, load the nodes incrementally. I assume that you have only two levels of nodes: records and then field values per record. Start by loading the records in the treeview and put a [+] sign to them without adding any child nodes by setting HasChildren to True. Then write an OnExpanding event handler that loads the child nodes (fields) of a record if they are not already loaded (the test for "not already loaded" is: if Node.HasChildren and not Assigned(Node.getFirstChild) then ...) This way at the time you populate the treeview you do a single loop instead of a double one. Also you do not load fields for a record in the treeview unless the user explicitly requests you to by clicking the [+] sign. HTH -- Constantine Back to top Harley Pebley Guest Posted: Tue Nov 11, 2003 9:22 pm    Post subject: Re: Filling Tree View Quote: I've tried your sugestion but i'm having trouble handling the OnExpanding event. Could someone help me please?! Perhaps, if you explained what trouble you're having. Back to top Ricardo Oliveira Guest Posted: Wed Nov 12, 2003 12:53 am    Post subject: Re: Filling Tree View Sorry my fault! I don't know how to handle the OnExpanding event. Maybe someone who did this before can help me. "Harley Pebley" <harley_pebley (AT) idahotech (DOT) com> escreveu na mensagem news:9bbni84ylege$.pog3p5k5uy8y.dlg (AT) 40tude (DOT) net... Quote: I've tried your sugestion but i'm having trouble handling the OnExpanding event. Could someone help me please?! Perhaps, if you explained what trouble you're having. Back to top Harley Pebley Guest Posted: Wed Nov 12, 2003 1:22 am    Post subject: Re: Filling Tree View Quote: I've tried your sugestion but i'm having trouble handling the OnExpanding event. Could someone help me please?! Perhaps, if you explained what trouble you're having. I don't know how to handle the OnExpanding event. Ah. You're given a Node parameter. Add the children to that node that should be there. For example, create a new, blank application. Drop a TreeView on it and attach the following code. When run, it will only have three things in the list at the start but as the user clicks, it will keep adding and adding and adding and... but only on the item which is clicked. The others will be empty until they are clicked on. procedure TForm1.FormCreate(Sender: TObject); begin TreeView1.Items.Add(nil, 'Item 1').HasChildren := True; TreeView1.Items.Add(nil, 'Item 2').HasChildren := True; TreeView1.Items.Add(nil, 'Item 3').HasChildren := True; end; procedure TForm1.TreeView1Expanding(Sender: TObject; Node: TTreeNode; var AllowExpansion: Boolean); begin TreeView1.Items.AddChild(Node, Node.Text+'.1').HasChildren := True; TreeView1.Items.AddChild(Node, Node.Text+'.2').HasChildren := True; TreeView1.Items.AddChild(Node, Node.Text+'.3').HasChildren := True; end; HTH, Harley Pebley Back to top Ricardo Oliveira Guest Posted: Wed Nov 12, 2003 1:33 am    Post subject: Re: Filling Tree View I'm so sorry but i can't quite explain me. I'm creating an object inherited from a treeview and I need to handle the OnExpanding event so that when the node is expanded I can fill it with it's children (read posts above). Sorry, I guess I need some sleep. :) "Harley Pebley" <harley_pebley (AT) idahotech (DOT) com> escreveu na mensagem news:tchstzeijrf0.1iq85vor51zq4$.dlg (AT) 40tude (DOT) net... Quote: I've tried your sugestion but i'm having trouble handling the OnExpanding event. Could someone help me please?! Perhaps, if you explained what trouble you're having. I don't know how to handle the OnExpanding event. Ah. You're given a Node parameter. Add the children to that node that should be there. For example, create a new, blank application. Drop a TreeView on it and attach the following code. When run, it will only have three things in the list at the start but as the user clicks, it will keep adding and adding and adding and... but only on the item which is clicked. The others will be empty until they are clicked on. procedure TForm1.FormCreate(Sender: TObject); begin TreeView1.Items.Add(nil, 'Item 1').HasChildren := True; TreeView1.Items.Add(nil, 'Item 2').HasChildren := True; TreeView1.Items.Add(nil, 'Item 3').HasChildren := True; end; procedure TForm1.TreeView1Expanding(Sender: TObject; Node: TTreeNode; var AllowExpansion: Boolean); begin TreeView1.Items.AddChild(Node, Node.Text+'.1').HasChildren := True; TreeView1.Items.AddChild(Node, Node.Text+'.2').HasChildren := True; TreeView1.Items.AddChild(Node, Node.Text+'.3').HasChildren := True; end; HTH, Harley Pebley Back to top Marc Rohloff Guest Posted: Wed Nov 12, 2003 2:03 pm    Post subject: Re: Filling Tree View Quote: I'm creating an object inherited from a treeview and I need to handle the OnExpanding event so that when the node is expanded I can fill it with it's children (read posts above). The first thing you need to be able to do is to figure out which node you are actually at given a TreeNode instance. This is necessary in all sorts of events so it is useful to get it right and maybe seperate it into a function. You could use the index, absoluteindex or parent values to figure this out. Another way is to store some information in the Data property of each node as you create it. A third alternative if you are subclassing the tree view is to supply your own custom implementation of Ttreenode. Once you can do this then in the OnExpanding event you can figure out the node you are in and then fill in all it's children. Marc Back to top Harley Pebley Guest Posted: Wed Nov 12, 2003 7:13 pm    Post subject: Re: Filling Tree View Quote: I'm creating an object inherited from a treeview and I need to handle the OnExpanding event so that when the node is expanded I can fill it with it's children (read posts above). Sorry, I guess I need some sleep. Ah. I think perhaps the piece you're missing is overriding the CanExpand method? For example, create a blank application and replace the code in Unit1.pas with: unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ComCtrls; type TForm1 = class(TForm) procedure FormCreate(Sender: TObject); private TreeView1: TTreeView; public { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} type TMyTreeView = class(TTreeView) protected function CanExpand(Node: TTreeNode): Boolean; override; end; procedure TForm1.FormCreate(Sender: TObject); begin TreeView1 := TMyTreeView.Create(Self); TreeView1.Parent := Self; TreeView1.Align := alClient; TreeView1.Items.Add(nil, 'Item 1').HasChildren := True; TreeView1.Items.Add(nil, 'Item 2').HasChildren := True; TreeView1.Items.Add(nil, 'Item 3').HasChildren := True; end; { TMyTreeView } function TMyTreeView.CanExpand(Node: TTreeNode): Boolean; begin result := inherited CanExpand(Node); if result then begin TMyTreeView(Node.TreeView).Items.AddChild(Node, Node.Text+'.1').HasChildren := True; TMyTreeView(Node.TreeView).Items.AddChild(Node, Node.Text+'.2').HasChildren := True; TMyTreeView(Node.TreeView).Items.AddChild(Node, Node.Text+'.3').HasChildren := True; end; end; end. Calling the inherited CanExpand will call the OnExpanding event handler. If that returns true, then your custom code can run. This allows users of your component to not expand the node if they so desire. If you don't ever want them to have this feature, then you should descend from TCustomTreeView and not expose the OnExpanding property. 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