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Delete a Treeview node

Posted on 2009-07-14
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Last Modified: 2012-05-07
Dear Experts,

I have made a little programm that has a Treeview, a RichEdit.
and 4 buttons on a Panel. 2 buttons are for loading and saving
the treeview nodes with its associating text on the RichtEdit
to a database. The other 2 buttons are for creating a Folder-node
and a File-node in the Treeview. Everything works perfect.

Now I want to make a fifth button on the panel for deleting
a Treeview node. Who can help me with this procedure:

procedure TItem.Delete;
begin
//
end;

I have put the example on my site:
http://members.home.nl/peterkiers/
You see a floppy disc.

I also found this! I dont know if its usable:

procedure TForm1.TreeView1Deletion(Sender: TObject; Node: TTreeNode);
begin
  if node.Data<>nil then
  begin
    TItem(node.data).free;
    node.data:=nil;
  end;
end;

Greetings, Peter Kiers
0
Comment
Question by:peterkiers
  • 3
4 Comments
 
LVL 18

Accepted Solution

by:
Johnjces earned 500 total points
Comment Utility
Same as previous post just use

TreeView1.Items[X].Delete;
0
 
LVL 1

Author Comment

by:peterkiers
Comment Utility
In the example I have a treeview build from TObject called TItem
My question was, what to put in the TItem.Delete procedure
and what to put in the procedure of the Delete-button.
0
 
LVL 1

Author Comment

by:peterkiers
Comment Utility
I have this procedure for deleting a file-node or a folder node.
And it works perfect:

procedure TForm1.DeleteItemClick(Sender: TObject);
var
   node : TTreeNode;
   mess, str : string;
   key_stat : integer;
begin
    Node := Treeview.Selected;
    if Assigned(Node) then
       begin
       str := Node.Text;
       mess := 'Are you sure that you want to delete the';
       Case Node.Level of
         0 : mess := mess + ' folder : ' +#13+#13 + str + '   ???' +#13+
                    'All folders, subfolders, items and subitems' +#13+ 'will be permanently deleted !!' +#13;
         1 : mess := mess + ' item : ' +#13+#13 + str + '   ???' + #13;
       end;
       with Application do
         begin
         NormalizeTopMosts;
         key_stat := MessageBox(pchar(mess), '         Confirmation', MB_YESNO);
         RestoreTopMosts;
       end;
       if key_stat = 7 then  Exit;         // 6 - YES ; 7 - N0
       TreeView.Items.Delete(Treeview.Selected);
       end
    else ShowMessage('Select a folder in the treeview first.');
end;

ACCEPT for one thing: The deleted node is still available in the database!!!
And it should be erased too. That's because the DeleteItemClick should call
for this procedure:

procedure TItem.Delete;
begin
//
end;

Greetings, Peter Kiers
0
 
LVL 1

Author Comment

by:peterkiers
Comment Utility
I guess no one will download the example. So i have put the code in the code-section.

unit Unit1;
 

interface
 

uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, DB, ADODB, ComCtrls, StdCtrls, ImgList, ExtCtrls;
 

type

  TForm1 = class(TForm)

    TreeView1: TTreeView;

    Splitter1: TSplitter;

    Panel1: TPanel;

    Button1: TButton;

    Button2: TButton;

    ADOQuery1: TADOQuery;

    ADOConnection1: TADOConnection;

    FolderBtn: TButton;

    FileBtn: TButton;

    ImageList1: TImageList;

    RichEdit1: TRichEdit;

    Button3: TButton;

    procedure Button3Click(Sender: TObject);

    procedure RichEdit1KeyUp(Sender: TObject; var Key: Word;

      Shift: TShiftState);

    procedure FolderBtnClick(Sender: TObject);

    procedure FileBtnClick(Sender: TObject);

    procedure TreeView1Change(Sender: TObject; Node: TTreeNode);

    procedure FormCreate(Sender: TObject);

    procedure Button2Click(Sender: TObject);

    procedure Button1Click(Sender: TObject);

    

  private

    { Private declarations }

    procedure savetree(t: ttreeview);

    procedure loadtree(t: TTreeView);

    procedure saveNode(n: TTreeNode);

    function findNode(t:TTreeView; id: integer): TTreeNode;

    procedure AddItem(aText: string; aIndex: Integer; aParent: TTreeNode);

  public

    { Public declarations }

  end;
 

var

  Form1: TForm1;
 

implementation
 

{$R *.dfm}
 

type

  TItem = class(TObject)

  private

    fStatus: byte;

    fParentID: integer;

    fNodeText: string;

    fID: integer;

    fData: string;

    fSaver: TAdoQuery;

    fChanged: Boolean;        

    fSaveImmediate: boolean;

    fIsNew: Boolean;

    fImageIndex: integer;

    procedure SetData(const Value: string);

    procedure SetNodeText(const Value: string);

    procedure SetParentID(const Value: integer);

    procedure SetStatus(const Value: byte);

    procedure SetImageIndex(const Value: integer);

  protected

    procedure Changed; dynamic;

  public

    constructor Create(aSaver: TAdoQuery; AId, AParentID: integer; AStatus: byte);

    constructor LoadFromDataset(aSaver: TAdoQuery);

    procedure BeginUpdate;

    procedure EndUpdate;

    procedure Delete;

    procedure Save;

  published

    property ID: integer read fID write fID;

    property ParentID: integer read fParentID write SetParentID;

    property ImageIndex: integer read fImageIndex write SetImageIndex;

    property Status: byte read FStatus write SetStatus;

    property Data: string read fData write SetData;

    property NodeText: string read fNodeText write SetNodeText;

  end;
 

{ TItem }
 

procedure TItem.BeginUpdate;

begin

  fSaveImmediate := false;                 

end;

(*---------------------------------------------------*)

procedure TItem.Changed;

begin

  fChanged := True;

  if fSaveImmediate then Save;

end;

(*---------------------------------------------------*)

constructor TItem.Create(aSaver: TAdoQuery; AId, AParentID: integer;

  AStatus: byte);

begin

  inherited Create;

  fChanged := False;

  fSaveImmediate := True;

  fIsNew := True;

  fSaver := aSaver;

  fID := AID;

  fParentID := AParentID;

  fStatus := AStatus;

  fNodeText := '';

  fData := '';

end;

(*---------------------------------------------------*)

procedure TItem.Delete;

begin

//

end;

(*---------------------------------------------------*)

procedure TItem.EndUpdate;

begin

  fSaveImmediate := True;

  if fChanged then Save;

end;

(*---------------------------------------------------*)

constructor TItem.LoadFromDataset(aSaver: TAdoQuery);

begin

  Create(aSaver, 0, 0, 0);

  if not aSaver.IsEmpty then

  begin

    fId := aSaver.FieldByName('ID').AsInteger;

    fParentID := aSaver.FieldByName('PARENT').AsInteger;

    fStatus := aSaver.FieldByName('STATUS').AsInteger;

    fNodeText := aSaver.FieldByName('NAME').AsString;

    if aSaver.FindField('DATA') <> nil then

      fData := aSaver.FieldByName('DATA').AsString;

    fImageIndex := aSaver.FieldByName('IMAGE_INDEX').AsInteger;

    fIsNew := False;

  end;

end;

(*---------------------------------------------------*)

procedure TItem.Save;

begin

  if fIsNew then

    fSaver.SQL.Text :=

      'insert into tree (parent, name, status, image_index, data) values (:v1, :v2, :v3, :v4, :v5)'

  else

    fSaver.SQL.Text :=

      'update tree set parent = :v1, name = :v2, status = :v3, image_index = :v4, data = :v5 where id = :v6';

  fSaver.Parameters.ParamByName('v1').Value := fparentID;

  fSaver.Parameters.ParamByName('v2').Value := fNodeText;

  fSaver.Parameters.ParamByName('v3').Value := fStatus;

  fSaver.Parameters.ParamByName('v4').Value := fImageIndex;

  fSaver.Parameters.ParamByName('v5').Value := fData;

  if not fIsNew then

    fSaver.Parameters.ParamByName('v6').Value := fId;

  fSaver.ExecSQL;

  if fIsNew then

  begin

    fSaver.SQL.Text :=

      'SELECT id from tree order by id desc';

    fSaver.Open;

    fId := fSaver.FieldByName('ID').asInteger;

    fSaver.Close;

    fIsNew := False;

  end;

  fChanged := False;

end;

(*---------------------------------------------------*)

procedure TItem.SetData(const Value: string);

begin

  if fData <> Value then

  begin

    fData := Value;

    Changed;

  end;

end;

(*---------------------------------------------------*)

procedure TItem.SetImageIndex(const Value: integer);

begin

  if fImageIndex <> Value then

  begin

    fImageIndex := Value;

    Changed;

  end;

end;

(*---------------------------------------------------*)

procedure TItem.SetNodeText(const Value: string);

begin

  if fNodeText <> Value then

  begin

    fNodeText := Value;

    Changed;

  end;

end;

(*---------------------------------------------------*)

procedure TItem.SetParentID(const Value: integer);

begin

  if fParentId <> Value then

  begin

    fParentID := Value;

    Changed;

  end;

end;

(*---------------------------------------------------*)

procedure TItem.SetStatus(const Value: byte);

begin

  if fStatus <> Value then

  begin

    FStatus := Value;

    Changed;

  end;

end;

(*---------------------------------------------------*)

procedure TForm1.AddItem(aText: string; aIndex: Integer; aParent: TTreeNode);

var n: TTreeNode;

  data: TItem;

  parentId: integer;

begin

  parentId := 0;

  if (aParent <> nil) and (TItem(aParent.Data) <> nil) then

    parentId := TItem(aParent.Data).ID;

  data := TItem.Create(AdoQuery1, -1, parentId, 0);

  data.NodeText := aText;

  data.ImageIndex := aIndex;

  n := TTreeNode.Create(TreeView1.Items);

  n.Text := data.NodeText;

  n.ImageIndex := data.ImageIndex;

  n.SelectedIndex := data.ImageIndex;

  TreeView1.Items.AddNode(n, aParent, aText, data, naAddChild);

end;

(*---------------------------------------------------*)

procedure TForm1.Button1Click(Sender: TObject);

begin

  loadTree(treeview1);

end;

(*---------------------------------------------------*)

procedure TForm1.Button2Click(Sender: TObject);

begin

  savetree(treeview1);

end;

procedure TForm1.Button3Click(Sender: TObject);

var

   node : TTreeNode;

   mess, str : string;

   key_stat : integer;

begin

    Node := Treeview1.Selected;

    if Assigned(Node) then

       begin

       str := Node.Text;

       mess := 'Are you sure that you want to delete the';

       Case Node.Level of

         0 : mess := mess + ' folder : ' +#13+#13 + str + '   ???' +#13+

                    'All folders, subfolders, items and subitems' +#13+ 'will be permanently deleted !!' +#13;

         1 : mess := mess + ' item : ' +#13+#13 + str + '   ???' + #13;

       end;

       with Application do

         begin

         NormalizeTopMosts;

         key_stat := MessageBox(pchar(mess), '         Confirmation', MB_YESNO);

         RestoreTopMosts;

       end;

       if key_stat = 7 then  Exit;         // 6 - YES ; 7 - N0

       TreeView1.Items.Delete(Treeview1.Selected);

       end

    else ShowMessage('Select a folder in the treeview first.');

end;

(*---------------------------------------------------*)

procedure TForm1.FileBtnClick(Sender: TObject);

var aText: string;

begin

  if (TreeView1.Selected <> nil) and (TreeView1.Selected.ImageIndex = 15) then

  begin

     if InputQuery('File', 'Enter a file name', aText) then

      AddItem(aText, 17, TreeView1.Selected);

  end else

    ShowMessage('Select a folder in the treeview first.');

end;

(*---------------------------------------------------*)

function TForm1.findNode(t: TTreeView; id: integer): TTreeNode;

var i:integer;

begin

  i:=0;

  while (i<t.items.count) and (TItem(t.items[i].data).ID<>id) do

    inc(i);

  if i<t.items.count then result:=t.items[i]

                     else result:=nil;

end;

(*---------------------------------------------------*)

procedure TForm1.FolderBtnClick(Sender: TObject);

var aText: string;

  aParent: TTreeNode;

begin

  aParent := nil;

  if TreeView1.Selected <> nil then

  begin

    if TreeView1.Selected.ImageIndex = 15 then

      aParent := TreeView1.Selected

    else

    begin

      ShowMessage('Select a folder first');

      Exit;

    end;

  end;

  if InputQuery('Folder', 'Enter a folder name', aText) then

    AddItem(aText, 15, aParent);

end;

(*---------------------------------------------------*)

procedure TForm1.FormCreate(Sender: TObject);

var

  conn_str:string;

begin

  conn_str:='provider=Microsoft.Jet.OLEDB.4.0;Persist Security Info=False;Data Source=';

  conn_str:=conn_str+IncludeTrailingPathDelimiter(ExtractFilePath(Application.Exename));

  conn_str:=conn_str+'test.pkd;';

  ADOConnection1.Connected:=False;

  ADOConnection1.ConnectionString:=conn_str;

  ADOConnection1.Connected:=True;

  ADOConnection1.Open;

end;

(*---------------------------------------------------*)

procedure TForm1.loadtree(t: TTreeView);

var

  p, n: TTreeNode;

  data: TItem;

begin

  t.Items.Clear;

  ADOQuery1.SQL.Text := 'select * from tree order by parent asc';

  ADoQuery1.Open;

  while not ADoQuery1.Eof do

  begin

    data := TItem.LoadFromDataset(AdoQuery1);

    p := FindNode(t, data.ParentID);

    n := t.items.AddChildObject(p, data.NodeText, data);

    n.ImageIndex := data.ImageIndex;

    n.SelectedIndex := data.ImageIndex;

    AdoQuery1.Next;

  end;

  AdoQuery1.Close;

end;

(*---------------------------------------------------*)

procedure TForm1.saveNode(n: TTreeNode);

var i, aParent: integer;

  item: TItem;

begin

  item := TItem(n.Data);

  if item <> nil then

  begin

    item.BeginUpdate;

    try

      Item.NodeText := n.Text;

      aParent := 0;

      if (n.Parent <> nil) and (TItem(n.Parent.Data) <> nil) then

        aParent := TItem(n.Parent.Data).ID;

      Item.ParentID := aParent;

      Item.ImageIndex := n.ImageIndex;

    finally

      Item.EndUpdate;

    end;

  end;

  for i := 0 to n.Count-1 do SaveNode(n.Item[i]);

end;

(*---------------------------------------------------*)

procedure TForm1.savetree(t: ttreeview);

var n: TTreeNode;

begin

  n := t.items.getFirstNode;

  while n <> nil do

  begin

    SaveNode(n);

    n := n.getNextSibling;

  end;

end;

(*---------------------------------------------------*)

procedure TForm1.TreeView1Change(Sender: TObject; Node: TTreeNode);

begin

  RichEdit1.Text := '';

  if (Node <> nil) and (Node.ImageIndex = 15) then

    RichEdit1.Text := TItem(Node.Data).Data;

end;

(*---------------------------------------------------*)

procedure TForm1.RichEdit1KeyUp(Sender: TObject; var Key: Word;

  Shift: TShiftState);

  var n: TTreeNode;

begin

        n := TreeView1.Selected;

        if (n <> nil) and (n.ImageIndex = 15) then

        begin

        TItem(n.Data).fSaveImmediate := False;

         TItem(N.Data).Data := RichEdit1.Text;

         end;

end;

(*---------------------------------------------------*)

end.

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