The following example uses the interposed class of the TComboBox component. The main difference from the original class is that the items are stored in the separate StoredItems property instead of
the Items as usually (used because of simplicity).
The StoredItems are being watched by the OnChange event and whenever you change them (for instance by adding or deleting from this string list), the current filter will reflect it even when the combo
list is dropped down.
The main point here is to catch the WM_COMMAND message notification CBN_EDITUPDATE which is being sent whenever the combo edit text is changed but not rendered yet. When it arrives, you just search through the StoredItems list for what you have typed in your combo edit and fill the Items property with matches.
For text searching is used the ContainsText so the search is case insensitive. Forgot to mention,
the AutoComplete feature has to be turned off because it has its own, unwelcomed, logic for this purpose.
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, StrUtils, ExtCtrls;
type
TComboBox = class(StdCtrls.TComboBox)
private
FStoredItems: TStringList;
procedure FilterItems;
procedure StoredItemsChange(Sender: TObject);
procedure SetStoredItems(const Value: TStringList);
procedure CNCommand(var AMessage: TWMCommand); message CN_COMMAND;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
property StoredItems: TStringList read FStoredItems write SetStoredItems;
end;
type
TForm1 = class(TForm)
ComboBox1: TComboBox;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
constructor TComboBox.Create(AOwner: TComponent);
begin
inherited;
AutoComplete := False;
FStoredItems := TStringList.Create;
FStoredItems.OnChange := StoredItemsChange;
end;
destructor TComboBox.Destroy;
begin
FStoredItems.Free;
inherited;
end;
procedure TComboBox.CNCommand(var AMessage: TWMCommand);
begin
// we have to process everything from our ancestor
inherited;
// if we received the CBN_EDITUPDATE notification
if AMessage.NotifyCode = CBN_EDITUPDATE then
// fill the items with the matches
FilterItems;
end;
procedure TComboBox.FilterItems;
var
I: Integer;
Selection: TSelection;
begin
// store the current combo edit selection
SendMessage(Handle, CB_GETEDITSEL, WPARAM(@Selection.StartPos),
LPARAM(@Selection.EndPos));
// begin with the items update
Items.BeginUpdate;
try
// if the combo edit is not empty, then clear the items
// and search through the FStoredItems
if Text <> '' then
begin
// clear all items
Items.Clear;
// iterate through all of them
for I := 0 to FStoredItems.Count - 1 do
// check if the current one contains the text in edit
if ContainsText(FStoredItems[I], Text) then
// and if so, then add it to the items
Items.Add(FStoredItems[I]);
end
// else the combo edit is empty
else
// so then we'll use all what we have in the FStoredItems
Items.Assign(FStoredItems)
finally
// finish the items update
Items.EndUpdate;
end;
// and restore the last combo edit selection
SendMessage(Handle, CB_SETEDITSEL, 0, MakeLParam(Selection.StartPos,
Selection.EndPos));
end;
procedure TComboBox.StoredItemsChange(Sender: TObject);
begin
if Assigned(FStoredItems) then
FilterItems;
end;
procedure TComboBox.SetStoredItems(const Value: TStringList);
begin
if Assigned(FStoredItems) then
FStoredItems.Assign(Value)
else
FStoredItems := Value;
end;
procedure TForm1.FormCreate(Sender: TObject);
var
ComboBox: TComboBox;
begin
// here's one combo created dynamically
ComboBox := TComboBox.Create(Self);
ComboBox.Parent := Self;
ComboBox.Left := 10;
ComboBox.Top := 10;
ComboBox.Text := 'Br';
// here's how to fill the StoredItems
ComboBox.StoredItems.BeginUpdate;
try
ComboBox.StoredItems.Add('Mr John Brown');
ComboBox.StoredItems.Add('Mrs Amanda Brown');
ComboBox.StoredItems.Add('Mr Brian Jones');
ComboBox.StoredItems.Add('Mrs Samantha Smith');
finally
ComboBox.StoredItems.EndUpdate;
end;
// and here's how to assign the Items of the combo box from the form
// to the StoredItems; note that if you'll use this, you have to do
// it before you type something into the combo's edit, because typing
// may filter the Items, so they would get modified
ComboBox1.StoredItems.Assign(ComboBox1.Items);
end;
end.
Does the IAutoComplete interface support fulltext search ?- No – TentedIAutoCompleteinterface does not support fulltext search, it works only with the text from the beginning. The only way is IMHO to implement it by yourself. Even messages likeCB_FINDSTRINGdoesn't count with the string matching in elsewhere than from on the beginning. – TentedIAutoComplete2option to includeACO_AUTOSUGGEST, it would do that... thanks. – Nonu.pasfile. I'm not sure where they implemented that, so I am not putting this as an answer. Try this. – NonuTComboBox. – Tented