http://forum.codecall.net/topic/75946-autocomplete-tedit/

Overview

Autocomplete feature really helpful for us speeding up our typing job.

For you who is not familiar with the term autocomplete,

it's when you type partial part of a word and then

you will be presented with a list of possible complete words.

You can just select the correct word from the list,

and that partial word will be automatically completed.

In programming, this feature very helpful to

"remember" class names, routine names, and variable name.

Not only to speed up the typing, autocomplete also very helpful to avoid typo.

In this tutorial I will show you a technique to implement autocomplete

in your Delphi program in order to provide your users the benefits of autocomplete.

I will implement autocomplete in a descendant of TEdit. I name it TAutocompleteEdit.

TAutoCompleteEdit

Behaviors

  1. Upon typing some chars, TAutocompleteEdit will check the typed word agains a word list. When no match found, do nothing.
  2. When one or more matches found, TAutocompleteEdit show the matches in a TListBox.We will call this TListBoxWordList.
  3. User can move between TAutocompleteEdit and WordList using down and up arrow.
  4. User select a complete word from WordList by highlighting the word and press Enter key.
  5. After user selected a word, the word will replace whatever content in TAutocompleteEdit.
  6. If user press Escape in TAutocompleteEdit or in WordList, WordList must dissapear.
  7. If TAutocompleteEdit lost focus, and the new focus is not in WordList, WordList must dissapear.
  8. If WordList lost focus, and the new focus is not in TAutocompleteEdit, WordList must dissapear.
  9. If later user type in another character and no match found, WordList must dissapear.

Key Methods

From the above behaviors, we decided to have the following methods.

  1. ShowWordList(AWords: TStrings).
    This method is responsible to create WordList TListBox when needed,
    populate it with words contained in AWords, and
    also to patch its events so we can achieve behavior #3, #4, #5, #6, and #8.
  2. HideWordList.
    This method is responsible to hide and clean up WordList.
  3. Change.
    This is where to respond when the content of TAutocompleteEdit changed.
    So this is where we do the checking.
    This method actually already exist in TAutocompleteEdit's parent.
    So what we are going to do is override it, and introduce our behavior.
  4. DoExit.
    This method also already exist in TAutocompleteEdit's parent.
    We are going to override it and introduce new behavior, in order to achieve behavior #7.
  5. KeyDown(var Key: Word; Shift: TShiftState).
    This method also already exist in TAutocompleteEdit's parent.
    We are going to override it to achieve behavior #3 and #6.

Key Methods Implementations

1. ShowWordList(AWords: TStrings).


procedure TAutocompleteEdit.ShowWordList(AWords: TStrings);

begin

  if FWordList=nil then

  begin

    FWordList := TListBox.Create(Self);

    FWordList.ParentCtl3D := False;

    FWordList.Ctl3D := False;

    FWordList.Parent := Self.Parent;

    FWordList.TabStop := False;

    FWordList.OnExit := HandleWordListLostFocus;

    FWordList.OnKeyPress := HandleWordListKeyPress;

    FWordList.OnKeyDown := HandleWordListKeyDown;

  end;

  FWordList.Items.Assign(AWords);

  if FWordListWidth <  then

    FWordList.SetBounds(Self.Left, Self.Top + Self.Height, Self.Width, FWordListHeight)

  else

    FWordList.SetBounds(Self.Left, Self.Top + Self.Height, FWordListWidth, FWordListHeight);

  FWordList.Show;

end;

2. HideWordList

procedure TAutocompleteEdit.HideWordList;

begin

  PostMessage(Self.Handle, MSG_HIDEWORDLIST, , );

end;

Note that in the above method we only post a custom message. The custom message handler in turn will call this private method.

procedure TAutocompleteEdit.HandleHideWordList;

begin

  FWordList.Free;

  FWordList := nil;

end;

3. Change.

procedure TAutocompleteEdit.Change;

var

  S: TStrings;

begin

  inherited;

  if AutocompleteMan.IsRecognized(Self.Text) then

  begin

    S := TStringList.Create;

    try

      if AutocompleteMan.IsRecognized(Self.Text, S) then

        ShowWordList(S);

    finally

      S.Free;

    end;

  end

  else

    HideWordList;

end;

4. DoExit.

procedure TAutocompleteEdit.DoExit;

begin

  if Assigned(FWordList) and FWordList.Visible and not FWordList.Focused then

    HideWordList;

  inherited;

end;

5. KeyDown(var Key: Word; Shift: TShiftState).

procedure TAutocompleteEdit.KeyDown(var Key: Word; Shift: TShiftState);

begin

  if Key=VK_ESCAPE then

    HideWordList

  else if (Key=VK_DOWN) and Assigned(FWordList) and FWordList.Visible then

  begin

    FCaretPos := Self.SelStart;

    FWordList.SetFocus;

    if FWordList.ItemIndex <  then

      FWordList.ItemIndex := ;

  end

  else

    inherited;

end;

Here is the complete source code of TAutocompleteEdit:

TEdit with Autocomplete.zip   1.84MB   603 downloads.

Feel free to use it or improve it for any kind of use.

Cheers!

 unit AutocompleteEdit;

 interface

 uses

   Windows

   , Classes

   , Vcl.StdCtrls

   , SysUtils

   , StrUtils

   , Messages

   ;

 const

   MSG_HIDEWORDLIST = WM_USER + ;

 type

   TAutocompleteEdit=class(TEdit)

   private

     FWordList: TListBox;

     FCaretPos: Integer;

     FWordListHeight: Integer;

     FWordListWidth: Integer;

     procedure HandleWordListLostFocus(ASender: TObject);

     procedure HandleWordListSelectItem(ASender: TObject);

     procedure HandleWordListKeyPress(Sender: TObject; var Key: Char);

     procedure HandleWordListKeyDown(ASender: TObject; var Key: Word; Shift: TShiftState);

     procedure HandleHideWordList(var AMsg); overload; message MSG_HIDEWORDLIST;

     procedure HandleHideWordList; overload;

     procedure SetWordListHeight(const Value: Integer);

     procedure SetWordListWidth(const Value: Integer);

     procedure RegainFocus;

   protected

     procedure ShowWordList(AWords: TStrings);

     procedure HideWordList;

     procedure Change; override;

     procedure KeyDown(var Key: Word; Shift: TShiftState); override;

     procedure DoExit; override;

   public

     constructor Create(AOwner: TComponent); override;

   published

     property WordListHeight: Integer read FWordListHeight write SetWordListHeight;

     property WordListWidth: Integer read FWordListWidth write SetWordListWidth;

   end;

   TAutocompleteMan=class

   private

     FWords: TStrings;

   public

     constructor Create;

     destructor Destroy; override;

     function IsRecognized(AWord: string): Boolean; overload;

     function IsRecognized(AWord: string; AWordList: TStrings): Boolean; overload;

     procedure LoadFromFile(const AFilename: string);

     procedure AddWord(const AWord: string);

     property Words: TStrings read FWords;

   end;

   procedure Register;

 var

   AutocompleteMan: TAutocompleteMan;

 implementation

 procedure Register;

 begin

   RegisterComponents('CodeCall', [TAutocompleteEdit]);

 end;

 { TAutocompleteMan }

 procedure TAutocompleteMan.AddWord(const AWord: string);

 begin

   FWords.Add(UpperCase(AWord) + '=' + AWord);

 end;

 constructor TAutocompleteMan.Create;

 begin

   FWords := TStringList.Create;

   TStringList(FWords).Duplicates := dupIgnore;

 end;

 destructor TAutocompleteMan.Destroy;

 begin

   FWords.Free;

   inherited;

 end;

 function TAutocompleteMan.IsRecognized(AWord: string): Boolean;

 var

   i: Integer;

 begin

   Result := False;

   AWord := UpperCase(AWord);

   for i :=  to FWords.Count- do

   begin

     Result := System.Pos(AWord, FWords.Names[i]) > ;

     if Result then

       Break;

   end;

 end;

 function TAutocompleteMan.IsRecognized(AWord: string;

   AWordList: TStrings): Boolean;

 var

   i: Integer;

 begin

   Result := False;

   AWord := UpperCase(AWord);

   AWordList.Clear;

   for i :=  to FWords.Count- do

   begin

     if System.Pos(AWord, FWords.Names[i]) >  then

     begin

       Result := True;

       AWordList.Add(FWords.ValueFromIndex[i]);

     end;

   end;

 end;

 procedure TAutocompleteMan.LoadFromFile(const AFilename: string);

 var

   i: Integer;

   F: TStrings;

 begin

   F := TStringList.Create;

   try

     F.LoadFromFile(AFilename);

     for i :=  to F.Count- do

       AddWord(F[i]);

   finally

     F.Free;

   end;

 end;

 { TAutocompleteEdit }

 procedure TAutocompleteEdit.Change;

 var

   S: TStrings;

 begin

   inherited;

   if AutocompleteMan.IsRecognized(Self.Text) then

   begin

     S := TStringList.Create;

     try

       if AutocompleteMan.IsRecognized(Self.Text, S) then

         ShowWordList(S);

     finally

       S.Free;

     end;

   end

   else

     HideWordList;

 end;

 procedure TAutocompleteEdit.HandleHideWordList(var AMsg);

 begin

   HandleHideWordList;

 end;

 constructor TAutocompleteEdit.Create(AOwner: TComponent);

 begin

   inherited;

   FWordListHeight := ;

 end;

 procedure TAutocompleteEdit.DoExit;

 begin

   if Assigned(FWordList) and FWordList.Visible and not FWordList.Focused then

     HideWordList;

   inherited;

 end;

 procedure TAutocompleteEdit.HandleHideWordList;

 begin

   FWordList.Free;

   FWordList := nil;

 end;

 procedure TAutocompleteEdit.HandleWordListKeyDown(ASender: TObject;

   var Key: Word; Shift: TShiftState);

 begin

   if (Key=VK_UP) and (FWordList.ItemIndex=) then

     RegainFocus;

 end;

 procedure TAutocompleteEdit.HandleWordListKeyPress(Sender: TObject;

   var Key: Char);

 begin

   case Key of

     #: begin

            Key := #;

            Self.Text := FWordList.Items[FWordList.ItemIndex];

            Self.SetFocus;

            Self.SelStart := Length(Self.Text);

            Self.SelLength := ;

            HideWordList;

          end;

     #: begin

            RegainFocus;

            HideWordList;

          end;

     else begin

       RegainFocus;

     end;

   end;

 end;

 procedure TAutocompleteEdit.HandleWordListLostFocus(ASender: TObject);

 begin

   if not Self.Focused then

     HideWordList;

 end;

 procedure TAutocompleteEdit.HandleWordListSelectItem(ASender: TObject);

 begin

   Self.Text := FWordList.Items[FWordList.ItemIndex];

   HideWordList;

 end;

 procedure TAutocompleteEdit.HideWordList;

 begin

   PostMessage(Self.Handle, MSG_HIDEWORDLIST, , );

 end;

 procedure TAutocompleteEdit.KeyDown(var Key: Word; Shift: TShiftState);

 begin

   if Key=VK_ESCAPE then

     HideWordList

   else if (Key=VK_DOWN) and Assigned(FWordList) and FWordList.Visible then

   begin

     FCaretPos := Self.SelStart;

     FWordList.SetFocus;

     if FWordList.ItemIndex <  then

       FWordList.ItemIndex := ;

   end

   else

     inherited;

 end;

 procedure TAutocompleteEdit.RegainFocus;

 begin

   Self.SetFocus;

   Self.SelStart := FCaretPos;

   Self.SelLength := ;

 end;

 procedure TAutocompleteEdit.SetWordListHeight(const Value: Integer);

 begin

   if FWordListHeight <> Value then

   begin

     FWordListHeight := Value;

     if Assigned(FWordList) then

       FWordList.Height := FWordListHeight;

   end;

 end;

 procedure TAutocompleteEdit.SetWordListWidth(const Value: Integer);

 begin

   if FWordListWidth <> Value then

   begin

     FWordListWidth := Value;

     if Assigned(FWordList) then

     begin

       if FWordListWidth <  then

         FWordList.Width := Self.Width

       else

         FWordList.Width := FWordListWidth;

     end;

   end;

 end;

 procedure TAutocompleteEdit.ShowWordList(AWords: TStrings);

 begin

   if FWordList=nil then

   begin

     FWordList := TListBox.Create(Self);

     FWordList.ParentCtl3D := False;

     FWordList.Ctl3D := False;

     FWordList.Parent := Self.Parent;

     FWordList.TabStop := False;

     FWordList.OnExit := HandleWordListLostFocus;

     FWordList.OnKeyPress := HandleWordListKeyPress;

     FWordList.OnKeyDown := HandleWordListKeyDown;

   end;

   FWordList.Items.Assign(AWords);

   if FWordListWidth <  then

     FWordList.SetBounds(Self.Left, Self.Top + Self.Height, Self.Width, FWordListHeight)

   else

     FWordList.SetBounds(Self.Left, Self.Top + Self.Height, FWordListWidth, FWordListHeight);

   FWordList.Show;

 end;

 initialization

   AutocompleteMan := TAutocompleteMan.Create;

 finalization

   AutocompleteMan.Free;

 end.

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