Autocomplete TEdit

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.