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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