Dialog Examples/sk

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Niektoré užitočné dialógy

Toto sú niektoré užitočné dialógy, ktoré nenájdete v Palete komonentov:

  • procedure ShowMessage (const Msg: string);
  • function MessageBox (Text, Caption : PChar; Flags: Word): Integer;
  • function MessageDlg (const Msg: string; AType: TMsgDlgType; AButtons: TMsgDlgButtons; HelpCtx: LongInt): Word;
  • function InputBox (const ACaption, APrompt, ADefault: string); string;
  • function InputQuery (const ACaption, APrompt: string; var Value: string): Boolean;
  • function PasswordBox(const ACaption, APrompt : String) : String;

Každý z týchto komponentov zobrazuje malé vyskakovacie dialógové okno, ktoré obsahuje nejaké informácie a vyžaduje odozvu používateľa: stlačenie tlačítka, zadanie textu alebo oboje. Programátor má minimálnu kontrolu nad formátom, veľkosťou alebo pozíciou týchto vyskakovacích okien, ale môže ovplyvňovať ich textový obsah.
Dôvodom prečo často existujú veľmi podobné alternatívy, je umožniť rôzne spôsoby volania komponentu, a získavania dát, z procedúr a funkcií.

Správové dialógy

Správové dialógy zobrazujú správu a čakajú na stlačenie klávesy alebo kliknutie myšou.

ShowMessage

<delphi> Procedure ShowMessage (const Msg: string);

{ Defined in Dialogs.pp }</delphi>

Najjednoduchší správový dialóg: prijíma jednoduchý textový prarmeter, zobrazí ho v stereotypnom okne a pred vrátením, do volajúcej rutiny alebo programu, čaká na kliknutie myšou alebo kláves enter.
Toto je modálne volanie procedúry, ktoré zobrazí okno, získa zameranie a tohoto sa nevzdá, pokiaľ nie je stlačené OK.

Príklad: <delphi> Program LazMessage;

Uses Dialogs;
begin
  ShowMessage ('This is a message from Lazarus')
end.</delphi>

MessageBox

<delphi> Function Application.MessageBox (Text, Caption: PChar; Flags: longint) : Integer;

{ Defined in Forms.pp as part of TApplication; hence must be called as Application.Messagebox () 
  or using the 'with Application do ...' construct }</delphi>

Parametre:

  • Text: reťazec, ktorý je v okne zobrazený ako otázka ale inštrukcia;
  • Caption: textový štítok, ktorý je zobrazený na vrchu okna správy;
  • Flags: longint - integer vytvorený sčítaním rôznych konštánt, ktorými je definovaný obsah a správanie okna, napríklad MB_ABORTRETRYIGNORE + MR_ICONQUESTION nastaví, že aplikácia zobrazí ikonu otázky (?) v okne s tromi tlačítkami: ABORT, RETRY a IGNORE.

Funkcia vracia hodnotu integer, ktorá zodpovedá stlačenému tlačítku; jej hodnota je daná odkazom na konštanty [IDOK..IDHELP]

Môže byť volaná ako procedúra (tj. formulácia 'MessageBox()' namiesto volania funkcie 'Variable := MessageBox()' – viz. príklad nižšie)

Príklad: <delphi> Uses Forms, Dialogs, LCLType;

Procedure DisplayMessageBox;
  var reply, boxstyle: integer;
  begin
    with application do begin
      boxstyle :=  MB_ICONQUESTION + MB_YESNO;
      reply :=  MessageBox ('Press either button', 'MessageBoxDemo', boxstyle);
      if reply = IDYES then MessageBox ('Yes       ', 'Reply',MB_ICONINFORMATION)
      else MessageBox ('No         ', 'Reply', MB_ICONHAND);
  end;</delphi>

Všimnite si, že v tomto príklade sú reťazce 'Yes' a 'No' doplnené medzerami; inak by okno nebolo dosť široké na správne zobrazenie titulku.

MessageBoxDemo.png ReplyYes.png

MessageDLG

<delphi> function MessageDlg(const aMsg: string; DlgType: TMsgDlgType;

                   Buttons: TMsgDlgButtons; HelpCtx: Longint): Integer;
function MessageDlg(const aCaption, aMsg: string; DlgType: TMsgDlgType; 
                   Buttons: TMsgDlgButtons; HelpCtx: Longint): Integer;</delphi>

Two versions of this function, ie first 'Caption' parameter is optional; if omitted, caption is missing from box

This is the most complete and elaborate of the message dialogs, and allows the programmer considerable control over the appearance of the dialog box. The parameters defining the kind of box and its icon are types rather than integer constants, and the buttons can be specified as a set in square brackets eg [mbRetry, mbIgnore, mbAbort, mbCancel]. The HelpCtx parameter is not currently implemented and should be set to zero. The return value from the Function is the identity of the button pressed, expressed as an integer (see the definitions below, [mrNone..mrAll]).

Príklad: <delphi> Uses forms, dialogs, lcltype, controls;

procedure TryMessageDlg;
begin
  if MessageDlg ('Question', 'Do you wish to Execute?', mtConfirmation, 
                 [mbYes, mbNo, mbIgnore],0) = mrYes
  then { Execute rest of Program };
 end;</delphi>
http://lazarus-ccr.sourceforge.net/kbdata/Question.png

Text input Dialogs

InputBox

Text input Dialogs: display a message and await user text input

<delphi>Function InputBox(const ACaption, APrompt, ADefault : String) : String;</delphi>

Displays a box with defined title and prompt, and expects user input in a text box. A default string can optionally be displayed in the text box. The user-entered or default string is returned as the function result.

Príklad: <delphi> Uses forms, lcltype, dialogs, controls;

procedure TryInputBox;
var userstring: string;
begin
  userstring := InputBox ('Get some text input', 
                         'Please type in some   information', 'Some sample text');
  ShowMessage (userstring)
end;</delphi>

InputQuery

<delphi> Function InputQuery(const ACaption, APrompt : String;

                    MaskInput : Boolean; var Value : String) : Boolean;
Function InputQuery(const ACaption, APrompt : String;
                    var Value : String) : Boolean;</delphi>

Two versions of this function which displays a prompt and expects user input of textual data; the first includes a MaskInput boolean parameter which determines whether the user input is masked out by asterisks in the text-input box (like during entry of a password), while the second omits this property. The text entered by the user is returned in the variable parameter 'Value'; the function result is a boolean which returns TRUE if the OK button was pressed, or FALSE if the box was closed by any other mechanism (such as clicking the 'Close' icon on the top title bar). Omitting the MaskInput parameter is equivalent to setting it FALSE.

Príklad: <delphi> Uses forms, lcltype, dialogs, controls;

procedure TryInputQuery;
var QueryResult: boolean;
  userstring: string;
begin
  if InputQuery ('Question', 'Type in some data', TRUE, userstring)
  then ShowMessage (userstring)
  else 
  begin
    InputQuery ('Dont be silly', 'Please try again', userstring);
    ShowMessage (userstring);
  end
end;</delphi>
http://lazarus-ccr.sourceforge.net/kbdata/MessageDlgQuestion.png
http://lazarus-ccr.sourceforge.net/kbdata/DontBeSillly.png

PasswordBox

<delphi> Function PasswordBox(const ACaption, APrompt : String) : String;</delphi>

Behaves very similarly to the InputQuery function with MaskInput = TRUE; the difference is that the password that was typed in is returned as the result of the function (like InputBox).

Constants and Types used in message dialogs

Several constants and types relevant for use with the dialog boxes are pre-defined in the LCL library:

<delphi> const { Defined in LCLType.pp }</delphi>

integer constants for defining the types of buttons and the icon for display in MessageBox

<delphi> MB_OK = $00000000;

MB_OKCANCEL = $00000001;
MB_ABORTRETRYIGNORE = $00000002;
MB_YESNOCANCEL = $00000003;
MB_YESNO = $00000004;
MB_RETRYCANCEL = $00000005;

MB_ICONHAND = $00000010;
MB_ICONQUESTION = $00000020;
MB_ICONEXCLAMATION = $00000030;
MB_ICONASTERICK = $00000040;
MB_ICONWARNING = MB_ICONEXCLAMATION;
MB_ICONERROR = MB_ICONHAND;
MB_ICONINFORMATION = MB_ICONASTERICK;</delphi>

integer constants defining the return value from MessageBox according to which button was pressed

<delphi> IDOK = 1; ID_OK = IDOK;

IDCANCEL = 2;	ID_CANCEL = IDCANCEL;
IDABORT = 3;	ID_ABORT = IDABORT;
IDRETRY = 4;	ID_RETRY = IDRETRY;
IDIGNORE = 5;	ID_IGNORE = IDIGNORE;
IDYES = 6;	ID_YES = IDYES;
IDNO = 7;	ID_NO = IDNO;
IDCLOSE = 8;	ID_CLOSE = IDCLOSE;
IDHELP = 9;	ID_HELP = IDHELP;</delphi>

define whether first, second or third button is default

<delphi> MB_DEFBUTTON1 = $00000000;

MB_DEFBUTTON2 = $00000100;
MB_DEFBUTTON3 = $00000200;
MB_DEFBUTTON4 = $00000300;</delphi>

The Flags parameter of MessageBox is constructed by adding a button constant [MB_OK..MB_RETRYCANCEL], an optional icon constant [MB_ICONHAND..MB_ICONINFORMATION] and an optional default button constant [MB_DEFBUTTON1..MB_DEFBUTTON3]

Types for use in MessageDlg, which needs parameters AType of TMsgDlgType and AButtons of TMSgDlgButtons

<delphi> { Defined in Dialogs.pp }

type
 TMsgDlgType    = (mtWarning, mtError, mtInformation,  mtConfirmation,
                   mtCustom);
 TMsgDlgBtn     = (mbYes, mbNo, mbOK, mbCancel, mbAbort, mbRetry, mbIgnore,
                  mbAll, mbNoToAll, mbYesToAll, mbHelp, mbClose);
 TMsgDlgButtons = set of TMsgDlgBtn;
 
const
 mbYesNoCancel = [mbYes, mbNo, mbCancel];
 mbOKCancel = [mbOK, mbCancel];
 mbAbortRetryIgnore = [mbAbort, mbRetry, mbIgnore];
 
 MsgDlgBtnToBitBtnKind: array[TMsgDlgBtn] of TBitBtnKind = (
  bkYes, bkNo, bkOK, bkCancel, bkAbort, bkRetry, bkIgnore,
   bkAll, bkNoToAll, bkYesToAll, bkHelp, bkClose
  );

 BitBtnKindToMsgDlgBtn: array[TBitBtnKind] of TMsgDlgBtn = (
   mbOk, mbOK, mbCancel, mbHelp, mbYes, mbNo,
   mbClose, mbAbort, mbRetry, mbIgnore, mbAll, mbNoToALl, mbYesToAll
   );

{ Defined in Controls.pp }
const
 mrNone = 0;
 mrOK = mrNone + 1;
 mrCancel = mrNone + 2;
 mrAbort = mrNone + 3;
 mrRetry = mrNone + 4;
 mrIgnore = mrNone + 5;
 mrYes = mrNone + 6;
 mrNo = mrNone + 7;
 mrAll = mrNone + 8;
 mrNoToAll = mrNone + 9;
 mrYesToAll = mrNone + 10;
 mrLast = mrYesToAll;</delphi>

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