Form event code

Form event code : Integer

Parámetros	Tipo		Descripción
Resultado	Integer	←	Form event number

This command is not thread-safe, it cannot be used in preemptive code.

Descripción

Form event code returns a numeric value identifying the type of form event that has just occurred. Usually, you will use Form event code from within a form or object method.

4D provides predefined constants (found in the Form Events theme) in order to compare the values returned by the Form event code command. Certain events are generic (generated for any type of object) and others are specific to a particular type of object.

For a description of events, please refer to the Form Events section.

Ejemplo 1

This example shows the On Validate event being used to automatically assign (to a field) the date that the record is modified:

  //Method of a form
 Case of
  // ...
    :(Form event code=On Validate)
       [aTable]Last Modified On:=Current date
 End case

Ejemplo 2

In this example, the complete handling of a drop-down list (initialization, user clicks, and object release) is encapsulated in the method of the object:

  //asBurgerSize Drop-down list Object Method
 Case of
    :(Form event code=On Load)
       ARRAY TEXT(asBurgerSize;3)
       asBurgerSize{1}:="Small"
       asBurgerSize{1}:="Medium"
       asBurgerSize{1}:="Large"
    :(Form event code=On Clicked)
       If(asBurgerSize#0)
          ALERT("You chose a "+asBurgerSize{asBurgerSize}+" burger.")
       End if
    :(Form event code=On Unload)
       CLEAR VARIABLE(asBurgerSize)
 End case

Ejemplo 3

This example is a template for a form method. It shows each of the possible events that can occur when a summary report uses a form as an output form:

  //Method of a form being used as output form for a summary report
 $vpFormTable:=Current form table
 Case of
  //...
    :(Form event code=On Header)
  //A header area is about to be printed
       Case of
          :(Before selection($vpFormTable->))
  //Code for the first break header goes here
          :(Level=1)
  //Code for a break header level 1 goes here
          :(Level=2)
  //Code for a break header level 2 goes here
  //...
       End case
    :(Form event code=On Printing Detail)
  //A record is about to be printed
  //Code for each record goes here
    :(Form event code=On Printing Break)
  //A break area is about to be printed
       Case of
          :(Level=0)
  //Code for a break level 0 goes here
          :(Level=1)
  //Code for a break level 1 goes here
  //...
       End case
    :(Form event code=On Printing Footer)
       If(End selection($vpFormTable->))
  //Code for the last footer goes here
       Else
  //Code for a footer goes here
       End if
 End case

Ejemplo 4

This example shows the template of a form method that handles the events that can occur for a form displayed using the DISPLAY SELECTION or MODIFY SELECTION commands. For didactic purposes, it displays the nature of the event in the title bar of the form window.

  //A form method
 Case of
    :(Form event code=On Load)
       $vsTheEvent:="The form is about to be displayed"
    :(Form event code=On Unload)
       $vsTheEvent:="The output form has been exited and is about to disappear from the screen"
    :(Form event code=On Display Detail)
       $vsTheEvent:="Displaying record #"+String(Selected record number([TheTable]))
    :(Form event code=On Menu Selected)
       $vsTheEvent:="A menu item has been selected"
    :(Form event code=On Header")
       $vsTheEvent:="The header area is about to be drawn"
    :(Form event code=On Clicked")
       $vsTheEvent:="A record has been clicked"
    :(Form event code=On Double Clicked")
       $vsTheEvent:="A record has been double clicked"
    :(Form event code=On Open Detail)
       $vsTheEvent:="The record #"+String(Selected record number([TheTable]))+" is double-clicked"
    :(Form event code=On Close Detail)
       $vsTheEvent:="Going back to the output form"
    :(Form event code=On Activate)
       $vsTheEvent:="The form's window has just become the frontmost window"
    :(Form event code=On Deactivate)
       $vsTheEvent:="The form's window is no longer the frontmost window"
    :(Form event code=On Menu Selected)
       $vsTheEvent:="A menu item has been chosen"
    :(Form event code=On Outside Call)
       $vsTheEvent:="A call from another has been received"
    Else
       $vsTheEvent:="What's going on? Event #"+String(Form event)
 End case
 SET WINDOW TITLE($vsTheEvent)

Ejemplo 5

For examples on how to handle On Before Keystroke and On After Keystroke events, see examples for the Get edited text, Keystroke and FILTER KEYSTROKE commands.

Ejemplo 6

This example shows how to treat clicks and double clicks in the same way in a scrollable area:

  //asChoices scrollable area object method
 Case of
    :(Form event code=On Load)
       ARRAY TEXT(asChoices;...)
  //...
       asChoices:=0
    :((Form event code=On Clicked)|(Form event code=On Double Clicked))
       If(asChoices#0)
  //An item has been clicked, do something here
  //...
       End if
  //...
 End case

Ejemplo 7

This example shows how to treat clicks and double clicks using a different response. Note the use of the element zero for keeping track of the selected element:

  //asChoices scrollable area object method
 Case of
    :(Form event code=On Load)
       ARRAY TEXT(asChoices;...)
  // ...
       asChoices:=0
       asChoices{0}:="0"
    :(Form event code=On Clicked)
       If(asChoices#0)
          If(asChoices#Num(asChoices))
  //A new item has been clicked, do something here
  //...
  //Save the new selected element for the next time
             asChoices{0}:=String(asChoices)
          End if
       Else
          asChoices:=Num(asChoices{0})
       End if
    :(Form event code=On Double Clicked)
       If(asChoices#0)
  //An item has been double clicked, do something different here
       End if
  // ...
 End case

Ejemplo 8

This example shows how to maintain a status text information area from within a form method, using the On Getting Focus and On Losing Focus events:

  //[Contacts];"Data Entry" form method
 Case of
    :(Form event code=On Load)
       var vtStatusArea : Text
       vtStatusArea:=""
    :(Form event code=On Getting Focus)
       RESOLVE POINTER(Focus object;$vsVarName;$vlTableNum;$vlFieldNum)
       If(($vlTableNum#0)&($vlFieldNum#0))
          Case of
             :($vlFieldNum=1) //Last name field
                vtStatusArea:="Enter the Last name of the Contact; it will be capitalized automatically"
  //...
             :($vlFieldNum=10) //Zip Code field
                vtStatusArea:="Enter a 5-digit zip code; it will be checked and validated automatically"
  //...
          End case
       End if
    :(Form event code=On Losing Focus)
       vtStatusArea:=""
  //...
 End case

Ejemplo 9

Este ejemplo muestra cómo responder a un evento de cierre de ventana con un formulario utilizado para la entrada de datos de registro:

  //Method for an input form
 $vpFormTable:=Current form table
 Case of
  //...
    :(Form event code=On Close Box)
       If(Modified record($vpFormTable->))
          CONFIRM("This record has been modified. Save Changes?")
          If(OK=1)
             ACCEPT
          Else
             CANCEL
          End if
       Else
          CANCEL
       End if
  //...
 End case

Ejemplo 10

This example shows how to capitalize a text or alphanumeric field each time its data source value is modified:

  //[Contacts]First Name Object method
 Case of
  //...
    :(Form event code=On Data Change)
       [Contacts]First Name:=Uppercase(Substring([Contacts]First Name;1;1))+Lowercase(Substring([Contacts]First Name;2))
  //...
 End case

Ejemplo 11

The following example illustrates how to manage a deletion action in a hierarchical list:

 ... //method of hierarchical list
:(Form event code=On Delete Action)
 ARRAY LONGINT($itemsArray;0)
 $Ref:=Selected list items(<>HL;$itemsArray;*)
 $n:=Size of array($itemsArray)
 
 Case of
    :($n=0)
       ALERT("No item selected")
       OK:=0
    :($n=1)
       CONFIRM("Do you want to delete this item?")
    :($n>1)
       CONFIRM("Do you want to delete these items?")
 End case
 
 If(OK=1)
    For($i;1;$n)
       DELETE FROM LIST(<>HL;$itemsArray{$i};*)
    End for
 End if

Ejemplo 12

In this example, the On Scroll form event allows us to synchronize the display of two pictures in a form. The following code is added in the "satellite" object method (picture field or variable):

 Case of
    :(Form event code=On Scroll)
  // we take the position of the left picture
       OBJECT GET SCROLL POSITION(*;"satellite";vPos;hPos)
  // and we apply it to the right picture
       OBJECT SET SCROLL POSITION(*;"plan";vPos;hPos;*)
 End case

Result: https://www.youtube.com/watch?v=YIRfsW1BmHE

Ejemplo 13

You want to draw a red rectangle around the selected cell of a list box, and you want the rectangle to move along with the list box if it is scrolled vertically by the user. In the list box object method, you can write:

 Case of
 
    :(Form event code=On Clicked)
       LISTBOX GET CELL POSITION(*;"LB1";$col;$raw)
       LISTBOX GET CELL COORDINATES(*;"LB1";$col;$raw;$x1;$y1;$x2;$y2)
       OBJECT SET VISIBLE(*;"RedRect";True) //initialize a red rectangle
       OBJECT SET COORDINATES(*;"RedRect";$x1;$y1;$x2;$y2)
 
    :(Form event code=On Scroll)
       LISTBOX GET CELL POSITION(*;"LB1";$col;$raw)
       LISTBOX GET CELL COORDINATES(*;"LB1";$col;$raw;$x1;$y1;$x2;$y2)
       OBJECT GET COORDINATES(*;"LB1";$xlb1;$ylb1;$xlb2;$ylb2)
       $toAdd:=LISTBOX Get headers height(*;"LB1") //height of the header so as not to overlap it
       If($ylb1+$toAdd<$y1)&($ylb2>$y2) //if we are inside the list box
  //to keep it simple, we only handle headers
  //but we should handle horizontal clipping
  //as well as scroll bars
          OBJECT SET VISIBLE(*;"RedRect";True)
          OBJECT SET COORDINATES(*;"RedRect";$x1;$y1;$x2;$y2)
       Else
          OBJECT SET VISIBLE(*;"RedRect";False)
       End if
 
 End case

As a result, the red rectangle follows the scrolling of the list box:

Ver también

Form Events CALL SUBFORM CONTAINER
Current form table
FILTER KEYSTROKE
FORM Event
Get edited text
Keystroke
POST OUTSIDE CALL
SET TIMER