Visão Geral

Form events are events that can lead to the execution of the form method and/or form object method(s). Form events allow you to control the flow of your application and to write code that is executed only when a specific event occurs.

In your code, you control the events using the FORM Event command, that returns the triggered event. Por exemplo:

//code of a button If(FORM Event.code=On Clicked) 
// do something when the button is clicked End if

Every form and every active object on the form can listen to a predefined set of events, but only the events that you enabled at the form level and/or at every object level will actually occur.

Event object

Each event is returned as an object by the FORM Event command. By default, it contains the following properties:

Propriedade	Tipo	Descrição
objectName	text	Name of the object triggering the event - Not included if the event is triggered by the form

Additional properties are returned when the event occurs on specific objects. Em particular:

• list boxes and list box columns return additional properties such as columnName or isRowSelected.
• 4D View Pro areas return for example sheetName or action properties in the On After Edit event object.

Eventos e métodos

When a form event occurs, 4D performs the following actions:

• First, it browses the objects of the form and calls the object method for any object (involved in the event) whose corresponding object event property has been selected.
• Second, it calls the form method if the corresponding form event property has been selected.

Do not assume that the object methods, if any, will be called in a particular order. The rule of thumb is that the object methods are always called before the form method. If an object is a subform, the object methods of the subform’s list form are called, then the form method of the list form is called. 4D then continues to call the object methods of the parent form. In other words, when an object is a subform, 4D uses the same rule of thumb for the object and form methods within the subform object.

Except for the On Load and On Unload events (see below), if the form event property is not selected for a given event, this does not prevent calls to object methods for the objects whose same event property is selected. In other words, enabling or disabling an event at the form level has no effect on the object event properties.

The number of objects involved in an event depends on the nature of the event.

Tabela de chamadas

The following table summarizes how object and form methods are called for each event type:

Evento	Métodos objecto	Método formulário	Objectos
On Load	Sim	Sim	Todos os objectos
On Unload	Sim	Sim	Todos os objectos
On Validate	Sim	Sim	Todos os objectos
On Clicked	Sim	Sim	Involved object only
On Double Clicked	Sim	Sim	Involved object only
On Before Keystroke	Sim	Sim	Involved object only
On After Keystroke	Sim	Sim	Involved object only
On After Edit	Sim	Sim	Involved object only
On Getting Focus	Sim	Sim	Involved object only
On Losing Focus	Sim	Sim	Involved object only
On Activate	Nunca	Sim	Nenhum
On Deactivate	Nunca	Sim	Nenhum
On Outside Call	Nunca	Sim	Nenhum
On Page Change	Nunca	Sim	Nenhum
On Begin Drag Over	Sim	Sim	Involved object only
On Drop	Sim	Sim	Involved object only
On Drag Over	Sim	Nunca	Involved object only
On Mouse Enter	Sim	Sim	Todos os objectos
On Mouse Move	Sim	Sim	Todos os objectos
On Mouse Leave	Sim	Sim	Todos os objectos
On Mouse Up	Sim	Nunca	Involved object only
On Menu Selected	Nunca	Sim	Nenhum
On Bound variable change	Nunca	Sim	Nenhum
On Data Change	Sim	Sim	Involved object only
On Plug in Area	Sim	Sim	Involved object only
On Header	Sim	Sim	Todos os objectos
On Printing Detail	Sim	Sim	Todos os objectos
On Printing Break	Sim	Sim	Todos os objectos
On Printing Footer	Sim	Sim	Todos os objectos
On Close Box	Nunca	Sim	Nenhum
On Display Detail	Sim	Sim	Todos os objectos
On Open Detail	Sim (List box)	Sim	Nenhuma exceto List boxes
On Close Detail	Sim (List box)	Sim	Nenhuma exceto List boxes
On Resize	Nunca	Sim	Nenhum
On Selection Change	Sim	Sim	Involved object only
On Load Record	Nunca	Sim	Nenhum
On Timer	Nunca	Sim	Nenhum
On Scroll	Sim	Nunca	Involved object only
On Before Data Entry	Sim (List box)	Nunca	Involved object only
On Column Moved	Sim (List box)	Nunca	Involved object only
On Row Moved	Sim (List box)	Nunca	Involved object only
On Column Resize	Sim (List box e área 4D View Pro)	Nunca	Involved object only
On Header Click	Sim (List box e área 4D View Pro)	Nunca	Involved object only
On Footer Click	Sim (List box)	Nunca	Involved object only
On After Sort	Sim (List box)	Nunca	Involved object only
On Long Click	Sim (Botão)	Sim	Involved object only
On Alternative Click	Sim (Botão e List box)	Nunca	Involved object only
On Expand	Sim (Hier. lista e list box)	Nunca	Involved object only
On Collapse	Sim (Hier. lista e list box)	Nunca	Involved object only
On Delete Action	Sim (Hier. lista e list box)	Nunca	Involved object only
On URL Resource Loading	Sim (Área Web)	Nunca	Involved object only
On Begin URL Loading	Sim (Área Web)	Nunca	Involved object only
On URL Loading Error	Sim (Área Web)	Nunca	Involved object only
On URL Filtering	Sim (Área Web)	Nunca	Involved object only
On End URL Loading	Sim (Área Web)	Nunca	Involved object only
On Open External Link	Sim (Área Web)	Nunca	Involved object only
On Window Opening Denied	Sim (Área Web)	Nunca	Involved object only
On VP Range Changed	Sim (Area 4D View Pro)	Nunca	Involved object only
On VP Ready	Sim (Area 4D View Pro)	Nunca	Involved object only
On Row Resize	Sim (Area 4D View Pro)	Nunca	Involved object only

Ter sempre em mente que, para qualquer evento, o método de um formulário ou de um objecto é chamado se a propriedade do evento correspondente for seleccionada para o formulário ou objectos. The benefit of disabling events in the Design environment (using the Property List of the Form editor) is that you can reduce the number of calls to methods and therefore significantly optimize the execution speed of your forms.

WARNING: The On Load and On Unload events are generated for objects if they are enabled for both the objects and the form to which the objects belong. If the events are enabled for objects only, they will not occur; these two events must also be enabled at the form level.