[Overview][Constants][Types][Classes][Procedures and functions][Variables][Index] | Reference for unit 'Forms' (#lcl)

# TApplication.OnDeactivate

Event handler signalled when a Deactivate message is handled in the application.

## Declaration

Source position: forms.pp line 1751

`public property TApplication.OnDeactivate : TNotifyEvent read FOnDeactivate write FOnDeactivate;`

## Description

OnDeactivate is a TNotifyEvent property with the event handler signalled when a Deactivate message is handled in the application.

It is signalled from the NotifyDeactivateHandler method, and occurs when the Deactivate method is called for the application. The event handler is also signalled (via Deactivate) from the WMActivate method in TCustomForm to ensure that the application is de-activated when its main form is de-activated.

Use the OnActivate event handler to perform actions needed when the application is activated.

Use the TApplicationProperties class to assign properties and event handlers at design-time that are applied to the application instance at run-time.

## See also

TApplication.NotifyDeactivateHandler |  | Notifies all Deactivate handlers for the application.
TApplication.AddOnDeactivateHandler |  | Adds an application deactivation handler.
TApplication.RemoveOnDeactivateHandler |  | Removes an application deactivation handler.
TApplicationHandlerType |  | Types of Application notification handlers.
TApplicationProperties |  | A component that provides access to the properties for the current application.