RAD Studio VCL Reference
TCustomActionList.OnUpdate Event

Occurs when the application is idle so that the action list can update a specific action in the list.

property OnUpdate: TActionEvent;
__property TActionEvent OnUpdate;

Write an OnUpdate event handler to configure the properties of a specified action in the list so that it reflects current conditions. 

When the application is idle, it cycles through every action in turn giving it a chance to update itself to reflect current conditions. For each action, the first event to occur in this sequence is the action list's OnUpdate event. If the OnUpdate event handler sets its Handled parameter to true, the action is considered updated, and processing stops there. This blocks the execution of any other event handlers or any built-in response by a predefined action class. 

If the OnUpdate event handler does not set its Handled parameter to true, the application's OnActionUpdate event occurs next. If the OnActionUpdate event does not update the action, the action object's OnUpdate event occurs. Finally, if the action does not have an OnUpdate event handler, the application executes any predefined update method implemented by the action object. 


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