Created
August 24, 2017 02:43
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Example code for TNotifyEvent Debouncing post at https://www.code-partners.com/tnotifyevent-debouncing-in-delphi/
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unit UDebouncedEvent; | |
interface | |
uses | |
System.Classes, System.SysUtils, System.DateUtils, FMX.Types; | |
type | |
TDebouncedEvent = class (TComponent) | |
private | |
FSourceEvent: TNotifyEvent; | |
FInterval: integer; | |
FTimer: TTimer; | |
FSender: TObject; | |
FLastcallTimestamp: TDateTime; | |
procedure DebouncedEvent(Sender: TObject); | |
procedure DoCallEvent(Sender: TObject); | |
procedure DoOnTimer(Sender: TObject); | |
protected | |
constructor Create(AOwner: TComponent; ASourceEvent: TNotifyEvent; | |
AInterval: integer); reintroduce; | |
public | |
class function Wrap(ASourceEvent: TNotifyEvent; AInterval: integer; | |
AOwner: TComponent): TNotifyEvent; | |
end; | |
implementation | |
{ TDebouncedEvent } | |
constructor TDebouncedEvent.Create(AOwner: TComponent; | |
ASourceEvent: TNotifyEvent; AInterval: integer); | |
begin | |
inherited Create(AOwner); | |
self.FSourceEvent := ASourceEvent; | |
self.FInterval := AInterval; | |
self.FTimer := TTimer.Create(self); | |
self.FTimer.Enabled := false; | |
self.FTimer.Interval := AInterval; | |
self.FTimer.OnTimer := self.DoOnTimer; | |
end; | |
procedure TDebouncedEvent.DebouncedEvent(Sender: TObject); | |
var | |
Between: int64; | |
begin | |
Between := MilliSecondsBetween(Now, self.FLastcallTimestamp); | |
// if timer is not enabled, it means that last call happened | |
// earlier than <self.FInteval> milliseconds ago | |
if Between >= self.FInterval then begin | |
self.DoCallEvent(Sender); | |
end | |
else begin | |
// adjusting timer, so interval between calls will never be more than <FInterval> ms | |
self.FTimer.Interval := self.FInterval - Between; | |
// reset the timer | |
self.FTimer.Enabled := false; | |
self.FTimer.Enabled := true; | |
// remember last Sender argument value to use it in a delayed call | |
self.FSender := Sender; | |
end; | |
end; | |
procedure TDebouncedEvent.DoCallEvent(Sender: TObject); | |
begin | |
self.FLastcallTimestamp := Now; | |
self.FSourceEvent(Sender); | |
end; | |
procedure TDebouncedEvent.DoOnTimer(Sender: TObject); | |
begin | |
self.FTimer.Enabled := false; | |
self.DoCallEvent(self.FSender); | |
end; | |
class function TDebouncedEvent.Wrap(ASourceEvent: TNotifyEvent; | |
AInterval: integer; AOwner: TComponent): TNotifyEvent; | |
begin | |
Result := TDebouncedEvent.Create(AOwner, ASourceEvent, AInterval).DebouncedEvent; | |
end; | |
end. |
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