reveal method
Reveals the whole scratcher, so than only original child is displayed.
Implementation
void reveal({Duration? duration}) {
setState(() {
transitionDuration = duration;
isFinished = true;
canScratch = false;
if (!thresholdReported && widget.threshold != null) {
thresholdReported = true;
widget.onThreshold?.call();
}
});
widget.onChange?.call(100);
}