/**
* Marks a given worker thread as currently working on behalf of this panel. If null is given, no
* worker is active. Any existing active thread is interrupted.
*
* @param worker worker thread
*/
private void setActive(MatchWorker worker) {
if (matchWorker_ != null && !matchWorker_.done_) {
matchWorker_.cancel();
}
matchWorker_ = worker;
updateState();
}
