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package cgeo.geocaching.utils;
import android.os.Handler;
import android.os.Message;
import java.lang.ref.WeakReference;
/**
* A PeriodicHandler class helps with the implementation of a periodic
* action embedded in a thread with a looper such as the UI thread.
* The onPeriodic() method of the listener will be called periodically.
* The clock may drift as the implementation does not target real-time
* actions.
*
* The handler will be interrupted if the device goes to sleep.
*
* The handler only keeps a weak reference to the listener. If the listener
* is garbage-collected without having stopped the timer, the handler will
* stop itself.
*/
final public class PeriodicHandler extends Handler {
public static interface PeriodicHandlerListener {
public void onPeriodic();
}
final static private int START = 0;
final static private int STOP = 1;
final static private int ACT = 2;
final private long period;
final private WeakReference<PeriodicHandlerListener> listenerRef;
/**
* Create a new PeriodicHandler object.
*
* @param period
* The period in milliseconds.
*/
public PeriodicHandler(final long period, final PeriodicHandlerListener listener) {
this.period = period;
listenerRef = new WeakReference<PeriodicHandlerListener>(listener);
}
@Override
public void handleMessage(final Message msg) {
switch (msg.what) {
case START:
removeMessages(ACT);
sendEmptyMessage(ACT);
break;
case STOP:
removeMessages(ACT);
break;
case ACT:
final PeriodicHandlerListener listener = listenerRef.get();
if (listener != null) {
sendEmptyMessageDelayed(ACT, period);
listener.onPeriodic();
}
break;
default:
throw new UnsupportedOperationException();
}
}
/**
* Start the periodic handler.
*
* Restarting a handler that is already started will only
* reset its clock.
*/
public void start() {
sendEmptyMessage(START);
}
/**
* Stop the periodic handler.
*
* If this method is called from the looper thread, this call is
* guaranteed to be synchronous.
*/
public void stop() {
sendMessageAtFrontOfQueue(obtainMessage(STOP));
}
}
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