DelayedMapListener.java

package org.osmdroid.events;

import android.os.Handler;
import android.util.Log;
import org.osmdroid.api.IMapView;

/*
 * A MapListener that aggregates multiple events called in quick succession.
 * After an event arrives, if another event arrives within <code>delay</code> milliseconds,
 * the original event is discarded.  Otherwise, the event is propagated to the wrapped
 * MapListener.  Note: This class is not thread-safe.
 *
 * @author Theodore Hong
 */
public class DelayedMapListener implements MapListener {

	/** Default listening delay */
	protected static final int DEFAULT_DELAY = 100;

	/** The wrapped MapListener */
	MapListener wrappedListener;

	/** Listening delay, in milliseconds */
	protected long delay;

	protected Handler handler;
	protected CallbackTask callback;

	/*
	 * @param wrappedListener The wrapped MapListener
	 * 
	 * @param delay Listening delay, in milliseconds
	 */
	public DelayedMapListener(final MapListener wrappedListener, final long delay) {
		this.wrappedListener = wrappedListener;
		this.delay = delay;
		this.handler = new Handler();
		this.callback = null;
	}

	/*
	 * Constructor with default delay.
	 * 
	 * @param wrappedListener The wrapped MapListener
	 */
	public DelayedMapListener(final MapListener wrappedListener) {
		this(wrappedListener, DEFAULT_DELAY);
	}

	@Override
	public boolean onScroll(final ScrollEvent event) {
		dispatch(event);
		return true;
	}

	@Override
	public boolean onZoom(final ZoomEvent event) {
		dispatch(event);
		return true;
	}

	/*
	 * Process an incoming MapEvent.
	 */
	protected void dispatch(final MapEvent event) {
		// cancel any pending callback
		if (callback != null) {
			handler.removeCallbacks(callback);
		}
		callback = new CallbackTask(event);

		// set timer
		handler.postDelayed(callback, delay);
	}

	// Callback tasks
	private class CallbackTask implements Runnable {
		private final MapEvent event;

		public CallbackTask(final MapEvent event) {
			this.event = event;
		}

		@Override
		public void run() {
			// do the callback
			if (event instanceof ScrollEvent) {
				wrappedListener.onScroll((ScrollEvent) event);
			} else if (event instanceof ZoomEvent) {
				wrappedListener.onZoom((ZoomEvent) event);
			} else {
				// unknown event; discard
                    Log.d(IMapView.LOGTAG,"Unknown event received: " + event);
			}
		}
	}
}