MarkerClusterer.java

package org.osmdroid.bonuspack.clustering;

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Point;
import android.view.MotionEvent;

import org.osmdroid.views.MapView;
import org.osmdroid.views.overlay.Marker;
import org.osmdroid.views.overlay.Overlay;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.ListIterator;

/** 
 * An overlay allowing to perform markers clustering. 
 * Usage: put your markers inside with add(Marker), and add the MarkerClusterer to the map overlays. 
 * Depending on the zoom level, markers will be displayed separately, or grouped as a single Marker. <br/>
 * 
 * This abstract class provides the framework. Sub-classes have to implement the clustering algorithm, 
 * and the rendering of a cluster. 
 * 
 * @author M.Kergall
 *
 */
public abstract class MarkerClusterer extends Overlay {

	/** impossible value for zoom level, to force clustering */
	protected static final int FORCE_CLUSTERING = -1;
	
	protected ArrayList<Marker> mItems = new ArrayList<Marker>();
	protected Point mPoint = new Point();
	protected ArrayList<StaticCluster> mClusters = new ArrayList<StaticCluster>();
	protected int mLastZoomLevel;
	protected Bitmap mClusterIcon;
	protected String mName, mDescription;
	
	// abstract methods: 
	
	/** clustering algorithm */
	public abstract ArrayList<StaticCluster> clusterer(MapView mapView);
	/** Build the marker for a cluster. */
	public abstract Marker buildClusterMarker(StaticCluster cluster, MapView mapView);
	/** build clusters markers to be used at next draw */
	public abstract void renderer(ArrayList<StaticCluster> clusters, Canvas canvas, MapView mapView);
	
	public MarkerClusterer() {
		super();
		mLastZoomLevel = FORCE_CLUSTERING;
	}

	public void setName(String name){
		mName = name;
	}
	
	public String getName(){
		return mName;
	}
	
	public void setDescription(String description){
		mDescription = description;
	}
	
	public String getDescription(){
		return mDescription;
	}
	
	/** Set the cluster icon to be drawn when a cluster contains more than 1 marker. 
	 * If not set, default will be the default osmdroid marker icon (which is really inappropriate as a cluster icon). */
	public void setIcon(Bitmap icon){
		mClusterIcon = icon;
	}
	
	/** Add the Marker. 
	 * Important: Markers added in a MarkerClusterer should not be added in the map overlays. */
	public void add(Marker marker){
		mItems.add(marker);
	}
	
	/** Force a rebuild of clusters at next draw, even without a zooming action. 
	 * Should be done when you changed the content of a MarkerClusterer. */
	public void invalidate(){
		mLastZoomLevel = FORCE_CLUSTERING; 
	}
	
	/** @return the Marker at id (starting at 0) */
	public Marker getItem(int id){
		return mItems.get(id);
	}
	
	/** @return the list of Markers. */
	public ArrayList<Marker> getItems(){
		return mItems;
	}
	
	@Override public void draw(Canvas canvas, MapView mapView, boolean shadow) {
		//if zoom has changed and mapView is now stable, rebuild clusters:
		int zoomLevel = mapView.getZoomLevel();
		if (zoomLevel != mLastZoomLevel && !mapView.isAnimating()){
        	mClusters = clusterer(mapView);
        	renderer(mClusters, canvas, mapView);
			mLastZoomLevel = zoomLevel;
		}
		
		for (StaticCluster cluster:mClusters){
			cluster.getMarker().draw(canvas, mapView, shadow);
        }
	}

	public Iterable<StaticCluster> reversedClusters() {
		return new Iterable<StaticCluster>() {
			@Override
			public Iterator<StaticCluster> iterator() {
				final ListIterator<StaticCluster> i = mClusters.listIterator(mClusters.size());
				return new Iterator<StaticCluster>() {
					@Override
					public boolean hasNext() {
						return i.hasPrevious();
					}

					@Override
					public StaticCluster next() {
						return i.previous();
					}

					@Override
					public void remove() {
						i.remove();
					}
				};
			}
		};
	}

	@Override public boolean onSingleTapConfirmed(final MotionEvent event, final MapView mapView){
		for (final StaticCluster cluster : reversedClusters()) {
			if (cluster.getMarker().onSingleTapConfirmed(event, mapView))
				return true;
		}
		return false;
	}
	
	@Override public boolean onLongPress(final MotionEvent event, final MapView mapView) {
		for (final StaticCluster cluster : reversedClusters()) {
			if (cluster.getMarker().onLongPress(event, mapView))
				return true;
		}
		return false;
	}

	@Override public boolean onTouchEvent(final MotionEvent event, final MapView mapView) {
		for (StaticCluster cluster : reversedClusters()) {
			if (cluster.getMarker().onTouchEvent(event, mapView))
				return true;
		}
		return false;
	}
}