listresetpcpolicy.java

openmap java写的开源数字地图程序. 用applet实现,可以像google map 那样放大缩小地图.

// **********************************************************************
// 
// <copyright>
// 
//  BBN Technologies
//  10 Moulton Street
//  Cambridge, MA 02138
//  [phone]
// 
//  Copyright (C) BBNT Solutions LLC. All rights reserved.
// 
// </copyright>
// **********************************************************************
// 
// $Source: /cvs/distapps/openmap/src/openmap/com/bbn/openmap/layer/policy/ListResetPCPolicy.java,v $
// $RCSfile: ListResetPCPolicy.java,v $
// $Revision: 1.6.2.2 $
// $Date: 2005/09/13 14:34:02 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.layer.policy;

import com.bbn.openmap.layer.OMGraphicHandlerLayer;
import com.bbn.openmap.event.LayerStatusEvent;
import com.bbn.openmap.event.ProjectionEvent;
import com.bbn.openmap.omGraphics.OMGraphicList;
import com.bbn.openmap.proj.Projection;
import com.bbn.openmap.util.Debug;

/**
 * ProjectionChangePolicy that uses a Layer SwingWorker to kick off a
 * thread to call layer.prepare() and deletes the current
 * OMGraphicList between projection changes. The standard behavior for
 * layers that gather new OMGraphics for new projections.
 */
public class ListResetPCPolicy implements ProjectionChangePolicy {

    /**
     * Don't let this be null.
     */
    protected OMGraphicHandlerLayer layer;

    /**
     * You MUST set a layer at some point.
     */
    public ListResetPCPolicy() {}

    /**
     * Don't pass in a null layer.
     */
    public ListResetPCPolicy(OMGraphicHandlerLayer layer) {
        this.layer = layer;
    }

    public void setLayer(OMGraphicHandlerLayer l) {
        layer = l;
    }

    public OMGraphicHandlerLayer getLayer() {
        return layer;
    }

    public void projectionChanged(ProjectionEvent pe) {
        if (layer != null) {
            Projection proj = layer.setProjection(pe);
            // proj will be null if the projection hasn't changed, a
            // signal that work does not need to be done.
            if (proj != null) {
                if (Debug.debugging("layer")) {
                    Debug.output(getLayer().getName()
                            + ": ListResetPCPolicy projectionChanged with NEW projection, resetting list.");
                }
                layer.setList(null);
                // Check to see if the projection is worth reacting to.
                if (layer.isProjectionOK(proj)) {
                    layer.doPrepare();
                }
            } else {
                if (Debug.debugging("layer")) {
                    Debug.output(getLayer().getName()
                            + ": ListResetPCPolicy projectionChanged with OLD projection, repainting.");
                }
                if (!layer.isWorking()) {
                    // This repaint may look redundant, but it handles
                    // the situation where a layer is removed from a
                    // map and readded when the projection doesn't
                    // change. Since it already had the projection,
                    // and remove() hasn't been called yet, the proj
                    // == null. When the new layer is added, it
                    // receives a projectionChanged call, and even
                    // though it's all set, it still needs to call
                    // repaint to have itself show up on the map.
                    layer.repaint();
                    layer.fireStatusUpdate(LayerStatusEvent.FINISH_WORKING);
                }
            }
        } else {
            Debug.error("ListResetPCPolicy.projectionChanged():  NULL layer, can't do anything.");
        }
    }

    /**
     * This is a subtle call, that dictates what should happen when
     * the LayerWorker has completed working in it's thread. The
     * LayerWorker.get() method returns whatever was returned in the
     * OMGraphicHandler.prepare() method, an OMGraphicList. In most
     * cases, this object should be set as the Layer's list at this
     * time. Some Layers, working asynchronously with their data
     * sources, might want nothing to happen and should use a policy
     * that overrides this method so that nothing does.
     */
    public void workerComplete(OMGraphicList aList) {
        if (layer != null) {
            layer.setList(aList);
        }
    }
}