basiclayer.java

来自「OpenMap是一个基于JavaBeansTM的开发工具包。利用OpenMap你」· Java 代码 · 共 150 行

// **********************************************************************
// 
// <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/learn/BasicLayer.java,v $
// $RCSfile: BasicLayer.java,v $
// $Revision: 1.1.2.2 $
// $Date: 2007/02/26 16:57:11 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.layer.learn;

import java.awt.BasicStroke;
import java.awt.Color;

import com.bbn.openmap.layer.OMGraphicHandlerLayer;
import com.bbn.openmap.omGraphics.OMGraphic;
import com.bbn.openmap.omGraphics.OMGraphicConstants;
import com.bbn.openmap.omGraphics.OMGraphicList;
import com.bbn.openmap.omGraphics.OMLine;
import com.bbn.openmap.omGraphics.OMPoint;
import com.bbn.openmap.omGraphics.OMTextLabeler;

/**
 * This layer is a good place to start learning how to create OpenMap layers. It
 * extends OMGraphicHandler, which contains a good bit of functionality, but
 * exposes only the methods you need to start putting features (OMGraphics) on
 * the map. If you want to learn more about interacting with your OMGraphics
 * after you get the hang of displaying them efficiently, then move to the
 * InteractionLayer.
 */
public class BasicLayer extends OMGraphicHandlerLayer {

    /**
     * The empty constructor is necessary for any layer being created using the
     * openmap.properties file, via the openmap.layers property. This method
     * needs to be public, too. Don't try to do too much in the constructor -
     * remember, this code gets executed whether the user turns the layer on
     * uses the layer or not. Performance-wise, it's better to do most
     * initialization the first time the layer is made part of the map. You can
     * test for that in the prepare() method.
     * 
     * @see #prepare
     */
    public BasicLayer() {
        // Sets the name of the layer that is visible in the GUI. Can also be
        // set with properties with the 'prettyName' property.
        setName("Basic Layer");
        // This is how to set the ProjectionChangePolicy, which
        // dictates how the layer behaves when a new projection is
        // received. The StandardPCPolicy is the default policy and you don't
        // need to set it, this method call is here to illustrate where and how
        // you would make that call with a different policy.
        setProjectionChangePolicy(new com.bbn.openmap.layer.policy.StandardPCPolicy(this, true));
    }

    /**
     * This is an important Layer method to override. The prepare method gets
     * called when the layer is added to the map, or when the map projection
     * changes. We need to make sure the OMGraphicList returned from this method
     * is what we want painted on the map. The OMGraphics need to be generated
     * with the current projection. We test for a null OMGraphicList in the
     * layer to see if we need to create the OMGraphics. This layer doesn't
     * change it's OMGraphics for different projections, if your layer does, you
     * need to clear out the OMGraphicList and add the OMGraphics you want for
     * the current projection.
     */
    public OMGraphicList prepare() {
        OMGraphicList list = getList();
        if (list == null) {
            list = init();
        }

        /*
         * This call to the list is critical! OMGraphics need to be told where
         * to paint themselves, and they figure that out when they are given the
         * current Projection in the generate(Projection) call. If an
         * OMGraphic's location is changed, it will need to be regenerated
         * before it is rendered, otherwise it won't draw itself. You generally
         * know you have a generate problem when OMGraphics show up with the
         * projection changes (zooms and pans), but not at any other time after
         * something about the OMGraphic changes.
         * 
         * If you want to be more efficient, you can replace this call to the
         * list as an else clause to the (list == null) check above, and call
         * generate(Projection) on all the OMGraphics in the init() method below
         * as you create them. This will prevent the
         * OMGraphicList.generate(Projection) call from making an addional loop
         * through all of the OMGraphics before they are returned.
         */
        list.generate(getProjection());

        return list;
    }

    /**
     * Called from the prepare() method if the layer discovers that its
     * OMGraphicList is null.
     * 
     * @return new OMGraphicList with OMGraphics that you always want to display
     *         and reproject as necessary.
     */
    public OMGraphicList init() {

        // This layer keeps a pointer to an OMGraphicList that it uses
        // for painting. It's initially set to null, which is used as
        // a flag in prepare() to signal that the OMGraphcs need to be
        // created. The list returned from prepare() gets set in the
        // layer.
        // This layer uses the StandardPCPolicy for new
        // projections, which keeps the list intact and simply calls
        // generate() on it with the new projection, and repaint()
        // which calls paint().

        OMGraphicList omList = new OMGraphicList();

        // Add an OMLine
        OMLine line = new OMLine(40f, -75f, 42f, -70f, OMGraphic.LINETYPE_GREATCIRCLE);
        // line.addArrowHead(true);
        line.setStroke(new BasicStroke(2));
        line.putAttribute(OMGraphicConstants.LABEL,
                new OMTextLabeler("Line Label"));

        omList.add(line);

        // Add a list of OMPoints.
        OMGraphicList pointList = new OMGraphicList();
        for (int i = 0; i < 100; i++) {
            OMPoint point = new OMPoint((float) (Math.random() * 89f), (float) (Math.random() * -179f), 3);
            point.setLinePaint(Color.green);
            pointList.add(point);
        }
        omList.add(pointList);

        return omList;
    }

}