Graphics2D 在地图上画一条线

Question

我正在尝试使用坐标在地图上绘制路径。我正在尝试使用 GeneralPath，但它不会创建一条线，只是在纬度/经度坐标所在的位置创建一堆点。我如何连接它们或者我可以使用其他东西吗？对 Graphics2D 不太熟悉..

region.add(new GeoPosition(47.2971, -122.3822));
region.add(new GeoPosition(47.2975, -122.3701));
region.add(new GeoPosition(47.3006, -122.3535));
region.add(new GeoPosition(47.2899, -122.3356));
region.add(new GeoPosition(47.2895, -122.3111));
region.add(new GeoPosition(47.2903, -122.2989));
region.add(new GeoPosition(47.2929, -122.2921));
region.add(new GeoPosition(47.2914, -122.2920));
region.add(new GeoPosition(47.2934, -122.2883));


Painter<JXMapViewer> overlay = new Painter<JXMapViewer>() {
    public void paint(Graphics2D g, JXMapViewer map, int w, int h) {
        g = (Graphics2D) g.create();
        //convert from viewport to world bitmap
        Rectangle rect = map.getViewportBounds();
        g.translate(-rect.x, -rect.y);          
        GeneralPath path = new GeneralPath();
        //Polygon poly = new Polygon();
        for(GeoPosition gp : region) {
            //convert geo to world bitmap pixel
            mapViewer.setZoom(60);
            Point2D pt = map.getTileFactory().geoToPixel(gp, map.getZoom());
            //poly.addPoint((int)pt.getX(),(int)pt.getY());
            path.moveTo((int)pt.getX(),(int)pt.getY());
            path.lineTo((int)pt.getX(),(int)pt.getY());                                                                         
        }           
        //do the drawing
        g.setColor(new Color(255,0,0,100));
        g.fill(path);           
        g.setColor(Color.RED);
        g.draw(path);           
        g.dispose();
    }

Answer 1

我相信您只需要一个 moveTo(...) 方法即可开始绘制线条。然后您执行多个 lineTo(...) 方法来绘制实际的线条。

这是我很久以前在网上找到的一个例子：

import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;

public class GraphicPane extends JFrame
{
    public GraphicPane()
    {
        super("polygon");

        this.setSize(600,600);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        MyPolygon mypolygon = new MyPolygon();
        getContentPane().add(mypolygon);

        this.setVisible(true);

        try
        {
            Thread.sleep(2000);
        }
        catch (InterruptedException e){}

        mypolygon.move();
    }

    class MyPolygon extends JPanel
    {
        Point[] p;
        GeneralPath shape;

        public MyPolygon()
        {
            p=new Point[4];
            p[0]=new Point(10,10);
            p[1]=new Point(100,10);
            p[2]=new Point(170,170);
            p[3]=new Point(80,180);
            shape =new GeneralPath();
        }

        public void move()
        {
            int x=300;
            int y=200;
            p[0].setLocation(x, y);
            shape = new GeneralPath();
            repaint();
        }

        public void paintComponent(Graphics grap)
        {
            super.paintComponent(grap);

            Graphics2D grap2D=(Graphics2D)grap;

            shape.moveTo((float)p[0].getX(),(float)p[0].getY());

            for(int i=1;i<p.length;i++)
            {
                shape.lineTo((float)p[i].getX(),(float)p[i].getY());
            }

            shape.closePath();
            grap2D.setColor(Color.red);
            grap2D.draw(shape);
            grap2D.setColor(Color.blue);
            grap2D.fill(shape);
        }
    }

    public static void main(String[] args)
    {
          GraphicPane graph = new GraphicPane();
    }
}