Question

我需要使用Android的MapView在Google地图上使用自定义地图创建形状。

换句话说，如果我在地图上绘制一个形状，当我缩小它时它应该缩小，覆盖地图的相同区域而不管缩放级别。

Android参考后面的示例：

  @Override
  public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when)
  {
      super.draw(canvas, mapView, shadow);

      //---translate the GeoPoint to screen pixels---
      Point screenPts = new Point();
      mapView.getProjection().toPixels(p, screenPts);

      Paint boxPaint = new Paint();
      boxPaint.setColor(android.graphics.Color.WHITE);
      boxPaint.setStyle(Paint.Style.FILL);
      boxPaint.setAlpha(140);
      canvas.drawCircle(screenPts.x, screenPts.y, 20, boxPaint);

      return true;
  }

这会在地图上显示一个白色圆圈，但如果缩小，则圆圈大小相同。也许使用canvas是不正确的方法？

我需要谷歌地图如何突出社区或城市：

有什么想法吗？提前谢谢！

Answer 1

我自己也有同样的问题，这里是一个带有演示位置的完整解决方案：

import java.util.*;

import android.graphics.*;
import android.graphics.Paint.Style;
import android.graphics.Region.Op;
import android.os.Bundle;

import com.google.android.maps.*;

public class ShapeOverlayTest extends MapActivity {
    private MapView m_map;

    @Override
    public void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        m_map = (MapView) findViewById(R.id.mapview);
        m_map.displayZoomControls(true);
        m_map.setBuiltInZoomControls(true);
    }

    @Override
    protected void onStart() {
        super.onStart();

        Loc[][] areas = {
            {
            new Loc(51.51695436113811, -0.28686325139653757),
            new Loc(51.5268179962453, -0.28118722558738923),
            new Loc(51.526498459594215, -0.27779666308279755),
            new Loc(51.52521530775356, -0.26943974607777654),
            new Loc(51.52292555645698, -0.25813738590178786),
            new Loc(51.52054465991048, -0.2498381618983569),
            new Loc(51.51012230470141, -0.24509233633017083),
            new Loc(51.50884762913046, -0.24465130560570497),
            new Loc(51.50732063336974, -0.2441767643132881),
            new Loc(51.50431624597833, -0.24473900326760137),
            new Loc(51.49756328092904, -0.2714528238165076),
            new Loc(51.50092541797557, -0.28360267232347336),
            new Loc(51.50205958485736, -0.28490018935582045),
            new Loc(51.50488447379555, -0.28681164237730944)
            },
            {
            new Loc(51.50368617913765, -0.25313579464343156),
            new Loc(51.51978611305675, -0.24842567405905958),
            new Loc(51.51039382684418, -0.24460628015366626),
            new Loc(51.508792552597576, -0.24397604687682156),
            new Loc(51.50713008309719, -0.24346350415674722),
            new Loc(51.502411013302684, -0.2508501075008919),
            new Loc(51.502377240039664, -0.25160073203846817),
            new Loc(51.50274364303565, -0.25204783703705536)
            },
            {
            new Loc(51.49924084955314, -0.2858705706471945),
            new Loc(51.50212820259818, -0.2791479893522646),
            new Loc(51.49724510427319, -0.27427453152961206),
            new Loc(51.49429724502515, -0.2799184038304611),
            new Loc(51.494270969987404, -0.28180678948730314)
            }
        };
        String[] areaNames = { "W3 Ealing", "W3 Hammersmith & Fulham", "W3 Hounslow" };

        // for (Map.Entry<String, List<Loc>> area : m_areas.entrySet()) {
        // // to have much less points and make sure they are in order
        // // the demo data already has these properties
        // // http://en.wikipedia.org/wiki/Gift_wrapping_algorithm#Pseudocode
        // area.setValue(Algo.convexHull(area.getValue()));
        // }

        Map<String, List<GeoPoint>> areaMap = new HashMap<String, List<GeoPoint>>();
        for (int i = 0; i < areaNames.length; i++) {
            List<GeoPoint> points = new ArrayList<GeoPoint>();
            for (int j = 0; j < areas[i].length; j++) {
                points.add(areas[i][j].toGeoPoint());
            }
            areaMap.put(areaNames[i], points);
        }
        m_map.getOverlays().add(new AreasOverlay(areaMap));

        // TODO determine location better, e.g. averaging area points
        GeoPoint center = new GeoPoint(51509704, -270710);
        m_map.getController().setCenter(center);
        m_map.getController().setZoom(15);
    }

    @Override
    protected boolean isRouteDisplayed() {
        return false;
    }

    static class Loc {
        private double  m_lat;
        private double  m_lon;

        public Loc(final double lat, final double lon) {
            m_lat = lat;
            m_lon = lon;
        }

        public GeoPoint toGeoPoint() {
            return new GeoPoint((int) (m_lat * 1e6), (int) (m_lon * 1e6));
        }
    };

    static class AreasOverlay extends Overlay {
        private final Map<String, List<GeoPoint>> m_areas;
        private final Paint m_paintFill;
        private final Paint m_paintStroke;
        private static final int ALPHA = 0x30ffffff; // 48 out of 255 transparent
        private static final int[] COLORS =
        { Color.YELLOW, Color.MAGENTA, Color.CYAN, Color.RED, Color.GREEN, Color.BLUE };
        static {
            for (int i = 0; i < AreasOverlay.COLORS.length; i++) {
                AreasOverlay.COLORS[i] &= AreasOverlay.ALPHA;
            }
        }

        public AreasOverlay(final Map<String, List<GeoPoint>> areaMap) {
            m_areas = areaMap;

            // prepare paints
            m_paintFill = new Paint();
            m_paintFill.setStyle(Paint.Style.FILL);
            m_paintStroke = new Paint(Paint.ANTI_ALIAS_FLAG);
            m_paintStroke.setStyle(Style.STROKE);
            m_paintStroke.setAntiAlias(true);
            m_paintStroke.setStrokeWidth(3);
        }

        @Override
        public void draw(final Canvas canvas, final MapView mapView, final boolean shadow) {
            super.draw(canvas, mapView, shadow);
            if (shadow) {
                return;
            }
            Projection projection = mapView.getProjection();

            List<Path> areaPaths = getPaths(projection, m_areas);
            drawPaths(canvas, areaPaths);
        }

        private List<Path> getPaths(final Projection projection, final Map<String, List<GeoPoint>> areas) {
            List<Path> areaPaths = new ArrayList<Path>(areas.size());
            for (Map.Entry<String, List<GeoPoint>> entry : areas.entrySet()) {
                List<GeoPoint> sourceList = entry.getValue();
                Path path = new Path();
                path.setFillType(Path.FillType.EVEN_ODD);
                Iterator<GeoPoint> it = sourceList.iterator();
                Point point = nextDrawPoint(projection, it);
                path.moveTo(point.x, point.y);
                while (it.hasNext()) {
                    point = nextDrawPoint(projection, it);
                    path.lineTo(point.x, point.y);
                }
                path.close();
                areaPaths.add(path);
            }
            return areaPaths;
        }

        /**
         * <ul>
         * <li>Draw with different colors.
         * <li>Draw strokes first for them to be always visible.
         * <li>Draw fills next with each removing from the drawable area.
         * </ul>
         */
        private void drawPaths(final Canvas canvas, final List<Path> areaPaths) {
            int currentColorIndex;

            currentColorIndex = 0;
            for (Path path : areaPaths) {
                int currentColor = AreasOverlay.COLORS[currentColorIndex++];
                currentColorIndex %= AreasOverlay.COLORS.length;
                m_paintStroke.setColor(currentColor & 0xff7f7f7f); // make it darker by clearing the high bit
                canvas.drawPath(path, m_paintStroke);
            }
            currentColorIndex = 0;
            for (Path path : areaPaths) {
                int currentColor = AreasOverlay.COLORS[currentColorIndex++];
                currentColorIndex %= AreasOverlay.COLORS.length;
                m_paintFill.setColor(currentColor);
                canvas.drawPath(path, m_paintFill);
                canvas.clipPath(path, Op.DIFFERENCE); // don't allow to draw over each other
            }
        }

        private Point nextDrawPoint(final Projection projection, final Iterator<GeoPoint> it) {
            GeoPoint geo = it.next();
            Point p = new Point();
            projection.toPixels(geo, p);
            return p;
        }
    }
}

Answer 2

drawCircle的半径以像素为单位，因此圆圈的大小始终相同。您必须根据缩放级别缩放半径。下面的示例将绘制将扩展的JTS拓扑套件中的几何图形。

public class MapOverlay extends Overlay {
    private static final String TAG = MapOverlay.class.getName();

    // Allocate once and reuse
    private final Paint mPaint = new Paint();
    private final Path mPath = new Path();

    // Region to highlight
    private Geometry mGeometry;

    /**
     * @param  geometry Region to highlight on map
     */
    public MapOverlay(Geometry geometry) {
            // Set region
            mGeometry = geometry;

            // Edit paint style
            mPaint.setDither(true);
            mPaint.setColor(Color.rgb(128, 136, 231));
            mPaint.setAlpha(100);
            mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
            mPaint.setStrokeJoin(Paint.Join.ROUND);
            mPaint.setStrokeCap(Paint.Cap.ROUND);
            mPaint.setStrokeWidth(6);
    }


    /**
     * Draw the overlay over the map.
     * 
     * @see com.google.android.maps.Overlay#draw(Canvas, MapView, boolean)
     */
    @Override
    public void draw(Canvas canvas, MapView mapv, boolean shadow) {
            super.draw(canvas, mapv, shadow);

            if (mGeometry != null) {
                    // TODO There could be more than one geometries  
                    Geometry g = mGeometry.getGeometryN(0);
                    final Point p = new Point();
                    boolean first = true;

                    mPath.reset();
                    for (Coordinate c : g.getCoordinates()) {
                            // Convert lat/lon to pixels on screen
                            // GeoPoint is immutable so allocation is unavoidable
                            Projection projection = mapv.getProjection();
                            projection.toPixels(new GeoPoint((int) (c.y * 1E6), (int) (c.x * 1E6)), p);

                            // Set path starting point to first coordinate
                            // otherwise default start is (0,0)
                            if (first) {
                                    mPath.moveTo(p.x, p.y);
                                    first = false;
                            }

                            // Add new point to path
                            mPath.lineTo(p.x, p.y);
                    }
            }

            // Draw the path with give paint
            canvas.drawPath(mPath, mPaint);
    }

改编自此处：MapSelectionOverlay.java

Answer 3

这可能是您正在寻找的内容：Can "overlay" size be zoomed together with the google map on android?

public class ImpactOverlay extends Overlay {

private static int CIRCLERADIUS = 0;
private GeoPoint geopoint;

public ImpactOverlay(GeoPoint point, int myRadius) {
    geopoint = point;
    CIRCLERADIUS = myRadius;
}

@Override
public void draw(Canvas canvas, MapView mapView, boolean shadow) {
    // Transfrom geoposition to Point on canvas
    Projection projection = mapView.getProjection();
    Point point = new Point();
    projection.toPixels(geopoint, point);

    // the circle to mark the spot
    Paint circle = new Paint();
    circle.setColor(Color.BLACK);
    int myCircleRadius = metersToRadius(CIRCLERADIUS, mapView, (double)geopoint.getLatitudeE6()/1000000);
    canvas.drawCircle(point.x, point.y, myCircleRadius, circle);
}

public static int metersToRadius(float meters, MapView map, double latitude) {
    return (int) (map.getProjection().metersToEquatorPixels(meters) * (1/ Math.cos(Math.toRadians(latitude))));         
}
}

Answer 4

您需要的是要在地图上绘制的每个形状的纬度/经度点列表。在onDraw方法中，您需要迭代该列表（对于您要绘制的每个形状），并执行以下操作：

//---translate the GeoPoint to screen pixels---
  Point screenPts = new Point();
  mapView.getProjection().toPixels(p, screenPts);

然后

在画布上绘制形状。无论缩放如何，IIRC都能正常工作，因为mapView知道缩放级别，并为该缩放级别的纬度/经度对提供合适的像素位置。

在Android MapView中绘制形状，与缩放级别无关

4 个答案: