地图点击上的规则形状多边形Android地图

Question

无论点击地图的顺序如何，我都想创建一个正多边形。目前我面临一个问题，如果单击地图以以下方式绘制多边形，那么它可以正常工作，顺序如下 左上 右下 右下 左下。如果保持这个顺序，那么如果我点击右上角、左上角、右下角，多边形绘制的效果也很好。如果当我更改一品脱的顺序时，它不会绘制正确形状的多边形 图片1

图片2

代码 2 绘制多边形如下

     gMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
            @Override
            public void onMapClick(LatLng latLng) {
                llClearSelection.setVisibility(View.VISIBLE);
                gMap.addMarker(new MarkerOptions().anchor(0.5f, 0.5f).icon(BitmapDescriptorFactory.fromResource(R.drawable.marker)).position(latLng));
                if (markerClicked) {
//                    latLngArrayListPolygon.clear();
                    if (polygon != null) {
                        polygon.remove();
                        polygon = null;
                    }

                    polygonOptions.add(latLng);
                    latLngArrayListPolygon.add(latLng);
                    polygonOptions.strokeColor(Color.RED);
                    polygonOptions.fillColor(shadeColor);
                    polygon = gMap.addPolygon(polygonOptions);
                    if (latLngArrayListPolygon.size() > 1)
                        ivSaveMap.setVisibility(View.VISIBLE);
                    else
                        ivSaveMap.setVisibility(View.GONE);
                } else {
                    if (polygon != null) {
                        polygon.remove();
                        polygon = null;
                    }
                    polygonOptions = new PolygonOptions().add(latLng);
                    latLngArrayListPolygon.add(latLng);
                    markerClicked = true;
                }
            }
        });

我担心的是我想绘制一个规则的形状，而不管点击地图的顺序如何

Answer 1

最后我得出了创建规则形状多边形的解决方案。这与凸包无关。 以下是创建规则形状多边形的步骤，无论您是在地图上顺时针单击还是在地图上逆时针单击。

1. 找到多边形边缘的中点
2. 通过查找每条边的中点与要绘制的坐标之间的距离来计算最近的坐标
3. 最近坐标=中点到要绘制的坐标距离最小的边
4. 通过向右移动数组来移动最后的最近坐标 以下是代码：

 ArrayList<LatLng> latLngArrayListPolygon = new ArrayList<>();
ArrayList<Double> distancesFromMidPointsOfPolygonEdges = new ArrayList<>();
    private void adjustPolygonWithRespectTo(LatLng point) {
        double minDistance = 0;

        if (latLngArrayListPolygon.size() > 2) {
            distancesFromMidPointsOfPolygonEdges.clear();
            //midPointsOfPolygonEdges?.removeAll()

            for (int i = 0; i < latLngArrayListPolygon.size(); i++) {
                // 1. Find the mid points of the edges of polygon
                ArrayList<LatLng> list = new ArrayList<>();

                if (i == (latLngArrayListPolygon.size() - 1)) {
                    list.add(latLngArrayListPolygon.get(latLngArrayListPolygon.size() - 1));
                    list.add(latLngArrayListPolygon.get(0));
                } else {
                    list.add((latLngArrayListPolygon.get(i)));
                    list.add((latLngArrayListPolygon.get(i + 1)));
                }


                LatLng midPoint = computeCentroid(list);

                // 2. Calculate the nearest coordinate by finding distance between mid point of each edge and the coordinate to be drawn
                Location startPoint = new Location("");
                startPoint.setLatitude(point.latitude);
                startPoint.setLongitude(point.longitude);
                Location endPoint = new Location("");
                endPoint.setLatitude(midPoint.latitude);
                endPoint.setLongitude(midPoint.longitude);
                double distance = startPoint.distanceTo(endPoint);

                distancesFromMidPointsOfPolygonEdges.add(distance);
                if (i == 0) {
                    minDistance = distance;
                } else {

                    if (distance < minDistance) {
                        minDistance = distance;
                    }
                }
                //midPointsOfPolygonEdges?.append(midPoint)
            }

            // 3. The nearest coordinate = the edge with minimum distance from mid point to the coordinate to be drawn
            int position = minIndex(distancesFromMidPointsOfPolygonEdges);


            // 4. move the nearest coordinate at the end by shifting array right
            int shiftByNumber = (latLngArrayListPolygon.size() - position - 1);

            if (shiftByNumber != latLngArrayListPolygon.size()) {
                latLngArrayListPolygon = rotate(latLngArrayListPolygon, shiftByNumber);
            }
        }

        // 5. Now add coordinated to be drawn
        latLngArrayListPolygon.add(point);
    }

    public static int minIndex(ArrayList<Double> list) {
        return list.indexOf(Collections.min(list));
    }

    public static <T> ArrayList<T> rotate(ArrayList<T> aL, int shift) {
        if (aL.size() == 0)
            return aL;

        T element = null;
        for (int i = 0; i < shift; i++) {
            // remove last element, add it to front of the ArrayList
            element = aL.remove(aL.size() - 1);
            aL.add(0, element);
        }

        return aL;
    }

    private LatLng computeCentroid(List<LatLng> points) {
        double latitude = 0;
        double longitude = 0;
        int n = points.size();

        for (LatLng point : points) {
            latitude += point.latitude;
            longitude += point.longitude;
        }

        return new LatLng(latitude / n, longitude / n);
    }

点击地图绘制多边形如下

 gMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
        @Override
        public void onMapClick(LatLng latLng) {
            gMap.addMarker(new MarkerOptions().anchor(0.5f, 0.5f).icon(BitmapDescriptorFactory.fromResource(R.drawable.marker)).position(latLng));
            if (markerClicked) {
                if (polygon != null) {
                    polygon.remove();
                    polygon = null;
                }
                adjustPolygonWithRespectTo(latLng);
                PolygonOptions polygonOptions = null;
                for (int i = 0; i < latLngArrayListPolygon.size(); i++)
                    if (i == 0)
                        polygonOptions = new PolygonOptions().add(latLngArrayListPolygon.get(0));
                    else
                        polygonOptions.add(latLngArrayListPolygon.get(i));
                polygonOptions.strokeColor(Color.BLACK);
                polygonOptions.strokeWidth(5f);
                polygonOptions.fillColor(shadeColor);
                polygon = gMap.addPolygon(polygonOptions);
            } else {
                if (polygon != null) {
                    polygon.remove();
                    polygon = null;
                }
                polygonOptions = new PolygonOptions().add(latLng);
                latLngArrayListPolygon.add(latLng);
                markerClicked = true;
            }
        }

    });

Answer 2

看看How can I determine whether a 2D Point is within a Polygon?

当您的用户点击地图时，您必须确定新顶点是在多边形内还是在多边形外。如果在里面，请忽略。否则，添加多边形并为多边形中的每个点运行算法。

希望这会有所帮助。