Question

我是编程android的新手，我正在处理一个地图应用程序的问题。该应用程序允许通过点击将圆圈放置在地图上，如果当前位置在圆圈内，则显示消息，如果在圆圈外显示不同的消息。问题是在圆圈的onStart检查期间，它仅检测最后创建的圆圈的内部或外部，而不是所有可用的圆圈。我不确定是什么导致了这个问题。代码片段如下：

     // Opening the sharedPreferences object
    sharedPreferences = getSharedPreferences("location", 0);

    // Getting number of locations already stored
    locationCount = sharedPreferences.getInt("locationCount", 0);

    // Getting stored zoom level if exists else return 0
    //String zoom = sharedPreferences.getString("zoom", "0");

    // If locations are already saved
    if(locationCount!=0){

        String lat = "";
        String lng = "";

        // Iterating through all the locations stored
        for(int i=0;i<locationCount;i++){

            // Getting the latitude of the i-th location
            lat = sharedPreferences.getString("lat"+i,"0");

            // Getting the longitude of the i-th location
            lng = sharedPreferences.getString("lng"+i,"0");

            double latitude = Double.parseDouble(lat);
            double longitude = Double.parseDouble(lng);

            startCircle = googleMap.addCircle(new CircleOptions().center(new LatLng (latitude, longitude)).radius(CIRCLE_RADIUS).fillColor(0x55888888));
        }

    }
public void onStart(){
    super.onStart();

    //Create a criteria object to retrieve provider
    Criteria criteria = new Criteria();
    // Set accuracy of criteria to address level
     criteria.setAccuracy(Criteria.ACCURACY_FINE);
    //Get the name of the best provider
    String provider = locationManager.getBestProvider(criteria, true);
    //Get Current Location
    Location myLocation = locationManager.getLastKnownLocation(provider);
    double lat = myLocation.getLatitude();
    double lon = myLocation.getLongitude();
    LatLng latlng = new LatLng(lat,lon);
    if(startCircle == null){
        return;
    }
    else{
        float[] distance = new float[2];
        marker = googleMap.addMarker(new MarkerOptions().position(latlng).visible(false));
      myLocation.distanceBetween( marker.getPosition().latitude, marker.getPosition().longitude,
                startCircle.getCenter().latitude, startCircle.getCenter().longitude, distance);

        if( distance[0] < startCircle.getRadius()){

            Toast.makeText(getBaseContext(), "Inside", Toast.LENGTH_LONG).show();
        } else {
            Toast.makeText(getBaseContext(), "Outside", Toast.LENGTH_LONG).show();

        }

    }
}

Answer 1

我使用的Javascript中的

：

google.maps.geometry.poly.containsLocation(pos, selectedPolygon);

此方法可在 google-maps API 3 中找到，（听起来你不能）

但是尝试根据圆形区域编写一些数学函数。

真的很容易。计算2个坐标之间的距离：

public static float distFrom2LocationsInMeter() {


    double lat1 = ...;
    double lng1 = ...;
    double lat2 = ...;
    double lng2 =...;


    //lat1 /= 1000000; // sometimes Android returns location in 10^6 form
    //lng1 /= 1000000;      

    //lat2 /= 1000000;          
    // lng2 /= 1000000; 



    double earthRadius = 3958.75;
    double dLat = Math.toRadians(lat2-lat1);
    double dLng = Math.toRadians(lng2-lng1);
    double a = Math.sin(dLat/2) * Math.sin(dLat/2) +
               Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2)) *
               Math.sin(dLng/2) * Math.sin(dLng/2);
    double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    double dist = earthRadius * c;


    int meterConversion = 1609;

    return Float.valueOf((float)(dist * meterConversion ));
    }

检查半径后：

如果R> distFrom2LocationsInMeter（）//你在里面

如果R < distFrom2LocationsInMeter（）//你在外面

Answer 2

The problem is during the onStart check of the circles it only detects inside or outside of the last created circle instead of all available ones. I am not sure what is causing this problem.

问题是，当您创建一个圆圈时，您将覆盖最后创建的圆圈，因此startCircle始终是最后创建的圆圈。您需要保留您在地图上绘制的所有圆圈的列表;

看看如何检查一个点是否在一个对象中我会查看这个链接，因为它在我需要这个时对我非常有用

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

Answer 3

Toast.makeText（MapActivity.this，String.valueOf（isInside（latitude_location_place，longitude_location_place，0.002，map.getMyLocation（）。getLatitude（），map.getMyLocation（）。getLongitude（））），Toast.LENGTH_SHORT。 show（）;

布尔布尔值isInside（double circle_x，double circle_y， double rad，double x，double y）{

    map.addCircle(new CircleOptions()
            .center(new LatLng(circle_x, circle_y))
            .radius(200)
            //its about 20 meter
            // you most set rad=0.002 for 20 meter
            .strokeColor(Color.RED)
            .fillColor(R.color.color_circle));

    map.addMarker(new MarkerOptions().position(new LatLng(x, y)));

    if ((x - circle_x) * (x - circle_x) +
            (y - circle_y) * (y - circle_y) <= rad*rad)
        return true;
    else
        return false;
}

Answer 4

示例：

Toast.makeText(MapActivity.this,String.valueOf(isInside(latitude_location_place, longitude_location_place,0.002,map.getMyLocation().getLatitude(),map.getMyLocation().getLongitude())) , Toast.LENGTH_SHORT).show();


public boolean isInside(double circle_x, double circle_y,
                            double rad, double x, double y) {


        map.addCircle(new CircleOptions()
                .center(new LatLng(circle_x, circle_y))
                .radius(200)
                //its about 20 meter
                // you most set rad=0.002 for 20 meter
                .strokeColor(Color.RED)
                .fillColor(R.color.color_circle));

        map.addMarker(new MarkerOptions().position(new LatLng(x, y)));

        if ((x - circle_x) * (x - circle_x) +
                (y - circle_y) * (y - circle_y) <= rad*rad)
            return true;
        else
            return false;
    }

如何检查点是否在谷歌地图上的一个或多个圈子内？

4 个答案: