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我是 android 编程新手，我正在开发的地图应用程序有问题。该应用程序允许通过单击将圆圈放置在地图上，如果当前位置在圆圈内，则会显示一条消息，如果在圆圈外，也会显示一条不同的消息。问题是在对圆圈进行 onStart 检查期间，它只检测到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();

        }

    }
}
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4 回答 4

0

在我使用的 Javascript 中：

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

这种方法在google-maps API 3中可用，（听起来你不能）

但是试着写一些基于圆面积的数学函数。

这真的很容易。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 ));
    }

只需检查您的半径后：

if R > distFrom2LocationsInMeter() // 你在里面

if R < distFrom2LocationsInMeter() // 你在外面

于 2013-07-15T18:43:40.763 回答
0

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圈子时，您会覆盖最后一个创建的圈子，因此startCircle始终是最后一个创建的圈子。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内，我会查看这个链接，因为当我需要这样做时，它对我非常有用

如何确定二维点是否在多边形内？

于 2013-07-15T18:49:30.607 回答
0

例子：

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;
    }
于 2020-05-18T12:29:10.647 回答
0

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;
}
于 2020-05-18T12:19:49.233 回答