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首页 > 解决方案 > 为什么是 mMap.addMarker (...) 和 map.getMyLocation(); 不工作并停止我的应用程序 android？

java - 为什么是 mMap.addMarker (...) 和 map.getMyLocation(); 不工作并停止我的应用程序 android？

问题描述

在sqlite中同样的方法工作，但是我把数据库改成Mysql，这个方法不行！

我从 AsyncTask 发送 arraylist(names) 以显示 MapsActivity 中的方法和 ligne
myLocation = mMap.getMyLocation(); 中的问题；和 mmap.addMarker(new MarkerOptions().position(dz).title("welcome to")).showInfoWindow();

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
public void mark(Double latitude, Double longitude) {
    LatLng dz = new LatLng(latitude, longitude);
    mMap.addMarker(new MarkerOptions().position(dz).title("welcome to")).showInfoWindow();
    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(dz, 16));
}

public float distanceBetween(Double latitude, Double longitude) {
    float result[] = new float[10];     
    Location myLocation = mMap.getMyLocation();
    Double mylatitude = myLocation.getLatitude();
    Double mylongitude = myLocation.getLongitude();
    myLocation.distanceBetween(mylatitude, mylongitude, latitude, longitude, result);
    return result[0];
}

 public void show ( ArrayList names) {
        ArrayList<String> arrList = new ArrayList<>();
        arrList = names;
        int c = arrList.size();
        Float t[] = new Float[10];
        Double company[] = new Double[3];

        if (c > 0) {
            int n = 0;
            int i = 0;
            while (c > 0) {
                Double latitude = Double.valueOf(arrList.get(n));
                Double longitude = Double.valueOf(arrList.get(n + 1));
                Double price = Double.valueOf(arrList.get(n + 2));

                t[i] = distanceBetween(latitude, longitude);

                if (n == 0) {
                    company[0] = latitude;
                    company[1] = longitude;
                    company[2] = price;
                }
                if ((i > 0) && (t[i] < t[i - 1])) {
                    t[i] = t[i - 1];
                    company[0] = latitude;
                    company[1] = longitude;
                    company[2] = price;
                }
                i = i + 1;
                n = n + 3;
                c = c - 3;
            }
            mark(company[0], company[1]);


        } else {
            Toast T = Toast.makeText(this, "product is not available ", Toast.LENGTH_SHORT);
            T.show();
        }
        Toast.makeText(this, "price of product = " + company[2], Toast.LENGTH_LONG).show();
    }
}
public class Parser2 extends AsyncTask<Void,Void,Integer> {

    Context c;
    String data;


    ArrayList<String> names=new ArrayList<>();

    public Parser2(Context c, String data) {
        this.c = c;
        this.data = data;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected Integer doInBackground(Void... params) {
        return this.parse();
    }

    @Override
    protected void onPostExecute(Integer integer) {
        super.onPostExecute(integer);

        if(integer==1)
        {
            MapsActivity m =new MapsActivity();
            m.show(names);
        }else {
            Toast.makeText(c,"Unable to Parse2",Toast.LENGTH_SHORT).show();
        }
    }
    private int parse()
    {
        try
        {
            JSONArray ja=new JSONArray(data);
            JSONObject jo=null;

            names.clear();

            int i;
            for( i=0;i<ja.length();i++)
            {
                jo=ja.getJSONObject(i);
                String latitude=jo.getString("latitude");
                String longitude=jo.getString("longitude");
                String price=jo.getString("price");
                names.add(latitude);
                names.add(longitude);
                names.add(price);}
            return 1;

        } catch (JSONException e) {
            e.printStackTrace();
        }

        return 0;
    }
}

标签： javaandroidapiandroid-studiogoogle-maps

解决方案

问题的原因似乎是因为 getMyLocation() 为空，而算法期望它不为空。请确保此对象包含值。您可以使用此代码检查用户的最后位置：

LocationManager service = (LocationManager) 

getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria();
String provider = service.getBestProvider(criteria, false);
Location location = service.getLastKnownLocation(provider);
LatLng userLocation = new LatLng(location.getLatitude(),location.getLongitude());

希望这些信息对您有帮助，祝您项目顺利！

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