我的应用程序是要找到附近的医院或银行等，但每次当我点击按钮“查找”什么都没有发生在Map上。我是完全新的Android Studio，所以我不知道如何写我的代码，它会工作的方式，我想要它。请你能帮我解决这个问题。
这是我的主活动代码：

Spinner spType;
    Button btnFind;
    SupportMapFragment supportMapFragment;
    GoogleMap map;
    FusedLocationProviderClient fusedLocationProviderClient;
    double currentLat = 0, currentLong = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        spType = findViewById(R.id.sp_type);
        btnFind = findViewById(R.id.bt_find);
        supportMapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.google_map);

        String[] placeTypeListe = {"atm", "bank", "hospital", "movie_theater", "restaurant"};
        String[] placeNameList = {"ATM", "Bank", "Hospital", "Movie Theatre", "Restaurant"};

        spType.setAdapter(new ArrayAdapter<>(MainActivity.this
                , android.R.layout.simple_spinner_dropdown_item, placeNameList));

        fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this);

        if (ActivityCompat.checkSelfPermission(MainActivity.this
                , Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            getCurrentLocation();
        } else {
            ActivityCompat.requestPermissions(MainActivity.this
                    , new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 44);

        }

        btnFind.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int i = spType.getSelectedItemPosition();
                String url = "https://maps.googleapis.com/maps/api/..." + "?location=" + currentLat + "," + currentLong + "&radius=5000" + "&type=" + placeTypeListe[i] + "&sensor=true" + "&key=" + getResources().getString(R.string.google_map_key);

                new PlaceTask().execute(url);
            }
        });

    }

    private void getCurrentLocation() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        Task<Location> task = fusedLocationProviderClient.getLastLocation();
        task.addOnSuccessListener(new OnSuccessListener<Location>() {
            @Override
            public void onSuccess(Location location) {
                if (location != null){
                    currentLat = location.getLatitude();
                    currentLong = location.getLongitude();
                    supportMapFragment.getMapAsync(new OnMapReadyCallback() {
                        @Override
                        public void onMapReady(@NonNull GoogleMap googleMap) {
                            map = googleMap;
                            map.animateCamera(CameraUpdateFactory.newLatLngZoom(
                                    new LatLng(currentLat,currentLong),10
                            ));
                        }
                    });
                }
            }
        });

    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == 44) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                getCurrentLocation();
            }
        }

    }

    private class PlaceTask extends AsyncTask<String,Integer,String> {
        @Override
        protected String doInBackground(String... strings) {
            String data = null;
            try {
                data = downloadUrl(strings[0]);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return data;
        }

        @Override
        protected void onPostExecute(String s) {
            new ParserTask().execute(s);
        }
    }

    private String downloadUrl(String string) throws IOException {
        URL url = new URL(string);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.connect();
        InputStream stream = connection.getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
        StringBuilder builder = new StringBuilder();
        String line = "";
        while ((line = reader.readLine()) != null){
            builder.append(line);
        }
        String data = builder.toString();

        reader.close();
        return data;
    }

    private class ParserTask extends AsyncTask<String,Integer, List<HashMap<String,String>>> {

        @Override
        protected List<HashMap<String, String>> doInBackground(String... strings) {
            JsonParser jsonParser = new JsonParser();
            List<HashMap<String,String>> mapList = null;
            JSONObject object = null;
            try {
                object = new JSONObject(strings[0]);
                mapList = jsonParser.parseResult(object);
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return mapList;
        }

        @Override
        protected void onPostExecute(List<HashMap<String, String>> hashMaps) {
            map.clear();
            for (int i=0;i<hashMaps.size();i++){
                HashMap<String,String> hashMapList = hashMaps.get(i);
                double lat = Double.parseDouble(hashMapList.get("lat"));
                double lng = Double.parseDouble(hashMapList.get("lng"));
                String name = hashMapList.get("name");
                LatLng latLng = new LatLng(lat,lng);
                MarkerOptions options = new MarkerOptions();
                options.position(latLng);
                options.title(name);
                map.addMarker(options);
            }
        }
    }
}

这是我的logcat错误显示：

FATAL EXCEPTION: AsyncTask #1
                                                                                                    Process: com.example.add, PID: 13706
                                                                                                    java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$4.done(AsyncTask.java:415)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:305)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:920)
                                                                                                    
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:121)
at org.json.JSONTokener.nextValue(JSONTokener.java:98)
at org.json.JSONObject.<init>(JSONObject.java:168)
at org.json.JSONObject.<init>(JSONObject.java:185)
at com.example.add.MainActivity$ParserTask.doInBackground(MainActivity.java:174)
at com.example.add.MainActivity$ParserTask.doInBackground(MainActivity.java:166)
at android.os.AsyncTask$3.call(AsyncTask.java:394)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:305) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) 
at java.lang.Thread.run(Thread.java:920)