我正在保存用户发布的帖子的坐标。我正在生成一个push id,然后使用它保存post和geofire坐标的数据。
我只想展示那些方圆0.5公里以内的柱子。我也在使用GeoFire库,但无法完成任务。
下面是我生成推送ID的方法:
itemID = databaseReferenceRequests.push().getKey();
以下是我如何使用它来保存geofire坐标以及帖子的数据:

geoFire.setLocation(itemID,
        new GeoLocation(Double.parseDouble(currentLat.getText().toString()),
        Double.parseDouble(currentLng.getText().toString())));

databaseReferenceRequests.child(itemID).setValue(hRequest);

它是这样被保存的:
android - 如何检索距离我的范围0.5公里范围内的帖子?-LMLPHP
问题是,当我试图只获取距离我所能到达的0.5公里内的那些帖子时,它不会发生,所有的帖子无论是近的还是远的都会被检索到。
以下是我如何检索的:
public void retrieveHelpRequests() {

            geoQuery = geoFire.queryAtLocation(new GeoLocation(currentLatDouble, currentLngDouble), 0.5);

            geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
                @Override
                public void onKeyEntered(String key, GeoLocation location) {
                    databaseReference.child("help-requests").addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        Map<String, String> newRequest = (Map<String, String>) dataSnapshot.getValue();
                        imageUID = newRequest.get("imageUIDh");
                        homelessDescription = newRequest.get("homelessDescription");
                        currentLat = newRequest.get("currentLat");
                        currentLng = newRequest.get("currentLng");
                        postedBy = newRequest.get("postedBy");
                        postedAtTime = newRequest.get("postedAtTime");
                        postedOnDate = newRequest.get("postedOnDate");
                        utcFormatDateTime = newRequest.get("utcFormatDateTime");

                        String timeStr = utcFormatDateTime;
                        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                        df.setTimeZone(TimeZone.getTimeZone("UTC"));
                        Date date = null;
                        try {
                            // error on line below
                            date = df.parse(timeStr);
                        } catch (ParseException e) {
                            e.printStackTrace();
                        }
                        df.setTimeZone(TimeZone.getDefault());
                        final String persisted = df.format(date);

                        // Parse string from DB - UTC timezone
                        Date parsed = null;
                        try {
                            parsed = df.parse(persisted);
                        } catch (ParseException e) {
                            e.printStackTrace();
                        }

                        // Now convert to whatever timezone for display purposes
                        final SimpleDateFormat displayFormat = new SimpleDateFormat("h:mm a");
                        displayFormat.setTimeZone(TimeZone.getDefault());

                        formattedTime = displayFormat.format(parsed);

                        prepareDataForRequests();
                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                        Snackbar snackbar = Snackbar
                                .make(coordinatorLayout, databaseError.getMessage(), Snackbar.LENGTH_LONG);
                        snackbar.setDuration(Snackbar.LENGTH_SHORT);
                        snackbar.show();
//                helpRequestsLoadingDialog.dismiss();
                        progressBarLoadingRequests.setVisibility(View.INVISIBLE);
                    }
                });

                    databaseReference.child("help-requests").addValueEventListener(new ValueEventListener() {
                        @Override
                        public void onDataChange(final DataSnapshot dataSnapshot) {
    //                adView.loadAd(request);
                            card_ads2.setVisibility(View.VISIBLE);
                            adView2.loadAd(request2);
                            if (snackbar != null) {
                                snackbar.dismiss();
                            }
                            progressBarLoadingRequests.setVisibility(View.INVISIBLE);

                            if (fastItemAdapter.getAdapterItemCount() == 0) {
                                emptyRVtext.setVisibility(View.VISIBLE);
                                emptyRVtexthh.setVisibility(View.VISIBLE);
                                card_ads2.setVisibility(View.INVISIBLE);
                            } else {
                                emptyRVtext.setVisibility(View.INVISIBLE);
                                emptyRVtexthh.setVisibility(View.INVISIBLE);
                            }

    //                progressBarLoadingRequests.setVisibility(View.INVISIBLE);
                        }

                        @Override
                        public void onCancelled(DatabaseError databaseError) {
                            Snackbar snackbar = Snackbar
                                    .make(coordinatorLayout, databaseError.getMessage(), Snackbar.LENGTH_LONG);
                            snackbar.setDuration(Snackbar.LENGTH_SHORT);
                            snackbar.show();
    //                hRequestsLoadingDialog.dismiss();
                            progressBarLoadingRequests.setVisibility(View.INVISIBLE);
                        }
                    });
                }

                @Override
                public void onKeyExited(String key) {

                }

                @Override
                public void onKeyMoved(String key, GeoLocation location) {

                }

                @Override
                public void onGeoQueryReady() {

                }

                @Override
                public void onGeoQueryError(DatabaseError error) {
                    Toast.makeText(getBaseContext(), "Error retriving geoquery", Toast.LENGTH_SHORT).show();
                }
            });

        }

错误如下:
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference

请告诉我如何只检索那些在0.5公里以内的帖子?

最佳答案

您只需更改queryAtLocation()的第二个参数

double radius = 0.5; // in km
geoQuery = geoFire.queryAtLocation(new GeoLocation(currentLatDouble, currentLngDouble), radius);

是否确实检索到距用户0.5公里以上的所有项目?
下面是如何验证它们
Location userLocation = new Location("userLocation");
userLocation.setLatitude(currentLatDouble);
userLocation.setLongitude(currentLngDouble);
geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
    @Override
    public void onKeyEntered(String key, GeoLocation location) {
        Location itemLocation = new Location("itemLocation");
        itemLocation.setLatitude(location.latitude);
        itemLocation.setLongitude(location.longitude);
        Log.d("distance to " + key" is", userLocation.distanceTo(itemLocation) + "");
    }

07-24 09:45
查看更多