你如何计算你自己的位置和标记之间的距离，并让它只有在足够近的时候才能点击？

Question

So, in short, we're working on an app to guide a tour for new students around the campus. We already have it working that you can click all markers on the map (they each go to their according info activity). Now we want that a user can only click a marker when they are close enough to the location. We already have the user location in the variable mLastKnownLocation . Now I did some research there is a tool in the SphericalUtil , computeDistanceBetween() , that calculates the distance between 2 points. But now I'm confused on how to implement this? As we work with one big If-statement for all the setOnMarkerClickListeners , do we need to get a new if statement inside the big one for every location to check if they are close enough or is there another way? This is our first project in appdesign and with Java, so it would be entirely possible that there are some big mistakes.

import android.annotation.SuppressLint;
import android.content.Intent;
import android.content.IntentSender;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;
import android.location.Location;
import android.os.Bundle;

import android.view.View;

import android.widget.RelativeLayout;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.gms.common.api.ResolvableApiException;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationCallback;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationResult;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.location.LocationSettingsRequest;
import com.google.android.gms.location.LocationSettingsResponse;
import com.google.android.gms.location.SettingsClient;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;

import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.android.libraries.places.api.Places;
import com.google.android.libraries.places.api.model.AutocompletePrediction;
import com.google.android.libraries.places.api.model.AutocompleteSessionToken;

import com.google.android.libraries.places.api.net.PlacesClient;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MapS extends AppCompatActivity implements OnMapReadyCallback {
    private GoogleMap mMap;
    private FusedLocationProviderClient mFusedLocationProviderClient;

    private List<AutocompletePrediction> predictionList;

    private Location mLastKnownLocation;
    private LocationCallback locationCallback;
    private final float DEFAULT_ZOOM = 18;



    private View mapView;
    private Marker kaka;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_map);


        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.kaart);
        mapFragment.getMapAsync(this);
        mapView = mapFragment.getView();

        mFusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(MapS.this);
        Places.initialize(MapS.this, ("My_APIkey"));





        final AutocompleteSessionToken token = AutocompleteSessionToken.newInstance();
    }

    @SuppressLint("MissingPermission")
    @Override
    public void onMapReady(GoogleMap googleMap) {
        int height = 100;
        int width = 100;
        BitmapDrawable bitmapdraw=(BitmapDrawable)getResources().getDrawable(R.drawable.marker_dark);
        Bitmap b=bitmapdraw.getBitmap();
        Bitmap smallMarker = Bitmap.createScaledBitmap(b, width, height, false);
        mMap = googleMap;
        mMap.setMyLocationEnabled(true);
        mMap.getUiSettings().setMyLocationButtonEnabled(true);





        //All that LatLng are stated here, removed them for privacy reasons





        //Code die markers zet en ze klikbaar maakt.
        //Hal A
        googleMap.addMarker(new MarkerOptions().position(HalA)
                .title("Hal A")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));
        mMap.setOnMarkerClickListener(new GoogleMap.OnMarkerClickListener() {
            @Override
            public boolean onMarkerClick(final Marker marker) {
                  if (marker.getTitle().equals("Hal A")) {
                      Intent halaIntent = new Intent(MapS.this, hala.class);
                      startActivity(halaIntent);
                      return false;
                  }
                  return false;
              }
          }
        );

        googleMap.addMarker(new MarkerOptions().position(stuvo)
                .title("Stuvo")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(bib)
                .title("Bib")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(acco)
                .title("Acco boekenhandel")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(rectoraat)
                .title("Hal Rectoraat")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(spina)
                .title("Spina")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(stilleRuimte)
                .title("Stille ruimte")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(A301)
                .title("Aula Stijn Streuvels (A301)")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(weetkelder)
                .title("Weetkelder")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(fietsena)
                .title("FietsenA")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(labos)
                .title("Labo's (gang 3)")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));


        //gebouw B
        googleMap.addMarker(new MarkerOptions().position(B422)
                .title("B422")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));


        googleMap.addMarker(new MarkerOptions().position(puc)
                .title("puc")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        //gebouw c
        googleMap.addMarker(new MarkerOptions().position(C611)
                .title("C611")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(gang7)
                .title("Gang 7")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        //gebouw E
        googleMap.addMarker(new MarkerOptions().position(E1001)
                .title("Aula Andreas Vesalius (E1001)")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(vaardigheidscentrum)
                .title("Vaardigheidscentrum")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(IRF)
                .title("IRF")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(fietsene)
                .title("fietsene")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        //residenties
        googleMap.addMarker(new MarkerOptions().position(spoelberg)
                .title("Spoelberg")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(studentendorp)
                .title("Studentendorp")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(corona)
                .title("Corona")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        //andere
        googleMap.addMarker(new MarkerOptions().position(IICK)
                .title("IICK")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(almaZweetkelder)
                        .title("Alma & Cantor en Zweetkelder")
                        .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        googleMap.addMarker(new MarkerOptions().position(ecolab)
                .title("Ecolab")
                .icon(BitmapDescriptorFactory.fromBitmap(smallMarker)));

        mMap.setOnMarkerClickListener(new GoogleMap.OnMarkerClickListener() {
              @Override
              public boolean onMarkerClick(final Marker marker) {
                  if (marker.getTitle().equals("Ecolab")) {
                      Intent ecolabIntent = new Intent(MapS.this, activity_ecolab.class);
                      startActivity(ecolabIntent);
                  }

                  else if (marker.getTitle().equals("Alma & Cantor en Zweetkelder")) {
                      Intent AlmaIntent = new Intent(MapS.this, activity_acz.class);
                      startActivity(AlmaIntent);
                  }

                  else if (marker.getTitle().equals("IICK")) {
                      Intent IICKIntent = new Intent(MapS.this, activity_iick.class);
                      startActivity(IICKIntent);

                  }

                  else if (marker.getTitle().equals("Corona")) {
                      Intent coronaIntent = new Intent(MapS.this, activity_corona.class);
                      startActivity(coronaIntent);
                  }

                  else if (marker.getTitle().equals("Studentendorp")){
                      Intent studentendorpIntent = new Intent(MapS.this, activity_studentendorp.class);
                      startActivity(studentendorpIntent);
                  }

                  else if (marker.getTitle().equals("Spoelberg")) {
                      Intent spoelbergIntent = new Intent(MapS.this, activity_spoelberg.class);
                      startActivity(spoelbergIntent);
                  }

                  else if (marker.getTitle().equals("fietsene")) {
                      Intent fietseneIntent = new Intent(MapS.this, activity_fietsene.class);
                      startActivity(fietseneIntent);
                  }

                  else if (marker.getTitle().equals("IRF")) {
                      Intent IRFIntent = new Intent(MapS.this, activity_irf.class);
                      startActivity(IRFIntent);
                  }

                  else if (marker.getTitle().equals("Vaardigheidscentrum")) {
                      Intent vaardigheidscentrumIntent = new Intent(MapS.this, activity_vaardigheid.class);
                      startActivity(vaardigheidscentrumIntent);
                  }

                  else if (marker.getTitle().equals("Aula Andreas Vesalius (E1001)")) {
                      Intent E1001Intent = new Intent(MapS.this, activity_e1001.class);
                      startActivity(E1001Intent);
                  }

                  else if (marker.getTitle().equals("Gang 7")) {
                      Intent gang7Intent = new Intent(MapS.this, activity_kantoren.class);
                      startActivity(gang7Intent);
                  }

                  else if (marker.getTitle().equals("C611")) {
                      Intent C611Intent = new Intent(MapS.this, activity_c611.class);
                      startActivity(C611Intent);
                  }

                  else if (marker.getTitle().equals("puc")) {
                      Intent pucIntent = new Intent(MapS.this, activity_puc.class);
                      startActivity(pucIntent);
                  }

                  else if (marker.getTitle().equals("B422")) {
                      Intent B422Intent = new Intent(MapS.this, activity_b422.class);
                      startActivity(B422Intent);
                  }

                  else if (marker.getTitle().equals("Labo's (gang 3)")) {
                      Intent labosIntent = new Intent(MapS.this, activity_labo.class);
                      startActivity(labosIntent);
                  }

                  else if (marker.getTitle().equals("FietsenA")) {
                      Intent fietsenaIntent = new Intent(MapS.this, activity_fietsena.class);
                      startActivity(fietsenaIntent);
                  }

                  else if (marker.getTitle().equals("Weetkelder")) {
                      Intent weetkelderIntent = new Intent(MapS.this, activity_weetkelder.class);
                      startActivity(weetkelderIntent);
                  }

                  else if (marker.getTitle().equals("Aula Stijn Streuvels (A301)")) {
                      Intent A301Intent = new Intent(MapS.this, activity_A301.class);
                      startActivity(A301Intent);
                  }

                  else if (marker.getTitle().equals("Stille ruimte")) {
                      Intent stilIntent = new Intent(MapS.this, activity_stil.class);
                      startActivity(stilIntent);
                  }

                  else if (marker.getTitle().equals("Spina")) {
                      Intent spinaIntent = new Intent(MapS.this, activity_spina.class);
                      startActivity(spinaIntent);
                  }

                  else if (marker.getTitle().equals("Hal Rectoraat")) {
                      Intent rectoraatIntent = new Intent(MapS.this, activity_rectoraat.class);
                      startActivity(rectoraatIntent);
                  }

                  else if (marker.getTitle().equals("Acco boekenhandel")) {
                      Intent accoIntent = new Intent(MapS.this, activity_acco.class);
                      startActivity(accoIntent);
                  }

                  else if (marker.getTitle().equals("Bib")) {
                      Intent bibIntent = new Intent(MapS.this, activity_onthaalbib.class);
                      startActivity(bibIntent);
                  }

                  else if (marker.getTitle().equals("Stuvo")) {
                      Intent stuvoIntent = new Intent(MapS.this, activity_secstuvo.class);
                      startActivity(stuvoIntent);
                  }

                  else if (marker.getTitle().equals("Hal A")) {
                      Intent halaIntent = new Intent(MapS.this, hala.class);
                      startActivity(halaIntent);
                  }
                  return true;
              }
          }
        );












        if(mapView != null && mapView.findViewById(Integer.parseInt("1")) != null)  {
            View locationButton = ((View) mapView.findViewById(Integer.parseInt("1")).getParent()).findViewById(Integer.parseInt("2"));
            RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) locationButton.getLayoutParams();
            layoutParams.addRule(RelativeLayout.ALIGN_PARENT_TOP, 0);
            layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, RelativeLayout.TRUE);
            layoutParams.setMargins(0,0,40,180);

        }

        // kijken of gps signaal aanstaat
        LocationRequest locationRequest = LocationRequest.create();
        locationRequest.setInterval(10000);
        locationRequest.setFastestInterval(5000);
        locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);

        LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder().addLocationRequest(locationRequest);
        SettingsClient settingsClient = LocationServices.getSettingsClient(MapS.this);
        Task<LocationSettingsResponse> task = settingsClient.checkLocationSettings(builder.build());
        task.addOnSuccessListener(MapS.this, new OnSuccessListener<LocationSettingsResponse>() {
            @Override
            public void onSuccess(LocationSettingsResponse locationSettingsResponse) {
                getDeviceLocation();
            }
        });

        task.addOnFailureListener(MapS.this, new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                if(e instanceof  ResolvableApiException) {
                    ResolvableApiException resolvable = (ResolvableApiException) e;
                    try{
                    resolvable.startResolutionForResult(MapS.this, 51);
                } catch (IntentSender.SendIntentException e1) {
                    e1.printStackTrace();
                }
            }
        }}





        );


    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 51) {
            if (resultCode == RESULT_OK) {
                getDeviceLocation();

            }
        }


    }
    @SuppressLint("MissingPermission")
    private void getDeviceLocation() {
        mFusedLocationProviderClient.getLastLocation()
                .addOnCompleteListener(new OnCompleteListener<Location>() {
                    @Override
                    public void onComplete(@NonNull Task<Location> task) {
                        if (task.isSuccessful()) {
                            mLastKnownLocation = task.getResult();
                            if (mLastKnownLocation != null) {
                                mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(mLastKnownLocation.getLatitude(), mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));
                            } else {
                                final LocationRequest locationRequest = LocationRequest.create();
                                locationRequest.setInterval(10000);
                                locationRequest.setFastestInterval(5000);
                                locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
                                locationCallback = new LocationCallback() {
                                    @Override
                                    public void onLocationResult(LocationResult locationResult) {
                                        super.onLocationResult(locationResult);
                                        if (locationResult == null) {
                                            return;
                                        }
                                        mLastKnownLocation = locationResult.getLastLocation();
                                        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(mLastKnownLocation.getLatitude(), mLastKnownLocation.getLongitude()), DEFAULT_ZOOM));
                                        mFusedLocationProviderClient.removeLocationUpdates(locationCallback);
                                    }
                                };
                                mFusedLocationProviderClient.requestLocationUpdates(locationRequest, locationCallback, null);

                            }
                        } else {
                            Toast.makeText(MapS.this, "Laatste gekende locatie kan niet worden ontvangen", Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }
}

Answer 1

The SphericalUtil class' computeDistanceBetween(LatLng from, LatLng to) takes LatLng objects, so first you'll have to convert the known location and marker location using

LatLng knownLatLng = new LatLng(mKnownLocation.getLatitude(), mKnownLocation.getLongitude());

Repeat for the marker Location object, or if they don't exist in your code yet, then instantiate a new LatLng for each marker using its latitude and longitude.

To check if the user is close enough, you can now call the computeDistanceBetween method to get a distance, eg.

double distanceBetween = SphericalUtil.computeDistanceBetween(knownLatLng, markerLatLng);

then modify your if statements to include a second conditional, eg.

if (marker.getTitle().equals("Ecolab")) {
    if (distanceBetween < 1) {

would check if the 'Ecolab' marker was clicked and also if the user was within a metre of the marker.