Question

In android studio, I want to get the user current location when he clicks on a button after asking him for the permission, store its latitude and longitude on double variables and then do calculations depends on the user location, How can I do that in maps activity? I want on click to be outside onCreate, I want inside on click to get double lat = latlong.getlatutide not to call function getlocation

Answer 1

Firstly, location fetching is a very tedious task. It involves a lot of boilerplate code . To remove this boilerplate code, I have made a utility class named LocationFetcher.java

LocationFetcher.java

package com.pratik.appedia.HomeworkLib1;

import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.IntentSender;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Looper;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;

import com.google.android.gms.common.api.ApiException;
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.LocationSettingsStatusCodes;
import com.google.android.gms.location.SettingsClient;
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;

class LocationFetcher {

    private Context context;
    private Activity activity;
    private FusedLocationProviderClient mFusedLocationClient;
    private SettingsClient mSettingsClient;
    private LocationRequest mLocationRequest;
    private LocationSettingsRequest mLocationSettingsRequest;
    private LocationCallback mLocationCallback;
    private Location mCurrentLocation;
    private LocationFetchedListener locationFetchedListener;
    private LocationFetcherInterface locationFetcherInterface;


    LocationFetcher(Context context) {
        this.context = context;
        this.activity = (Activity) context;
    }

    void setLocationFetchedListener(LocationFetchedListener locationFetchedListener) {
        this.locationFetchedListener = locationFetchedListener;
    }

    void setLocationFetcherInterface(LocationFetcherInterface locationFetcherInterface) {
        this.locationFetcherInterface = locationFetcherInterface;
    }

    private void init() {
        mFusedLocationClient = LocationServices.getFusedLocationProviderClient(context);
        mSettingsClient = LocationServices.getSettingsClient(context);
        createLocationCallback();
        createLocationRequest();
        buildLocationSettingsRequest();
        startLocationUpdates();
    }

    private void createLocationCallback() {
        mLocationCallback = new LocationCallback() {
            @Override
            public void onLocationResult(LocationResult locationResult) {
                super.onLocationResult(locationResult);

                mCurrentLocation = locationResult.getLastLocation();
                if (mCurrentLocation != null) {
                    double lat = mCurrentLocation.getLatitude();
                    double longi = mCurrentLocation.getLongitude();
                    locationFetchedListener.onUserLatLongFetched(lat, longi);
                }
            }
        };
    }

    private void createLocationRequest() {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(5000);
        mLocationRequest.setFastestInterval(1000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    }

    private void buildLocationSettingsRequest() {
        LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder();
        builder.addLocationRequest(mLocationRequest);
        mLocationSettingsRequest = builder.build();
    }

    private void startLocationUpdates() {
        mSettingsClient.checkLocationSettings(mLocationSettingsRequest)
                .addOnSuccessListener(activity, new OnSuccessListener<LocationSettingsResponse>() {
                    @Override
                    public void onSuccess(LocationSettingsResponse locationSettingsResponse) {

                        //noinspection MissingPermission
                        if (ActivityCompat.checkSelfPermission(context, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                            locationFetcherInterface.onLocationPermissionsNeeded();
                            return;
                        }
                        mFusedLocationClient.requestLocationUpdates(mLocationRequest, mLocationCallback, Looper.myLooper());
                    }
                })
                .addOnFailureListener(activity, new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        int statusCode = ((ApiException) e).getStatusCode();
                        switch (statusCode) {
                            case LocationSettingsStatusCodes.RESOLUTION_REQUIRED:
                                try {
                                    // Show the dialog by calling startResolutionForResult(), and check the
                                    // result in onActivityResult().
                                    ResolvableApiException rae = (ResolvableApiException) e;
                                    rae.startResolutionForResult(activity, 100);
                                } catch (IntentSender.SendIntentException sie) {
                                    sie.printStackTrace();
                                }
                                break;
                            case LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE:
                                break;
                        }
                    }
                });
    }

    void stopLocationUpdates() {
        mFusedLocationClient.removeLocationUpdates(mLocationCallback)
                .addOnCompleteListener(activity, new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                    }
                });

        if (mFusedLocationClient != null) {
            mFusedLocationClient.removeLocationUpdates(mLocationCallback);
        }
        mFusedLocationClient = null;
    }

    void getUserLatLong() {
        init();
    }

    public interface LocationFetchedListener {
        void onUserLatLongFetched(double latitude, double longitude);
    }

    public interface LocationFetcherInterface{
        void onLocationPermissionsNeeded();
    }

}

This utility class can then be used anywhere in the project. Consider the MapsActivity as below

MapsActivity.java

package com.pratik.appedia.HomeworkLib1;

import android.Manifest;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.support.annotation.Nullable;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AlertDialog;
import android.util.Log;
import android.view.View;
import android.widget.Toast;

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.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback
        , View.OnClickListener
        , LocationFetcher.LocationFetchedListener, LocationFetcher.LocationFetcherInterface {

    private GoogleMap mMap;
    private LocationFetcher locationFetcher;
    private static final String TAG = MapsActivity.class.getSimpleName();
    private FloatingActionButton floatingActionButton;
    public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        if(mapFragment != null)
            mapFragment.getMapAsync(this);
        floatingActionButton = findViewById(R.id.floatingActionButton);
        floatingActionButton.setOnClickListener(this);
        locationFetcher  = new LocationFetcher(this);
        locationFetcher.setLocationFetchedListener(this);
        locationFetcher.setLocationFetcherInterface(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.floatingActionButton) {
            locationFetcher.getUserLatLong();
        }
    }

    @Override
    public void onUserLatLongFetched(double latitude, double longitude) {
        // Do here whatever you want with your double values
        locationFetcher.stopLocationUpdates();
        Toast.makeText(getApplicationContext(),"Latitude = "+latitude+"\tLongitude = "+longitude,Toast.LENGTH_LONG).show();
        Log.d(TAG,"Latitude = "+latitude+"\tLongitude = "+longitude);
    }


    @Override
    public void onLocationPermissionsNeeded() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission.ACCESS_FINE_LOCATION)) {
            new AlertDialog.Builder(this)
                    .setTitle(R.string.title_location_permission)
                    .setMessage(R.string.text_location_permission)
                    .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            ActivityCompat.requestPermissions(MapsActivity.this,
                                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                                    MY_PERMISSIONS_REQUEST_LOCATION);
                        }
                    })
                    .create()
                    .show();
        } else {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                    MY_PERMISSIONS_REQUEST_LOCATION);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_LOCATION: {
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    if (ContextCompat.checkSelfPermission(this,
                            Manifest.permission.ACCESS_FINE_LOCATION)
                            == PackageManager.PERMISSION_GRANTED) {
                        locationFetcher.getUserLatLong();
                    }
                } else {
                    Toast.makeText(getApplicationContext(), "Location has been denied. Sorry !", Toast.LENGTH_SHORT).show();
                }
            }

        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        switch (requestCode){
            case 100:
                if(resultCode == 0){
                    Toast.makeText(getApplicationContext(),"You didn't put your GPS on !",Toast.LENGTH_SHORT).show();
                } else{
                    locationFetcher.getUserLatLong();
                }
                Log.d(TAG,"Result code = "+resultCode);
                break;
        }
    }
}

All you need to do is

1. Create an object of LocationFetcher class

2. In the onClick method (which is outside onCreate) check the id of the view clicked. If it matches with the button id

then invoke the getUserLatLong() method of the LocationFetcher class using the object made in step 1.

3. Override the callback methods defined inside the LocationFetcher class .

a. We have an interface to listen for lack of permissions

b. We have an interface to listen for successful fetching of user location

4. The onUserLatLongFetched() method is called when the LocationFetcher successfully fetches the user location.

5. In this callback now you can play with your double values.

6. Advantage of this code is it is clean and concise and easy to maintain.

activity_maps.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/constraintLayout_Root"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MapsActivity" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/floatingActionButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp"
        android:clickable="true"
        android:focusable="true"
        android:src="@drawable/ic_my_location"
        map:layout_constraintBottom_toBottomOf="parent"
        map:layout_constraintEnd_toEndOf="parent"
        map:layout_constraintHorizontal_bias="1.0"
        map:layout_constraintStart_toStartOf="@+id/map"
        map:layout_constraintTop_toTopOf="parent"
        map:layout_constraintVertical_bias="1.0" />

</android.support.constraint.ConstraintLayout>

strings.xml

<resources>
    <string name="app_name">Chegg1</string>
    <string name="title_activity_maps">Map</string>
    <string name="ok">Ok</string>
    <string name="title_location_permission">Access to location</string>
    <string name="text_location_permission">We need to know your location for better functionality</string>
</resources>