Android how use javaclass.this in a Fragmentclass

Question

I am trying to use GPS system in my Android app. And I am following this tutorial.

And When I am trying to call my javaclass.this I am getting an error in context How to do it.

Here is my java Class

import android.support.v4.app.Fragment;
import com.lifesymb.lifesymb.R;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.Toast;

    public class gps extends Fragment {


         Button btnShowLocation;

            // GPSTracker class
            GPSTracker gps;
            public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {

                if (container == null) {

                    return null;
                }

                RelativeLayout mRelativeLayout = (RelativeLayout) inflater.inflate(R.layout.gps,
                                container, false);



                // note that we're looking for a button with id="@+id/myButton" in your inflated layout
                // Naturally, this can be any View; it doesn't have to be a button


                      // note that we're looking for a button with id="@+id/myButton" in your inflated layout
                    // Naturally, this can be any View; it doesn't have to be a button
                btnShowLocation = (Button) mRelativeLayout.findViewById(R.id.gps1);
             // show location button click event
                btnShowLocation.setOnClickListener(new View.OnClickListener() {

                    @Override
                    public void onClick(View arg0) {        
                        // create class object
                        gps = new GPSTracker(gps.this);

                        // check if GPS enabled     
                        if(gps.canGetLocation()){

                            double latitude = gps.getLatitude();
                            double longitude = gps.getLongitude();

                            // \n is for new line
                            Toast.makeText(getActivity(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();    
                        }else{
                            // can't get location
                            // GPS or Network is not enabled
                            // Ask user to enable GPS/network in settings
                            gps.showSettingsAlert();
                        }

                    }
                });

Iam Having an error at the following Lines

gps = new GPSTracker(gps.this) ( The constructor GPSTracker(gps) is undefined)

Here is my GPSTracker.java file

import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;

public class GPSTracker extends Service implements LocationListener {

    private final Context mContext;

    // flag for GPS status
    boolean isGPSEnabled = false;

    // flag for network status
    boolean isNetworkEnabled = false;

    // flag for GPS status
    boolean canGetLocation = false;

    Location location; // location
    double latitude; // latitude
    double longitude; // longitude

    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    public GPSTracker(Context context) {
        this.mContext = context;
        getLocation();
    }

    public Location getLocation() {
        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(LOCATION_SERVICE);

            // getting GPS status
            isGPSEnabled = locationManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);

            // getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if (!isGPSEnabled && !isNetworkEnabled) {
                // no network provider is enabled
            } else {
                this.canGetLocation = true;
                // First get location from Network Provider
                if (isNetworkEnabled) {
                    locationManager.requestLocationUpdates(
                            LocationManager.NETWORK_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    Log.d("Network", "Network");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
                // if GPS Enabled get lat/long using GPS Services
                if (isGPSEnabled) {
                    if (location == null) {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                        Log.d("GPS Enabled", "GPS Enabled");
                        if (locationManager != null) {
                            location = locationManager
                                    .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                            if (location != null) {
                                latitude = location.getLatitude();
                                longitude = location.getLongitude();
                            }
                        }
                    }
                }
            }

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

        return location;
    }

    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app
     * */
    public void stopUsingGPS(){
        if(locationManager != null){
            locationManager.removeUpdates(GPSTracker.this);
        }       
    }

    /**
     * Function to get latitude
     * */
    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }

    /**
     * Function to get longitude
     * */
    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }

    /**
     * Function to check GPS/wifi enabled
     * @return boolean
     * */
    public boolean canGetLocation() {
        return this.canGetLocation;
    }

    /**
     * Function to show settings alert dialog
     * On pressing Settings button will lauch Settings Options
     * */
    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS is settings");

        // Setting Dialog Message
        alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });

        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }

    @Override
    public void onLocationChanged(Location location) {
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

}

So Can tell me How to do this. I have tried in Normal class but I am unable to understand the Fragment class usage.

score 2 · Accepted Answer · edited May 23 '17 at 12:03

2

Use getActivity() in fragment class.

getActivity() returns the Activity this fragment is associated with.

this refers to the current context. gps is a Fragment. So use getActivity()

java.lang.Object
   ↳    android.content.Context           // see this
       ↳    android.content.ContextWrapper
           ↳    android.view.ContextThemeWrapper
               ↳    android.app.Activity // see this

And Fragment

java.lang.Object
   ↳    android.app.Fragment

public class GPSTracker extends Service is a Service.

You have this

  gps = new GPSTracker(gps.this)

Instead start the service or bind the service to the activity.

You can use getApplicationContext()

To give you a better idea check the detailed answer by commonsware

When to call activity context OR application context?

edited May 23 '17 at 12:03

Community

1
1

answered Jan 09 '14 at 05:01

Raghunandan

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Thank you it is working can explain me what is different between Getactivity() and class.this this type of calling. – user3144005 Jan 09 '14 at 05:07
@user3144005 you should start a service or bind a service to the activity instead of instantiating it. check the link in my post – Raghunandan Jan 09 '14 at 05:18

score 2 · Answer 2 · answered Jan 09 '14 at 05:04

Fragment does not extend from Context, so you can't pass in a Fragment (or consequently a gps object) into the GPSTracker constructor. You can however call .getActivity() on a Fragment to get it's associated Activity which does inherit from Context.

gps = new GPSTracker(gps.this.getActivity());

Gopal Gopi · Answer 3 · 2014-01-09T05:18:05.380

at first, already your GPSTracker class in extending Service means it is extending Context... then why you need parameterized Constructor for GPSTracker with Context as parameter? directly you can call getApplicationContext() in Service or you can refer with this as Service is a Context.

second, it is not recommended(I think not a way) to have a parameterized Constructor for a Service (even for Activity, BroadCastReceiver etc). if you have Parameterized constructor, then you must define a default Constructor.

third, this is not a way to create the Object(instance) for a Service manually even though Service is a simple Java class. System will take care about instantiating Service

and finally as other answers said, Fragment does not extend Context. so you should use getActivity()

Android how use javaclass.this in a Fragmentclass

3 Answers3