在 oncreate 方法中请求位置更新

Question

I am trying to implement a location alarm kind of application. But whenever my application opens. my current location shows as null.

Below is my code.

package com.hrupin;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class HelloAndroidGpsActivity extends Activity implements OnClickListener, android.content.DialogInterface.OnClickListener, LocationListener {


    private TextView setLat, setLong, destLat, destLong, currLat, currLong, tjd, fromhome, toward;
    private Button setmyLoc, setDest;

    private EditText editLat, editLong;

    private LocationManager orgManager;
    //private LocationListener orgListener;
    // private LocationListener destListener = new destListener();

    private boolean gps_enabled = false;
    private boolean network_enabled = false;

    private String bestProvider;


    double orginLongitude, orginLatitude, destLongtitude, destLatitude, currLatitude, currLongtitude;
    float firstLat, firstLang, secLat, secLang;
    Location destinationLocation = new Location("gps");
    Location originLocation = new Location("gps");
    Location currLocation = new Location("gps");

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        setLat = (TextView) findViewById(R.id.setLat);
        setLong = (TextView) findViewById(R.id.setLong);
        destLat = (TextView) findViewById(R.id.destLat);
        destLong = (TextView) findViewById(R.id.destLong);
        currLat = (TextView) findViewById(R.id.currLat);
        currLong = (TextView)findViewById(R.id.currLong);
        tjd = (TextView)findViewById(R.id.setmeter);
        fromhome = (TextView)findViewById(R.id.destmeter);
        toward = (TextView)findViewById(R.id.currmeter);

        setDest = (Button)findViewById(R.id.SetLocation);

        editLat = (EditText)findViewById(R.id.editLat);
        editLong = (EditText)findViewById(R.id.editLong);

        orgManager = (LocationManager)this.getSystemService(Context.LOCATION_SERVICE);


        try {
            gps_enabled = orgManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);
        } catch (Exception ex) {
            Log.i("gps_enabled", ex.toString());
        }
        try {
            network_enabled = orgManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);
        } catch (Exception ex) {
            Log.i("network_enabled", ex.toString());
        }

        // don't start listeners if no provider is enabled
        if (!gps_enabled && !network_enabled) {
            AlertDialog.Builder builder = new Builder(
                    HelloAndroidGpsActivity.this);
            builder.setTitle("Attention!");
            builder.setMessage("Sorry, location is not determined. Please enable location providers");
            builder.setPositiveButton("OK",
                    HelloAndroidGpsActivity.this);
            builder.setNeutralButton("Cancel",
                    HelloAndroidGpsActivity.this);
            builder.create().show();
        }


        Criteria criteria = new Criteria();
        bestProvider = orgManager.getBestProvider(criteria, false);
        orgManager.requestLocationUpdates(bestProvider, 0, 0, this);
        Location location = orgManager.getLastKnownLocation(bestProvider);

        if (location!=null){
            setLat.setText("Latitude:" + currLatitude);
            setLong.setText("Longitude:" + currLongtitude);
            originLocation.setLatitude(currLatitude);
            originLocation.setLongitude(currLongtitude);
        }
        //else Toast.makeText(getBaseContext(), "Error in GPS", Toast.LENGTH_SHORT).show();

        setDest.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {


                destLat.setText("Lat:"+editLat.getText().toString().trim());
                destLong.setText("Long"+editLong.getText().toString().trim());

                destLatitude = Double.parseDouble(String.valueOf(editLat.getText().toString().trim()));
                destLongtitude = Double.parseDouble(String.valueOf(editLong.getText().toString().trim()));

                destinationLocation.setLatitude(destLatitude);
                destinationLocation.setLongitude(destLongtitude);

                float distance = originLocation.distanceTo(destinationLocation);
                tjd.setText(String.valueOf(distance/1000)+ " Kms ");

            }
        });
    }

    /** Register for the updates when Activity is in foreground */
    @Override
    protected void onResume() {
        super.onResume();
        orgManager.requestLocationUpdates(bestProvider, 60000, 1, this);
    }

    /** Stop the updates when Activity is paused */
    @Override
    protected void onPause() {
        super.onPause();
        orgManager.removeUpdates(this);
    }

    public void onClick(DialogInterface dialog, int which) {
        if (which == DialogInterface.BUTTON_NEUTRAL) {
            setLat.setText("Sorry, location is not determined. To fix this please enable location providers");
        } else if (which == DialogInterface.BUTTON_POSITIVE) {
            startActivity(new Intent(
                    android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS));
        }
    }

    public void onClick(View v) {
        // TODO Auto-generated method stub

    }

    public void onLocationChanged(Location location) {
        // TODO Auto-generated method stub
        if (location != null) {
            // This needs to stop getting the location data and save the
            // battery power.
            //orgManager.removeUpdates(orgListener);

            currLatitude = location.getLatitude();
            currLongtitude = location.getLongitude();

            currLocation.setLatitude(currLatitude);
            currLocation.setLongitude(currLongtitude);

            currLat.setText(String.valueOf(currLatitude));
            currLong.setText(String.valueOf(currLongtitude));

            float fromhome = originLocation.distanceTo(currLocation);

            float toward = currLocation.distanceTo(destinationLocation);

            HelloAndroidGpsActivity.this.fromhome.setText(String.valueOf(fromhome/1000)+ " Kms ");
            HelloAndroidGpsActivity.this.toward.setText(String.valueOf(toward/1000) + " Kms ");

            if (toward/1000 <= 14 ){

                Toast.makeText(getBaseContext(), "You are "+ toward/1000 + " Kms towards Destination ", Toast.LENGTH_SHORT).show();
            }
        }
    }


    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub

    }

    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub

    }

    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }
}

I know this kind of question has been million times. I have tried all methods which has been specified in answers. But i havent got any output. Please help.

Answer 1

You should not call requestLocationUpdates on onCreate as it is redundant since your code will call it on onResume. The flow is onCreate --> onStart --> onResume.

Answer 2

To get Current Location, this is working pretty fine with me check this out.

our Activity is like this

---

public class MainActivity extends Activity implements OnClickListener, android.content.DialogInterface.OnClickListener {
/** Called when the activity is first created. */

private EditText showLocation;
private Button btnGetLocation;
private ProgressBar progress;

private LocationManager locManager;
private LocationListener locListener = new myLocationListener();

private boolean gps_enabled = false;
private boolean network_enabled = false;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    showLocation = (EditText) findViewById(R.id.txtShowLoc);
    showLocation.setEnabled(false);

    progress = (ProgressBar) findViewById(R.id.progressBar);
    progress.setVisibility(View.GONE);

    btnGetLocation = (Button) findViewById(R.id.btnGetLoc);
    btnGetLocation.setOnClickListener(this);

    locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);


}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub

    progress.setVisibility(View.VISIBLE);

    try{
        gps_enabled = locManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
    }
    catch(Exception ex){            
    }
    try{
        network_enabled = locManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);           
    }
    catch(Exception ex){

    }       

    if (!gps_enabled && !network_enabled) {
        AlertDialog.Builder builder = new Builder(this);
        builder.setTitle("Attention!");
        builder.setMessage("Sorry, location is not determined. Please enable location providers");
        builder.setPositiveButton("OK", this);
        builder.setNeutralButton("Cancel", this);
        builder.create().show();
        progress.setVisibility(View.GONE);
    }

    if (gps_enabled) {
        locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locListener);
    }
    if (network_enabled) {
        locManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locListener);
    }       
}

private class myLocationListener implements LocationListener{

    @Override
    public void onLocationChanged(Location location) {
        // TODO Auto-generated method stub
        if(location!=null){

            locManager.removeUpdates(locListener);

            String Speed = "Device Speed: " +location.getSpeed();
            String longitude = "Longitude: " +location.getLongitude();
            String latitude = "Latitude: " +location.getLatitude();
            String altitiude = "Altitiude: " + location.getAltitude();
            String accuracy = "Accuracy: " + location.getAccuracy();
            String time = "Time: " + location.getTime();

            String cityName=null;

            Geocoder gcd = new Geocoder(getBaseContext(), Locale.getDefault());
            //public List<Address> addresses= gcd.getFromLocation (double latitude1, double longitude1, int maxResults)


            List<Address> addresses;
            try {
                addresses = gcd.getFromLocation(location.getLatitude(), location.getLongitude(), 1);
                if (addresses.size() > 0)
                    System.out.println(addresses.get(0).getLocality());
                cityName=addresses.get(0).getLocality();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }



            showLocation.setText("City Name: "+cityName+"\n"+Speed + "\n"+longitude + "\n" + latitude + "\n" + altitiude + "\n" + accuracy + "\n" + time);
            progress.setVisibility(View.GONE);
        }
    }

    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }

}

@Override
public void onClick(DialogInterface dialog, int which) {
    // TODO Auto-generated method stub
    if(which == DialogInterface.BUTTON_NEUTRAL){
        showLocation.setText("location is not getting due to location provider");

    }
    else if (which == DialogInterface.BUTTON_POSITIVE){
        startActivity(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS));

    }
}}

---

and main.xml is

---

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:weightSum="1">
<TextView android:id="@+id/textView1" android:layout_width="match_parent" android:text="My Location is:" android:textSize="25sp" android:layout_height="wrap_content"></TextView>
<EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:layout_weight="0.24" android:lines="5" android:id="@+id/txtShowLoc">
    <requestFocus></requestFocus>
</EditText>
<LinearLayout android:id="@+id/linearLayout2" android:layout_height="wrap_content" android:layout_width="match_parent" android:gravity="center">
    <ProgressBar android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/progressBar"></ProgressBar>
</LinearLayout>
<LinearLayout android:id="@+id/linearLayout1" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center">
    <Button android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="Get Current Location" android:id="@+id/btnGetLoc"></Button>
</LinearLayout>

---

and my manifest file is

---

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="rdc.getCurrentLocaion"
  android:versionCode="1"
  android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"></uses-permission>
<application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="true">
    <activity android:name=".MainActivity"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>

---

let me know if you get any trouble!!

Answer 3

@Ramdhan Thanks for your code. But i corrected a mistake made in my code.

  Criteria criteria = new Criteria();
        bestProvider = orgManager.getBestProvider(criteria, false);
        orgManager.requestLocationUpdates(bestProvider, 0, 0, this);
        Location location = orgManager.getLastKnownLocation(bestProvider);

    if (location!=null){
        setLat.setText("Latitude:" + currLatitude);
        setLong.setText("Longitude:" + currLongtitude);
        originLocation.setLatitude(currLatitude);
        originLocation.setLongitude(currLongtitude);
    } 

Cheanged code:

if (location != null) {
        setLat.setText("Latitude:" + location.getLatitude());
        setLong.setText("Longitude:" + location.getLongitude());
        originLocation.setLatitude(location.getLatitude());
        originLocation.setLongitude(location.getLongitude());
    }

Answer 4

For requesting location update from OnCreate Methode

LocationManager locationManager=(LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
    LocationListener locationListener=new LocationListener() {
        @Override
        public void onLocationChanged(Location location) {

        }

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

        }

        @Override
        public void onProviderEnabled(String provider) {

        }

        @Override
        public void onProviderDisabled(String provider) {

        }
    } if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)!= PackageManager.PERMISSION_GRANTED){
        ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.ACCESS_FINE_LOCATION},1);
    }