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OpenCV app - Android camera keeps showing black screen

Background
I had started out this project on Android Studio with the intent of creating a OpenCV application that could process frames using the camera on my OnePlus android device. After running the application, I was gratified to see it finally launch on my device. However, the application shows up with a black screen where the camera preview should be. Here is my code for my MainActivity, activity_main, and AndroidManifest files:
EDIT: While the application launched on my device, I did give the application permission to use camera
MainActivity.java
package com.example.cv;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceView;
import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.JavaCameraView;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.imgproc.Imgproc;
public class MainActivity extends AppCompatActivity implements CameraBridgeViewBase.CvCameraViewListener2
{
private static String TAG = "MainActivity";
JavaCameraView javaCameraView;
Mat mRGBA, mRGBAT;
BaseLoaderCallback baseLoaderCallback = new BaseLoaderCallback(MainActivity.this) {
#Override
public void onManagerConnected(int status)
{
if (status == BaseLoaderCallback.SUCCESS) {
javaCameraView.enableView();
} else {
super.onManagerConnected(status);
}
}
};
static
{
if (OpenCVLoader.initDebug())
{
Log.d(TAG, "OpenCV is Configured or Connected successfully.");
}
else
{
Log.d(TAG, "OpenCV not Working or Loaded.");
}
}
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
javaCameraView = (JavaCameraView) findViewById(R.id.my_camera_view);
javaCameraView.setVisibility(SurfaceView.VISIBLE);
javaCameraView.setCvCameraViewListener(MainActivity.this);
}
#Override
public void onCameraViewStarted(int width, int height)
{
mRGBA = new Mat(height, width, CvType.CV_8UC4);
}
#Override
public void onCameraViewStopped()
{
mRGBA.release();
}
#Override
public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame)
{
mRGBA = inputFrame.rgba();
mRGBAT = mRGBA.t();
Core.flip(mRGBA.t(), mRGBAT, 1);
Imgproc.resize(mRGBAT, mRGBAT, mRGBA.size());
return mRGBAT;
}
#Override
public void onPointerCaptureChanged(boolean hasCapture) {
}
#Override
protected void onDestroy() {
super.onDestroy();
if (javaCameraView != null)
{
javaCameraView.disableView();
}
}
#Override
protected void onPause() {
super.onPause();
if (javaCameraView != null)
{
javaCameraView.disableView();
}
}
#Override
protected void onResume() {
super.onResume();
if (OpenCVLoader.initDebug())
{
Log.d(TAG, "OpenCV is Configured or Connected successfully.");
baseLoaderCallback.onManagerConnected(BaseLoaderCallback.SUCCESS);
}
else
{
Log.d(TAG, "OpenCV not Working or Loaded.");
OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION, this, baseLoaderCallback);
}
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<org.opencv.android.JavaCameraView
android:id="#+id/my_camera_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
</RelativeLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.cv">
<uses-permission android:name="android.permission.CAMERA"/>
<uses-feature android:name="android.hardware.camera"/>
<uses-feature android:name="android.hardware.camera.autofocus"/>
<uses-feature android:name="android.hardware.camera.front"/>
<uses-feature android:name="android.hardware.camera.front.autofocus"/>
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

The issue you are facing is actually with the camera permission check
Starting from Android Marshmallow, the CAMERA permission is considered a dangerous one and the user must explicitly agree on its usage at runtime, clicking on the system dialog
This wouldn't happen for "normal permissions" [e.g. INTERNET] that are granted by default. If you are interested in which ones are dangerous and which not you can check for the one of interest directly in the Android documentation
What's happening with your initial code is that you are mentioning you will require the camera permission in your manifest file and then you are enabling it from the Android Settings [toggling the Camera slider]. But then, when you start the app there is nothing in the code that goes and checks that toggle. Then you get a black screen because Android assumes that the user has not given explicit consent
This link from the Android documentation should help you understand more. Here the snippet that will make your code work. In a nutshell, with onCreate() you go and check if the user has already granted the permission and if not you will ask it. In onRequestPermissionResult() there is the check we were talking about before. If the user agreed the camera will start, otherwise it won't
private static final int MY_CAMERA_REQUEST_CODE = 100;
int activeCamera = CameraBridgeViewBase.CAMERA_ID_FRONT;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
javaCameraView = (JavaCameraView) findViewById(R.id.my_camera_view);
// checking if the permission has already been granted
if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
== PackageManager.PERMISSION_GRANTED) {
Log.d(TAG, "Permissions granted");
initializeCamera(javaCameraView, activeCamera);
} else {
// prompt system dialog
Log.d(TAG, "Permission prompt");
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, MY_CAMERA_REQUEST_CODE);
}
}
// callback to be executed after the user has givenapproval or rejection via system prompt
#Override
public void onRequestPermissionsResult(int requestCode, #NonNull String[] permissions, #NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == MY_CAMERA_REQUEST_CODE) {
if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// camera can be turned on
Toast.makeText(this, "camera permission granted", Toast.LENGTH_LONG).show();
initializeCamera(javaCameraView, activeCamera);
} else {
// camera will stay off
Toast.makeText(this, "camera permission denied", Toast.LENGTH_LONG).show();
}
}
}
private void initializeCamera(JavaCameraView javaCameraView, int activeCamera){
javaCameraView.setCameraPermissionGranted();
javaCameraView.setCameraIndex(activeCamera);
javaCameraView.setVisibility(CameraBridgeViewBase.VISIBLE);
javaCameraView.setCvCameraViewListener(this);
}

Right way of requesting permissions for location coordinates in Android 10

Below code does not work on Android 10 until you manually enable the location from settings. When I go through the Android 10 documentation, it says if you are fetching location from the visible activity, if that was the case you don't need any foreground service, that's the reason I haven't used any service here.
And also as per Android 10 guidelines, after permission getting granted I am calling getLastLocation function.
Implementation is like, on main activity I am fetching location coordinates.
Please help, where in the code am I going wrong?
MainActivity.java
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.net.Uri;
import android.os.Bundle;
import android.provider.Settings;
import androidx.annotation.NonNull;
import com.google.android.material.snackbar.Snackbar;
import androidx.core.app.ActivityCompat;
import androidx.appcompat.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import java.util.Locale;
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
private static final int REQUEST_PERMISSIONS_REQUEST_CODE = 34;
private FusedLocationProviderClient mFusedLocationClient;
protected Location mLastLocation;
private String mLatitudeLabel;
private String mLongitudeLabel;
private TextView mLatitudeText;
private TextView mLongitudeText;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
mLatitudeLabel = getResources().getString(R.string.latitude_label);
mLongitudeLabel = getResources().getString(R.string.longitude_label);
mLatitudeText = (TextView) findViewById((R.id.latitude_text));
mLongitudeText = (TextView) findViewById((R.id.longitude_text));
mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
}
#Override
public void onStart() {
super.onStart();
if (!checkPermissions()) {
requestPermissions();
} else {
getLastLocation();
}
}
#SuppressWarnings("MissingPermission")
private void getLastLocation() {
mFusedLocationClient.getLastLocation()
.addOnCompleteListener(this, new OnCompleteListener<Location>() {
#Override
public void onComplete(#NonNull Task<Location> task) {
if (task.isSuccessful() && task.getResult() != null) {
mLastLocation = task.getResult();
Log.d("raviraj", "lat is " +mLastLocation.getLatitude());
Log.d("raviraj", "long is " +mLastLocation.getLongitude());
mLatitudeText.setText(String.format(Locale.ENGLISH, "%s: %f",
mLatitudeLabel,
mLastLocation.getLatitude()));
mLongitudeText.setText(String.format(Locale.ENGLISH, "%s: %f",
mLongitudeLabel,
mLastLocation.getLongitude()));
} else {
Log.w("RAVIRAJ", "getLastLocation:exception" +task.getException());
showSnackbar(getString(R.string.no_location_detected));
}
}
});
}
private void showSnackbar(final String text) {
View container = findViewById(R.id.main_activity_container);
if (container != null) {
Snackbar.make(container, text, Snackbar.LENGTH_LONG).show();
}
}
private void showSnackbar(final int mainTextStringId, final int actionStringId,
View.OnClickListener listener) {
Snackbar.make(findViewById(android.R.id.content),
getString(mainTextStringId),
Snackbar.LENGTH_INDEFINITE)
.setAction(getString(actionStringId), listener).show();
}
private boolean checkPermissions() {
int permissionState = ActivityCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION);
return permissionState == PackageManager.PERMISSION_GRANTED;
}
private void startLocationPermissionRequest() {
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
REQUEST_PERMISSIONS_REQUEST_CODE);
}
private void requestPermissions() {
boolean shouldProvideRationale =
ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION);
if (shouldProvideRationale) {
Log.i(TAG, "Displaying permission rationale to provide additional context.");
showSnackbar(R.string.permission_rationale, android.R.string.ok,
new View.OnClickListener() {
#Override
public void onClick(View view) {
// Request permission
startLocationPermissionRequest();
}
});
} else {
Log.i(TAG, "Requesting permission");
startLocationPermissionRequest();
}
}
#Override
public void onRequestPermissionsResult(int requestCode, #NonNull String[] permissions,
#NonNull int[] grantResults) {
Log.i(TAG, "onRequestPermissionResult");
if (requestCode == REQUEST_PERMISSIONS_REQUEST_CODE) {
if (grantResults.length <= 0) {
// If user interaction was interrupted, the permission request is cancelled and you
// receive empty arrays.
Log.i(TAG, "User interaction was cancelled.");
} else if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission granted.
getLastLocation();
} else {
showSnackbar(R.string.permission_denied_explanation, R.string.settings,
new View.OnClickListener() {
#Override
public void onClick(View view) {
// Build intent that displays the App settings screen.
Intent intent = new Intent();
intent.setAction(
Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
Uri uri = Uri.fromParts("package",
BuildConfig.APPLICATION_ID, null);
intent.setData(uri);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
}
});
}
}
}
}
Manifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.google.android.gms.location.sample.basiclocationsample" >
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/Theme.Base" >
<meta-data
android:name="com.google.android.geo.API_KEY"
android:value="#string/google_maps_key" />
<activity
android:name=".NewMain"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

Well there is a problem. Official documentation states that it can be null in some cases
https://developer.android.com/training/location/retrieve-current
Location is turned off in the device settings. The result could be null even if the last location was previously retrieved because disabling location also clears the cache.
The device never recorded its location, which could be the case of a new device or a device that has been restored to factory settings.
Google Play services on the device has restarted, and there is no active Fused Location Provider client that has requested location after the services restarted. To avoid this situation you can create a new client and request location updates yourself. For more information, see Receiving Location Updates.
In your case you can get location only if GPS is ON. Even for last known location.
https://developer.android.com/training/location/retrieve-current#last-known

Please add this permission in AndroidManifest.xml
<uses-permission android:name="android.permission.INTERNET" />
and add this to application tag
android:usesCleartextTraffic="true"

Activities lifecycle after pushed android button "recents" create new activity but dont destroy old activity

When i push android button "recents" and select my app again to go back to de app, the lifecycle of MapsActivity execute onCreate again and create a new instance of MapsActivity.
That´s ok, but the old MapsActivity still running in background and that´s a problem because both MapsActivity have counters and still running and counting with different values in the same variables, like independent new variables.
The counter is in onLocationChanged() and called as "clock".
onLocationChanged() update automaticaly ever 5 seconds.
example:
counter is running : 1, 2, 3, 4, 5, ...
at this point i push android button "recent" (the system execute onCreate)
counter still running like that : 6, 1, 7, 2, 8, 3, ...
at this point a push again android button "recent" (execute onCreate)
counter still running like that : 9, 4, 1, 10, 5, 2, 11, 6, 3, ...
I suppose the lifecycle of MapsActivity not destroy old activities.
I need only one sequencial counter running, and i guess the old MapsActivity must die :)
any idea to solve my problem ? Thanks a lot!
below the manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.sasse.myapplication">
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<meta-data
android:name="com.google.android.geo.API_KEY"
android:value="#string/google_maps_key" />
<activity
android:name=".MapsActivity"
android:label="#string/title_activity_maps">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
layout activity_maps.xml
<fragment 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/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.sasse.myapplication.MapsActivity" />
Maps_activity
package com.example.sasse.myapplication;
import android.*;
import android.Manifest;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Build;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
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 LocationListener, ConnectionCallbacks, OnConnectionFailedListener, OnMapReadyCallback {
private static final String TAG = "MapsActivity";
private GoogleMap mMap;
protected GoogleApiClient mGoogleApiClient;
protected LocationRequest mLocationRequest;
public int clock = 0;
#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);
mapFragment.getMapAsync(this);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
checkLocationPermission();
}
}
#Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
//Initialize Google Play Services
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (ContextCompat.checkSelfPermission(this,
android.Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
} else {
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
}
public void onLocationChanged(Location location) {
clock++;
if (clock>=10) {
Toast.makeText(this, "clock : "+clock, Toast.LENGTH_SHORT).show();
clock=0;
}
Log.i(TAG, "= = = = = >>> clock : "+clock);
}
// ---------------------------------------------------------------------------------------------
// ---------------- VERIFICAÇÃO DA CONEXÃO COM O SERVIDOR DO GOOGLE MAPS-----------------------
// ---------------------------------------------------------------------------------------------
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
public boolean checkLocationPermission() {
if (ContextCompat.checkSelfPermission(this,
android.Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// Asking user if explanation is needed
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
android.Manifest.permission.ACCESS_FINE_LOCATION)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions(this,
new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
} else {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(this,
new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
return false;
} else {
return true;
}
}
public void onRequestPermissionsResult(int requestCode, #NonNull String permissions[], #NonNull int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_LOCATION: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// permission was granted. Do the
// contacts-related task you need to do.
if (ContextCompat.checkSelfPermission(this,
android.Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
if (mGoogleApiClient == null) {
buildGoogleApiClient();
}
mMap.setMyLocationEnabled(true);
}
} else {
// Permission denied, Disable the functionality that depends on this permission.
Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
}
}
// other 'case' lines to check for other permissions this app might request.
// You can add here other case statements according to your requirement.
}
}
protected synchronized void buildGoogleApiClient() {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
mGoogleApiClient.connect();
}
public void onConnected(Bundle bundle) {
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(5000);
mLocationRequest.setFastestInterval(5000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
}
public void onConnectionSuspended(int i) {
}
public void onConnectionFailed(#NonNull ConnectionResult connectionResult) {
}
}

Try using launchMode="singleTop" for activity

LocationClient getLastLocation() returning null

I'm new to Android programming and wanted to start by creating a very basic app that displays the latitude and longitude of the current location on screen.
I'm developing for my Samsung Galaxy S3 and read that you need to kickstart the phone to return the GPS.
I've tried doing this in the onConnected() method with the requestLocationUpdates() method call on the LocationManager. However I find that the LocationClient is still returning a null location.
Can anyone tell me what I'm doing wrong?
Here's my MainActivity:
import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesClient;
import com.google.android.gms.location.LocationClient;
public class MainActivity extends FragmentActivity implements
GooglePlayServicesClient.ConnectionCallbacks,
GooglePlayServicesClient.OnConnectionFailedListener {
private LocationClient mLocationClient;
private Location mCurrentLocation;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mLocationClient = new LocationClient(this, this, this);
}
#Override
protected void onStart() {
super.onStart();
mLocationClient.connect();
}
#Override
protected void onStop() {
mLocationClient.disconnect();
super.onStop();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public void onConnectionFailed(ConnectionResult arg0) {
// TODO Auto-generated method stub
}
#Override
public void onConnected(Bundle arg0) {
Toast.makeText(this, "Connected", Toast.LENGTH_SHORT).show();
LocationManager manager = (LocationManager) this
.getSystemService(Context.LOCATION_SERVICE);
manager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0,
new LocationListener() {
#Override
public void onStatusChanged(String provider, int status,
Bundle extras) {
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onProviderDisabled(String provider) {
}
#Override
public void onLocationChanged(final Location location) {
}
});
mCurrentLocation = mLocationClient.getLastLocation();
TextView latTextView = (TextView) findViewById(R.id.latitude_text);
latTextView.setText(Double.toString(mCurrentLocation.getLatitude()));
TextView longTextView = (TextView) findViewById(R.id.longitude_text);
longTextView.setText(Double.toString(mCurrentLocation.getLongitude()));
}
#Override
public void onDisconnected() {
Toast.makeText(this, "Disconnected. Please re-connect.",
Toast.LENGTH_SHORT).show();
}
}
My Android manifest looks like this:
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.willigetwet.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
When running the debugger I find that mCurrentLocation is null after the call to mLocationClient.getLastLocation().
I'd be very grateful for any help!

mLocationClient.getLastLocation(); might return null if you don't have any last location saved by the device. If you read its documentation, it says;
It returns the best most recent location currently available.
If a location is not available, which should happen very rarely, null will be returned
Also inside the onLocationChanged method you might want to set the Location to the latest location, when your location gets changed.
#Override
public void onLocationChanged(final Location location) {
mCurrentLocation = location;
}

How to make this location finder (GPS) on android works?

i was made an finding location application that show a latitude and longitude in the textview.. here's my code :
package com.application.geocoding;
import android.app.Activity;
import android.os.Bundle;
import android.content.Context;
import android.location.Location;
import android.location.LocationManager;
import android.widget.TextView;
public class main extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LocationManager locationManager;
String context = Context.LOCATION_SERVICE;
locationManager = (LocationManager)getSystemService(context);
String provider = LocationManager.GPS_PROVIDER;
Location location =
locationManager.getLastKnownLocation(provider);
updateWithNewLocation(location);
}
private void updateWithNewLocation(Location location) {
String latLongString;
TextView myLocationText;
myLocationText=(TextView)findViewById(R.id.textView1);
if (location != null) {
double lat = location.getLatitude();
double lng = location.getLongitude();
latLongString = "Lat:" + lat + "\nLong:" + lng;
} else {
latLongString = "No location found";
}
myLocationText.setText("Your Current Position is:\n" +
latLongString);
}
}
and here's the manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.application.geocoding"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".main"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
that code is still not works and only can display "No location found" textview.. has anyone know how to solve that problem?? thanks..

You can use this:
LocationListener myLocationListener = new LocationListener() {
public void onLocationChanged(Location location) {
String latLongString;
TextView myLocationText;
myLocationText=(TextView)findViewById(R.id.textView1);
double lat = location.getLatitude();
double lng = location.getLongitude();
latLongString = "Lat:" + lat + "\nLong:" + lng;
myLocationText.setText("Your Current Position is:\n" +
latLongString);
}
}
public void onProviderDisabled(String provider) {
}
public void onProviderEnabled(String provider) {
}
public void onStatusChanged(String provider, int status,
Bundle extras) {
}
};
int t = 5000; // millisekunder
int dist = 5; // meter
locationManager.requestLocationUpdates(provider, t, dist, myLocationListener);

from your activity start it will get the gps coordinate but at that time if you don't send the gps coordinate from the ddms then it will return null
while this will give you just one time value if you want to getting the continue gps value you need to define listener for that like LocationListener
see the tutorial link
http://developer.android.com/guide/topics/location/obtaining-user-location.html
http://www.firstdroid.com/2010/04/29/android-development-using-gps-to-get-current-location-2/
http://www.androidcompetencycenter.com/?s=GPS

Have you tried implementing LocationListener and overriding onLocationChanged(Location loc) ? Also, are you using the emulator? EDIT: You can find an example here.

You're not actually invoking a GPS location acquisition, but asking for the last one. If it's never been invoked, it will always return null.
A better approach would be registering a LocationListener in onResume() and unregistering it in onPause() through locationManager.requestLocattionUpdates() and locationManager.removeUpdates(), respectfully.