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Sending intents from a worker to an activity in a separate app

I have an app that writes to its local storage depending on user actions; said contents need to
be forwarded to another app.
My approach:
create a worker thread with a file observer pointed to local storage
start worker from the apps main activity
worker thread creates and sends intents with updated contents to separate app
I'm not sure (maybe need to open a separate question), but everything created in an activity gets destroyed when the activity is stopped, right? meaning that adding workers, file observers have the same life span as the activity they're defined in, right?
Code:
MainActivity.java:
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
private static final String FILE_OBSERVER_WORK_NAME = "file_observer_work";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.i(TAG, "Creating file observer worker");
WorkManager workManager = WorkManager.getInstance(getApplication());
WorkContinuation continuation = workManager
.beginUniqueWork(FILE_OBSERVER_WORK_NAME,
ExistingWorkPolicy.REPLACE,
OneTimeWorkRequest.from(APIWorker.class));
Log.i(TAG, "Starting worker");
continuation.enqueue();
final Button button = findViewById(R.id.button2);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Log.i(TAG, "Button clicked!");
String stuffToWriteToFile = getStuff();
String cwd = getApplicationInfo().dataDir;
String stuffFilePath= cwd + File.separator + "stuff.json";
PrintWriter stuffFile= null;
try {
stuffFile = new PrintWriter(stuffFilePath, "UTF-8");
stuffFile.println(stuffToWriteToFile);
stuffFile.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
});
}
#Override
public void onResume(){
super.onResume();
// start worker here?
}
#Override
public void onStart() {
super.onStart();
// start worker here?
}
}
APIWorker.java:
public class APIWorker extends Worker {
public APIWorker(#NonNull Context context, #NonNull WorkerParameters workerParams) {
super(context, workerParams);
}
private static final String TAG = APIWorker.class.getSimpleName();
#NonNull
#Override
public Result doWork() {
Context applicationContext = getApplicationContext();
Log.d(TAG, "Observing stuff file");
FileObserver fileObserver = new FileObserver(cwd) {
#Override
public void onEvent(int event, #Nullable String path) {
if(event == FileObserver.CREATE ||
event == FileObserver.MODIFY) {
String cwd = applicationContext.getApplicationInfo().dataDir;
String stuffFilePath = cwd + File.separator + "stuff.json";
String fileContents;
File observedFile = new File(stuffFilePath);
long length = observedFile.length();
if (length < 1 || length > Integer.MAX_VALUE) {
fileContents = "";
Log.w(TAG, "Empty file: " + observedFile);
} else {
try (FileReader in = new FileReader(observedFile)) {
char[] content = new char[(int)length];
int numRead = in.read(content);
if (numRead != length) {
Log.e(TAG, "Incomplete read of " + observedFile +
". Read chars " + numRead + " of " + length);
}
fileContents = new String(content, 0, numRead);
Log.d(TAG, "Sending intent ");
String packageName = "com.cam.differentapp";
Intent sendIntent = applicationContext.getPackageManager().
getLaunchIntentForPackage(packageName);
if (sendIntent == null) {
// Bring user to the market or let them choose an app?
sendIntent = new Intent(Intent.ACTION_VIEW);
sendIntent.setData(Uri.parse("market://details?id=" + packageName));
}
// sendIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, fileContents);
sendIntent.setType("application/json");
applicationContext.startActivity(sendIntent);
Log.d(TAG, "Intent sent ");
}
catch (Exception ex) {
Log.e(TAG, "Failed to read file " + path, ex);
fileContents = "";
}
}
}
}
};
fileObserver.startWatching();
return null;
}
}
Looking at the docs:
https://developer.android.com/guide/components/activities/background-starts
there are restrictions as to when activities can be started from the background but also exceptions, namely:
The app has a visible window, such as an activity in the foreground.
meaning (I think?) that as long as the user interacts with the app (MainActivity) the background worker should run, correct? It's stopped if the activity is paused/destroyed, right?

Usually you would use a Service if you have background processing to do that doesn't need user interaction (display or user input). If your app is in the foreground then your Service can launch other activities using startActivity().
Your architecture seems very strange to me. You are using a Worker, which has a maximum 10 minute lifetime. You are starting the Worker which then creates a FileObserver to detect creation/modification of files. It then reads the file and starts another Activity. This is a very complicated and roundabout way of doing things. I have doubts that you can get this working reliably.
Your Activity is writing the data to the file system. It could just call a method (on a background thread) after it has written the file that then forwards the data to another Activity. This would be much more straightforward and has a lot less moving parts.
I don't know exactly how the lifecycle of the Activity effects the Workers. I would assume that they are not directly linked to the Activity and therefore would not stop when the Activity is paused or destroyed.
I also notice that you are writing to a file on the main (UI) thread (in your OnClickListener). This is not OK and you should do file I/O in a background thread, because file I/O can block and you don't want to block the main (UI) thread.

how to increase preview camera quality in ARCore

I'm using ARCore in my android project. It has one activity, MainActivity.java and one CustomArFragment.java.
The problem is that the camera quality is very low. how can I increase the camera preview resolution. In future , I need the recognize the text using camera and having such low quality, its difficult to recognize. I am not able to find the solution on google. Tried many things but got no success. Anyone please tell how to increase camera quality. I'm totally new in AR and android field.
Thanks :)
MainActivity.java :
public class MainActivity extends AppCompatActivity {
private CustomArFragment arFragment;
private TextView textView;
private AugmentedImageDatabase aid;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
arFragment = (CustomArFragment) getSupportFragmentManager().findFragmentById(R.id.arFragment);
textView = findViewById(R.id.textView);
arFragment.getArSceneView().getScene().addOnUpdateListener(this::onUpdate);
findViewById(R.id.registeredBtn).setOnClickListener(v -> {
if(ActivityCompat.checkSelfPermission(this,
Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
return;
}
registeredImage();
});
}
private void registeredImage() {
File file = new File(getExternalFilesDir(null) + "/db.imgdb");
try {
FileOutputStream outputStream = new FileOutputStream(file);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.earth);
aid.addImage("earth",bitmap);
aid.serialize(outputStream);
outputStream.close();
Toast.makeText(this, "image Registered", Toast.LENGTH_SHORT).show();
} catch (IOException e) {
e.printStackTrace();
}
}
private void onUpdate(FrameTime frameTime) {
frame = arFragment.getArSceneView().getArFrame();
Collection<AugmentedImage> images = frame.getUpdatedTrackables(AugmentedImage.class);
for(AugmentedImage image : images){
if(image.getTrackingMethod() == AugmentedImage.TrackingMethod.FULL_TRACKING){
if(image.getName().equals("lion")){
textView.setText("LION is visible");
}
else if(image.getName().equals("download")){
textView.setText("download is visible");
}
else{
textView.setText("Nothing is visible till now");
}
Log.d("Value of textView : "," " + textView.getText());
}
Log.d("Value of textView1 : "," " + textView.getText());
}
}
public void loadDB(Session session, Config config){
//InputStream dbStream = getResources().openRawResource(R.raw.imagedb);
try {
File file = new File(getExternalFilesDir(null) + "/db.imgdb");
FileInputStream dbStream = new FileInputStream(file);
aid = AugmentedImageDatabase.deserialize(session, dbStream);
config.setAugmentedImageDatabase(aid);
session.configure(config);
Log.d("TotalImages"," : " + aid.getNumImages());
}catch (IOException e){
e.printStackTrace();
}
}
CustomArFragment.java
public class CustomArFragment extends ArFragment {
#Override
protected Config getSessionConfiguration(Session session){
getPlaneDiscoveryController().setInstructionView(null);
Config config = new Config(session);
config.setUpdateMode(Config.UpdateMode.LATEST_CAMERA_IMAGE);
MainActivity activity = (MainActivity) getActivity();
activity.loadDB(session,config);
this.getArSceneView().setupSession(session);
return config;
}
}

I added some info regarding a similar topic in this other question. But answering yours, check what CameraConfig is used by default (use getCameraConfig() on the Session). Then you can get the one that is of your interest (high GPU texture size) through getSupportedCameraConfigs() and configure the Session with it through setCameraConfig.
Reading your question again, if you need in the future to recognize some text on the image, you might want to get a higher CPU image instead of GPU texture size. You can still use CameraConfig to check that and choose your favorite, but keep in mind that higher CPU images decreases the performance quite a bit. You might want to check my answer in the question I mentioned earlier.
EDIT: Use this code snippet to check the CameraConfig being used and adapt it to your needs:
Session session = new Session(requireActivity());
// ...
Size selectedSize = new Size(0, 0);
CameraConfig selectedCameraConfig = null;
CameraConfigFilter filter = new CameraConfigFilter(session);
List<CameraConfig> cameraConfigsList = session.getSupportedCameraConfigs(filter);
for (CameraConfig currentCameraConfig : cameraConfigsList) {
Size cpuImageSize = currentCameraConfig.getImageSize();
Size gpuTextureSize = currentCameraConfig.getTextureSize();
Log.d("TAG", "CurrentCameraConfig CPU image size:" + cpuImageSize + " GPU texture size:" + gpuTextureSize);
// Adapt this check to your needs
if (gpuTextureSize.getWidth() > selectedSize.getWidth()) {
selectedSize = gpuTextureSize;
selectedCameraConfig = currentCameraConfig;
}
}
Log.d("TAG", "Selected CameraConfig CPU image size:" + selectedCameraConfig.getImageSize() + " GPU texture size:" + selectedCameraConfig.getTextureSize());
session.setCameraConfig(selectedCameraConfig);
// ...
// Don't forget to configure the session afterwards
session.configure(config);

LocationListner no longer listen for gps status change after upgrade to Android 7

After updated my app to support Android 7 the GPS listner no longer is invoked when the GPS on/off is triggerd. If I refresh my activity it works as expected on Android 6, but not in Android 7. Does anyone have any idea. I have added both my listner, and code releated to gps change in my activity.
I have if its difficult a theory to override the backpressed or activity resumed to recreate view, but havn't suceeded with that either .
GPSListner.java
public abstract class GPSListener implements LocationListener {
private Context context;
public GPSListener(Context context) {
this.context = context;
}
#Override
public void onProviderEnabled(String provider) {
onGPSOn();
}
#Override
public void onProviderDisabled(String provider) {
onGPSOff();
}
public abstract void onGPSOff();
public abstract void onGPSOn();
#Override
public void onLocationChanged(Location location) {
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
}
My class
gpsListener = new GPSListener(this) {
#Override
public void onGPSOff() {
gpsImg.setImageResource(R.drawable.notok);
}
#Override
public void onGPSOn() {
gpsImg.setImageResource(R.drawable.ok);
}
};
final LocationManager manager;
manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
final ImageView gpsImg = (ImageView) findViewById(R.id.gpsstatus);
if (manager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
gpsImg.setImageResource(R.drawable.ok);
} else {
gpsImg.setImageResource(R.drawable.notok); //not ok
}
This last method opens the gps settings.
public View.OnClickListener onButtongpsClick = new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent gpsOptionsIntent = new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(gpsOptionsIntent);
}
};

Obtaining location is a bit tricky itself. Only GPS can have line-of-sight issues and would vary depending on device too, not just Android version. Over the years Android location services have matured and using up-to-date standard practices does result in higher consistency with respect to results.
By the way, LocationClient is deprecated. FusedLocationProviderApi does not use it anymore.
It works through a GoogleApiClient and this part makes the GooglePlayServices mandatory. You have options if this does not suit your app.
Making your app location aware suggests:
The Google Play services location APIs are preferred over the Android
framework location APIs (android.location) as a way of adding location
awareness to your app. If you are currently using the Android
framework location APIs, you are strongly encouraged to switch to the
Google Play services location APIs as soon as possible.
You can break it into parts to understand it better, like;
Building the GoogleApiClient
protected synchronized void buildGoogleApiClient() {
mGoogleApiClient = new GoogleApiClient.Builder(this) //this = activity
.addApi(LocationServices.API)
.addConnectionCallbacks(this) //interfaces implemented
.addOnConnectionFailedListener(this)
.build();
}
Requesting location,
// Create the location request
mLocationRequest = LocationRequest.create()
.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
.setInterval(UPDATE_INTERVAL)
.setFastestInterval(FASTEST_INTERVAL);
// Request location updates
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient,
mLocationRequest, this);
Try the last known location, if that requirement works for you,
#Override
public void onConnected(Bundle bundle) {
Location mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
...}
onConnected() is the callback from GoogleApiClient...
So there is more to location than initialising a client and implementing the listener. I recommend you go through a few questions or android docs to ensure you implement what suits your requirement.
Also,
instead of
Intent gpsOptionsIntent = new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS); ,
use SettingsApi
can refer to Enabling location mode...
Some useful Q&As:
Comprehensive answer for obtaining location
Good to go through LocationRequest part here if you want to avoid reading in detail

final LocationManager manager;
manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Do i even have to comment on this one? Read it again and you will understand what is wrong with it.
Hint. Try:
final LocationManager manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

You can used fused location api to get the location
Fused Location Api :
Fused Location Provider automatically decides best location from the available options for that it uses GPS and Network Provider, So if the device GPS is off we can still get the location from Network provider vice versa.
Why Fused Location Api ?
Consumption of power while fetching location.
It will give accurate
location based on user priority.
Piggyback which means you can get
location every time when other application hits for location for you
advantage is user not blame you for that you just getting those
location which other application request.
We don’t have to pick the
provider(GPS or network provider)
please refer code for following for getting location.
LocationService : We required these for getting continues location and these register as pending intent so whenever device got new location these service invoke.
public class LocationService extends IntentService {
private String TAG = this.getClass().getSimpleName();
public LocationService() {
super("Fused Location");
}
public LocationService(String name) {
super("Fused Location");
}
#Override
protected void onHandleIntent(Intent intent) {
Location location = intent.getParcelableExtra(LocationClient.KEY_LOCATION_CHANGED);
if(location !=null){
Log.i(TAG, "onHandleIntent " + location.getLatitude() + "," + location.getLongitude());
// write your code here.
}
}
}
MainActivity : which register callbacks for it which tell us whether we are connected or disconnected with api.
public class MainActivity extends Activity implements GooglePlayServicesClient.ConnectionCallbacks,GooglePlayServicesClient.OnConnectionFailedListener,LocationListener {
private String TAG = this.getClass().getSimpleName();
private LocationClient locationclient;
private LocationRequest locationrequest;
private Intent mIntentService;
private PendingIntent mPendingIntent;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mIntentService = new Intent(this,LocationService.class);
mPendingIntent = PendingIntent.getService(this, 1, mIntentService, 0);
int resp =GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
if(resp == ConnectionResult.SUCCESS){
locationclient = new LocationClient(this,this,this);
locationclient.connect();
}
else{
Toast.makeText(this, "Google Play Service Error " + resp, Toast.LENGTH_LONG).show();
}
}
public void buttonClicked(View v){
if(v.getId() == R.id.btnLastLoc){
if(locationclient!=null && locationclient.isConnected()){
Location loc =locationclient.getLastLocation();
Log.i(TAG, "Last Known Location :" + loc.getLatitude() + "," + loc.getLongitude());
txtLastKnownLoc.setText(loc.getLatitude() + "," + loc.getLongitude());
}
}
if(v.getId() == R.id.btnStartRequest){
if(locationclient!=null && locationclient.isConnected()){
if(((Button)v).getText().equals("Start")){
locationrequest = LocationRequest.create();
locationrequest.setInterval(Long.parseLong(etLocationInterval.getText().toString()));
locationclient.requestLocationUpdates(locationrequest, this);
((Button) v).setText("Stop");
}
else{
locationclient.removeLocationUpdates(this);
((Button) v).setText("Start");
}
}
}
if(v.getId() == R.id.btnRequestLocationIntent){
if(((Button)v).getText().equals("Start")){
locationrequest = LocationRequest.create();
locationrequest.setInterval(100);
locationclient.requestLocationUpdates(locationrequest, mPendingIntent);
((Button) v).setText("Stop");
}
else{
locationclient.removeLocationUpdates(mPendingIntent);
((Button) v).setText("Start");
}
}
}
#Override
protected void onDestroy() {
super.onDestroy();
if(locationclient!=null)
locationclient.disconnect();
}
#Override
public void onConnected(Bundle connectionHint) {
Log.i(TAG, "onConnected");
txtConnectionStatus.setText("Connection Status : Connected");
}
#Override
public void onDisconnected() {
Log.i(TAG, "onDisconnected");
txtConnectionStatus.setText("Connection Status : Disconnected");
}
#Override
public void onConnectionFailed(ConnectionResult result) {
Log.i(TAG, "onConnectionFailed");
txtConnectionStatus.setText("Connection Status : Fail");
}
#Override
public void onLocationChanged(Location location) {
if(location!=null){
Log.i(TAG, "Location Request :" + location.getLatitude() + "," + location.getLongitude());
}
}
}
For more reference refer below link
https://github.com/riteshreddyr/fused-location-provider
https://github.com/kpbird/fused-location-provider-example
Hope these help you.

To many AsyncTask with upload at same time

please excuse my bad English I hope my explanations are understandable.
I am working on app, wich communicate with my server. It has different tasks. One of them is to upload my pictures from my smartphone to my server. I want, that my app do this in the background, with minimized use of memory and bandwidth.
Basically it works, but when I have to many new pictures, there are to many AsyncTask at the same time and reduce memory and bandwidth perceptible.
First I use a BroadcastReceiver, which start every 30 min my picture scanner.
The Scanner frist check, if the External Storage is readable, if is WIFI on and if there is a Internet Connection.
When that is true it query a list from pictures, which are already uploaded, from the database.
Then it request all pictures from the MediaStore library, check some minimum values (size, height, width) and if the pic isn't uploaded. When everything is ok, it start an AsyncTask for resize the image and upload it:
public class Scanner {
private Context context;
private PicDAO picDAO;
private Helper helper;
public Scanner(Context context) {
this.context = context;
picDAO = new PicDAO(context);
helper = new Helper(context);
}
public void startScan(){
if(helper.isExternalStorageReadable()
&& helper.isWifiOn()
&& helper.checkInternet()){
HashMap<Integer, String> pics = picDAO.picsHashMap();
Cursor mCursor = context.getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,null,null,null,MediaStore.Images.Media.DEFAULT_SORT_ORDER);
if(mCursor != null){
mCursor.moveToFirst();
while(!mCursor.isAfterLast()) {
PicClass pic = new PicClass(
mCursor.getInt(mCursor.getColumnIndex(MediaStore.Images.Media._ID)),
mCursor.getString(mCursor.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME)),
mCursor.getString(mCursor.getColumnIndex(MediaStore.Images.Media.DATA)),
mCursor.getInt(mCursor.getColumnIndex(MediaStore.Images.Media.WIDTH)),
mCursor.getInt(mCursor.getColumnIndex(MediaStore.Images.Media.HEIGHT)),
mCursor.getInt(mCursor.getColumnIndex(MediaStore.Images.Media.SIZE)),
context
);
if(pic.getSize() > 25000
&& pic.getHeight() > 200
&& pic.getWidth() > 200
&& ( pics.get(pic.getIdent()) == null || !pics.get(pic.getIdent()).equals(pic.getDisplay_name()))
){
CreateThumb createThumb = new CreateThumb(context);
createThumb.execute(new PicClass[]{pic});
}
mCursor.moveToNext();
}
mCursor.close();
}
}
}
}
The creatThumb looks resize the Image and start a upload (using the volley library):
public class CreateThumb extends AsyncTask {
private Context context;
public CreateThumb(Context context) {
this.context = context;
}
#Override
protected PicClass doInBackground(PicClass... pics) {
Helper helper = new Helper(context);
String encodedString = "";
if(helper.isWifiOn() && helper.checkInternet()){
double dWidth = 1000;
double dHeight = 1000;
if(pics[0].getWidth() < (int) dWidth && pics[0].getHeight() < (int) dHeight){
dWidth = pics[0].getWidth();
dHeight = pics[0].getHeight();
}else{
if (pics[0].getWidth() > pics[0].getHeight()){
double div = pics[0].getWidth() / dWidth;
dHeight = pics[0].getHeight() / div;
}else{
double div = pics[0].getHeight() / dHeight;
dWidth = pics[0].getWidth() / div;
}
}
int width = (int) dWidth;
int height = (int) dHeight;
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
Bitmap bitmap = BitmapFactory.decodeFile(pics[0].getPath(),bmOptions);
Bitmap thumbnail = ThumbnailUtils.extractThumbnail(bitmap,width,height,0);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
thumbnail.compress(Bitmap.CompressFormat.JPEG, 90, stream);
byte[] byte_arr = stream.toByteArray();
encodedString = Base64.encodeToString(byte_arr, 0);
}
pics[0].setThumb_file(encodedString);
return pics[0];
}
#Override
protected void onPostExecute(final PicClass pic) {
if(!pic.getThumb_file().equals("")){
RequestQueue queue = Volley.newRequestQueue(context);
String url ="http://example.de/upload.php";
StringRequest postRequest = new StringRequest(Request.Method.POST, url, new Response.Listener<String>(){
#Override
public void onResponse(String response) {
if(response.equals("OK")){
PicDAO picDAO = new PicDAO(context);
picDAO.savePic(pic);
}
}
},
new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {}
}
){
#Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<>();
params.put("img",pic.getThumb_file());
params.put("filename",pic.getDisplay_name() + ".jpg");
return params;
}
};
queue.add(postRequest);
}
}
}
The script on my server:
<?php
$base = $_POST['img'];
$filename = $_POST['filename'];
$binary = base64_decode($base);
$file = fopen('uploadedimages/'.$filename, 'wb');
fwrite($file, $binary);
fclose($file);
echo "OK";
The Problem is, when I have to many new pictures, it slow down the device and the internet connection, and I get this errors:
W/art: Suspending all threads took: 278.260ms
D/Volley: [2790] BasicNetwork.logSlowRequests: HTTP response for request=<[ ] http://example.de/upload.php 0x8a9f5792 NORMAL 1> [lifetime=3447], [size=2], [rc=200], [retryCount=1]
How can I optimize my code or prevent that I have to many uploads simultaneously.
EDIT
I tried to rebuild the scanner part and use only one Queue where I add the request. But it seems like it doesn't work. When there is only one picture it works, but when the script add more than on request, it get no response an on the server is just the first picture.
public class Scanner {
private Context context;
private PicDAO picDAO;
private Helper helper;
public Scanner(Context context) {
this.context = context;
picDAO = new PicDAO(context);
helper = new Helper(context);
}
public void startScan(){
if(helper.isDeviceReady()){
Cursor mCursor = context.getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,null,null,null,MediaStore.Images.Media.DEFAULT_SORT_ORDER);
if(mCursor != null){
final RequestQueue mRequestQueue = Volley.newRequestQueue(context);
mCursor.moveToFirst();
while(!mCursor.isAfterLast()) {
final PicClass pic = new PicClass(mCursor, context);
if(pic.checkSize() && !picDAO.picExist(pic)){
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
Bitmap bitmap = BitmapFactory.decodeFile(pic.getPath(),bmOptions);
Bitmap thumbnail = ThumbnailUtils.extractThumbnail(bitmap,pic.getNewSize()[0],pic.getNewSize()[1],0);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
thumbnail.compress(Bitmap.CompressFormat.JPEG, 90, stream);
byte[] byte_arr = stream.toByteArray();
pic.setThumb_file(Base64.encodeToString(byte_arr, 0));
StringRequest postRequest = new StringRequest(Request.Method.POST, "http://example.de/upload.php", new Response.Listener<String>(){
#Override
public void onResponse(String response) {
Log.d("DEBUG",response);
if(response.equals("OK")){
PicDAO picDAO = new PicDAO(context);
picDAO.savePic(pic);
}
}
},
new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
VolleyLog.e("Error: ", error.getMessage());
}
}
){
#Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<>();
params.put("img",pic.getThumb_file());
params.put("filename",pic.getDisplay_name() + ".jpg");
return params;
}
};
mRequestQueue.add(postRequest);
}
mCursor.moveToNext();
}
mCursor.close();
}
}
}
}

How can I optimize my code or prevent that I have to many uploads simultaneously
I'd drop AsyncTask in favor of using IntentService, which executes one job at the time and queues all the other. Of course the whole process is not as trivial as it may look so maybe using dedicated libraries like Android Priority Job Queue would be even better.

Well, to start don't make a new request queue for every upload. THe idea of a queue is that you add a bunch of requests to it, then run the queue and let Volley slowly go through the requests a small group of them at a time. You're creating dozens of queues, and I don't even see a call to run the queue.
I'd also be using a Thread rather than an AsyncTask. AsyncTasks should be one offs. In fact by using this many tasks you're starving out all the other things that may need a task, since they share a common Thread.

Why is my String initialization throwing a NullPointerError?

I've been writing an android application in Android Studio with the purpose of getting a JSONObject from the Google directions API (using the Volley library), then passing it to a new activity (where it will then just be printed, so that I can debug prior to working on parsing it). However upon running the app on my phone through ADB, LogCat returns this.
The method called by a submit button's onClick (which is when the app crashes) is:
public void submit(View view) {
Location location = LocationServices.FusedLocationApi.getLastLocation(locationClient);
String destination = findViewById(R.id.destinationInput).toString();
String url = "https://maps.googleapis.com/maps/api/directions/json?origin="
+ location.getLatitude()
+ location.getLongitude()
+ "&destination=" + destination
+ "&mode=driving"
+ avoids()
+ "departure_time=now"
+ "&key=" + getString(R.string.API_KEY);
RequestQueue requestQueue;
// Instantiate the cache
Cache cache = new DiskBasedCache(getCacheDir(), 1024 * 1024); // 1MB cap
// Set up the network to use HttpURLConnection as the HTTP client.
Network network = new BasicNetwork(new HurlStack());
// Instantiate the RequestQueue with the cache and network.
requestQueue = new RequestQueue(cache, network);
// Start the queue
requestQueue.start();
JsonObjectRequest jsObjRequest = new JsonObjectRequest
(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject dirs) {
Intent intent;
intent = new Intent(getApplicationContext(), DisplayDirections.class);
intent.putExtra("DIRECTIONS", dirs.toString());
startActivity(intent);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
}
});
// Add the request to the RequestQueue.
requestQueue.add(jsObjRequest);
}
private String avoids() {
String avoid = "avoid=";
boolean any = false;
if(((Switch) findViewById(R.id.avoidTollsSwitch)).isChecked()) {
avoid += "tolls";
any = true;
}
if(((Switch) findViewById(R.id.avoidMotorwaysSwitch)).isChecked()) {
if(any) avoid += "|";
avoid += "highways";
any = true;
}
if(((Switch) findViewById(R.id.avoidFerriesSwitch)).isChecked()) {
if(any) avoid += "|";
avoid += "ferries";
any = true;
}
if(any) return avoid;
else return "";
}
The LogCat log links to the line String url =, but I'm confused as to what's wrong with this line. As far as I can tell, my code should work...
Volley tutorial: https://developer.android.com/training/volley/simple.html

Are you sure that location is not null? Put a breakpoint on the String url = line and see what its value is.

If you are running it on the emulator you need to have sent coordinates to the emulator. Otherwise location will be null.
I was pulling my hair over it the first time I used geolocation services.
Just do a check like
if (location!=null) {
foo.doSomethingWithLocation(bar);
} else {
Log.d(TAG, "Sorry. Location is null");
}
before you call anything