Develop Reference

how to stay connected to the server

I'm trying to stay connected with a url but I don't know how.
I'm working on a quiz app so I need to refresh the question every time that user lose or win.
but it takes long time to connect to the url every time.
so I just want to connected once and then just get new questions from that url.
I'm using volley library to connect to a url.
And This is my code.
public static void getQuestionsData(Activity activity,
OnDoneLintenter onDoneListener) {
String url = "https://opentdb.com/api.php?amount=15&type=multiple";
RequestQueue queue = VolleySingleton.getInstance().getRequestQueue();
JsonObjectRequest jsonObjectRequest =
new JsonObjectRequest(ColumnStructure.GET, url, null,
jsonObject -> {
try {
JSONArray array
= jsonObject.getJSONArray(ColumnStructure.COL_RESULTS);
for (int i = 0; i < array.length(); i++) {
setColumnStructureFields(array, i);
}
onDoneListener.onDone();
} catch (JSONException e) {
Log.e("Log", "there is not result : " + e.getMessage());
}
},
volleyError -> {
Log.e("Log", "volley error : " + volleyError.getMessage());
});
queue.add(jsonObjectRequest);
}
I use this code at the beginning and every time user lose or win.So is there any way to stay connected with the url or at least get the json faster.

Getting the calling fragment within an asynchronous task

Aim
In a fragment, I have a search bar which looks for online news about what the user typed. I would want to display these news (title + description + date of publication + ... etc.) in the GUI, as vertical blocks.
Implementation
Explanations
In the fragment, within the search event handling, I instanciated an asynchronous task and execute it with the good URL REST API I use to do the search.
In the asynchronous task, I make use of this REST API (thanks to the URL and some required parameters as an authorization key, etc.). When my asynchronous task gets answered, it must update the fragment's GUI (i.e.: it must vertically stack GUI blocks containing the titles, descriptions, etc. of the got news).
Sources
You will find sources in the last part of this question.
My question
In the asynchronous task (more precisely: in its function that is executed after having got the answer), I don't know how to get the calling fragment. How to do this?
Sources
Fragment part
private void getAndDisplayNewsForThisKeywords(CharSequence keywords) {
keywords = Normalizer.normalize(keywords, Normalizer.Form.NFD).replaceAll("[^\\p{ASCII}]", "");
new NetworkUseWorldNews().execute("https://api.currentsapi.services/v1/search?keyword=" + keywords + "&language=en&country=US");
}
Asynchronous task part
public class NetworkUseWorldNews extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String[] urls) {
StringBuilder string_builder = new StringBuilder();
try {
URL url = new URL(urls[0]);
HttpsURLConnection https_url_connection = (HttpsURLConnection) url.openConnection();
https_url
_connection.setRequestMethod("GET");
https_url_connection.setDoOutput(false);
https_url_connection.setUseCaches(false);
https_url_connection.addRequestProperty("Authorization", "XXX");
InputStream input_stream = https_url_connection.getInputStream();
BufferedReader buffered_reader = new BufferedReader(new InputStreamReader(input_stream));
String line;
while((line = buffered_reader.readLine()) != null) {
string_builder.append(line);
}
buffered_reader.close();
} catch (IOException e) {
e.printStackTrace();
}
return string_builder.toString();
}
#Override
protected void onPostExecute(String result) {
try {
JSONObject news_response_http_call = new JSONObject(result);
switch(news_response_http_call.getString("status")) {
case "ok":
JSONArray news = news_response_http_call.getJSONArray("news");
for(int i = 0; i < news.length(); i++) {
JSONObject a_news = news.getJSONObject(i);
String title = a_news.getString("title");
String description = a_news.getString("description");
String date_of_publication = a_news.getString("published");
String url = a_news.getString("url");
String image = a_news.getString("image");
System.out.println(title + ": " + date_of_publication + "\n" + image + "\n" + url + "\n" + description);
WorldNewsFragment world_news_fragment = ...;
}
break;
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}

If I am right, you want to update View of your caller Fragment. if FragmentA called service then FragmentA should be update.
However the approach you are asking is wrong. Instead of getting caller Fragment in your AsyncTask response. You should do it with Callback.
So now you will need to pass callback in AsyncTask. So instead of posting full code, here are already answers with this problem.
Finally your calling syntax will look like.
NetworkUseWorldNews task = new NetworkUseWorldNews(new OnResponseListener() {
#Override
public void onResponse(String result) {
// Either get raw response, or get response model
}
});
task.execute();
Actually I am still very unclear about your question. Let me know in comments if you have more queries.
Must checkout
Retrofit or Volley for calling Rest APIs
Gson for parsing JSON response automatically to models

Firebase: Allow access depending on time difference (server-side-time)

So I have a database that looks like this:
Posts
|
|
|----post_id_1
|
|---post_title = "...."
|---post_body = "...."
|---post_time = "ServerValue.TIME_STAMP"
|
|----post_id_2
|.......
|.......
What I want to do:
I want to prevent a user to read a post that is greater than or equal a month from the day that it was posted?
What I tried:
I tried to use this method by android:
//current time of device
long current_time = System.currentTimeMillis();
//month in millisecond
long month = .....;
if(curent_time - post_time >= month){
//this post was there for a month from the time that it was posted.
}
Problem:
If I use the above method then if a user was smart enough he/she will change the time of the device to enter a post (when they shouldn't).
Question:
Any stable way of doing this?
Thanks.
NOTE: WITHOUT GETTING THE TIME STAMP FROM THE SERVER.

I have been through the same issue, how I solved that was pinging Google for the time, and then just store that time in Firebase, that way I can compare the last time the user did something and that time will be server time and can't be changed.
So, in my case I upload that server time each time my app enters in the onStop or onDestroy method, but you can use it anywhere you need to save to your database.
Here is the snippet to get server time, I use an asyncTask in order to fetch the server time and then just post it in my reference. Just call the asyncTask where you want to update something with server time.
public class getGoogleTime extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... voids) {
try {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = httpclient.execute(new HttpGet("https://google.com/"));
StatusLine statusLine = response.getStatusLine();
if (statusLine.getStatusCode() == HttpStatus.SC_OK) {
DateFormat df = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss z", Locale.ENGLISH);
dateStr = response.getFirstHeader("Date").getValue();
Date startDate = df.parse(dateStr);
dateStr = String.valueOf(startDate.getTime() / 1000);
long actualTime = java.lang.Long.parseLong(dateStr);
//Here I do something with the Date String
} else {
//Closes the connection.
response.getEntity().getContent().close();
throw new IOException(statusLine.getReasonPhrase());
}
} catch (IOException e) {
Log.d("SAF_GTG_Response", e.getMessage());
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
// can use UI thread here
protected void onPostExecute(final Void unused) {
mDatabase.child("Posts").child(post_id_1).child("currentTime").setValue(dateStr, new DatabaseReference.CompletionListener() {
#Override
public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
Log.d("SAF_GTG_TAG", "Success");
}
});
}
}
To work with Firebase you can do this:
ref = FirebaseDatabase.getInstance().getReference();
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Long timestamp = (Long) snapshot.getValue();
System.out.println(timestamp);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
ref.setValue(ServerValue.TIMESTAMP);
NOTE: this method just returns UTC time, you can convert it the way you want to display it to each user.
If you are worried about network usage, just ping Google and see how many bytes and packages are being used.
Pinging google.com [172.217.162.14] with 32 bytes of data:
Reply from 172.217.162.14: bytes=32 time=17ms TTL=53
Reply from 172.217.162.14: bytes=32 time=17ms TTL=53
Reply from 172.217.162.14: bytes=32 time=17ms TTL=53
Reply from 172.217.162.14: bytes=32 time=16ms TTL=53
Ping statistics for 172.217.162.14:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 16ms, Maximum = 17ms, Average = 16ms
From the docs:
The bandwidth consumption of a simple ping command, being run one time
per second, is relatively small. The smallest ping packet possible
(including the Ethernet frame header and the IP + ICMP headers, plus
the minimum 32 bytes of the ICMP payload) takes 74 bytes
around 0,074 kilobytes.

I would store the TIME_STAMP as UTC and get the time from the server, not use the time from the device.
In that case the user cannot change the time on the device to modify the output from the database.
I would recommend to always store all dates as UTC and just convert them to the user timezone when the user views them.

How to get aws-iot thing shadow on android app

want to start development with AWS IOT using Android app
I am seeking for example for IOT in android. need to start basic configuration on AWS console and android app. i already tested temperature demo but didn't get any clue from that! need a basic steps on shadow, policy , role. how to configure them step by step and use of cognito.
below getshadow() method is called onCreate , need to update value on real time basis not ony onCreate.
public void getShadows() {
GetShadowTask getControlShadowTask = new GetShadowTask("TemperatureControl");
getControlShadowTask.execute();
}
private class GetShadowTask extends AsyncTask<Void, Void, AsyncTaskResult<String>> {
private final String thingName;
public GetShadowTask(String name) {
thingName = name;
}
#Override
protected AsyncTaskResult<String> doInBackground(Void... voids) {
try {
GetThingShadowRequest getThingShadowRequest = new GetThingShadowRequest()
.withThingName(thingName);
GetThingShadowResult result = iotDataClient.getThingShadow(getThingShadowRequest);
// Toast.makeText(getApplication(),result.getPayload().remaining(),Toast.LENGTH_LONG).show();
byte[] bytes = new byte[result.getPayload().remaining()];
result.getPayload().get(bytes);
String resultString = new String(bytes);
return new AsyncTaskResult<String>(resultString);
} catch (Exception e) {
Log.e("E", "getShadowTask", e);
return new AsyncTaskResult<String>(e);
}
}
#Override
protected void onPostExecute(AsyncTaskResult<String> result) {
if (result.getError() == null) {
JsonParser parser=new JsonParser();
JsonObject jsonObject= (JsonObject) parser.parse(result.getResult());
response=result.getResult();
setPoint=jsonObject.getAsJsonObject("state").getAsJsonObject("reported")
.get("current_date").getAsString();
textView.setText(setPoint);
// Toast.makeText(getApplication(),setPoint,Toast.LENGTH_LONG).show();
Log.i(GetShadowTask.class.getCanonicalName(), result.getResult());
} else {
Log.e(GetShadowTask.class.getCanonicalName(), "getShadowTask", result.getError());
Toast.makeText(getApplication(),result.getError().toString(),Toast.LENGTH_LONG).show();
}
}
}
UPDATE
Thing Shadow
{
"desired": {
"welcome": "aws-iot"
},
"reported": {
"welcome": "aws-iot",
"current_date": "06-Sep-2017 1:26:40 PM"
}
}

AWS has provided a complete Github repo of Android samples. In the samples do the PubSubWebSocket to connect, subscribe and publish the data to the shadow.
If you have a closer look into the PubSubWebSocket example you will find a detailed information on how to to make a thing policy and role. It cannot be more concise and clear than that.
For understanding and using Cognito follow AmazonCognitoAuthDemo example to make the identity pool and use it in the PubSubWebSocket example.
To get a better understanding of roles and Cognito. Please read the AWS documentation.
Update:
In the IoT thing policy did you give appropriate permissions to connect, subscribe and publish. The option can be found in AWS IoT->Security->Policy->Create Policy.
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "iot:*",
"Resource": "arn:aws:iot:us-east-2:293751794947:topic/replaceWithATopic"
}
]
}
The above policy gives all access to the user. Also, make sure your pool which you created is for unauthenticated users.
To get the changes to the shadow type the following in the sample android(WebSocketAwsPubSub) edit box $aws/things/thing_name/shadow/update/accepted
And to publish the data to the shadow type $aws/things/thing_name/shadow/update
Update 2:
Android Code where you will receive the reported messaged. Its suscribing to the device. Its the copy of the snippet from PubSubWebSocketSample.
public void AwsSubscribe(){
final String topic = "$aws/things/D1/shadow/update/accepted";
Log.d(LOG_TAG, "topic = " + topic);
try {
mqttManager.subscribeToTopic(topic, AWSIotMqttQos.QOS0,
new AWSIotMqttNewMessageCallback() {
#Override
public void onMessageArrived(final String topic, final byte[] data) {
runOnUiThread(new Runnable() {
#Override
public void run() {
try {
String message = new String(data, "UTF-8");
Log.d(LOG_TAG, "Message arrived:");
Log.d(LOG_TAG, " Topic: " + topic);
Log.d(LOG_TAG, " Message: " + message);
tvLastMessage.setText(message);
} catch (UnsupportedEncodingException e) {
Log.e(LOG_TAG, "Message encoding error.", e);
}
}
});
}
});
} catch (Exception e) {
Log.e(LOG_TAG, "Subscription error.", e);
}
}

If you want to create a topic, just change the value of this variable final String topic = "YOUR TOPIC" then subscribe to it by using the sample code.

Android: Am I doing client-side or server-side Geocoding?

So in my app I am making use of google map apis and I'm using Geocoding to determine the Address based on the user's current location. I was using the Geocoder Android Class but I've found that it truly works terribly. It's just not reliable. So I used a post I saw here at SO to create my own Geocoder. Problem is, I now don't know if I'm using server side or client side geocoding. This is kind of important because one has a limit and the other really doesn't. All of my code is in Android though.
Here's some code, this is within my "MyGeocoder" Class:
public List<Address> getFromLocation(double latitude, double longitude,
int maxResults) throws IOException, LimitExceededException {
if (latitude < -90.0 || latitude > 90.0) {
throw new IllegalArgumentException("latitude == " + latitude);
}
if (longitude < -180.0 || longitude > 180.0) {
throw new IllegalArgumentException("longitude == " + longitude);
}
if (isLimitExceeded(context)) {
throw new LimitExceededException();
}
final List<Address> results = new ArrayList<Address>();
final StringBuilder url = new StringBuilder(
"http://maps.googleapis.com/maps/api/geocode/json?sensor=true&latlng=");
url.append(latitude);
url.append(',');
url.append(longitude);
url.append("&language=");
url.append(Locale.getDefault().getLanguage());
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url.toString());
try {
HttpResponse response = httpclient.execute(httppost);
String jsonResult = inputStreamToString(
response.getEntity().getContent()).toString();
Gson gson = new Gson();
MyGeocodeResponse geocodeResponse = gson.fromJson(jsonResult, MyGeocodeResponse.class);
final Address current = new Address(Locale.getDefault());
if(geocodeResponse.getStatus().equals(STATUS_OK)) {
MyGeocode locGeocode= geocodeResponse.getResults().get(0);
String streetAddress = "";
for(MyAddressComponent component : locGeocode.getAddress_components()) {
for(String type : component.getTypes()) {
if(type.equals("locality")) {
current.setLocality(component.getLong_name());
}
if(type.equals("administrative_area_level_1")) {
current.setAdminArea(component.getLong_name());
}
if(type.equals("street_number")) {
if(streetAddress.length() != 0) {
current.setAddressLine(0, component.getLong_name() + " " + streetAddress);
} else {
streetAddress = component.getLong_name();
}
}
if(type.equals("route")) {
if(streetAddress.length() != 0) {
current.setAddressLine(0, streetAddress + " " + component.getShort_name());
} else {
streetAddress = component.getShort_name();
}
}
}
}
current.setLatitude(latitude);
current.setLongitude(longitude);
results.add(current);
}
Log.i("TEST", "Got it");
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return results;
}
Edit:
And I guess a further questions is, if this is server-side Geocoding, then can this code only be run 2,500 times per day period, or can it be run 2,500 times daily per user of the app? If it's the first option I'm still ok, but if it's the 2nd option I don't see how any app that wants to have a half-way big user base can use server-side geocoding without hitting that limit.

I now don't know if I'm using server side or client side geocoding
after looking to your code you wrote http://maps.googleapis.com/maps/api/geocode/json?sensor=true&latlng=,so it is server side reverse geocoding as you are calling geocoding api by making an extra External http call.
if this is server-side Geocoding, then can this code only be run 2,500 times per day period, or can it be run 2,500 times daily per user of the app?
2,500 request limit is per IP address(basically it is mentioning 2500 request per day),yah this code only be run 2,500 times per day for all of your user.One thing you should keep in mind you are making http call to geocoder api so it doesn't matter from where you are making this call from server or from client.
you should have a look on this google link where they have mention "When to Use Client-Side Geocoding" and "When to Use Server-Side Geocoding".