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my listview does not print out my array list after importing it from my file

The listview does not show the string array file and I cant seem to view string that the user input
public class ReadActivity extends ListActivity {
String[] mStringArray;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ListView listview = getListView();
FileWritter fl = new FileWritter();
List<String> mStringList = fl.loadlist2("DiaryNames.txt",this);
mStringArray = new String[mStringList.size()];
mStringArray = mStringList.toArray(mStringArray);
ArrayAdapter<String> adapter = new ArrayAdapter<String>
(this,android.R.layout.simple_list_item_1,mStringArray);
listview.setAdapter(adapter);
setListAdapter(adapter);
So far this is the code where I think has the problem for loadlist2 so this is for the list to import file from diarynames.txt which has input from another function is
public List<String> loadlist2(String title, Context context)
{
List<String> list = new ArrayList<>();
try {
BufferedReader in = new BufferedReader(
new FileReader(title));
String mystring;
while ((mystring = in.readLine()) != null) {
list.add(mystring);
}
}
catch (IOException e) {
System.out.println("Exception Occurred" + e);
}
return list;
}
}

Are you sure you don't get
System.out.println("Exception Occurred" + e); ?

#BabyYakuza - Before I start with my answer, I would like to ask you; can you please post the contents of the file DiaryNames.txt? If you don't have it, can you tell us the format of the text in this file? Also, where is this file present (I mean in your directory structure)? This is because, everything else you are doing seems to be okay.
I ran through your code in my IDE. I am using the following contents for DiaryNames.txt
Ashish Raghavan
Sushant Shivaprasad
Piyush Murari
Mohan Nair
Tushar Nair
When I run through your code,
List<String> list = new ArrayList<>();
try {
BufferedReader in = new BufferedReader(
new FileReader(title));
String mystring;
while ((mystring = in.readLine()) != null) {
list.add(mystring);
}
}
catch (IOException e) {
System.out.println("Exception Occurred" + e);
}
return list;
I get the correct output of 5 strings as in the number of names mentioned in the file DiaryNames.txt.
Also, you don't need the context argument in loadlist2 as you are not using that anywhere. Anyhow, here is my pastebin code Main method and FileWritter.java.
Please modify the path for the file DiaryNames.txt if you use this code. Also, I have not passed anything in the loadlist2() method because it is always the filename DiaryNames.txt and the Context variable, which is unused in the method.
Most probably, the format of the text in DiaryNames.txt is not what you are expecting. If you can post some sample content of the file DiaryNames.txt, it would really help us help you.

How to integrate fetched JSON data with Room Persistence library

I am developing an Android Application (Android Studio - Java) which includes a sign in and registration process. I took care of the sign in and registration processes by implementing a connection between PHP files and a MySQL database through http. In short, I just created an AsyncTask class in java --called from another class-- and used it to post data to a PHP file, from there I just used the appropriate SQL commands. This part works fine.
This first part with the login and registration is important because every user will see a slightly different layout once they login. The layout is a RecyclerView composed of detailed CardView elements. Each CardView has a few TextViews with some details. The details are held by an Object i created in a separate class. To fill in the CardView elements a fetched some JSON data using a separate PHP file (and one more http connection). Parsing the data from JSON into Strings and ints was a straightforward endeavor, as was adding them to the list of custom objects. There is some code below showing how I fetched the data and added it to the Object list.
This is the complete AsyncTask class:
public class ScheduleWorker extends AsyncTask<String, Void, String> {
Context context;
AlertDialog alertDialog;
ScheduleWorker (Context ctx) { context = ctx; }
#Override
protected void onPreExecute() { super.onPreExecute(); }
#Override
protected void onPostExecute (String s) {
super.onPostExecute(s);
Toast.makeText(context, s, Toast.LENGTH_SHORT).show();
try {
loadJSON(s);
} catch (JSONException e) {
e.printStackTrace();
}
}
#Override
protected String doInBackground(String... params) {
final String fetch_url = "http://192.168.1.70/newfetcher.php";
try {
String ussr_name = params[0];
URL url = new URL(fetch_url);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("POST");
con.setDoOutput(true);
con.setDoInput(true);
OutputStream outputStream = con.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
String post_data = URLEncoder.encode("user_name", "UTF-8")+"="+URLEncoder.encode(ussr_name, "UTF-8");
bufferedWriter.write(post_data);
bufferedWriter.flush();
bufferedWriter.close();
outputStream.close();
StringBuilder sb = new StringBuilder();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String json;
while ((json = bufferedReader.readLine()) != null) {
sb.append(json + "\n");
}
return sb.toString().trim();
} catch (Exception e) {
return null;
}
}
private void loadJSON(String json) throws JSONException {
JSONArray jsonArray = new JSONArray(json);
Course course;
List<Course> courses = new ArrayList<Course>();
int len = jsonArray.length();
String[] titles = new String[len];
String[] types = new String[len];
String[] teachers = new String[len];
int[] pics = new int[len];
for (int i = 0; i < len; i++) {
JSONObject obj = jsonArray.getJSONObject(i);
titles[i] = obj.getString("title");
types[i] = obj.getString("type");
teachers[i] = obj.getString("teacher");
pics[i] = obj.getInt("pic");
course = new Course(titles[i], types[i], teachers[i], pics[i]);
courses.add(course);
}
}
}
Now, where I encountered problems is when I tried saving the List of Objects (and their details) to a Room Persistent Database. I based my code for the Room Database off an example from Google Developer CodeLabs. I adapted the code for my particular needs but I kept the underlying class structure. The structure includes: an Entity, a DAO, a RoomDatabase, a Repository, a ViewModel, a ViewHolder, an Adapter for the RecyclerView, and a class to populate the database. Everything seems fine except for the part where I populate the database. The example populates the database by using a callback and an AsyncTask within the RoomDatabase class.
Here is populating AsyncTask:
private static RoomDatabase.Callback sRoomDatabaseCallback = new RoomDatabase.Callback() {
#Override
public void onOpen(#NonNull SupportSQLiteDatabase db) {
super.onOpen(db);
// If you want to keep the data through app restarts,
// comment out the following line.
new PopulateDbAsync(INSTANCE).execute();
}
};
/**
* Populate the database in the background.
* If you want to start with more words, just add them.
*/
private static class PopulateDbAsync extends AsyncTask<Void, Void, Void> {
private final WordDao mDao;
PopulateDbAsync(WordRoomDatabase db) {
mDao = db.wordDao();
}
#Override
protected Void doInBackground(final Void... params) {
// Start the app with a clean database every time.
// Not needed if you only populate on creation.
Word word = new Word("Hello");
mDao.insert(word);
word = new Word("World");
mDao.insert(word);
return null;
}
}
My question is how do I populate the database with the detail arrays and/or the Object list? The example executes the callback every time a adding activity is called. I just want to populate the database when the user registers.

AsyncTask doInBackground to return multiple strings

I'm trying to build a very basic weather app in android studio. I am using AsyncClass to return multiple strings.
As you can see in the code, I used a class named "Wrapper" that is used to store my strings so I can just return a class object and use it in the onPostExecute method of the AsyncTask. The problem I am facing is that when I test the app, all of the returned Strings somehow are undefined (the default for the Wrapper class). This means the strings are not being updated in the doInBackground method and I can't seem to figure out why!
My Activity
#Override
public void onConnectionFailed(ConnectionResult connectionResult) {
Log.i(MainActivity.class.getSimpleName(), "Can't connect to Google Play Services!");
}
private class Wrapper
{
String Temperature = "UNDEFINED";
String city = "UNDEFINED";
String country = "UNDEFINED";
}
private class GetWeatherTask extends AsyncTask<String, Void, Wrapper> {
private TextView textView;
public GetWeatherTask(TextView textView) {
this.textView = textView;
}
#Override
protected Wrapper doInBackground(String... strings) {
Wrapper w = new Wrapper();
String Temperature = "x";
String city = "y";
String country = "z";
try {
URL url = new URL(strings[0]);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
InputStream stream = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));
StringBuilder builder = new StringBuilder();
String inputString;
while ((inputString = bufferedReader.readLine()) != null) {
builder.append(inputString);
}
JSONObject topLevel = new JSONObject(builder.toString());
JSONObject main = topLevel.getJSONObject("main");
JSONObject cityobj = topLevel.getJSONObject("city");
Temperature = String.valueOf(main.getDouble("temp"));
city = cityobj.getString("name");
country = cityobj.getString("country");
w.Temperature= Temperature;
w.city= city;
w.country=country;
urlConnection.disconnect();
} catch (IOException | JSONException e) {
e.printStackTrace();
}
return w;
}
#Override
protected void onPostExecute(Wrapper w) {
textView.setText("Current Temperature: " + w.Temperature + " C" + (char) 0x00B0
+"\n" + "Current Location: "+ w.country +"\n" + "City: "+ w.city );
}
}
}
UPDATE:
turned out that that I was using the wrong url in my code,I was using :
http://api.openweathermap.org/data/2.5/weather?lat=%f&lon=%f&units=%s&appid=%s
Instead I should've been using:
http://api.openweathermap.org/data/2.5/forecast?lat=%f&lon=%f&units=%s&appid=%s
-aka instead of weather I should've been using forcast

Your error starts here
JSONObject main = topLevel.getJSONObject("main");
Probably because the topLevel object has no "main" key.
{
"city":{ },
"cod":"200",
"message":0.1859,
"cnt":40,
"list":[ ]
}
Throw your JSON into here. https://jsonformatter.curiousconcept.com/
You'll notice that there are many, many "main" keys that are within the "list" element, but you have to parse those starting from getJSONArray("list").
Basically, something like this
String city = "undefined";
String country = "undefined";
List<Double> temperatures = new ArrayList<Double>();
try {
JSONObject object = new JSONObject(builder.toString());
JSONObject jCity = object.getJSONObject("city");
city = jCity.getString("name");
country = jCity.getString("country");
JSONArray weatherList = object.getJSONArray("list");
for (int i = 0; i < weatherList.length(); i++) {
JSONObject listObject = weatherList.getJSONObject(i);
double temp = listObject.getJSONObject("main").getDouble("temp");
temperatures.add(temp);
}
} catch (JSONException e) {
e.printStackTrace();
}
return new Wrapper(city, country, temperatures);

After studying your code, either your try block is failing, which is returning your object, but empty, or there is something wrong with your JSON parsing. If you could show us the JSON you are trying to parse that would be a great help.
That being said, the fact that it is still showing as "UNDEFINED" is because that is how you initialised it, and becuase (the JSON parse is likely failing), the object is being returned in an un-edited state.
EDIT:
You are parsing the JSON wrong. You are trying to find an object called "main" in the top directory, however the main object only exists inside of an array called list!
Please look here for a more easy to see and visual representation: http://prntscr.com/dlhlrk
You can use this site to help visualise your JSON and create an appropriate soluton based upon it. https://jsonformatter.curiousconcept.com/

Looking at the API you posted earlier (api.openweathermap.org) you are trying to access variables that don't exist. I suggest you have a look at what the API returns and try getting the variables one by one if you are getting a JSONException
EDIT:
What API you are using? In your initial post you said it was http://api.openweathermap.org/data/2.5/weather but in a comment above you said it was http://api.openweathermap.org/data/2.5/forecast.
If you're using the weather API (as initially stated) you can use the below:
#Override
protected Wrapper doInBackground(String... strings) {
Wrapper w = new Wrapper();
try {
URL url = new URL(strings[0]);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
InputStream stream = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));
StringBuilder builder = new StringBuilder();
String inputString;
while ((inputString = bufferedReader.readLine()) != null) {
builder.append(inputString);
}
Log.d("JSON", builder.toString());
JSONObject topLevel = new JSONObject(builder.toString());
JSONObject main = topLevel.getJSONObject("main");
JSONObject sys = topLevel.getJSONObject("sys");
w.Temperature = String.valueOf(main.getDouble("temp"));
w.city = topLevel.getString("name");
w.country = sys.getString("country");
urlConnection.disconnect();
} catch (IOException | JSONException e) {
e.printStackTrace();
}
return w;
}

Java code gets not executed

I developing android app and now I have problem. Below is a part of my code, and it keeps skipping the "for" part. When I put a breakpoint inside for statement, it stops at the point, and executes the lines very well and makes an output that I want. When I just 'run' app, it skips that part so "String locations" value doesn't change. I googled and some say it's thread-related problem. So I put synchroinzed on the method, still not working. Any other suggestions?
UPDATE
I was trying to show code only related to the problem, but I think now showing the whole would be more useful for those who try to help so here's my entire code on showMapActivity. You can see I've tried some ways around and nothing worked. Saving path's information into String url is where I'm having problem. I tested, and other parts seem to work fine. I know my code is really massy, that was why I only posted parts of the code. TMap related classes are imported from .jar file.
public class showMapActivity extends Activity {
TMapData tmapdata=new TMapData();
TMapView tmapView;
TMapPoint origin, dest;
volatile ArrayList<TMapPoint> points=new ArrayList<>();
private TextView x;
private TextView y;
private HashMap<String,LatLng> coordinates;
private HashMap<LatLng,Double> finalpoint;
static private ConcurrentHashMap<Double,Double> path;
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show_map);
coordinates=new HashMap<>();
Intent intent=getIntent();
tmapView=new TMapView(this);
path=new ConcurrentHashMap<>();
coordinates=(HashMap<String,LatLng>)intent.getSerializableExtra("coordinate");
path=getPathPoints(coordinates);
int i=0;
String url=getUrl();
//String url = "https://maps.googleapis.com/maps/api/elevation/json?locations=";
//String locations="";
/*
Iterator<Double> keys= path.keySet().iterator();
while(keys.hasNext()){
Double key=keys.next();
//String lat=String.valueOf(key);
//String lng=String.valueOf(path.get(key));
locations=locations+String.valueOf(key)+","+String.valueOf(path.get(key));
if(keys.hasNext())
locations=locations+"|";
}path.entrySet()
*/
/*
for(ConcurrentHashMap.Entry<Double,Double> elem : path.entrySet())
{
String lat=String.valueOf(elem.getKey());
String lng=String.valueOf(elem.getValue());
locations=locations+lat+","+lng;
i++;
if(i!=path.size())
{
locations=locations+"|";
}
}
*/
//url=url+locations+"&key=AIzaSyDD88VFMPIfC5sr0XsFL0PDCE-QRN8gQto";
//String url=getUrl(path);
FetchUrl fetchUrl=new FetchUrl();
fetchUrl.execute(url);
}
private ConcurrentHashMap<Double,Double> getPathPoints(HashMap<String,LatLng> coordinates)
{
final ConcurrentHashMap<Double,Double> Path=new ConcurrentHashMap<>();
tmapView.setSKPMapApiKey("6bb5b7f3-1274-3c5e-ba93-790aee876673");
origin=new TMapPoint(coordinates.get("origin").latitude,coordinates.get("origin").longitude);
dest=new TMapPoint(coordinates.get("dest").latitude,coordinates.get("dest").longitude);
tmapdata.findPathData(origin, dest, new TMapData.FindPathDataListenerCallback() {
#Override
public void onFindPathData(TMapPolyLine polyLine) {
points=polyLine.getLinePoint();
for(TMapPoint point : points )
Path.put(point.getLatitude(),point.getLongitude());
}
});
return Path;
}
//ConcurrentHashMap<Double,Double> path
private synchronized String getUrl() {
int i=0;
String url = "https://maps.googleapis.com/maps/api/elevation/json?locations=";
String locations="";
for(HashMap.Entry<Double,Double> elem : path.entrySet())
{
String lat=String.valueOf(elem.getKey());
String lng=String.valueOf(elem.getValue());
locations=locations+lat+","+lng;
i++;
if(i!=path.size())
{
locations=locations+"|";
}
}
url=url+locations+"&key=AIzaSyDD88VFMPIfC5sr0XsFL0PDCE-QRN8gQto";
//https://maps.googleapis.com/maps/api/elevation/json?locations=
// 39.7391536,-104.9847034|36.455556,-116.866667&key=AIzaSyDD88VFMPIfC5sr0XsFL0PDCE-QRN8gQto
// Output format
return url;
}
private class FetchUrl extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... url) {
// For storing data from web service
String data = "";
try {
// Fetching the data from web service
//downloadURL
data = downloadUrl(url[0]);
Log.d("Background Task data", data.toString());
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
//ParserTask
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
}
private String downloadUrl(String strUrl) throws IOException {
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try {
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
//읽은 데이터를 버퍼에 저장
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while ((line = br.readLine()) != null) {
sb.append(line);
}
data = sb.toString();
Log.d("downloadUrl", data.toString());
br.close();
} catch (Exception e) {
Log.d("Exception", e.toString());
} finally {
iStream.close();
urlConnection.disconnect();
}
return data;
}
private class ParserTask extends AsyncTask<String, Integer, ArrayList<Double>> {
// Parsing the data in non-ui thread
#Override
protected ArrayList<Double> doInBackground(String... jsonData) {
JSONObject jObject;
ArrayList<Double> altitude = null;
try {
jObject = new JSONObject(jsonData[0]);
Log.d("ParserTask",jsonData[0].toString());
//DataParser class 호출
DataParser parser = new DataParser();
Log.d("ParserTask", parser.toString());
// Starts parsing data
altitude = parser.parse(jObject);
Log.d("ParserTask","Getting Altitudes");
Log.d("ParserTask",altitude.toString());
} catch (Exception e) {
Log.d("ParserTask",e.toString());
e.printStackTrace();
}
return altitude;
}
// Executes in UI thread, after the parsing process
#Override
protected void onPostExecute(ArrayList<Double> result) {
finalpoint=new HashMap<>();
LatLng latLng;
int i=0;
for(HashMap.Entry<Double,Double> elem : path.entrySet() )
{
latLng=new LatLng(elem.getKey(),elem.getValue());
finalpoint.put(latLng,result.get(i++));
}
x = (TextView) findViewById(R.id.textView5);
y = (TextView) findViewById(R.id.textView6);
x.setText(String.valueOf(finalpoint.get(coordinates.get("origin"))));
y.setText(String.valueOf(finalpoint.get(coordinates.get("dest"))));
}
}
}

(Apologies for posting this as an answer - I don't yet have the required reputation to comment)
Simply adding synchronized to a method doesn't necessarily guarantee thread safety.
How and when is path being populated?
Update after additional information provided
The problem seems to be that the path points are being generated asynchronously, and you are trying to use them before the generation process has finished (or perhaps even started). This happens because the findPathData simply starts the generation process and returns immediately (i.e. before the generation process has finished). In your code, you then go on and build the URL which is supposed to contain the point data immediately. At this point the background point generation process may not have finished, and may not have even started. As a result the point map may be empty or incomplete, and your URL will not be generated as you expect.
You need to find a way to wait until all of the path point data has been returned by the asynchronous processing before creating the URL. This looks like it could be very difficult, if not impossible, with the version of the findPathData method you are using, because it returns points via the callback one at a time and you may not know how many will be generated.
I had a quick look at the API for TMapData and it has a findPathDataAll method which seems to generate all the points and return them in a single callback call rather than one by one. If this is indeed what it does (sorry, I can't read Korean), you could use this method and then generate the URL from the callback, because when it's called you know that the generation process has been completed. If you do this, be careful to make sure that you're on the main thread before interacting with the UI or Activity.
Hope that helps.

get JSON object with API client

Im trying to get JSONobject from api but i cant get this piece of code to work.
I am new to android and java and JSON. i keep getting the error: in JSONobject cannot be applied
Main code:
try {
APIClientJSONObject api = new APIClientJSONObject();
JSONObject result = null;
try {
result = api.execute(URL).get();
} catch (Exception e) {
e.printStackTrace();
}
List<CustomListView> contents = new ArrayList<CustomListView>();
try {
JSONObject row = result.getJSONObject(result**ERROR HERE**);
String content = row.optString("FormattedName");
String content2 = row.optString("Title");
String content3 = row.optString("Subtitle");
String content4 = row.optString("Text");
EditText name = (EditText) findViewById(R.id.etInternNaam);
name.setText(content);
EditText titel = (EditText) findViewById(R.id.etName);
titel.setText(content2);
EditText ondertitel = (EditText) findViewById(R.id.etOndertitel);
ondertitel.setText(content3);
EditText EditText = (EditText) findViewById(R.id.etTekst);
EditText.setText(Html.fromHtml(content4));
} catch (JSONException e) {
e.printStackTrace();
}
Api client:
public class APIClientJSONObject extends AsyncTask<String, Void, JSONObject> {
#Override
protected JSONObject doInBackground(String... params) {
JSONObject result = null;
try {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse httpResponse = httpclient.execute(new HttpGet(params[0]));
InputStream inputStream = httpResponse.getEntity().getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder builder = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
result = new JSONObject(builder.toString());
}
catch (Exception e) {
e.printStackTrace();
}
return result;
}
}
JSON output:
{
"FormattedName": "Home page | Footer grijs",
"Title": null,
"Subtitle": null,
"Text": "<div style=\"text-align: center;\"><img style=\"max-width: 80%;\" src=\"/MoxieManager/code.PNG\" alt=\"\"></div>",
"WebsiteId": "6869a7a1-0d65-4cfa-9df1-b0b0d346212e",
"Id": "b9906cb0-cdb2-484a-b603-020e8b64f97b",
"DateCreated": "2016-01-25T12:09:50.367",
"DateModified": "2016-02-11T08:51:54.223",
"CreatedBy": "Drie-O Automatisering",
"ModifiedBy": "Drie-O Automatisering",
"SortOrder": 0
}

Reason:
You are already getting the JSONObject from AsycnTask. There is no need of
JSONObject row = result.getJSONObject(result);
When you try to used this it means you are trying to find a object result inside object result. Which is not the case here.
Solution:
You should remove the above mentioned call and use result in these calls like below.
String content = result.optString("FormattedName");
String content2 = result.optString("Title");
String content3 = result.optString("Subtitle");
String content4 = result.optString("Text");

Is the error coming at this line?
JSONObject row = result.getJSONObject(result);
result is a JSONObject, and the method requires a String.
Why not try to convert result to String and pass it. Something like.
JSONObject resultJson = new JSONObject();
result.toString();
JSONObject row = result.getJSONObject(resultJson );

You have already got the JSON output as given from the APIClient.
JSONObject row = result.getJSONObject(result);
this line is redundant unless your real response is an array list enclosed object and you are getting only a row from it.
Directly you can access internal elements in main object now.