Develop Reference

Parsing OkHttp in android?

textView = findViewById(R.id.textVieww);
String url = "https://zenquotes.io/api/random";
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(url)
.build();
client.newCall(request).enqueue(new Callback() {
#Override
public void onFailure(Call call, IOException e) {
e.printStackTrace();
}
#Override
public void onResponse(Call call, Response response) throws IOException {
if (response.isSuccessful()) {
final String myResponse = response.body().string();
try {
JSONArray jsonarray = new JSONArray(myResponse);
for(int i=0; i<jsonarray.length(); i++) {
JSONObject obj = jsonarray.getJSONObject(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
Quote.this.runOnUiThread(() ->
textView.setText(myResponse));
}
}
});
}
This is the part im stuck on i think im on the right track but not sure where to go from here im trying to get the "q" information from the returned url and the "a" information but it just outputs everything any suggestions?

What was your problem
Even when you parsed JSON string, you were still using the myResponse string in your textView.setText() method.
Continuing your code snippet
your code snippet is quite short, but i do think i can quite understand what you mean.
So let's say that we have Activity, which is called MainActivity and in that activity we have two views, one TextView called that has an id of tv_author_and_quote and one Button which has a xml id btn_request_quote.
The button has an OnClickListener which calls method requestForQuote().
Our onCreate + the variables of Button and TextView looks like this:
TextView tvAuthorAndQuote;
Button btnRequestQuote;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvAuthorAndQuote = findViewById(R.id.tv_author_and_quote);
btnRequestQuote = findViewById(R.id.btn_request_quote);
btnRequestQuote.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
requestForQuote();
}
});
}
And then we have a code itself for method requestForQuote():
public void requestForQuote() {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(URL)
.build();
client.newCall(request).enqueue(new Callback() {
#Override
public void onFailure(#NotNull Call call, #NotNull IOException e) {
e.printStackTrace();
}
#Override
public void onResponse(#NotNull Call call, #NotNull Response response) throws IOException {
if (response.isSuccessful()) {
final String myResponse = Objects.requireNonNull(response.body()).string();
String myFormattedQuote = "";
try {
JSONArray jsonarray = new JSONArray(myResponse);
for(int i=0; i<jsonarray.length(); i++) {
JSONObject obj = jsonarray.getJSONObject(i);
String quote = obj.getString("q");
String author = obj.getString("a");
Log.d(TAG, "onResponse: quote:" + quote);
Log.d(TAG, "onResponse: author:" + author);
myFormattedQuote = author + ": " + quote;
}
} catch (JSONException e) {
e.printStackTrace();
}
final String myFinalQuote = myFormattedQuote;
MainActivity.this.runOnUiThread(() -> {
if (!myFinalQuote.equals("")) {
tvAuthorAndQuote.setText(myFinalQuote);
} else {
tvAuthorAndQuote.setText(myResponse);
}
});
}
}
});
}
The code above basically uses your existing solution, but instead of setting the text of textView with myResponse string, it parses the json array and gets a quote and an author from it. Then it just logs it (just for testing purposes), then it constructs the string which gets displayed to the if there is any, otherwise it prints the response. That it is.
Using Gson library
import it into your gradle dependecies
implementation 'com.google.code.gson:gson:2.8.7'
Write short "holder" class called Quote
public class Quote {
public Quote() {
}
String q;
String a;
String h;
public String getQ() {
return q;
}
public void setQ(String q) {
this.q = q;
}
public String getA() {
return a;
}
public void setA(String a) {
this.a = a;
}
public String getH() {
return h;
}
public void setH(String h) {
this.h = h;
}
#NonNull
#NotNull
#Override
public String toString() {
return a + ": " + q;
}
}
Then the requestForQuote() method could look something like this:
public void requestForQuoteWithGson() {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(URL)
.build();
client.newCall(request).enqueue(new Callback() {
#Override
public void onFailure(#NotNull Call call, #NotNull IOException e) {
e.printStackTrace();
}
#Override
public void onResponse(#NotNull Call call, #NotNull Response response) throws IOException {
if (response.isSuccessful()) {
final String myResponse = Objects.requireNonNull(response.body()).string();
Type listType = new TypeToken<ArrayList<Quote>>(){}.getType();
List<Quote> yourClassList = new Gson().fromJson(myResponse, listType);
if (yourClassList != null && yourClassList.size() > 0) {
final Quote quote = yourClassList.get(0);
if (quote != null) {
myQuotes.add(quote);
MainActivity.this.runOnUiThread(() ->
tvAuthorAndQuote.setText(quote.toString())
);
}
}
}
}
});
}

Update global variable by using a interface

I have a async class in my MainActivity.java
class Register extends AsyncTask<String, String, JSONObject> {
JSONObject json;
#Override
protected JSONObject doInBackground(String[] args) {
String function = args[3];
String email = args[2];
String password = args[1];
String name = args[0];
ContentValues params = new ContentValues();
params.put("username", name);
params.put("password", password);
params.put("function", function);
if (email.length() > 0)
params.put("email", email);
String URL = "https://lamp.ms.wits.ac.za/home/s2090704/index.php";
new PhpHandler().makeHttpRequest(act, URL, params, new RequestHandler() {
#Override
public void processRequest(String response) throws JSONException {
json = new JSONObject(response);
System.out.println(json); //outputs {response: " ...",message:"..."}
}
});
System.out.println(json); //outputs null
return json;
}
}
in doInBackground() PhpHandler processes details using OkHttp.
public class PhpHandler {
JSONObject json;
static String responseData = "";
public void makeHttpRequest(final Activity a, String url,
ContentValues params, final RequestHandler rh) {
// Making HTTP request
OkHttpClient client = new OkHttpClient();
FormBody.Builder builder = new FormBody.Builder();
for (String key : params.keySet()) {
builder.add(key, params.getAsString(key));
}
final Request request = new Request.Builder()
.url(url)
.post(builder.build())
.build();
client.newCall(request).enqueue(new Callback() {
#Override
public void onFailure(#NotNull Call call, #NotNull IOException e) {
}
#Override
public void onResponse(#NotNull Call call, #NotNull Response response) throws IOException {
responseData = Objects.requireNonNull(response.body()).string();
//System.out.println(responseData);
a.runOnUiThread(new Runnable() {
#Override
public void run() {
try {
rh.processRequest(responseData);
} catch (JSONException e) {
e.printStackTrace();
}
}
});
}
});
}
}
RequestHandler is an interface that processes request on the mainUiThread.
package com.example.registration;
import org.json.JSONException;
public interface RequestHandler{
void processRequest(String response) throws JSONException;
}
Now json doesn't update out of the processRequest method in doInBackground method of my async class Register.I know that interfaces make variables static and final is there any way to update the value of json?

processRequest method will be executed long after you return json from doInBackground, because makeHttpRequest performs an asynchronous http request.
Knowing this, you will probably want to re-design this class (there is no need to wrap already asynchronous request in AsyncTask), but if you really want to do it this way, you would have to wait for your request to complete before returning the json (for example, by using CountDownLatch).
CountDownLatch latch = new CountDownLatch(1);
someField = null;
AtomicReference<String> someValue = new AtomicReference<>();
// don't start new threads like this, im just trying to keep this example simple
new Thread() {
Thread.sleep(1000); // sleep for 1 second
someValue.set("abc"); // notice that because when using AtomicReference you assign it's value using `set` method instead of `=` operator, you can keep it as local variable instead of field class
latch.countDown(); // reduce latch count by one
}.run();
System.out.println(someValue.get()); // null - because the assignation will happen in one second
latch.await(); // this will force current thread to wait until the latch count reaches zero (initial was 1, passed to constructor)
System.out.println(someValue.get()); // "abc"
read more

How do I reference a variable through multiple sequential, dependent AsyncTasks in Java for Android?

I need to submit a sequence of API calls where the response of the first call contains the API address needed for the second call. I then want to send the results of the second call back into MainActivity. Additionally, each response is updated over time as results of those calls are returned.
I have set up my code to use a sequence of AsyncTasks with success and fail criteria to keep them active. Despite researching practically every article I can on this, none of them seem to show how to reference and parse a returned variable from the execute() method in the code instead of directly updating the GUI. I also need to do all of this without leaking memory or blocking the main threads.
class CheckItemStatus extends AsyncTask<Void, Void, String> {
private final String itemName;
String mResponse = "";
String submitReportURL = "stackoverflow.com";
public CheckItemStatus(String itemName) {
this.itemName = itemName;
}
protected String doInBackground(Void... urls) {
new RetrieveFeedTask(submitReportURL).execute();
return mResponse;
}
protected void onPostExecute(String response) {
super.onPostExecute(response);
String reportURLResponse = "";
// TODO: Retrieve new response
Log.i("APP", "Item check submitted! Response: " + reportURLResponse);
String reportURL = ""; // TODO: Parse new response for report URL
new CheckReportResults(itemName, reportURL).execute();
}
}
class CheckReportResults extends AsyncTask<Void, Void, String> {
private final String itemName;
private final String reportURL;
String mResponse = "";
public CheckReportResults(String itemName, String reportURL) {
this.itemName = itemName;
this.reportURL = reportURL;
}
protected String doInBackground(Void... urls) {
Log.i("APP", "Waiting for results for item " + itemName);
new RetrieveFeedTask(reportURL).execute();
return mResponse;
}
protected void onPostExecute(String response) {
super.onPostExecute(response);
}
}
class RetrieveFeedTask extends AsyncTask<Void, Void, String> {
String URL;
public RetrieveFeedTask(String URL) {
this.URL = URL;
}
protected String doInBackground(Void... urls) {
String response="{\n" +
" \"reportURL\": \"stackoverflow.com\"\n" +
"}";
// Open Connection and Get Response
return response;
}
protected void onPostExecute(String response) {
super.onPostExecute(response);
if (response == null) {
response = "THERE WAS AN ERROR";
}
Log.i("INFO", "Response: " + response);
}
}
Currently, the code runs, but I have no idea how to parse and reference those responses outside of the AsyncTask class.

Managing multiple Async tasks in android

Hey everyone so I am just starting a part two for online training app and trying to adapt my async task to get movie reviews from the movie db. Having a totally different async task just for that seems like there should be a better way. Here is the current async task implementation that only gets the movie data.
The question is how do I add another async task to this in order to retrive the movie reviews as well from this url /movie/{id}/videos.
public FetchMovieData(Context context, GridView grid, boolean sortType, ITaskCompleteListener listener) {
mContext = context;
this.mMoviesGrid = grid;
this.mSortByMostPopular = sortType;
this.mTaskCompleteListener = listener;
}
#Override
protected Void doInBackground(String... params) {
// These two need to be declared outside the try/catch
// so that they can be closed in the finally block.
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
try {
URL url;
if(mSortByMostPopular)
url = new URL(mContext.getString(R.string.picasso_url_popular_movies));
else
url = new URL(mContext.getString(R.string.picasso_url_highest_rated));
// Create the request to OpenWeatherMap, and open the connection
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// Read the input stream into a String
InputStream inputStream = urlConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null) {
// Nothing to do.
mMovieJsonStr = null;
}
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
// Since it's JSON, adding a newline isn't necessary (it won't affect parsing)
// But it does make debugging a *lot* easier if you print out the completed
// buffer for debugging.
buffer.append(line + "\n");
}
if (buffer.length() == 0) {
// Stream was empty. No point in parsing.
mMovieJsonStr = null;
}
mMovieJsonStr = buffer.toString();
} catch (IOException e) {
Log.e("PlaceholderFragment", "Error ", e);
// If the code didn't successfully get the weather data, there's no point in attempting
// to parse it.
mMovieJsonStr = null;
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("PlaceholderFragment", "Error closing stream", e);
}
}
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
if(mMovieJsonStr != null)
Constants.mMovies = MovieDataParser.getMovieData(mMovieJsonStr);
mTaskCompleteListener.onTaskCompleted(); //Task completed alert UI that we have our data
}
So some one had suggested using Retrofit instead of having multiple async tasks. This seems like a good idea but I am having a lot of trouble understanding how it is supposed to work. Currently I have a WebService class an interface and am trying to use it to retrieve both movies and am going to add reviews then trailers. The issue is if I set the base url as "http://api.themoviedb.org" I get url must start with "/" in logcat.
Current code:
public class WebService {
public List<Movie> getMovies() {
RestAdapter retrofit = new RestAdapter.Builder()
.setEndpoint("http://api.themoviedb.org")
.build();
MovieDBService service = retrofit.create(MovieDBService.class);
return service.listMovies("movies");
}
}
public interface MovieDBService {
#GET("/3/discover/{switchterm}sort_by=popularity.desc&api_key=d273a1a1fb9390dab9 7ac0032b12366a")
List listMovies(#Path("switchterm") String switchterm);
}
//In code getting movies
WebService service = new WebService();
List movies = service.getMovies();

I think you have a lots of possibilities for doing this.You can follow this approach: add a second call to another AsyncTask when the first is finish, and pass to it a list of strings with the video ids:
public class FetchMovieData extends AsyncTask<Void, Void, Void> {
protected Boolean doInBackground() {
try {
String movieJSONString = getJSONMovies();
String[] ids = parseIdsFromJSON(movieJSONString);
if(ids.lenth != 0) {
FetchMovieReviews moviesReviewsAsyncTask = new FetchMovieReviews();
moviesReviewsAsyncTask.execute(ids);
} else {
return false;
}
return true;
} catch (Exception e) {
return false;
}
}
protected String getJSONMovies() {
//with the code you post, return the json string
}
protected String[] parseIdsFromJSON(String JSON) {
//parse the json and get the ids and return
//return {"1","2","3"}
}
}
public class FetchMovieReviews extends AsyncTask<String[], Void, Void> {
protected Void doInBackground(String[]... params) {
for(String id : params[0]) {
//call the web service and pass the id
}
return null;
}
}
You can put all the functionality for manage the calls to the web services in a MoviesRESTCalls class, and for manage the json in a MoviesJSONParser class or something like that, and the code is going to be much more clear.

So what I ended up with was this using the the Retrofit library for the web service. Thanks for the help everyone and let me know your thoughts.
public Context mContext;
private MovieJSON mMovieData;
private ReviewJSON mMovieReviews;
private VideoJSON mMovieVideos;
public boolean mSortByMostPopular;
ITaskCompleteListener mTaskCompleteListener;
public FetchMovieData(Context context, boolean sortType, ITaskCompleteListener listener) {
mContext = context;
this.mSortByMostPopular = sortType;
this.mTaskCompleteListener = listener;
}
public void getMovies() {
new FetchMovies().execute();
}
public void getReviews() {
new FetchReviews().execute();
}
public void getVideos() {
new FetchTrailers().execute();
}
private class FetchMovies extends AsyncTask<String, Void, Void > {
#Override
protected Void doInBackground(String... params) {
WebService service = new WebService();
//TODO Re-Implement sorting
mMovieData = service.getMovies();
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
if(mMovieData != null)
Constants.mMovies = MovieDataParser.getMovieData(mMovieData);
mTaskCompleteListener.onTaskCompleted(); //Task completed alert UI that we have our data
}
}
private class FetchReviews extends AsyncTask<String, Void, Void > {
#Override
protected Void doInBackground(String... params) {
WebService service = new WebService();
mMovieReviews = service.getReviews();
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
if(mMovieReviews != null)
Constants.mReviews = MovieDataParser.getReviewData(mMovieReviews);
mTaskCompleteListener.onTaskCompleted(); //Task completed alert UI that we have our data
}
}
private class FetchTrailers extends AsyncTask<String, Void, Void > {
#Override
protected Void doInBackground(String... params) {
WebService service = new WebService();
mMovieVideos = service.getVideos();
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
if(mMovieVideos != null)
Constants.mTrailers = MovieDataParser.getVideoData(mMovieVideos);
mTaskCompleteListener.onTaskCompleted(); //Task completed alert UI that we have our data
}
}
//web service
public class WebService {
RestAdapter mRetrofit;
MovieDBService mService;
public WebService() {
mRetrofit = new RestAdapter.Builder()
.setEndpoint("http://api.themoviedb.org")
.build();
mService = mRetrofit.create(MovieDBService.class);
}
public MovieJSON getMovies() {
return mService.listMovies("");
}
public ReviewJSON getReviews() {
return mService.listReviews("76341");
}
public VideoJSON getVideos() {
return mService.listVideos("76341");
}
}

how to replace AsyncTask with Volley

This is regarding Weatherforecastapp using Volley..
How do we replace the following code with Volley?
Since we are new to android we are finding it difficult to implement Volley.
private class JSONWeatherTask extends AsyncTask<String, Void, Weather> {
#Override
protected Weather doInBackground(String... params) {
Weather weather = new Weather();
String data = ( (new WeatherHttpClient()).getWeatherData(params[0], params[1]));
try {
weather = JSONWeatherParser.getWeather(data);
System.out.println("Weather ["+weather+"]");
// Let's retrieve the icon
weather.iconData = ( (new WeatherHttpClient()).getImage(weather.currentCondition.getIcon()));
} catch (JSONException e) {
e.printStackTrace();
}
return weather;
}
#Override
protected void onPostExecute(Weather weather) {
super.onPostExecute(weather);
if (weather.iconData != null && weather.iconData.length > 0) {
Bitmap img = BitmapFactory.decodeByteArray(weather.iconData, 0, weather.iconData.length);
imgView.setImageBitmap(img);
}
cityText.setText(weather.location.getCity() + "," + weather.location.getCountry());
temp.setText("" + Math.round((weather.temperature.getTemp() - 275.15)));
condDescr.setText(weather.currentCondition.getCondition() + "(" + weather.currentCondition.getDescr() + ")");
}
}

The good news is that Volley is much easier to use than AsyncTask! :)
Volley has a a few types of requests that it can make. For your implementation, it looks like you are retrieving JSON. Volley has special request for JSONObject and JSONArray, so you would use whichever makes sense for you.
Here is a basic outline of how you would replace your code with Volley. Note that the onResponse is the callback (like onPostExecute in AsyncTask).
private class WeatherTask{
public void getWeatherData() {
// Create a single queue
RequestQueue queue = Volley.newRequestQueue(this);
// Define your request
JsonObjectRequest getRequest = new JsonObjectRequest(url,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JsonObject jsonObject) {
// Parse JSON here
}
}
}
, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError volleyError) {
// Show Error message
Log.e("Error Response: ", volleyError.toString());
}
}
);
// add it to the Request Queue
queue.add(getRequest);
}
}
Here is a great talk on Volley, to learn more about it: https://developers.google.com/events/io/sessions/325304728