I am currently working with the tab host and fragment. Currently I set fragment a to download json A and fragment B to download json B , the problem is when I switch fragment, the fragment A onPostExecute function will fall into the fragment B one , is there any way to fix this?
Thanks
Tab host:
tabHost = (FragmentTabHost) findViewById(R.id.tabhost);
tabHost.setup(this, getSupportFragmentManager(), R.id.tabcontent);
tabHost.addTab(
tabHost.newTabSpec("Home").setIndicator("",
res.getDrawable(R.drawable.btn_about)), Home.class,
null);
tabHost.addTab(
tabHost.newTabSpec("About").setIndicator("",
res.getDrawable(R.drawable.btn_about)), About.class,
null);
The async task
public class JSONReader {
public static final String TAG = "JSONReader";
public ArrayList<Record> records;
public Record myRecordObj;
public ArrayList<GalleryImage> images;
public String url;
public int failCount = 0; // retry twice
public Context ctx;
public String readCase;
public JSONReader(String _url, Context _ctx , String _readCase) {
url = _url;
ctx = _ctx;
readCase = _readCase;
}
public void getJSON() {
new JSONDownload().execute(url);
}
private class JSONDownload extends AsyncTask<String, Void, JSONObject> {
// TODO Auto-generated method stub
StringBuilder builder = new StringBuilder();
String temp = "";
String json = ""; // json content
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
#Override
protected JSONObject doInBackground(String... params) {
// TODO Auto-generated method stub
try {
Log.d(TAG, "Start reading: " + url);
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK)
return null;
// return "Server returned HTTP " + connection.getResponseCode()
// + " " + connection.getResponseMessage();
input = connection.getInputStream();
BufferedReader reader = new BufferedReader(
new InputStreamReader(input));
while ((temp = reader.readLine()) != null) {
builder.append(temp);
}
json = builder.toString();
} catch (Exception e) {
return null;
} finally {
try {
if (input != null)
input.close();
if (output != null)
output.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
try {
return new JSONObject(json);
} catch (JSONException e) {
e.printStackTrace();
return null;
}
}
#Override
protected void onPostExecute(JSONObject result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
onJSONDownloaded(result);
}
}
public void onJSONDownloaded(JSONObject result) {
// TODO Auto-generated method stub
if (result != null) {
failCount = 0;
if (readCase.equals("leaderBoard")){
records = new ArrayList<Record>();
try {
JSONObject myRecord = result.getJSONObject("myRecord");
if (myRecord != null) {
myRecordObj = new Record(myRecord.getString("pic"),myRecord.getString("name"),myRecord.getString("score"));
}
JSONArray topRecords = result.getJSONArray("topRecord");
for (int i = 0; i < topRecords.length(); i++) {
JSONObject topRecord = topRecords.getJSONObject(i);
String topName = topRecord.getString("name");
String topPic = topRecord.getString("pic");
String topScore = topRecord.getString("score");
records.add(new Record(topPic, topName, topScore));
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
((LeaderBoardDetail)ctx).setData(records,myRecordObj);
} else if (readCase.equals("galleryList")){
images = new ArrayList<GalleryImage>();
try {
JSONArray imageList = result.getJSONArray("images");
for (int i = 0; i < imageList.length(); i++) {
JSONObject image = imageList.getJSONObject(i);
images.add(new GalleryImage(image.getString("url"),image.getString("thumbUrl"),image.getString("category"),image.getString("userPic"),image.getString("name")));
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//exception
if (((FragmentActivity) ctx).getSupportFragmentManager().findFragmentById(R.id.tabcontent).getTag().equals("Gallery")) {
PhotoGallery galleryFragment = (PhotoGallery) ((FragmentActivity) ctx).getSupportFragmentManager().findFragmentById(R.id.tabcontent);
galleryFragment.setData(images);
}
}
} else {
if (failCount <= 1) { // check global_conf twice if fail
failCount++;
Log.d(TAG, "No of retry" + failCount);
new JSONDownload().execute(url); // Retry download json
} else {
failCount = 0;
}
}
}
}
I used it in my app this way which works for me and answer is a bit similar to another answer but few additions and more detail. Hope it help you too.
NOTE: This is just a idea, u need to try, it may vary as per your app architect.
At your activity make the task object global [make sure set task obj null once task is finish]
JSDownload js = null;
public void getJSON() {
if(js != null && js.getStatus() == AsyncTask.Status.RUNNING)
{
js.cancel(true);
if(js.isCancelled())
{
js = new JSONDownload();
js.execute(url);
}
else
{
js = new JSONDownload();
js.execute(url);
}
}
At the Async class side....[make sure u take care null result # onpostExcute]
class JSONDownload extends AsyncTask<String, Void, JSONObject>
{
protected JSONObject doInBackground(String... params) {
// TODO Auto-generated method stub
try {
if(!this.isCancelled())
{
//make http connection ..
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
//as we are in steps in bg check iscancel .. again
//if its a loop here we call break; and return null once only..
if(this.isCancelled())
return null;
// connection status check and get buffer etc .. code here
if(this.isCancelled())
return null;
//read data
return data;
}
} catch (Exception e) {
return null;
}
}
#Override
protected void onCancelled(){
// If you write your own implementation, do not call super.onCancelled(result).
}
}
Use the global async task variable
LongOperation LongOperationOdeme = new LongOperation();
and set:
LongOperationOdeme.cancel(true);
This will stop any async task running at that moment, it's what the back button does
If you are not looking for a simplest answer but for a maybe more interesting and elegant, have a peek at this article, especially if you find functional programming interesting.
It's easier than it looks, i was almost unfamiliar to FP before this article but it covers common problems related to AsyncTask and asynchronicity in Android in general, so I got the gist and consider to use Observables instead of AsyncTask in the future projects myself. It is RxJava and it can solve your problem gracefully: "The fromFragment call transforms the given source observable in such a way that events will only be emitted to the fragment if it’s still alive and attached to its host activity."
One more citation form the article: "What if the user decides to back out of the Activity that triggered the task, and we are holding on to a stale reference. This not only creates a substantial memory leak, but is also worthless because meanwhile it has been detached from the application window. A problem that everyone is well aware of."
Related
I got an api token for my api but don't know how to implement it in my code...
this is the code i have for reaching my api:
public class DataVoetbalWebservice extends AsyncTask<VoetbalDataInterface, Void, JSONArray> {
private static final int CONNECTION_TIMEOUT = 12000;
private static final int DATARETRIEVAL_TIMEOUT = 12000;
VoetbalDataInterface listener;
private ProgressDialog dialog;
Context context;
public void setActivity(Context context) {
this.context = context;
dialog = new ProgressDialog(context);
}
#Override
protected void onPreExecute() {
dialog.setMessage("De Verschillende competities ophalen, even geduld aub.");
dialog.show();
}
#Override
protected JSONArray doInBackground(VoetbalDataInterface... params) {
listener = params[0];
// execute search
disableConnectionReuseIfNecessary();
HttpURLConnection urlConnection = null;
try {
// create connection
//URL urlToRequest = new URL("http://datatank.stad.gent/4/bevolking/geboortes.json?%2Fbevolking%2Fgeboortes=");
URL urlToRequest = new URL("http://api.football-data.org/v1/competitions");
urlConnection = (HttpURLConnection)
urlToRequest.openConnection();
urlConnection.setConnectTimeout(CONNECTION_TIMEOUT);
urlConnection.setReadTimeout(DATARETRIEVAL_TIMEOUT);
// handle issues
int statusCode = urlConnection.getResponseCode();
if (statusCode == HttpURLConnection.HTTP_UNAUTHORIZED) {
} else if (statusCode != HttpURLConnection.HTTP_OK) {
// handle any other errors, like 404, 500,..
}
// create JSON object from content
InputStream in = new BufferedInputStream(
urlConnection.getInputStream());
return new JSONArray(getResponseText(in));
} catch (MalformedURLException e) {
// URL is invalid
Log.d("Info", e.getMessage());
} catch (SocketTimeoutException e) {
// data retrieval or connection timed out
Log.d("Info", e.getMessage());
} catch (IOException e) {
// could not read response body
// (could not create input stream)
Log.d("Info", e.getMessage());
} catch (JSONException e) {
// response body is no valid JSON string
Log.d("Info", e.getMessage());
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
return null;
}
#Override
protected void onPostExecute(JSONArray json) {
if (dialog.isShowing()) {
dialog.dismiss();
}
ArrayList <Competitie> competities = new ArrayList<>();
try {
for (int i = 0; i < json.length(); i++) {
Competitie competitie = new Competitie();
JSONObject jsonObject = json.getJSONObject(i);
competitie.setId(jsonObject.getInt("id"));
competitie.setCaption(jsonObject.getString("caption"));
competitie.setLeague(jsonObject.getString("league"));
competitie.setYear(jsonObject.getString("year"));
competitie.setCurrentMatchday(jsonObject.getInt("currentMatchday"));
competitie.setNumberOfMatchdays(jsonObject.getInt("numberOfMatchdays"));
competitie.setNumberOfTeams(jsonObject.getInt("numberOfTeams"));
competitie.setNumberOfGames(jsonObject.getInt("numberOfGames"));
JSONObject links = jsonObject.getJSONObject("_links");
JSONObject teams = links.getJSONObject("teams");
JSONObject stand = links.getJSONObject("leagueTable");
competitie.setTeamString(teams.getString("href"));
competitie.setStandUrl(stand.getString("href"));
competities.add(competitie);
}
} catch (JSONException e) {
e.printStackTrace();
}
listener.updateScreenCompetities(competities);
}
/**
* required in order to prevent issues in earlier Android version.
*/
private static void disableConnectionReuseIfNecessary() {
// see HttpURLConnection API doc
if (Integer.parseInt(Build.VERSION.SDK)
< Build.VERSION_CODES.FROYO) {
System.setProperty("http.keepAlive", "false");
}
}
private static String getResponseText(InputStream inStream) {
// very nice trick from
// http://weblogs.java.net/blog/pat/archive/2004/10/stupid_scanner_1.html
return new Scanner(inStream).useDelimiter("\\A").next();
}
}
where do i add the token so i can contact the api?..
because for know i can't read anymore data because the request capacity is full. i already got my api token emailed to me.
This is the documentation for the api, how do i add the request header?
Documentation about token use
thanks in advance
EDIT
added this line of code and now it works!
urlConnection.setRequestProperty("X-Auth-Token","6a0c52afadac44f5bc65bd0dcfb363c2");
i am using simple asynctask function for getting values from mysql database through json.it was working fine with emulator but if i am trying from the mobile i am getting error. like Java.lang.NullPointerExceprtion:Attempt to invke virtual metho 'java.lang.string.java.lang.stringbuilder.toString() on a null object reference.
I tried with new project but result is same. this application is not working in all the devices except emulator. can you help me on this.
My Code is -
public class MainActivity extends AppCompatActivity {
private static final String Latest_Products7 = "Questions";
JSONArray productsArray7 = null;
public static final int CONNECTION_TIMEOUT7=100000;
public static final int READ_TIMEOUT7=150000;
HashMap<String,ArrayList<WorldPopulation>> hasmap = new HashMap<String,ArrayList<WorldPopulation>>();
ArrayList<WorldPopulation> arraylist7 = null;
StringBuilder result7;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new AsyncLogin7().execute();
}
private class AsyncLogin7 extends AsyncTask<String, String, StringBuilder> {
ProgressDialog pdLoading = new ProgressDialog(MainActivity.this);
HttpURLConnection conn7;
URL url7 = null;
#Override
protected void onPreExecute() {
super.onPreExecute();
pdLoading.setMessage("\tLoading...");
pdLoading.setCancelable(false);
pdLoading.show();
}
#Override
protected StringBuilder doInBackground(String... params) {
try {
// Enter URL address where your php file resides
url7 = new URL("http:/Samplesite/****/somephp.php");
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
// Setup HttpURLConnection class to send and receive data from php and mysql
conn7 = (HttpURLConnection)url7.openConnection();
conn7.setReadTimeout(READ_TIMEOUT7);
conn7.setConnectTimeout(CONNECTION_TIMEOUT7);
conn7.setRequestMethod("POST");
// setDoInput and setDoOutput method depict handling of both send and receive
conn7.setDoInput(true);
conn7.setDoOutput(true);
// Append parameters to URL
Uri.Builder builder7 = new Uri.Builder().appendQueryParameter("reg_id", "hai") ;
String query7 = builder7.build().getEncodedQuery();
// Open connection for sending data
OutputStream os7 = conn7.getOutputStream();
BufferedWriter writer7 = new BufferedWriter(new OutputStreamWriter(os7, "UTF-8"));
writer7.write(query7);
writer7.flush();
writer7.close();
os7.close();
conn7.connect();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
int response_code7 = conn7.getResponseCode();
// Check if successful connection made
if (response_code7 == HttpURLConnection.HTTP_OK) {
// Read data sent from server
InputStream input7 = conn7.getInputStream();
BufferedReader reader7 = new BufferedReader(new InputStreamReader(input7));
result7 = new StringBuilder();
String line7;
while ((line7 = reader7.readLine()) != null) {
result7.append(line7);
}
// Pass data to onPostExecute method
}
} catch (IOException e) {
e.printStackTrace();
} finally {
conn7.disconnect();
}
return result7;
}
#Override
protected void onPostExecute(StringBuilder result7) {
super.onPostExecute(result7);
Log.e("dai",result7.toString());
Toast.makeText(MainActivity.this,result7.toString(),Toast.LENGTH_LONG).show();
pdLoading.dismiss();
/* Intent intnt = new Intent(Checklist_activity.this,Task_main.class);
intnt.putExtra("task",hasmap);
startActivity(intnt);*/
}
}
}
Change
try {
int response_code7 = conn7.getResponseCode();
// Check if successful connection made
if (response_code7 == HttpURLConnection.HTTP_OK) {
// Read data sent from server
InputStream input7 = conn7.getInputStream();
BufferedReader reader7 = new BufferedReader(new InputStreamReader(input7));
result7 = new StringBuilder();
String line7;
while ((line7 = reader7.readLine()) != null) {
result7.append(line7);
}
// Pass data to onPostExecute method
}
} catch (IOException e) {
e.printStackTrace();
} finally {
conn7.disconnect();
}
return result7;
To
try {
int response_code7 = conn7.getResponseCode();
result7 = new StringBuilder();
// Check if successful connection made
if (response_code7 == HttpURLConnection.HTTP_OK) {
// Read data sent from server
InputStream input7 = conn7.getInputStream();
BufferedReader reader7 = new BufferedReader(new InputStreamReader(input7));
String line7;
while ((line7 = reader7.readLine()) != null) {
result7.append(line7);
}
// Pass data to onPostExecute method
}
} catch (IOException e) {
e.printStackTrace();
} finally {
conn7.disconnect();
}
return result7;
Try something like this
Log.e("dai",MainActivity.this.result7.toString());
Toast.makeText(MainActivity.this,MainActivity.this.result7.toString(),Toast.LENGTH_LONG).show();
OR
#Override
protected void onPostExecute(StringBuilder result) {
super.onPostExecute(result);
Log.e("dai",result.toString());
Toast.makeText(MainActivity.this,result.toString(),Toast.LENGTH_LONG).show();
pdLoading.dismiss();
/* Intent intnt = new Intent(Checklist_activity.this,Task_main.class);
intnt.putExtra("task",hasmap);
startActivity(intnt);*/
}
}
I am storing the data that I parsed from the JSON that is returned by my API request into the Firebase database.
submitButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String APIURL = "https://api.github.com/users/" + idInput.getText().toString();
String repoURL = "https://api.github.com/users/" + idInput.getText().toString() + "/repos";
new JSONTask().execute(APIURL);
//new JSONTask().execute(repoURL);
String parsedUserID = idInput.getText().toString();
SM.sendDataToProfile(parsedUserID);
viewPager.setCurrentItem(1);
//addUser(parsedUserID);
}
});
When the button is clicked, it calls a new JSONTask (asynctask) on the APIURL.
JSONTask
public class JSONTask extends AsyncTask<String, String, String> {
#Override
// Any non-UI thread process is running in this method. After completion, it sends the result to OnPostExecute
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
try {
// Pass in a String and convert to URL
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
// Reads the data line by line
reader = new BufferedReader(new InputStreamReader(stream));
StringBuffer strBuffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
strBuffer.append(line);
}
// If we are able to get the data do below :
String retreivedJson = strBuffer.toString();
return retreivedJson;
// When we are not able to retreive the Data
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (connection != null) {
// close both connection and the reader
connection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
And it does parsing in another function.
My question is, as you can see on my setOnClickListener, I tried to make two JSONTask on two different URLs because the first URL gives me the information of the user and the second URL (repoURL) gives me the information of the user's repositories. I tried to fetch the repo info of the user and store it into the DB, but it seems like this is a wrong approach.
What is a right way to call two separate AsyncTasks on two different URLs?
EDIT
private void addUserRepo(final String githubID, final String[] repoList) {
DatabaseReference users = databaseReference.child("users");
users.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List list = new ArrayList<String>(Arrays.asList(repoList));
databaseReference.child("users").child(githubID).child("Repos").setValue(list);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Using data parsed from
public void formatJSONArray(String results){
try {
JSONArray jsonArray = new JSONArray(results);
RepoInfo[] repoList = new RepoInfo[jsonArray.length()];
for(int i = 0; i < jsonArray.length(); i++){
JSONObject jsonObject=jsonArray.getJSONObject(i);
if(jsonObject.optString("name") != null) {
repoList[i].setRepoName(jsonObject.getString("name"));
//repoNameList.add(jsonObject.getString("name"));
}
if(jsonObject.optString("description") != null) {
repoList[i].setDescription(jsonObject.getString("description"));
//descriptionList.add(jsonObject.getString("description"));
}
if(jsonObject.optJSONObject("owner") != null){
JSONObject ownerObject=jsonObject.getJSONObject("owner");
if(ownerObject.optString("login")!=null) {
repoList[i].setOwner(ownerObject.getString("login"));
//userNameList.add(ownerObject.getString("login"));
}
}
}
} catch (JSONException jsonException){
}
}
The response of two different URLs will surely not be similar. So you need different parse methods for them.
One lazy way would be to use two different AsyncTasks subclasses for two different urls.
Another way would be to store a flag inside the asynctask indicating whether it is dealing with user or repo.
public class JSONTask extends AsyncTask <String , String , String> {
boolean fetchingRepo;
#Override
protected String doInBackground (String... params) {
fetchingRepo = params[0].endsWith("/repos");
//other statements
}
Now inside onPostExecute:
if(fetchingRepo){
//parse one way
} else {
//parse another way
}
So here in Java I've written a typical class, to send json to a rest server. (I'll include the whole class below for clarity.) So that's a file "Fetcher.java"
Now for the callback you need an interface. The interface is trivial, just one function with a string.
public interface FetcherInterface {
public void fetcherDone(String result);
}
Annoyingly you need a whole file for that, "FetcherInterface.java"
So this interface is nothing but "one callback with a string". Often all you need is just "one callback with no arguments".
In fact ........ are there some sort of standard interfaces I can use, or something like that?
It seems kind of annoying to have to put in a whole interface for such a simple "standard" interface.
What's the deal on this? What's the javaly solution?
It seems you CAN NOT put it in the same file:
Perhaps I misunderstand something there. If you could put it in the same file, that would be convenient at least.
(Lambdas are not yet practically available. Anyway, sometimes you want an interface.)
Just for clarity, here's how you call the class
JSONObject j = new JSONObject();
try {
j.put("height", 2.1);
j.put("width", 2.5);
j.put("command", "blah");
} catch (JSONException e) {
e.printStackTrace();
}
new Fetcher("mobile/login", j, new FetcherInterface() {
#Override
public void fetcherDone(String result) {
Log.d("DEV","all done");
doSomething(result);
}
}
).execute();
or indeed
public class HappyClass extends Activity implements FetcherInterface {
...
private void someCall() {
JSONObject j = new JSONObject();
try {
j.put("height", 2.1);
j.put("width", 2.5);
j.put("command", "blah");
} catch (JSONException e) {
e.printStackTrace();
}
new Fetcher("mobile/data", j, this).execute();
devBlank();
}
#Override
public void fetcherDone(String result) {
Log.d("DEV","all done" +result);
doSomething(result);
}
Here's the whole class... Fetcher.java file
public class Fetcher extends AsyncTask<Void, Void, String> {
private String urlTail;
private JSONObject jsonToSend;
private FetcherInterface callback;
// initializer...
Fetcher(String ut, JSONObject toSend, FetcherInterface cb) {
urlTail = ut;
jsonToSend = toSend;
callback = cb;
}
#Override
protected String doInBackground(Void... params) {
HttpURLConnection urlConnection = null; // declare outside try, to close in finally
BufferedReader reader = null; // declare outside try, to close in finally
String rawJsonResultString = null;
String json = jsonToSend.toString();
Log.d("DEV","the json string in Fetcher is " +json);
try {
URL url = new URL("https://falcon.totalfsm.com/" + urlTail);
Log.d("DEV","the full URL in Fetcher is " +url);
// open a json-in-the-body type of connection.......
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("POST");
urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
urlConnection.setDoOutput(true);
urlConnection.setDoInput(true);
urlConnection.setConnectTimeout(5000);
// urlConnection.setDoOutput(false); // can be important?
urlConnection.connect();
OutputStream os = urlConnection.getOutputStream();
os.write(json.getBytes("UTF-8"));
os.close();
// annoyingly, you have to choose normal versus error stream...
InputStream inputStream;
int status = urlConnection.getResponseCode();
if (status != HttpURLConnection.HTTP_OK)
inputStream = urlConnection.getErrorStream();
else
inputStream = urlConnection.getInputStream();
if (inputStream == null) { // nothing to do.
return null;
}
StringBuffer buffer = new StringBuffer();
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) { // adding newlines makes debugging easier
buffer.append(line + "\n");
}
if (buffer.length() == 0) { // stream was empty
return null;
}
rawJsonResultString = buffer.toString();
return rawJsonResultString;
} catch (IOException e) {
Log.e("PlaceholderFragment", "Error ", e);
return null;
} finally{
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("PlaceholderFragment", "Error closing stream", e);
}
}
}
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
Log.d("DEV", "Fetcher done");
if (s==null) {
Log.d("DEV","applying anti-null measures in Fetcher!");
s = "message from app communications layer: 'null' returned from servers for that call at " +urlTail;
}
callback.fetcherDone(s);
}
}
I feel bad answering my own question, but as there were no other answers this info may be helpful.
DaveNewton and Rowtang have supplied the exact answers here:
(Point 1) If you want a genuinely public interface, it goes in its own file. That's how Java works. There's no alternative.
(Point 2) Normally, use protected interface and declare the interface inside the class. It can then be used throughout the app.
So...
public class Fetcher extends AsyncTask<Void, Void, String> {
protected interface FetcherInterface {
public void fetcherDone(String result);
}
private String urlTail;
private JSONObject jsonToSend;
private FetcherInterface callback;
Fetcher(String ut, JSONObject toSend, FetcherInterface cb) {
urlTail = ut;
jsonToSend = toSend;
callback = cb;
}
#Override
protected String doInBackground(Void... params) {
....
(c# programmers would maybe call it "IFetcher".)
I tried the code below and also tried the AsyncTaskLoader approach. The app crashes when I instantiate the AsyncTask. Pleas advise me on the best approach to load JSON in a list fragment inside tab host.
The code below is the tab fragment (I use action bar tabs in main activity):
public class TabTop extends ListFragment {
Context context = getActivity().getBaseContext();
String API_URL = "http://api.rottentomatoes.com/api/public/v1.0/movies/770672122/similar.json?apikey=crhhxb4accwwa6cy6fxrm8vj&limit=1";
ArrayList<Deal> deals;
DealsListAdapter adapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
#SuppressWarnings("unused")
int a = 0;
return super.onCreateView(inflater, container, savedInstanceState);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
GetTopDeals getTopDeals = new GetTopDeals(context);
getTopDeals.execute(API_URL);
super.onActivityCreated(savedInstanceState);
}
class GetTopDeals extends AsyncTask<String, Void, ArrayList<Deal>>{
ProgressDialog progressDialog;
public GetTopDeals(Context activity) {
this.progressDialog = new ProgressDialog(activity);
}
#Override
protected void onPostExecute(ArrayList<Deal> result) {
adapter = new DealsListAdapter(context, result);
setListAdapter(adapter);
super.onPostExecute(result);
}
#Override
protected void onPreExecute() {
progressDialog.setCancelable(true);
progressDialog.setProgress(0);
progressDialog.setMessage("loading Top deals...");
progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
super.onPreExecute();
}
#Override
protected ArrayList<Deal> doInBackground(String... urls) {
String response = sendRequest(urls[0]); // make request for json
return processResponse(response); // parse the Json and return ArrayList to postExecute
}
private String sendRequest(String apiUrl) {
BufferedReader input = null; // get the json
HttpURLConnection httpCon = null; // the http connection object
StringBuilder response = new StringBuilder(); // hold all the data from the jason in string separated with "\n"
try {
URL url = new URL(apiUrl);
httpCon = (HttpURLConnection) url.openConnection();
if (httpCon.getResponseCode() != HttpURLConnection.HTTP_OK) { // check for connectivity with server
return null;
}
input = new BufferedReader(new InputStreamReader(httpCon.getInputStream())); // pull all the json from the site
String line;
while ((line = input.readLine()) != null) {
response.append(line + "\n");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (input != null) {
try {
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (httpCon != null) {
httpCon.disconnect();
}
}
return response.toString();
}
}
public ArrayList<Deal> processResponse(String response) {
try {
JSONObject responseObject = new JSONObject(response); // Creates a new JSONObject with name/value mappings from the JSON string.
JSONArray results = responseObject.getJSONArray("movies"); // Returns the value mapped by name if it exists and is a JSONArray.
deals = new ArrayList<Deal>();
for (int i = 0; i < results.length(); i++) { // in this loop i copy the json array to movies arraylist in order to display listView
JSONObject jMovie = results.getJSONObject(i);
int api_id = jMovie.getInt("id");
String name = jMovie.getString("title");
String content = jMovie.getString("synopsis");
JSONObject posters = jMovie.getJSONObject("posters");
String image_url = posters.getString("profile");
}
}catch (JSONException e) {
e.printStackTrace();
}
return deals;
}
#Override
public void onStart() {
super.onStart();
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
Intent intent = new Intent(getActivity().getBaseContext(), DealInformation.class);
startActivity(intent);
super.onListItemClick(l, v, position, id);
}
}
Make your asynctask in his own file.
And when your asynctask is finish, implement OnPostExecute which is automatically call. Notify your adapter by a notifyDataSetChanged like that :
#Override
protected void onPostExecute(List<NewItem> list) {
Adapter.getListe().clear();
Adapter.getListe().addAll(list);
Adapter.notifyDataSetChanged();
}
thank you guys,
i want to post my answer. after some research i decided to go with AsyncTaskLoader.
this is my code
public class TabOurPicks extends ListFragment implements LoaderCallbacks<String[]> {
// when activity loads- onActivityCreated() calls the initLoader() who activate onCreateLoader()
#Override
public void onActivityCreated(Bundle savedInstance) {
super.onActivityCreated(savedInstance);
setListAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, new String[]{}));
getLoaderManager().initLoader(0, null,this).forceLoad();
}
// onCreateLoader instantiate the asynctaskloaser who work in bg
#Override
public RSSLoader onCreateLoader(int arg0, Bundle arg1) {
return new RSSLoader(getActivity()); //
}
// after bg process invoke onLoadFinished() who work in ui thread
#Override
public void onLoadFinished(Loader<String[]> loader, String[] data) {
setListAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, data
) );
}
#Override
public void onLoaderReset(Loader<String[]> arg0) {
// TODO Auto-generated method stub
}
and this is the inner class for the loader:
static public class RSSLoader extends AsyncTaskLoader<String[]>
{
public RSSLoader(Context context) {
super(context);
}
#Override
public String[] loadInBackground() {
String url = "http://api.rottentomatoes.com/api/public/v1.0/movies/770672122/similar.json?apikey=crhhxb4accwwa6cy6fxrm8vj&limit=1";
String response = sendRequest(url);
return processResponse(response);
}
private String sendRequest(String url) {
BufferedReader input = null; // get the json
HttpURLConnection httpCon = null; // the http connection object
StringBuilder response = new StringBuilder(); // hold all the data from the jason in string separated with "\n"
try {
URL apiUrl = new URL(url);
httpCon = (HttpURLConnection) apiUrl.openConnection();
if (httpCon.getResponseCode() != HttpURLConnection.HTTP_OK) { // check for connectivity with server
return null;
}
input = new BufferedReader(new InputStreamReader(httpCon.getInputStream())); // pull all the json from the site
String line;
while ((line = input.readLine()) != null) {
response.append(line + "\n");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (input != null) {
try {
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (httpCon != null) {
httpCon.disconnect();
}
}
return response.toString();
}
private String[] processResponse(String response) {
String[] deals = null;
try {
JSONObject responseObject = new JSONObject(response); // Creates a new JSONObject with name/value mappings from the JSON string.
JSONArray results = responseObject.getJSONArray("movies"); // Returns the value mapped by name if it exists and is a JSONArray.
deals = new String[10];
for (int i = 0; i < 9; i++) { // in this loop i copy the json array to movies arraylist in order to display listView
JSONObject jMovie = results.getJSONObject(i);
String name = jMovie.getString("title");
deals[i] = name;
}
}catch (JSONException e) {
e.printStackTrace();
}
return deals;
}
}
}
It doesn't matter if your asynctask has its own file. You just don't want your activity to extends asynctask as this would make your activity asynchronous - but this is impossible to do anyways due to java's double inheritance rule.
Based on the architecture of your app and your programming style the asyntask can be an inner class in the activity. on the PostExecute method make sure you have given data to your adapter and that the adapter is set to the list, then just run notifyDataSetChanged().
Assuming your asynctask is loading data from cache or the network you are on the right track with your approach to this.