Develop Reference

Async HttpRequest Timing Out

The Problem
I have an AsyncTask task called from an Activity's OnCreate method. This task makes an http request. The HTTP request hangs. Once the "CODE HANGS HERE" code in the code below is executed, I observe in the debugger that the Async threads are perpetually 'running' and never return anything.
The Code
Here's the OnCreate method of the activity:
protected void onCreate(Bundle savedInstanceState) {
asyncRequest.delegate = this;
super.onCreate(savedInstanceState);
setContentView(R.layout.activty_attach);
Button retakeButton = (Button) (findViewById(R.id.retake_button));
retakeButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(AttachActivity.this, MainActivity.class);
startActivity(intent);
}
});
try {
URL url;
url = new URL("http://btl-cromwell:9000/api/engine/v1/version");
asyncRequest.execute(url);
} catch (Exception e) {
Log.e(logtag, e.toString());
}
}
Note the URL that is passed to he async task should just return JSON containing the version number of the service receiving the request.
The async task (asyncRequest) code is below:
public class AsyncRequest extends AsyncTask<URL, Void, List<String>> {
private String logtag = "AsyncRequestTask";
public AsyncResponse delegate;
List<String> projects = new ArrayList<String>();
#Override
protected void onPreExecute(){
super.onPreExecute();
}
#Override
protected List<String> doInBackground(URL... urls) {
try {
// Creating & connection Connection with url and required Header.
HttpURLConnection urlConnection = (HttpURLConnection) urls[0].openConnection();
urlConnection.setRequestProperty("Content-Type", "application/json");
urlConnection.setRequestMethod("GET"); //POST or GET
urlConnection.setRequestProperty("User-Agent", "Test");
// CODE HANGS HERE
int responseCode = urlConnection.getResponseCode();
String responseMessage = urlConnection.getResponseMessage();
projects.add(responseMessage);
} catch (Exception e) {
Log.e(logtag, e.toString());
}
return projects;
}
#Override
protected void onPostExecute(List<String> result){
delegate.processFinish(result);
}
}
Once I have the request working I will populate the projects variable with what I actually want to return but for now I just have it set to responseMessage. I'm sure this is just something to do with my unfamiliarity in making requests in Java, but I have spent days on this and can't figure it out. Any help is greatly appreciated.

asyncRequest.execute(url);
asyncRequest.getStatus();
String[] projects = asyncRequest.get();
It is not possible to do both an .execute and a .get().
As you should never use .get(), you better remove that statement.
Remove all code after asyncRequest.execute(url); and put that code in the onPostExecute of your AsyncTask.

Finish procedure before starting a new one

I am beginner in Android and I need some help. So, I have a procedure with sub-procedures inside. How can I finish one before starting a new one. Here is a code to better understand:
public void onCellLocationChanged(CellLocation lokacija) {
super.onCellLocationChanged(lokacija);
location = (GsmCellLocation) Phone.getCellLocation();
textCellId.setText(String.valueOf(location.getCid() % 65536));
textCellLac.setText(String.valueOf(location.getLac()));
String JSON_URL_string=JSON_URL + "?cellid=" + String.valueOf(location.getCid()%65636);
getJSON(JSON_URL_string);
myJSONString = textCellNameSakriven.getText().toString();
ParseJSON(myJSONString);
}
Problem is that myJSONString is empty, cause textCEllNameSkriven is also empty. That textView textCellNameSkriven is made when getJSON(JSON_URL_string) is finished. If I run debugger and go step by step, app goes directly from getJSON(JSON_URL_string) row to the next one and the next etc
Edit: Maybe the problem is that onPostExecute is not finished before starting ParseJSON. Here is also a code for getJSON:
private void getJSON(String url) {
class GetJSON extends AsyncTask<String, Void, String> {
ProgressDialog loading;
#Override
protected void onPreExecute() {
super.onPreExecute();
loading = ProgressDialog.show(MainActivity.this, "Please Wait...", null, true, true);
}
#Override
protected String doInBackground(String... params) {
String uri = params[0];
BufferedReader bufferedReader = null;
try {
URL url = new URL(uri);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
StringBuilder sb = new StringBuilder();
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;
}
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loading.dismiss();
textCellNameSakriven.setText(s);
}
}
GetJSON gj = new GetJSON();
gj.execute(url);
}

Since you are running a async task it practically runs on a different thread, so your getJson method need not wait for post execute and can return after starting the async task, so you can never be sure in this way that parseJson gets executed after textView is populated. You are running into classic race condition issue.
Your issue could be easily solved, if you have a callback which is called after postExecute is done, and you can handle parseJson there
So, something simple like , create interface MyCallback
public interface MyCallback {
public OnReadJsonDone();
}
Let your activity implement this MyCallback
public MainActivity implements MyCallback
{
...........
#Override
public OnReadJsonDone(){
parseJson();
}
Now change signature of getJson to
getJSON(string json, final MyCallback callback) {
Now in onpostexecute
//call OnReadJsonDone
callback.OnReadJsonDone()
So, all you now need is while calling getJSon pass this as second param
getJSON(JSON_URL_string,this);
Haven't tested this but you get the idea

Multiple backend call with Retrofit at same time [duplicate]

I'm using Android SDK 4.0.3 API15 and I want to run multiple AsyncTasks parallely. I'm getting my data from web server and animating(10 fps) it real-time. But depending on user operations I need to send some data to web server also. When this occurs my animation pauses for a short time (sending data gets into queue and getting data waits it to finish ) and therefore I can't catch the real-time.
This answer is quite explaining but I couldn't make it work. So any help will be very appreciated.
I think I need to use this function to achieve that:
AsyncTask.executeOnExecutor(Executor exec, Params... params)
But I can't pass an executor as a parameter and I can't instantiate an executor. This is my AsyncTask class:
public class GetPlayers extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
rawData="";
for (String url : urls) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse execute = client.execute(httpGet);
InputStream content = execute.getEntity().getContent();
BufferedReader buffer = new BufferedReader(new InputStreamReader(content));
if((rawData = buffer.readLine()) == null){
rawData = "error";
}
} catch (Exception e) {
e.printStackTrace();
}
}
return rawData;
}
#Override
protected void onPostExecute(String result) {
manipulate();
}
}
And I execute it like this:
GetPlayers task = new GetPlayers();
requestString = "web adress is here...";
task.execute(new String[] { requestString });

This is how I do that:
if( Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ) {
new MyAsyncTask().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
} else {
new MyAsyncTask().execute();
}
where MyAsyncTask is regular AsyncTask subclass. Or you can wrap this all in helper class:
class TaskHelper {
public static <P, T extends AsyncTask<P, ?, ?>> void execute(T task) {
execute(task, (P[]) null);
}
#SuppressLint("NewApi")
public static <P, T extends AsyncTask<P, ?, ?>> void execute(T task, P... params) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, params);
} else {
task.execute(params);
}
}
}
and then just do:
TaskHelper.execute( new MyTask() );
or
TaskHelper.execute( new MyTask(), args );
or
TaskHelper.execute( new MyTask(constructorParams), args );

This problem occured to me, when updating my app in AndroidStudio to
sdk 25 from Intelliy using Android 2.3
Just the little change (executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, string1, ...); ) works perfectly.
I have an AsyncTask running in a Service for download and
create AsyncTasks for upload in no service.

Convert android AsyncTask call to a separate class and call from all activities

I am new to android development. I have a AsyncTask function in my application. Calling http request from all activities. Now in each activity I am using the following class to connect to server, in some activities I even called twice !!.
Basically I am a web developer and in such cases we use a single class which can be accessed from entire application(web) and use the common function to do the same activity. The only difference is input and out put will be changed.
My doubt is in this case can I use ( convert) this to such a function or class ?
My assume is
Create an android class ( which can be accessed from all the activities )
Just make the JSON string we need with specific server ( for process in server )
Just pass the created json to the created class and then made the http connect )
Process the returned data from server
Pass that to the corresponding activity
So that I can use the same function for all the activities and I can avoid duplicate query
Can I convert this code to such a manner ?
My Code
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
setContentView(R.layout.activity_main);
LogIN loginUser = new LogIN();
LoginUser.execute("");
}
private class LogIN extends AsyncTask<String, Integer, String> {
#Override
protected String doInBackground(String... sUrl) {
try {
String path = "http://www.domain_name.com/app/checkSession.php";
HttpClient client = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(client.getParams(), 10000);
HttpResponse response;
JSONObject json = new JSONObject();
try {
HttpPost post = new HttpPost(path);
json.put("access_token", "123456");
post.setHeader("json", json.toString());
StringEntity se = new StringEntity(json.toString());
se.setContentEncoding((Header) new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
post.setEntity(se);
response = client.execute(post);
/* Checking response */
if (response != null) {
InputStream in = response.getEntity().getContent();
String a = convertStreamToString(in);
JSONObject jsono = stringToJsonobj(a);
String passedStringValue = jsono.getString("result");
if(passedStringValue.equals("1")){
flags=1;
//Log.v("TAGG", "Success");
}
else {
flags=0;
//Log.v("TAGG", "Failed !");
}
}
} catch (Exception e) {
e.printStackTrace();
}
} catch (Exception e) {
}
return null;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
showDialogue("Login Processing", "Loading");
}
#Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
}
#Override
protected void onPostExecute(String result) {
if(flags.equals(1)){
Itent homepage = new Intent(MainActivity.this, RegisterDevice.class);
startActivity(homepage);
finish();
}
else {
Intent homepage = new Intent(MainActivity.this, LoginActivity.class);
startActivity(homepage);
finish();
}
super.onPostExecute(result);
}
}
}
Please any one help/advise
Thanks in advance

Extract your class to a different file and make it public
public class LogIN extends AsyncTask<Object, Integer, String> {
private ILoginListener listener;
#Override
protected String doInBackground(Object... arg0) {
try {
this.listener = (ILoginListener) arg0[0];
//You can also send the url in the obj array
String theUrl = (String) arg0[1];
String path = "http://www.domain_name.com/app/checkSession.php";
HttpClient client = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(client.getParams(), 10000);
HttpResponse response;
JSONObject json = new JSONObject();
try {
HttpPost post = new HttpPost(path);
json.put("access_token", "123456");
post.setHeader("json", json.toString());
StringEntity se = new StringEntity(json.toString());
se.setContentEncoding((Header) new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
post.setEntity(se);
response = client.execute(post);
/* Checking response */
if (response != null) {
InputStream in = response.getEntity().getContent();
String a = convertStreamToString(in);
JSONObject jsono = stringToJsonobj(a);
String passedStringValue = jsono.getString("result");
if(passedStringValue.equals("1")){
flags=1;
//Log.v("TAGG", "Success");
}
else {
flags=0;
//Log.v("TAGG", "Failed !");
}
}
} catch (Exception e) {
e.printStackTrace();
}
} catch (Exception e) {
}
return null;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
showDialogue("Login Processing", "Loading");
}
#Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
}
#Override
protected void onPostExecute(String result) {
listener.logInSessionCheckListener(flag.equals(1));
super.onPostExecute(result);
}
}
Regarding your other question, I normally have an interface for that, something like this:
public interface ILoginListener {
public void logInSessionCheckListener(SomeNeeded Value);
}
I implement the interface in the class where i need the postExecute result and in the overriden method you can to what you want with the result of your task.
Your class where you user it will look something like this:
public class SomeClass implements ILoginListener {
//Call it like this from any class:
LogIN loginTask = new LogIn();
Object[] someParams = new Object[2];
//add the listener
someParams[0] = SomeClass.this
//add the url
someParams[1] = someUrlString;
loginTask.execute(someParams);
#Override
public void logInSessionCheckListener(SomeNeeded Value){
//do Stuff with your results
}
}

You can do it like make separate class for everything inside doInBackground() method and called it in all activity with passing parameter to
LogIN loginUser = new LogIN(yourparameter);
LoginUser.execute("");
and check parameter in AsyncTask Class constructor like
public LogIN(Myparameter){
// Your data
}

On the other hand you can use this great framework for android : android-query and the async API.
It allows you to perform asynchroneous network tasks from activities and easily work with the results of your requests.

You should use interfaces to implement a callback to your ui activity.
Have a look at this thread, it might be useful:
android asynctask sending callbacks to ui
And your asyntask class should be in a seperate java file with public acces.
And to pass the parametres you simply have to call a new LogIN async Task like this:
new LogIN().execute(urls);
Hope it helped :)

Remember that you can never know when AsyncTask is going to finish. So if you're using this to authenticate users and then perform task X, task Y, or task Z,
then maybe it's better to create a Login helper class
public class LoginHelper {
public boolean login(params){
// Authenticate user and return true if successfull
}
}
and then have in your Activity classes
private class X extends AsyncTask {
#Override
protected String doInBackground(String... sUrl) {
...
boolean authenticated = LoginHelper.login(params...);
if(authenticated == true) {
// Perform task X here...
} else {
// Inform the user that the login failed...
}
}

First of all
You have to pass the context in which you are calling your async task
Sample Code
Login loginTask = new Long(getContext());
loginTask.execute();
You class Login should have a constructor that accepts the Context
Sample Code
public class Login extends AsyncTask<String, Integer, String> {
private Context mContext ;
private ProgressDialog pd;
private Handler handler = new Handler { };
public Login (Context context){
mContext = context ;
}
.....
Then make sure to create the method showDialog inside Login class to show the progress dialog
Note
You can add what ever Constructors you need to customize the behaviour of your Login task
for example : pass boolean parameter to tell that the Login Task is cancelable....
Hope that help you :)

Getting a hold of doInBackground(String... params)

In some way I do understand the Handler, but I'm not sure what to do with the params and how to let the code wait until the job is done in the background. I want the UI to be normally working and in the background I want to do an exchange rate calculation.
I have the following:
I call new getOnlineExchangeRate().execute(""); //Get Exchange Rate in BG
After that I want to have a result=amount*exchangerate, but the code is not waiting for the result.
Can somebody tell me how the calculation waits till we have an exchangerate. Do I have to send some params and how would that look?
.
.
.
.
.
public double getYahooExchangeRate(String ER){
double exchangerate=0;
try {
s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+ER+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
//s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject jObj;
jObj = new JSONObject(s);
String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
exchangerate=Double.parseDouble(exResult);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
ALS.Toast(myContext.getString(R.string.conversionerror), false);
}
catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
ALS.Toast(myContext.getString(R.string.conversionerror), false);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
ALS.Toast(myContext.getString(R.string.conversionerror), false);
}
return exchangerate;
}
public String getJson(String url)throws ClientProtocolException, IOException {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return build.toString();
}
public class getOnlineExchangeRate extends AsyncTask<String, Void, String> {
#Override
protected void onPostExecute(String result) {
// execution of result of Long time consuming operation
ALS.Toast(myContext.getString(R.string.exchangeratesupdated), true);
}
#Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
// perform long running operation operation
getYahooExchangeRate(USDEUR);
return null;
}

I think your problem is in this line:
#Override
protected String doInBackground(String... params) {
getYahooExchangeRate(USDEUR);
return null;
You want to return the result of getYahooExchangeRate and not null :)
So change this and the return-value should be a double. So change this to:
#Override
protected Double doInBackground(String... params){
return getYahooExchangeRate(USDEUR);
}
You also have to change your class header:
public class getOnlineExchangeRate extends AsyncTask<String, Void, Double> {
AsyncTask<Params, Progress, Result>
The generic part tells the AsyncTask which Informationstypes are handled.
The first is the type for the params of doInBackground(Params... )
The second is the type of the progress-Information
The last explains which type is returned by doInBackground(), so it changes the method-header from
protected Result doInBackground(Params... params){ };
to
protected double doInBackground(Params... params){};
To bring back the Result i would use and Observer oder Callback-Pattern.
Edit: changed double to Double, because primitives cannot be used for Generics.

the code is not waiting for the result. Can somebody tell me how the calculation waits till we have an exchangerate. Do I have to send some params and how would that look?
You could use AsyncTask#get() to force the code to wait, but this blocks the main thread until the AsyncTask completes which defies the purpose of using an asynchronous task.
It is best to design your Activity to proceed without the exchange rate, just like my mail app loads allowing me to compose messages and read old messages while the new messages are being fetched. When the asynchronous data loads then you can update your UI with the new information. (I believe this is what you are trying to do.)
To add on to user1885518 code, you should use your AsyncTask as a subclass in your Activity like this:
public class MainActivity extends Activity {
private class getOnlineExchangeRate extends AsyncTask<Void, Void, Double> {
#Override
protected Double doInBackground(Void... params) {
return getYahooExchangeRate(params[0]);
}
#Override
protected void onPostExecute(Double rate) {
// Do something with rate
}
}
...
}
Once you know which exchange rate you want, call:
new getOnlineExchangeRate().execute(USDEUR); //Get Exchange Rate in BG
Now when you have gotten the rate from online, the code calls onPostExecute() with your desired rate. Inside on onPostExceute() you can call whatever method you want in your ACtivity to calculate result=amount*exchangerate and display result wherever it is appropriate.