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Stop the onPostExecute of an Async Task in java

I have the following code. My problem is, that I can't get the JSON.execute() to stop/cancel. I spend quite some time looking up possible answers but I wasn't able to find anything that really worked (e.g. JSON.cancel(true)). As soon as I turn the trackerswitch on, the AsnycTask starts running every 3 seconds just like it's supposed to. Is there a way to easily stop the AsyncTask from executing as soon as the trackerswitch is turned off?
private boolean tracking = false;
private Switch trackerswitch;
private final Timer timer= new Timer();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.table_layout);
final Handler handler=new Handler();
final int delay = 4000;
trackerswitch=findViewById(R.id.trackerswitch);
trackerswitch.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
NetworkAccess JSON = new NetworkAccess();
if(trackerswitch.isChecked()){
trackerswitch.setText("Tracking...");
tracking=true;
handler.postDelayed(new Runnable() {
#Override
public void run() {
NetworkAccess JSON = new NetworkAccess();
JSON.execute();
handler.postDelayed(this, delay);
}
},delay);
}
else{
tracking=false;
trackerswitch.setText("Start Tracking");
}
}
});
}
}
This is what's called in the network class:
public class NetworkAccess extends AsyncTask<Void, Void, Void> {
public ArrayList<String> alldata = new ArrayList<>();
public ArrayList<String> locationlist = new ArrayList<>();
int stride;
String data;
#Override
protected Void doInBackground(Void... voids) {//4B4ADC
SOME CODE WHICH ISN'T IMPORTANT FOR MY PROBLEM
alldata.addAll(elementlist);
locationlist.addAll(loctrack);
}
}
catch(IOException | JSONException e){
MainActivity.field1.setText(e.getClass().getCanonicalName());
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
MainActivity.field1.setText(String.format("%20s %20s", alldata.get(0), alldata.get(1)));
COUPLE MORE OF THESE SETTEXT COMMANDS TO FILL A TABLE WITH DATA
}
}
Thanks for your help!

handler.postDelayed() adds objects of the Runnable you provide to the message queue, to be run at the specified interval. You need to remove all the queued objects from the message queue in order to cancel the execution. Calling JSON.cancel(true) does not affect other objects that are already added to the queue.
You'll have to retain a reference to your Runnable implementation and then call handler.removeCallbacks(r) to prevent further executions. Instead of using an anonymous class in handler.postDelayed().
This documentation page sheds more light on the matter.
Also refer this page for what happens when you call cancel(true) on an AsyncTask.

Android: “BadTokenException: Unable to add window; is your activity running?

I am opening a progressdialog with AsyncTask in doInBackground method the question is loading from database and after question successfully loaded the progress dialog box will be closed
but my problem is some time I am getting following error
android.view.WindowManager$BadTokenException: Unable to add window -- token android.view.ViewRoot$W#44757528 is not valid; is your activity running?
by doing some googling I have found that there may be i am holding on to a reference to a Context (either explicitly, or by creating a Dialog or Toast or some other dependent item) that has been destroyed (typically because you are using the onCreateDialog or you passed the Activity to some other process that didn't get destroyed when the Activity was destroyed).
So I have put below code that dismiss progressdialog in-case if activity is destroyed before dialog box is dismissed
protected void onDestroy() {
if (pdForNewQuestion != null)
pdForNewQuestion.dismiss();
super.onDestroy();
}
but I still face the issue. I am not destroying any activity but still the error suddenly comes sometimes and sometimes it works properly
the async code is below
// Start new question in every 60 seconds :)
new Thread(new Runnable() {
public void run() {
while (true) {
try {
Thread.sleep(1000);
mProgressStatus++;
} catch (Exception e) {
e.printStackTrace();
}
runOnUiThread(new Runnable() {
public void run() {
mProgress.setProgress(mProgressStatus);
txtCountingNum.setText((timer--) + "\nSec.");
if (timer < 0) {
questionLoadWithAsyncTask();
}
}
});
}
}
}).start();
public void questionLoadWithAsyncTask() {
new AsyncTask<Void, Void, Void>() {
#Override
protected void onPreExecute() {
pdForNewQuestion = new ProgressDialog(QuizActivity.this);
pdForNewQuestion.setTitle("Please wait...");
pdForNewQuestion.setMessage("Question is loading...");
pdForNewQuestion.setCancelable(false);
pdForNewQuestion.setIndeterminate(true);
pdForNewQuestion.show();
}
#Override
protected Void doInBackground(Void... arg0) {
wordsCursor = dbHelper.getRandomWords();
return null;
}
#Override
protected void onPostExecute(Void result) {
if (pdForNewQuestion != null) {
pdForNewQuestion.dismiss();
}
}
}.execute();
}

Check whether the dialog is showing or not if dialog is showing then only dismiss like this..
#Override
protected void onDestroy() {
if (pdForNewQuestion != null) {
if (pdForNewQuestion.isShowing()) {
pdForNewQuestion.dismiss();
pdForNewQuestion = null;
}
}
super.onDestroy();
}

you are running infinite loop inside new Thread but not breaking the loop and stopping that Thread. It runs infinitely in the background even when activity goes background. try stopping the Thread once work is finished.

First of all why are you starting your AsyncTask inside a Thread? As i understand you are trying to start an AsyncTask every 60 seconds and populate a new question. There is a much better way to do this using only a Handler and AsyncTask.
Create a Handler and post Runnable which runs every seconds and depending on the result start your AsyncTask :
int mSeconds = 0;
Handler mHandler = new Handler();
mHandler.postDelayed(new Runnable() {
#Override
public void run() {
if(mSeconds == 60){
new QuestionLoader().execute();
mSeconds = 0;
}
mHandler.postDelayed(this, 1000);
mSeconds++;
}
}, 1000);
and you can create your AsyncTask like this :
private class QuestionLoader extends AsyncTask<Void, Void, Void>{
#Override
protected void onPreExecute(){
super.onPreExecute();
pdForNewQuestion = new ProgressDialog(MainActivity.this);
pdForNewQuestion.setTitle("Please wait...");
pdForNewQuestion.setMessage("Question is loading...");
pdForNewQuestion.setCancelable(false);
pdForNewQuestion.setIndeterminate(true);
pdForNewQuestion.show();
}
#Override
protected Void doInBackground(Void... params) {
wordsCursor = dbHelper.getRandomWords();
return null;
}
#Override
protected void onPostExecute(Void result){
super.onPostExecute(result);
if(pdForNewQuestion != null && pdForNewQuestion.isShowing()){
pdForNewQuestion.dismiss();
}
}
}

This is usually caused by your app trying to display a dialog using a previously-finished Activity as a context. Then check that the activity is not closed by some other apps or other triggers before showing the dialog
if (!isFinishing()) {
//showdialog here
}

ProgressDialog while loading data

I am encountering a problem in my Android application. I am creating a currency converter. I need to create a progressdialog that appears when you convert a value from one currency to another.
Here is part of my code:
if (text1.equals("US Dollar - USD") && text2.equals("Euro - EUR") && edittextdollars.length() > 0 && edittexteuros.length()==0) {
dialog1 = ProgressDialog.show(getActivity(), "", "Calculating...");
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
try{
convertvalues("USD", "EUR");
handler.sendEmptyMessage(0);
}
catch (Exception e) {
edittexteuros.setText("Error");
}
}
});
thread.start();
}
private Handler handler = new Handler () {
public void handleMessage(android.os.Message msg) {
switch (msg.what) {
case 0:
dialog1.dismiss();
break;
}
}
};
The progressdialog comes up and goes away, but nothing happens in the background. Here are a few pics of what my app looks like:
This is before the progressdialog comes.
When I press calculate:
After the progressdialog finishes:
As you can see, after the progressdialog goes away, my values don't convert.
In my code,
convertvalues("USD", "EUR");
just gets actual currency value from the internet and multiplies it with the value in my edittext. There is nothing wrong with it and it worked without the progressdialog. I have tested it many times myself.
What am I doing wrong here? I have checked Google for over a week, but I could not find a single solution. Any help regarding this problem is greatly appreciated.

Just like how you update your progressdialog in a handler, you must also update EditTexts in the handler (as it must run on the UI thread). So ideally you would return the result from convertvalues and then pass it to the handler via a message.

From what I can see, your code is fine but you aren't updating the TextView/EditText values when you dismiss the dialog. This means that although it looks like nothing is happening, it actually is - you just aren't updating to see the results.
So, assuming convertvalues() has the converted values stored somewhere, before you call dismiss() you should set your TextViews based on those values.

you can use asynctask in android
see following code may be it will help you..
private class asyncTask extends AsyncTask<Void, Void, Boolean>
{
Context context;
ProgressDialog pd;
asyncTask(Context context)
{
this.context = context;
pd = new ProgressDialog(activityContext);
}
protected void onPreExecute()
{
pd.setTitle("Loading..");
pd.setMessage("Please wait ...");
pd.setCancelable(false);
pd.show();
}
protected void onPostExecute(Boolean result)
{
if(pd.isShowing()) pd.dismiss();
}
#Override
protected Boolean doInBackground(Void... params)
{
convertvalues();
return boolean_value;
}
}
And Just Call this asynctask with
new asyncTask(Your_Context).execute();

Async Task with Media Player isn't Firing PublishProgress

I've written a AsyncTask:
public class AudioTransition extends AsyncTask <Void, Void, MediaPlayer>
{
private int goalID;
private int milliseconds;
private MediaPlayer tempPlayer;
AudioTransition(int ID, int Milliseconds)
{
goalID = ID;
milliseconds = (int)(((float)Milliseconds)/100);
}
#Override
protected void onPreExecute()
{
tempPlayer = MediaPlayer.create(context, goalID);
tempPlayer.setVolume(0, 0);
tempPlayer.setLooping(true);
tempPlayer.start();
}
#Override
protected MediaPlayer doInBackground(Void... arg0) {
for (int i = 0; i < 100; i++)
{
value = i;
publishProgress();
try {
Thread.sleep(milliseconds);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (!player.isPlaying())
tempPlayer.pause();
}
return tempPlayer;
}
#Override
protected void onProgressUpdate(Void... v) {
super.onProgressUpdate(v);
player.setVolume(100-value, 100-value);
tempPlayer.setVolume(value, value);
}
#Override
protected void onPostExecute( MediaPlayer result ) {
super.onPostExecute(result);
player.reset();
player = tempPlayer;
player.setVolume(100,100);
transitioning = false;
}
}
But the volume doesn't fade out. It just starts both tracks, then stops. The MediaPlayers are not updated until doInBackground completes. How can I make the MediaPlayers get updated within this type of background worker? It seems like the publishProgress() thing should work.

Oh lord. Dont be sleeping threads inside of AsyncTask! You are completely misusing AsyncTask. You couldn't think of another way to do a timer type thing, so you're latching onto the idea of publishprogress from AsyncTask (which doesn't even work how I think you think it works) even though AsyncTask should be used for one thing and one thing only: doing heavy work off of the main (UI) thread.
If you just wanted to fade the volume out then use something like this: (this goes somewhere outside of any method).
private Runnable VolumeFadeRunnable = new Runnable() {
#Override
public void run() {
volume--;
player.setVolume(volume, volume);
if(volume>0)
handler.postDelayed(this, 1000);
else
handler.removeCallbacks(this);
}
};
just initialize your handler as a field inside of onCreate or whatever and make sure that and the counter variable are visible inside of that runnable.

Can't get publishProgress to work properly. Help?

I have an AsyncTask that takes urls and gets the content length for all urls that are passed through. I'd like to have the progress bar update in the titlebar and have an alertbox display when it is done getting the final value. But I'm having trouble understanding how to make this all function together. The code I have now moves the progress bar but will not have the alertbox show. I don't have a custom title bar, instead I'm calling the requestWindowFeature(FEATURE_PROGRESS). Any help would be appreciated.
This is my Async Class
private class MyClass extends AsyncTask<URL, Integer, Float>
{
protected Float doInBackground(URL... urls)
{
try
{
for(int i = 0; i<urls.length; i++)
{
url = urls[i];
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
urlConnection.connect();
size = urlConnection.getContentLength();
total += size;
while(progress<total)
{
progress++;
publishProgress(progress);
}
}
}
catch(MalformedURLException e)
{
e.printStackTrace();
}
catch(IOException iox)
{
iox.printStackTrace();
}
finally
{
urlConnection.disconnect();
}
return total;
}
protected void onProgressUpdate(Integer... values)
{
setProgressBarVisibility(true);
setProgress(values[0]);
}
Edit: I understand that publishProgress passes data to onProgressUpdate from the doInBackground method. But with this code above, all the urls content length are being added to "total". And I think the above code is correct. My implementation of this is: Push a button from the main class. That button passes all the urls to the AsyncTask. While the urls get the length and add to total (in background) a progress bar appears in the title bar until the background work is done. Then an alert dialog prompts the user for a choice.
What is happening though is the progress bar reaches the end and the alert dialog doesn't show up. Before I started adding this progress bar, the alert dialog showed up. Now it doesn't. How can I go about getting the progress bar to increment properly with the url content length....dismiss the progress bar.....then load the alert dialog in onPostExecute?
protected void onPostExecute(final Float result)
{
setProgressBarVisibility(false);
AlertDialog.Builder alertbox = new AlertDialog.Builder(Vacation.this);
alertbox.setMessage(TEXT STUFF);
alertbox.setPositiveButton("Yes", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface arg0, int arg1)
{
}
});
alertbox.setNegativeButton("No", new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface arg0, int arg1)
{
}
});
alertbox.show();
}

sat is right but u can do that in onPostExecute() methode which is having the UI thread access always remember only doInBackground() does not have UI thread access rest all 3 methode has. if you need more than be specific and show the code where you are finding difficulty.