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How i can use Asynctask correctly?

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I'm developing an Android application but Asynctask and Looper create to me more problem and i don't understand how to solve this problem... This is my main activity:

@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public class MainActivity extends Activity {
 private ProgressDialog progress = null;
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);  


  //Check if the connectivity is available   
  CheckConnectivity check = new CheckConnectivity();
  Boolean conn = check.checkNow(this.getApplicationContext());
  //if connectivity is available
  if(conn == true){
   //Create the action bar
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {  
    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);

    ActionBar actionBar = getActionBar();
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setDisplayHomeAsUpEnabled(false);
    actionBar.setHomeButtonEnabled(false);
    actionBar.setBackgroundDrawable(new ColorDrawable(Color.parseColor("#0170a5")));
   }
   setContentView(R.layout.activity_main);
   GetNews getNews = new GetNews();
   getNews.execute();
  }else{
      connectivityMessage("Nessuna connessione presente, assicurati di avere il traffico dati oppure il Wi-Fi attivato e riprova."); 
  }
 } 

/******************************************************************************************************/
 private class GetNews extends AsyncTask<Void, Void, String>{

   @Override
   protected String doInBackground(Void... params) {
    Looper.prepare(); 
    ReadServer read = new ReadServer();
    String result = read.readserver("list_news","homepage");
    return result;
   }

   @Override
   protected void onCancelled() {
    super.onCancelled();
   }

   @Override
   protected void onPreExecute() {
    progress = ProgressDialog.show(
    MainActivity.this, null, "Caricamento notizie...");
    super.onPreExecute();
  }

    @Override
    protected void onPostExecute(String result) {
    super.onPostExecute(result);
    try {
     String url_img = null;
     String path = "http://www.MYPATH.it";

     TableLayout MainTable = (TableLayout) findViewById(R.id.main_table);
     JSONArray Jobj = new JSONArray(result);

     for (int i = 0; i < Jobj.length(); i++) {
     TableRow row = new TableRow(getApplicationContext());
     row.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT, TableRow.LayoutParams.WRAP_CONTENT));


     JSONObject news_preview = Jobj.getJSONObject(i);
     Integer news_id = news_preview.getInt("id_articolo");
     String news_title = news_preview.getString("titolo");
     String news_image = news_preview.getString("immagine");

     // Check if image url is relative or absolute
     Pattern p = Pattern.compile("^(https?|ftp|file)://[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]");
     Matcher m = p.matcher(news_image);

     if (m.matches() == false) {
         url_img = path + news_image;
     } else if (m.matches() == true) {
        url_img = news_image;
     }

     // Call Html Parser to parse text
     HtmlParser parsed_string = new HtmlParser();
     Spanned title_nohtml = parsed_string.htmlparser(news_title);

     final ImageView img = new ImageView(getApplicationContext());
     final TextView txt = new TextView(getApplicationContext());
     LayoutParams params = new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
     img.setAdjustViewBounds(true);
     Bitmap bitmap = BitmapFactory.decodeStream((InputStream) new URL(url_img).getContent());
     Bitmap resized = null;

     int screenLayout = getApplicationContext().getResources().getConfiguration().screenLayout;
     screenLayout &= Configuration.SCREENLAYOUT_SIZE_MASK;

     switch (screenLayout) {
      case Configuration.SCREENLAYOUT_SIZE_SMALL:
       row.setPadding(0, 7, 2, 7);   
       resized = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
       txt.setTextSize(18);
     break;

      case Configuration.SCREENLAYOUT_SIZE_NORMAL:
       row.setPadding(0, 14, 2, 14);
       resized = Bitmap.createScaledBitmap(bitmap, 140, 140, true);
       txt.setTextSize(18);
      break;

      case Configuration.SCREENLAYOUT_SIZE_LARGE:
       row.setPadding(0, 14, 2, 14);
       resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
       txt.setTextSize(24);
      break;

      case Configuration.SCREENLAYOUT_SIZE_XLARGE:
       row.setPadding(0, 14, 2, 14);
       resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
       txt.setTextSize(24);
      break;

      default:

      break;
     }

     img.setImageBitmap(resized);
     txt.setGravity(Gravity.LEFT | Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL);
     txt.setLayoutParams(params);
     txt.setBackgroundColor(Color.WHITE);
     txt.setTypeface(null, Typeface.BOLD);
     txt.setTextColor(Color.BLACK);
     txt.setId(news_id);
     txt.setText(title_nohtml);
     txt.setClickable(true);

     row.addView(img);
     row.addView(txt);
     MainTable.addView(row);

     txt.setOnClickListener(new OnClickListener() {
      public void onClick(View v) {
       Intent intent = new Intent(MainActivity.this, NewsDetail.class);
       Bundle extras = new Bundle();
       extras.putInt("id_news", txt.getId());
       intent.putExtras(extras);
       startActivity(intent);
      }
     });
    }
   }catch (Exception e) {
     AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this);
     alertDialog.setTitle("Si è verificato un errore");
     alertDialog.setMessage("Errore 001" + "\n" + "Non è stato possibile soddisfare la tua richiesta, riprova più tardi.");
     alertDialog.show();
    }
    progress.dismiss();
    Looper.loop();
    Looper.getMainLooper().quitSafely();
    change();
   }

   @Override
    protected void onProgressUpdate(Void... values) {
     super.onProgressUpdate(values);
   }
  }
 /******************************************************************************************************/
 @Override
 public void onStart() {
  super.onStart();
  Tracker tracker = GoogleAnalytics.getInstance(this).getTracker("UA-49974758-1");
  tracker.set(Fields.SCREEN_NAME, "Visualizzazione prima pagina");
  tracker.send(MapBuilder.createAppView().set(Fields.customDimension(1), "Premium").build());
 }
 /******************************************************************************************************/
 public void change(){
  ChangeLog cl = new ChangeLog(this);
  if (cl.firstRun())
  cl.getLogDialog().show();
}
 /******************************************************************************************************/
 @Override
 public void onDestroy() {
  super.onDestroy();
  if ( progress!=null && progress.isShowing() ){
      progress.cancel();
  }
 }

/******************************************************************************************************/
 @Override
 public void onPause() {
  super.onPause();
  if ( progress!=null && progress.isShowing() ){
      progress.cancel();
  }
 }

***** EDIT *****

Video Gallery code :

@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public class VideoGallery extends Activity {
 private ProgressDialog progress = null;


 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);

  //Check if the connectivity is available   
  CheckConnectivity check = new CheckConnectivity();
  Boolean conn = check.checkNow(this.getApplicationContext());
  //if connectivity is available
  if(conn == true){
   //Create the action bar
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {  
    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);

    ActionBar actionBar = getActionBar();
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setDisplayHomeAsUpEnabled(false);
    actionBar.setHomeButtonEnabled(false);
    actionBar.setBackgroundDrawable(new ColorDrawable(Color.parseColor("#0170a5")));
   }
   setContentView(R.layout.activity_main);
   GetVideo getVideo = new GetVideo();
   getVideo.execute();
  }else{
     connectivityMessage("Nessuna connessione presente, assicurati di avere il traffico dati oppure il Wi-Fi attivato e riprova."); 
  } 
 }
/************************************************************************/
 private class GetVideo extends AsyncTask<Void, Void, String>{

   @Override
   protected String doInBackground(Void... params) {
    Looper.prepare();  <---- LINE 86
    ReadServer read = new ReadServer();
    String result = read.readserver("id_gallery", "gall_video");
    return result;
   }

   @Override
   protected void onCancelled() {
    super.onCancelled();
   }

   @Override
   protected void onPreExecute() {
    progress = ProgressDialog.show(
    VideoGallery.this, null, "Caricamento video...");
    super.onPreExecute();
  }

    @Override
    protected void onPostExecute(String result) {
    super.onPostExecute(result);
    try{      
     TableLayout MainTable = (TableLayout)findViewById(R.id.main_table); 
     JSONArray Jobj = new JSONArray(result);
     String url_img = null;
     String url_video = null;

     for (int i = 0; i < Jobj.length(); i++){
      TableRow row = new TableRow(getApplicationContext()); 
      row.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT, TableRow.LayoutParams.WRAP_CONTENT));


      JSONObject list_video = Jobj.getJSONObject(i);
      Integer video_id = list_video.getInt("id_video");
      String video_title = list_video.getString("nome_video");
      String video_image = list_video.getString("video_img");
      String video_url = list_video.getString("url_video");

      Pattern p = Pattern.compile("^(https?|ftp|file)://[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]");
      Matcher m = p.matcher(video_image);

      Pattern v = Pattern.compile("^/video/[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]");
      Matcher vm = v.matcher(video_url);

      //Path video
      if(vm.matches() == false){
       url_video = path_youtube+video_url;
      }else if(vm.matches() == true){
       url_video = path_an_tv+video_url;
      }

      //Path image
      if(m.matches() == false){
       url_img = path+video_image;
      }else if(m.matches() == true){
       url_img = video_image;
      }

      final ImageView img = new ImageView(getApplicationContext());
      final TextView txt = new TextView(getApplicationContext());
      LayoutParams params;
      img.setAdjustViewBounds(true); 
      img.setScaleType(ImageView.ScaleType.CENTER_CROP);
      txt.setGravity(Gravity.LEFT | Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL );
      Bitmap bitmap = BitmapFactory.decodeStream((InputStream)new URL(url_img).getContent());
      Bitmap resized = null;

      int screenLayout = getApplicationContext().getResources().getConfiguration().screenLayout;
      screenLayout &= Configuration.SCREENLAYOUT_SIZE_MASK;

      switch (screenLayout) {
       case Configuration.SCREENLAYOUT_SIZE_SMALL:
        row.setPadding(0, 7, 0, 7);
        resized = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
        params =  new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 70);
        txt.setLayoutParams(params); 
        txt.setTextSize(18); 
      break;

       case Configuration.SCREENLAYOUT_SIZE_NORMAL:
        row.setPadding(0, 14, 0, 14);
        resized = Bitmap.createScaledBitmap(bitmap, 140, 140, true);
        params =  new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 140);
        txt.setLayoutParams(params); 
        txt.setTextSize(18);  
      break;

       case Configuration.SCREENLAYOUT_SIZE_LARGE:
       row.setPadding(0, 14, 0, 14);
       resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
       params =  new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 200);
       txt.setLayoutParams(params);
       txt.setTextSize(24);
       break;

       case Configuration.SCREENLAYOUT_SIZE_XLARGE:
        row.setPadding(0, 14, 0, 14);
        resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true); 
        params =  new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 200);
        txt.setLayoutParams(params);
        txt.setTextSize(24);
       break;

       default:

       break;
      }

      txt.setBackgroundColor(Color.WHITE);
      txt.setTypeface(null, Typeface.BOLD); 
      txt.setTextColor(Color.BLACK); 
      txt.setId(video_id); 
      txt.setTag(url_video); 
      txt.setText(video_title); 
      txt.setClickable(true);         
      img.setImageBitmap(resized);

      row.addView(img);
      row.addView(txt); 
      MainTable.addView(row);

      txt.setOnClickListener(new OnClickListener(){
       public void onClick(View v) {
        startActivity(new Intent(Intent.ACTION_VIEW,Uri.parse((String) txt.getTag())));
       }
      });
     }
    }catch(Exception e){
     AlertDialog.Builder alertDialog = new AlertDialog.Builder(VideoGallery.this);
     alertDialog.setTitle("Si è verificato un errore");
     alertDialog.setMessage("Errore 001" +"\n"+"Non è stato possibile soddisfare la tua richiesta, riprova più tardi.");
     alertDialog.show();        
    } 
    progress.dismiss();
    Looper.loop();
    Looper.getMainLooper().quitSafely();
   }

   @Override
    protected void onProgressUpdate(Void... values) {
     super.onProgressUpdate(values);
   }
  }

/******************************************************************************************************/
 @Override
 public void onStart() {
  super.onStart();
  Tracker tracker = GoogleAnalytics.getInstance(this).getTracker("UA-49974758-1");
  tracker.set(Fields.SCREEN_NAME, "Visualizzazione video");
  tracker.send(MapBuilder.createAppView().set(Fields.customDimension(1), "Premium").build());
 }

/******************************************************************************************************/
 @Override
 public void onDestroy() {
  super.onDestroy();
  if ( progress!=null && progress.isShowing() ){
      progress.cancel();
  }
 }

/******************************************************************************************************/
 @Override
 public void onPause() {
  super.onPause();
  if ( progress!=null && progress.isShowing() ){
      progress.cancel();
  }
 }

When i change activity to another that contain again an asynctask an error occurred:

11-14 11:49:18.196: E/AndroidRuntime(18749): FATAL EXCEPTION: AsyncTask #1
11-14 11:49:18.196: E/AndroidRuntime(18749): java.lang.RuntimeException: An error occured while executing doInBackground()
11-14 11:49:18.196: E/AndroidRuntime(18749):    at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at java.util.concurrent.FutureTask.run(FutureTask.java:239)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at java.lang.Thread.run(Thread.java:841)
11-14 11:49:18.196: E/AndroidRuntime(18749): Caused by: java.lang.RuntimeException: Only one Looper may be created per thread
11-14 11:49:18.196: E/AndroidRuntime(18749):    at android.os.Looper.prepare(Looper.java:78)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at android.os.Looper.prepare(Looper.java:73)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at com.miaapplicazione.VideoGallery$GetVideo.doInBackground(VideoGallery.java:86)
11-14 11:49:18.196: E/AndroidRuntime(18749):    at com.miaapplicazione.VideoGallery$GetVideo.doInBackground(VideoGallery.java:1)

**** EDIT 2 ****

If i delete Looper.prepare(); in video gallery another error occurred:

11-14 12:01:48.357: E/AndroidRuntime(20476): FATAL EXCEPTION: AsyncTask #2
11-14 12:01:48.357: E/AndroidRuntime(20476): java.lang.RuntimeException: An error occured while executing doInBackground()
11-14 12:01:48.357: E/AndroidRuntime(20476):    at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at java.util.concurrent.FutureTask.run(FutureTask.java:239)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at java.lang.Thread.run(Thread.java:841)
11-14 12:01:48.357: E/AndroidRuntime(20476): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
11-14 12:01:48.357: E/AndroidRuntime(20476):    at android.os.Handler.<init>(Handler.java:197)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at android.os.Handler.<init>(Handler.java:111)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at android.app.Activity.<init>(Activity.java:759)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at com.alessandrianews.ReadServer.<init>(ReadServer.java:17)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at com.alessandrianews.VideoGallery$GetVideo.doInBackground(VideoGallery.java:86)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at com.alessandrianews.VideoGallery$GetVideo.doInBackground(VideoGallery.java:1)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
11-14 12:01:48.357: E/AndroidRuntime(20476):    at java.util.concurrent.FutureTask.run(FutureTask.java:234)
11-14 12:01:48.357: E/AndroidRuntime(20476):    ... 4 more

How i can solve this problem ?? I read all other question but the solutions doesn't help me.

android android-asynctask android-looper
Original Q&A
2

There are 2 answers

1
Akash Moradiya On BEST ANSWER

If you want to use AsyncTask so use it, you shouldn't mix it with Lopper...

protected Integer doInBackground(Void... params) {}

already working on background thread and there is no reason to call Lopper, for what?

If your application need to do some kind of long computation so AsyncTask is very good tool for it because offers methods which working on UI Thread and allow to update UI with some progress of work because every User that will use your application should know that application "doing something" (when it takes more than 2-5 seconds).

Also it's generic and that provide some benefits.

If you do not need to update UI just use for example Handler.

so remove Looper.prepare();

0
AudioBubble On

Try to add:

if (Looper.myLooper() == null) Looper.prepare;

It worked for me

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