How to implement ASyncTask in Android

Question

Can someone tell me how to update the user interface using ASyncTask and give an example?

I get value from two web services. From two web services, I get a value in two arraylist by the post method, which will not return a value that will be rounded in a loop. How can I return from onPostExecuteMethod?

This is my asynchronous class:

public class HomeTask extends AsyncTask<Void,Void,Bundle> { private Context ctx; public HomeTask(Context context) { ctx = context; } @Override protected void onPreExecute() { //super.onPreExecute(); //setContentView(R.layout.splash); dlg = new ProgressDialog(getDialogContext()); dlg.setMessage("Loading...."); dlg.show(); //setContentView(R.layout.splash); } @Override protected Bundle doInBackground(Void... params) { Bundle b=new Bundle(); // TODO Auto-generated method stub try { WebService tableservice=new WebService(); tableservicevalue=tableservice.callTableServer(SOAP_ACTION,"",strUsername,strPassWord,questGroupId,URL); tableservicevalue=decodeXMLData(tableservicevalue); DomTableParser parser=new DomTableParser(); parser.setTableservicevalue(tableservicevalue); parsedValue=parser.parseXmlFile(tableservicevalue); Log.d("1234%%%%$$$$$$$parsed value$$$$$", parsedValue.toString()); WebService service=new WebService(); webservicevalue=service.callHomeServer(SOAP_ACTION,"",strUsername,strPassWord,questGroupId,URL); webservicevalue=decodeXMLData(webservicevalue); ArticleParser articleParser=new ArticleParser(); articleParsedValue=articleParser.parseXmlArticle(webservicevalue); //b.putStringArrayList("articleParsedValue", articleParsedValue); Log.d("(((((((parsed value is",parsedValue.toString()); b.putStringArrayList("parsedValue", parsedValue); b.putStringArrayList("articleParsedValue", articleParsedValue); Log.d("(((((((parsed value is",articleParsedValue.toString()); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } return b; } @Override protected void onPostExecute(Bundle b) { Log.d("vijay checking","checking&&&&"); Log.d("****","*********"); Log.d("calling","handler"); Log.d("****","*********"); parsedValue1=b.getStringArrayList("parsedValue"); articleParsedValue1=b.getStringArrayList("articleParsedValue"); } 

onupdating user interface

 new HomeTask(HomeActivity2.this).execute(null); for(int i=0;i<parsedValue1.size();i++) { DomParserTableDataSet dataSet=(DomParserTableDataSet)parsedValue1.get(i); if(i==0) { Log.d("&&&&&&index name is", dataSet.getIndexName()); Log.d("&&&&&&index name is", dataSet.getLastValue()); Log.d("&&&&&&index name is",dataSet.getChangePercentage() ); txtindex0.setText(dataSet.getIndexName()); txtlast0.setText(dataSet.getLastValue()); txtchange0.setText(dataSet.getChangePercentage()); } if(i==1) { Log.d("&&&&&&index name is", dataSet.getIndexName()); Log.d("&&&&&&index name is", dataSet.getLastValue()); Log.d("&&&&&&index name is",dataSet.getChangePercentage() ); txtindex1.setText(dataSet.getIndexName()); txtlast1.setText(dataSet.getLastValue()); txtchange1.setText(dataSet.getChangePercentage()); } if(i==2) { Log.d("&&&&&&index name is", dataSet.getIndexName()); Log.d("&&&&&&index name is", dataSet.getLastValue()); Log.d("&&&&&&index name is",dataSet.getChangePercentage() ); txtindex2.setText(dataSet.getIndexName()); txtlast2.setText(dataSet.getLastValue()); txtchange2.setText(dataSet.getChangePercentage()); } if(i==3) { Log.d("&&&&&&index name is", dataSet.getIndexName()); Log.d("&&&&&&index name is", dataSet.getLastValue()); Log.d("&&&&&&index name is",dataSet.getChangePercentage() ); txtindex3.setText(dataSet.getIndexName()); txtlast3.setText(dataSet.getLastValue()); txtchange3.setText(dataSet.getChangePercentage()); } } // for(int i=0;i<articleParsedValue1.size();i++) { System.out.println("for loop checking i is"+i); ArticleDataSet articleDataset=(ArticleDataSet)articleParsedValue1.get(i); System.out.println("articleDataset.getArticle_title()"+articleDataset.getArticle_title()); HashMap<String, String> mapValue=new HashMap<String, String>(); WebView webviewcontent=new WebView(HomeActivity2.this); if(articleDataset.getArticle_summary().length()>75) { summary=articleDataset.getArticle_summary().substring(0,75)+"..."; } else { summary=articleDataset.getArticle_summary(); } String html ="<html><body><div><label> <font face=\"verdana\" color=\"#C1002B\" size=\"4\"><b>"+articleDataset.getArticle_title()+"</b> </font> </label>"+ "<label> <font color=\"#000000\" size=\"2\" face=\"verdana\">"+"|"+"</font></label> "+"<label> <font color=\"#AAAAAA\" face=\"verdana\" size=\"2\">"+articleDataset.getArticle_date()+" </font></label></div>"; html=html+"<div><label> <font color=\"#000000\" face=\"verdana\" size=\"2\">"+summary+" </font></label></div></body></html>" ; webviewcontent.getSettings().setJavaScriptEnabled(true); webviewcontent.clearCache(true); final Activity activity = HomeActivity2.this; webviewcontent.loadData(html, "text/html", "utf-8"); if(i==articleParsedValue1.size()-1) { webviewcontent.setWebViewClient(new WebViewClient() { public boolean shouldOverrideUrlLoading(WebView view, String url) { view.loadUrl(url); return true; } public void onPageFinished(WebView view, String url) { // setContentView(R.layout.home); if (dlg.isShowing()) { dlg.dismiss(); dlg = null; } splash.setVisibility(View.GONE); // setContentView(repl); } }); } mainlinear4.addView(webviewcontent); //webviewcontent.setOnTouchListener(HomeActivity2.this); } } 

Answer 1

 List<String> data; // declare here so that we can use it in onPostExecute(). public class YourActivity extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); starttask(); } private void starttask() { new FileAsync().execute("start"); Toast toast = Toast.makeText(yourActivity.this," start:" , 7);toast.show(); } class FileAsync extends AsyncTask<String, String, String> { @Override protected void onPreExecute() { super.onPreExecute(); m_ProgressDialog = ProgressDialog.show(yourActivity.this, "", "Loading ...", true); } @Override protected String doInBackground(String... aurl) { // These methods are calling data from web service made // in sperate class but you can do this here as well. TempDAO tempDAO = new TempDAOImpl(); data = tempDAO.getDataList(arg1,arg2); return null; } protected void onProgressUpdate(String... progress) { Log.d("ANDRO_ASYNC",progress[0]); } @Override protected void onPostExecute(String unused) { TextView textData= new TextView(YourActivity.this); textData.setText(data.get(1)); textData.setTextColor(Color.WHITE); textData.setGravity(Gravity.CENTER); setContentView(textData); m_ProgressDialog.dismiss(); } } 

Answer 2

 private class HttpAsyncTask extends AsyncTask<String, Void, String> { AlertDialog.Builder builder; protected void onPreExecute() { super.onPreExecute(); builder = new AlertDialog.Builder(TabGroup2ProductsActivity.this); } @Override protected String doInBackground(String... urls) { if (urls.length == 1) { return POST(urls[0]); } else { if ("pdf".equalsIgnoreCase(urls[1])) { downloadPDF(urls[0]); return ""; } else { downloadImage(urls[0]); return ""; } } } @Override protected void onPostExecute(String result) { } } public String POST(String url) { System.out.println("I am in post data./.............................."); HttpClient httpclient = new DefaultHttpClient(); HttpGet httppost = new HttpGet(url); String result = null; try { HttpResponse response = httpclient.execute(httppost); int status = response.getStatusLine().getStatusCode(); System.out.println("Status is : " + status); ParseProductJson parseJson = new ParseProductJson(); if (status == 200) { result = EntityUtils.toString(response.getEntity()); System.out .println("################result1###############################" + result); FileOutputStream fos = openFileOutput("productsJson.json", Context.MODE_PRIVATE); fos.write(result.getBytes()); fos.close(); System.out.println("Done"); HashMap<String, List<Product>> hashmap = parseJson .parseProductJson(readProductsJSON("productsJson.json")); arrGroupelements = parseJson.getHeadingArray(hashmap); arrChildelements = parseJson.get2dArray(hashmap); statusClass = status; } else { statusClass = 400; result = "Did not work!"; } } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return result; } } and from Activity onCreate(){ int statusClass = 2; new HttpAsyncTask() .execute("http://104.130.240.26:8080/bhn/service/products/"); do { try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } while (statusClass == 2); } 

Async task example for webservice request

Answer 3

The following is a way to create AsyncTask:

  private class AsyncTaskGetPlaces extends AsyncTask<Void, Void, AsyncTaskResult<Object>> { @Override protected void onPreExecute() { super.onPreExecute(); } @Override protected AsyncTaskResult<Object> doInBackground(Void... params) { try { LibHttp libHttp = new LibHttp(); String res = libHttp.listBusiness("21"," [e-mail] "); return new AsyncTaskResult<Object>(res); } catch (Exception e) { e.printStackTrace(); return new AsyncTaskResult<Object>(e); } } @Override protected void onPostExecute(AsyncTaskResult<Object> result) { if(result.getError()!= null) { showOKAlertMsg("App",getResources().getString(R.string.txt_data_not_found), false); } else { String res = result.getResult().toString(); try { JSONObject resObj = new JSONObject(res); if(resObj.getString("status_code").equals("1")){ //parse // Do your task here } } catch (JSONException e) { e.printStackTrace(); showOKAlertMsg("",getResources().getString(R.string.txt_internal_server_error), false); } } } } 

Where is AsyncTaskResult -

  public class AsyncTaskResult<T> { private T result; private Exception error; public T getResult() { return result; } public Exception getError() { return error; } public AsyncTaskResult(T result) { this.result = result; } public AsyncTaskResult(Exception error) { this.error = error; } }