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POAsyncTask with ProgressDialog vs orientation change
 

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    <p>after few desperate days I have finally created almost working example. </p> <p><strong>The goal:</strong> in onCreate I want to download and parseXML files in AsyncTask, show progress dialog, update UI and close the dialog.</p> <p><strong>The problem:</strong> When orientation changes Activity is restarted and AsyncTask loses reference to it. There are a lot of questions and blogs about it. But I cant find out why this particular solution doesnt work. Or how android handles dialogs in this case.</p> <p><strong>The state:</strong> When I start an app everything is ok. I can rotate the device and I can manually start the task again via menu. BUT after task finishes and I change the orientation again dialogs pops up (as expected) and nothing else happens. No progress change, no dialog dismiss. AsyncTask finishes normally.</p> <p><strong>The code:</strong></p> <pre><code>package com.test; import java.io.*; import java.net.URL; import java.net.URLConnection; import java.util.*; public class Test extends TabActivity { DownloadFileAsync task; ProgressDialog progressDialog; static final int PROGRESS_DIALOG = 0; private static Data data; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); /* - Run from different locations bug - */ //http://code.google.com/p/android/issues/detail?id=2373 if (!isTaskRoot()) { final Intent intent = getIntent(); final String intentAction = intent.getAction(); if (intent.hasCategory(Intent.CATEGORY_LAUNCHER) &amp;&amp; intentAction != null &amp;&amp; intentAction.equals(Intent.ACTION_MAIN)) { finish(); } } /* - /Run from different locations bug */ /* -------------- Tabs ---------------- */ Resources res = getResources(); TabHost mTabHost = getTabHost(); mTabHost.addTab(mTabHost.newTabSpec("overview").setIndicator("MYTAB1",res.getDrawable(R.drawable.ic_tab_home)).setContent(R.id.tab1)); mTabHost.setCurrentTab(0); /* -------------- /Tabs --------------- */ /* -------------- /Data --------------- */ task = (DownloadFileAsync)getLastNonConfigurationInstance(); if(task!= null) { task.setActivity(this); } else { if(data == null) { File datafile = this.getFileStreamPath("data.dat"); if(datafile.exists()){ //Log.d("log", "File exists!"); try { long time = System.currentTimeMillis(); ObjectInputStream obj = new ObjectInputStream(new FileInputStream(datafile)); data = (Data)obj.readObject(); obj.close(); Log.d("time", "loaded in:"+(System.currentTimeMillis()- time)); if(data.isUpToDate() || !isOnline()){ update(); } } catch (Exception e) { e.printStackTrace(); datafile.delete(); data = null; } //Log.d("log", "Passed?"); } } /* DEBUG if(data == null || !data.isUpToDate())*/ this.synchronize(); } /* -------------- /Data --------------- */ } @Override public boolean onCreateOptionsMenu(Menu menu) { menu.add("Synchronize").setIcon(R.drawable.ic_menu_refresh); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { synchronize(); return super.onOptionsItemSelected(item); } @Override public Object onRetainNonConfigurationInstance() { if(task != null) task.setActivity(null); return(task); } protected Dialog onCreateDialog(int id) { switch (id) { case PROGRESS_DIALOG: progressDialog = new ProgressDialog(this); progressDialog.setMessage("Aktualizuji ..."); progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); progressDialog.setCancelable(false); //progressDialog.show(); return progressDialog; default: return null; } } public void update() { } private void onTaskCompleted() { task = null; dismissDialog(PROGRESS_DIALOG); Log.d("tok","Task.onComplete"); update(); } public void synchronize(){ if(isOnline()) { showDialog(PROGRESS_DIALOG); progressDialog.setProgress(0); // &lt;-- this is the last time progressDialog updates task = new DownloadFileAsync(this); task.execute(); } } public boolean isOnline() { ConnectivityManager cm = (ConnectivityManager) getSystemService(WaspActivity.CONNECTIVITY_SERVICE); NetworkInfo netInfo = cm.getActiveNetworkInfo(); if (netInfo != null &amp;&amp; netInfo.isConnectedOrConnecting()) { return true; } return false; } private static class DownloadFileAsync extends AsyncTask&lt;String, String, String&gt; { private Data tempData; private Test activity; private int progress = 0; private File metafile; private File tempDir; private FileOutputStream fos; public DownloadFileAsync(Test activity) { this.setActivity(activity); ... some more init ... } public void setActivity(Test activity) { this.activity = activity; } @Override protected void onPreExecute() { super.onPreExecute(); tempData = new Data(); } @Override protected String doInBackground(String... aurl) { try { ... some heavy load ... //this.progress = someValue; } catch (Exception e) { Log.d("Error", "Error while processing files. Code:"+e.getMessage()); e.printStackTrace(); } //Log.d("time","Task "+(System.currentTimeMillis() - time)); return null; } protected void onProgressUpdate(String... progress) { if(activity != null) activity.progressDialog.setProgress(this.progress); } @Override protected void onPostExecute(String unused) { data = tempData; tempData = null; if(activity != null) { activity.onTaskCompleted(); activity = null; } } } } </code></pre>
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    1. COLook [here](http://www.codeproject.com/Articles/162201/Painless-AsyncTask-and-ProgressDialog-Usage). You can find an answer to your question there. It's a very elegant solution.
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    2. COCheck out my post on this topic: [**Handling Configuration Changes with `Fragment`s**](http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html)
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