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POAsyncTask and changes of orientation
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  1. POAsyncTask and changes of orientation
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    copied!<p>I've problem with the re-creation of the activity, the progress dialog and the Async Task when change the orientation of the screen. I saw some solutions here and i decided to use the onRetainCustomNonConfigurationInstance() to save the instance of AsyncTask. Well, in onCreate i check if there is an instance of AsyncTask and, if exist, i show a new Progress Dialog. But this dialog blocks the UI in an infinite loop (in the onPostExecute there is dialog.dismiss() ) and the activity doesn't show the results of course. </p> <p><strong>onCreate</strong></p> <pre class="lang-java prettyprint-override"><code>getDirection = (GetDirection) getLastCustomNonConfigurationInstance(); if(getDirection != null) { dialog = new ProgressDialog(RouteActivity.this); dialog.setMessage(getResources().getString(R.string.loading_data)); dialog.setIndeterminate(false); dialog.setCancelable(false); dialog.show(); } else { getDirection = new GetDirection(); getDirection.execute(); } </code></pre> <p><strong>onRetainCustomNonConfigurationInstance</strong></p> <pre class="lang-java prettyprint-override"><code>@Override public Object onRetainCustomNonConfigurationInstance() { return getDirection; } @Override protected void onDestroy() { super.onDestroy(); if (dialog.isShowing()) { dialog.dismiss(); } } </code></pre> <p><strong>EDIT #1</strong>: I adopted the solution of Kingfisher with Fragment and Retained Fragment but there is a NPE on Expandable Listview when i change the orientation during the doInBackground of AsyncTask. </p> <pre class="lang-java prettyprint-override"><code>08-14 12:50:40.866: E/AndroidRuntime(22739): FATAL EXCEPTION: main 08-14 12:50:40.866: E/AndroidRuntime(22739): java.lang.NullPointerException 08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.adapter.ListRouteExpandableAdapter.getGroupCount(ListRouteExpandableAdapter.java:78) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.widget.ExpandableListConnector.getCount(ExpandableListConnector.java:399) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.widget.ListView.setAdapter(ListView.java:460) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.widget.ExpandableListView.setAdapter(ExpandableListView.java:470) 08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.activity.RouteActivity.onPostExecute(RouteActivity.java:792) 08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:244) 08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:1) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.AsyncTask.finish(AsyncTask.java:631) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.AsyncTask.access$600(AsyncTask.java:177) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.Handler.dispatchMessage(Handler.java:99) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.Looper.loop(Looper.java:137) 08-14 12:50:40.866: E/AndroidRuntime(22739): at android.app.ActivityThread.main(ActivityThread.java:4895) 08-14 12:50:40.866: E/AndroidRuntime(22739): at java.lang.reflect.Method.invokeNative(Native Method) 08-14 12:50:40.866: E/AndroidRuntime(22739): at java.lang.reflect.Method.invoke(Method.java:511) 08-14 12:50:40.866: E/AndroidRuntime(22739): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994) 08-14 12:50:40.866: E/AndroidRuntime(22739): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761) 08-14 12:50:40.866: E/AndroidRuntime(22739): at dalvik.system.NativeStart.main(Native Method). </code></pre> <p><strong>Here the code in Fragment:</strong></p> <pre class="lang-java prettyprint-override"><code>public class GetDirectionFragment extends Fragment { private Map&lt;Leg, List&lt;Step&gt;&gt; legsCollection; private ArrayList&lt;Object&gt; legsAndSteps; private List&lt;Leg&gt; legs; private List&lt;Poi&gt; pois; private List&lt;LatLng&gt; polyz; /** * Callback interface through which the fragment will report the * task's progress and results back to the Activity. */ public static interface TaskCallbacks { void onPreExecute(); void onPostExecute(); List&lt;Poi&gt; getListPoiByRoute(); void setLegs(List&lt;Leg&gt; legs, Map&lt;Leg, List&lt;Step&gt;&gt; legsCollection); void setPolyline(List&lt;LatLng&gt; polyz); } private TaskCallbacks callbacks; private GetDirectionTask getDirectionTask; /** * Hold a reference to the parent Activity so we can report the * task's current progress and results. The Android framework * will pass us a reference to the newly created Activity after * each configuration change. */ @Override public void onAttach(Activity activity) { super.onAttach(activity); try { callbacks = (TaskCallbacks) activity; } catch(ClassCastException e) { throw new ClassCastException(activity.toString() + " must implement TaskCallbacks"); } pois = callbacks.getListPoiByRoute(); } /** * This method will only be called once when the retained * Fragment is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Retain this fragment across configuration changes. setRetainInstance(true); // Create and execute the background task. getDirectionTask = new GetDirectionTask(); getDirectionTask.execute(); } /** * Set the callback to null so we don't accidentally leak the * Activity instance. */ @Override public void onDetach() { super.onDetach(); callbacks = null; } private class GetDirectionTask extends AsyncTask&lt;Void, Integer, Void&gt; { @Override protected void onPreExecute() { if (callbacks != null) { callbacks.onPreExecute(); } } /** * Note that we do NOT call the callback object's methods * directly from the background thread, as this could result * in a race condition. */ @Override protected Void doInBackground(Void... ignore) { List&lt;String&gt; lats = new ArrayList&lt;String&gt;(); List&lt;String&gt; longs = new ArrayList&lt;String&gt;(); for(Poi poi: pois) { lats.add(poi.getCoordinates().getLatitude()); longs.add(poi.getCoordinates().getLongitude()); } String stringUrl = "http://maps.googleapis.com/maps/api/directions/" + "json?"; //if(actualLanguage.equals("en")) { // stringUrl += "language=en_EN"; //} else { stringUrl += "language=it"; //} stringUrl+="&amp;mode=walking&amp;units=metric&amp;origin=" + lats.get(0) + "," + longs.get(0); stringUrl += "&amp;destination=" + lats.get(pois.size()-1) + "," + longs.get(pois.size()-1) + "&amp;" + "waypoints="; for(int i = 1; i&lt;=lats.size()-2 &amp;&amp; i&lt;=longs.size()-2; i++) { stringUrl += lats.get(i)+","+longs.get(i); if(i==(lats.size()-2) &amp;&amp; i==(longs.size()-2)) { stringUrl += "&amp;sensor=false"; } else { stringUrl +="|"; } } Log.i("urlgoogle", stringUrl); StringBuilder response = new StringBuilder(); try { URL url = new URL(stringUrl); HttpURLConnection httpconn = (HttpURLConnection) url .openConnection(); if (httpconn.getResponseCode() == HttpURLConnection.HTTP_OK) { BufferedReader input = new BufferedReader( new InputStreamReader(httpconn.getInputStream()), 8192); String strLine = null; while ((strLine = input.readLine()) != null) { response.append(strLine); } input.close(); } String jsonOutput = response.toString(); JSONObject jsonObject = new JSONObject(jsonOutput); // routesArray contains ALL routes JSONArray routesArray = jsonObject.getJSONArray("routes"); // Grab the first route JSONObject route = routesArray.getJSONObject(0); JSONArray legsArray = route.getJSONArray("legs"); legs = new ArrayList&lt;Leg&gt;(); legsAndSteps = new ArrayList&lt;Object&gt;(); String htmlInstructions; legsCollection = new LinkedHashMap&lt;Leg, List&lt;Step&gt;&gt;(); for(int i=0; i&lt;legsArray.length(); i++) { List&lt;Step&gt; steps = new ArrayList&lt;Step&gt;(); Leg leg = new Leg(); //int idLeg = 0; JSONObject legJson = legsArray.getJSONObject(i); leg.setDistance(legJson.getJSONObject("distance").getString("text")); leg.setDuration(legJson.getJSONObject("duration").getString("text")); leg.setEndAddress(legJson.getString("end_address")); leg.setStartAddress(legJson.getString("start_address")); leg.setIdLeg(pois.get(i).getId()); leg.setStartPoiName(pois.get(i).getName()); leg.setEndPoiName(pois.get(i+1).getName()); legsAndSteps.add(leg); JSONArray stepsArray = legJson.getJSONArray("steps"); for(int j=0; j&lt;stepsArray.length(); j++) { Step step = new Step(); JSONObject stepJson = stepsArray.getJSONObject(j); step.setDistance(stepJson.getJSONObject("distance").getString("text")); step.setDuration(stepJson.getJSONObject("duration").getString("text")); htmlInstructions = android.text.Html.fromHtml(stepJson.getString("html_instructions")).toString(); step.setInstructions(htmlInstructions); //step.setIdLeg(idLeg); //Aggiunto per Exp steps.add(step); legsAndSteps.add(step); } legsCollection.put(leg, steps); legs.add(leg); } JSONObject poly = route.getJSONObject("overview_polyline"); String polyline = poly.getString("points"); polyz = decodePoly(polyline); callbacks.setLegs(legs, legsCollection); callbacks.setPolyline(polyz); } catch (Exception e) { } return null; } @Override protected void onPostExecute(Void ignore) { if (callbacks != null) { callbacks.onPostExecute(); } } } /* Method to decode polyline points */ private List&lt;LatLng&gt; decodePoly(String encoded) { [code...] } </code></pre> <p>}</p> <p><strong>Here the code in Activity</strong>:</p> <pre class="lang-java prettyprint-override"><code> @Override public void onPostExecute() { expListView = (ExpandableListView) findViewById(R.id.lv_routepoi); ListRouteExpandableAdapter expListAdapter = new ListRouteExpandableAdapter( getApplicationContext(), legs, legsCollection); expListView.setAdapter(expListAdapter); setGroupIndicatorToRight(); expListView.setChildDivider(getResources().getDrawable(R.drawable.divider_route)); [code...] dialog.dismiss(); } @Override public void setLegs(List&lt;Leg&gt; legs, Map&lt;Leg, List&lt;Step&gt;&gt; legsCollection) { this.legs = legs; this.legsCollection = legsCollection; } @Override public void setPolyline(List&lt;LatLng&gt; polyz) { this.polyz = polyz; } </code></pre> <p><strong>EDIT #2</strong>: I tried the new solution of Kingfisher but there is always an NPE in doInBackground method. If i don't change the orientation of screen during the loading, app doesn't crash and show data on listview.</p> <pre class="lang-java prettyprint-override"><code>08-14 17:27:44.897: I/AsyncTask(30604): java.lang.NullPointerException 08-14 17:27:44.897: E/AndroidRuntime(30604): FATAL EXCEPTION: main 08-14 17:27:44.897: E/AndroidRuntime(30604): java.lang.NullPointerException 08-14 17:27:44.897: E/AndroidRuntime(30604): at com.pasquini.activity.RouteActivity.onPostExecute(RouteActivity.java:847) 08-14 17:27:44.897: E/AndroidRuntime(30604): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:253) 08-14 17:27:44.897: E/AndroidRuntime(30604): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:1) 08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.AsyncTask.finish(AsyncTask.java:631) 08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.AsyncTask.access$600(AsyncTask.java:177) 08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644) 08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.Handler.dispatchMessage(Handler.java:99) 08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.Looper.loop(Looper.java:137) 08-14 17:27:44.897: E/AndroidRuntime(30604): at android.app.ActivityThread.main(ActivityThread.java:4895) 08-14 17:27:44.897: E/AndroidRuntime(30604): at java.lang.reflect.Method.invokeNative(Native Method) 08-14 17:27:44.897: E/AndroidRuntime(30604): at java.lang.reflect.Method.invoke(Method.java:511) 08-14 17:27:44.897: E/AndroidRuntime(30604): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994) 08-14 17:27:44.897: E/AndroidRuntime(30604): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761) 08-14 17:27:44.897: E/AndroidRuntime(30604): at dalvik.system.NativeStart.main(Native Method) </code></pre> <p><strong>Here the code in Fragment:</strong></p> <pre class="lang-java prettyprint-override"><code>public class GetDirectionFragment extends Fragment { private Map&lt;Leg, List&lt;Step&gt;&gt; legsCollection; private ArrayList&lt;Object&gt; legsAndSteps; private List&lt;Leg&gt; legs; private List&lt;Poi&gt; pois; private List&lt;LatLng&gt; polyz; /** * Callback interface through which the fragment will report the * task's progress and results back to the Activity. */ public static interface TaskCallbacks { void onPreExecute(); void onPostExecute(); List&lt;Poi&gt; getListPoiByRoute(); void setLegs(List&lt;Leg&gt; legs, Map&lt;Leg, List&lt;Step&gt;&gt; legsCollection); void setPolyline(List&lt;LatLng&gt; polyz); } private TaskCallbacks callbacks; private GetDirectionTask getDirectionTask; /** * Hold a reference to the parent Activity so we can report the * task's current progress and results. The Android framework * will pass us a reference to the newly created Activity after * each configuration change. */ @Override public void onAttach(Activity activity) { super.onAttach(activity); try { callbacks = (TaskCallbacks) activity; } catch(ClassCastException e) { throw new ClassCastException(activity.toString() + " must implement TaskCallbacks"); } pois = callbacks.getListPoiByRoute(); } /** * This method will only be called once when the retained * Fragment is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Retain this fragment across configuration changes. setRetainInstance(true); // Create and execute the background task. getDirectionTask = new GetDirectionTask(); getDirectionTask.execute(); } /** * Set the callback to null so we don't accidentally leak the * Activity instance. */ @Override public void onDetach() { super.onDetach(); callbacks = null; } private class GetDirectionTask extends AsyncTask&lt;Void, Integer, Void&gt; { @Override protected void onPreExecute() { if (callbacks != null) { callbacks.onPreExecute(); } } /** * Note that we do NOT call the callback object's methods * directly from the background thread, as this could result * in a race condition. */ @Override protected Void doInBackground(Void... ignore) { List&lt;String&gt; lats = new ArrayList&lt;String&gt;(); List&lt;String&gt; longs = new ArrayList&lt;String&gt;(); for(Poi poi: pois) { lats.add(poi.getCoordinates().getLatitude()); longs.add(poi.getCoordinates().getLongitude()); } String stringUrl = "http://maps.googleapis.com/maps/api/directions/" + "json?"; //if(actualLanguage.equals("en")) { // stringUrl += "language=en_EN"; //} else { stringUrl += "language=it"; //} stringUrl+="&amp;mode=walking&amp;units=metric&amp;origin=" + lats.get(0) + "," + longs.get(0); stringUrl += "&amp;destination=" + lats.get(pois.size()-1) + "," + longs.get(pois.size()-1) + "&amp;" + "waypoints="; for(int i = 1; i&lt;=lats.size()-2 &amp;&amp; i&lt;=longs.size()-2; i++) { stringUrl += lats.get(i)+","+longs.get(i); if(i==(lats.size()-2) &amp;&amp; i==(longs.size()-2)) { stringUrl += "&amp;sensor=false"; } else { stringUrl +="|"; } } Log.i("urlgoogle", stringUrl); StringBuilder response = new StringBuilder(); try { URL url = new URL(stringUrl); HttpURLConnection httpconn = (HttpURLConnection) url .openConnection(); if (httpconn.getResponseCode() == HttpURLConnection.HTTP_OK) { BufferedReader input = new BufferedReader( new InputStreamReader(httpconn.getInputStream()), 8192); String strLine = null; while ((strLine = input.readLine()) != null) { response.append(strLine); } input.close(); } String jsonOutput = response.toString(); JSONObject jsonObject = new JSONObject(jsonOutput); // routesArray contains ALL routes JSONArray routesArray = jsonObject.getJSONArray("routes"); // Grab the first route JSONObject route = routesArray.getJSONObject(0); JSONArray legsArray = route.getJSONArray("legs"); legs = new ArrayList&lt;Leg&gt;(); legsAndSteps = new ArrayList&lt;Object&gt;(); String htmlInstructions; legsCollection = new LinkedHashMap&lt;Leg, List&lt;Step&gt;&gt;(); for(int i=0; i&lt;legsArray.length(); i++) { List&lt;Step&gt; steps = new ArrayList&lt;Step&gt;(); Leg leg = new Leg(); //int idLeg = 0; JSONObject legJson = legsArray.getJSONObject(i); leg.setDistance(legJson.getJSONObject("distance").getString("text")); leg.setDuration(legJson.getJSONObject("duration").getString("text")); leg.setEndAddress(legJson.getString("end_address")); leg.setStartAddress(legJson.getString("start_address")); leg.setIdLeg(pois.get(i).getId()); leg.setStartPoiName(pois.get(i).getName()); leg.setEndPoiName(pois.get(i+1).getName()); legsAndSteps.add(leg); JSONArray stepsArray = legJson.getJSONArray("steps"); for(int j=0; j&lt;stepsArray.length(); j++) { Step step = new Step(); JSONObject stepJson = stepsArray.getJSONObject(j); step.setDistance(stepJson.getJSONObject("distance").getString("text")); step.setDuration(stepJson.getJSONObject("duration").getString("text")); htmlInstructions = android.text.Html.fromHtml(stepJson.getString("html_instructions")).toString(); step.setInstructions(htmlInstructions); //step.setIdLeg(idLeg); steps.add(step); legsAndSteps.add(step); } legsCollection.put(leg, steps); legs.add(leg); } JSONObject poly = route.getJSONObject("overview_polyline"); String polyline = poly.getString("points"); polyz = decodePoly(polyline); setLegs(legs, legsCollection); setPolyline(polyz); } catch (Exception e) { Log.i(TAG, e.toString()); } return null; } @Override protected void onPostExecute(Void ignore) { if (callbacks != null) { callbacks.onPostExecute(); } } } /* Method to decode polyline points */ private List&lt;LatLng&gt; decodePoly(String encoded) { [code...] } public void setLegs(List&lt;Leg&gt; legs, Map&lt;Leg, List&lt;Step&gt;&gt; legsCollection) { this.legs = legs; this.legsCollection = legsCollection; } public void setPolyline(List&lt;LatLng&gt; polyz) { this.polyz = polyz; } public List&lt;Leg&gt; getLegs() { return this.legs; } public Map&lt;Leg, List&lt;Step&gt;&gt; getMap() { return this.legsCollection; } public List&lt;LatLng&gt; getPolyline() { return this.polyz; } </code></pre> <p>}</p> <p><strong>Here the code in Activity</strong>:</p> <pre class="lang-java prettyprint-override"><code>@Override protected void onCreate(Bundle savedInstanceState) { [code...] FragmentManager fm = getSupportFragmentManager(); getDirectionFragment = (GetDirectionFragment) fm.findFragmentByTag(TASK_FRAGMENT_TAG); // If the Fragment is non-null, then it is currently being // retained across a configuration change. if (getDirectionFragment == null) { getDirectionFragment = new GetDirectionFragment(); fm.beginTransaction().add(getDirectionFragment, TASK_FRAGMENT_TAG).commit(); [code...] } @Override public void onPostExecute() { legs = getDirectionFragment.getLegs(); legsCollection = getDirectionFragment.getMap(); polyz = getDirectionFragment.getPolyline(); expListView = (ExpandableListView) findViewById(R.id.lv_routepoi); ListRouteExpandableAdapter expListAdapter = new ListRouteExpandableAdapter( getApplicationContext(), legs, legsCollection); expListView.setAdapter(expListAdapter); setGroupIndicatorToRight(); expListView.setChildDivider(getResources().getDrawable(R.drawable.divider_route)); [code...] } </code></pre>
 

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