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Thread in fragment with setRetainInstance(true) - android

I have a fragment with a thread inside it, starting in its onCreate method.
After thread finishes his work i need to send a message to the activity (myActivity) through the "clickButtonOperation".
This is the onCreate() method of my fragment:
public class HolderFragment extends My_Fragment{
private Thread myThread;
.
.
.
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
printf("MyActivity attached is: "+myActivity);
myThread=new Thread(new Runnable(){
#Override
public void run() {
int i=0;
while (i<3){
printf("Working...");
try {
Thread.sleep(2000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
i++;
}
myActivity.clickButtonOperation(new Object[]{
HolderFragment.this.toString()
});
}
});
myThread.start();
}
onCreateView returns NULL.
My question is:
Is it guaranteed that my "clickButonOperation" gets called after the new activity has been attached? or could this method be called before this process?
TEMPORARY SOLUTION:
I created a custom Thread class:
public abstract class My_Thread extends Thread {
private boolean runnable=true;
private boolean paused=false;
private Object[] arguments;
private My_ThreadHolder myHolder;
protected void onPostExecute(Object[] arguments){
while(paused);
runnable=false;
}
protected abstract void execute(Object[] arguments);
protected void notifyUpdate(){
while (paused);
}
protected boolean isRunnable(){
return runnable;
}
public void setArguments(Object[] arguments){
this.arguments=arguments;
}
public Object[] getArguments() {
return arguments;
}
public final void run(){
while (runnable){
execute(arguments);
onPostExecute(arguments);
}
}
public void attach(My_ThreadHolder holder){
myHolder=holder;
}
public My_ThreadHolder getHolder() {
return myHolder;
}
public void startThread(){
runnable=true;
start();
}
public void stopThread(){
runnable=false;
}
public void pauseThread(){
paused=true;
printf("Thread paused");
}
public void resumeThread(){
paused=false;
printf("Thread resumed");
}
}
And created these two:
public class My_ThreadHolder extends My_Fragment{
private TestThread myThread;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
printf("MyActivity attached is: "+myActivity);
myThread=new TestThread();
myThread.attach(this);
myThread.startThread();
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (myThread!=null)myThread.resumeThread();
}
#Override
public void onDetach() {
super.onDetach();
myThread.pauseThread();
}
protected void onNotifyUpdateReceived(Object[] arguments){
myActivity.clickButtonOperation(arguments);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {return null;}
#Override
protected void setGraphics(View view, Bundle savedInstanceState) {}
}
class TestThread extends My_Thread{
#Override
protected void onPostExecute(Object[] arguments) {
super.onPostExecute(arguments);
printf("Thread finished");
}
#Override
protected void execute(Object[] arguments) {
int i=0;
while(i<3){
printf("Working...");
try {
Thread.sleep(2000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
i++;
Object[] myArguments= new Object[2];
myArguments[0]=0;
myArguments[1]=i;
setArguments(myArguments);
notifyUpdate();
}
}
#Override
protected void notifyUpdate() {
super.notifyUpdate();
getHolder().onNotifyUpdateReceived(getArguments());
}
}

You cannot touch the UI from a background thread.. you need to use runOnUiThread method from Activity class, something like this
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
printf("MyActivity attached is: "+myActivity);
myThread = new Thread(new Runnable() {
#Override
public void run() {
int i = 0;
while (i < 3) {
printf("Working...");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
i++;
}
myActivity.runOnUiThread(new Runnable() {
#Override
public void run() {
myActivity.clickButtonOperation(new Object[]{
HolderFragment.this.toString()
});
}
});
}
});
myThread.start();
}

Related

I working with this app - https://github.com/googlesamples/android-AppUsageStatistics . I'm new in android and I'm trying to refresh the view in every second. Now the view is refreshing in onCreate() or onResume().
I'm trying to use this:
public class MainActivity extends AppCompatActivity implements UsageContract.View {
private ProgressBar progressBar;
private TextView permissionMessage;
private UsageContract.Presenter presenter;
private UsageStatAdapter adapter;
public static Context myContext;
private long getStartTime() {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
progressBar = (ProgressBar) findViewById(R.id.progress_bar);
permissionMessage = (TextView) findViewById(R.id.grant_permission_message);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new UsageStatAdapter();
recyclerView.setAdapter(adapter);
permissionMessage.setOnClickListener(v -> openSettings());
presenter = new UsagePresenter(this, this);
Thread t = new Thread() {
#Override
public void run() {
try {
while (!isInterrupted()) {
Thread.sleep(1000);
runOnUiThread(new Runnable() {
#Override
public void run() {
presenter.retrieveUsageStats();
throw new RuntimeException(e);
}
});
}
} catch (InterruptedException e) {
}
}
};
t.start();
}
private void openSettings() {
startActivity(new Intent(Settings.ACTION_USAGE_ACCESS_SETTINGS));
}
#Override
protected void onResume() {
super.onResume();
showProgressBar(true);
presenter.retrieveUsageStats();
}
#Override
public void onUsageStatsRetrieved(List<UsageStatsWrapper> list) {
showProgressBar(false);
permissionMessage.setVisibility(GONE);
adapter.setList(list);
}
#Override
public void onUserHasNoPermission() {
showProgressBar(false);
permissionMessage.setVisibility(VISIBLE);
}
private void showProgressBar(boolean show) {
if (show) {
progressBar.setVisibility(VISIBLE);
} else {
progressBar.setVisibility(GONE);
}
} }
but is not working. What am I doing wrong? Why the view in not refreshing? Does anybody have an idea?

Ideally your view wouldn't be polling the presenter for updates, but to continue this way try using a timer to run your recurring task, eg:
private Timer updateTimer;
#Override
protected void onStart() {
super.onStart();
updateTimer = new Timer();
updateTimer.schedule(new TimerTask() {
#Override
public void run() {
presenter.retrieveUsageStats();
}
}, 0, 1000);
}
#Override
protected void onStop() {
super.onStop();
if(updateTimer != null) {
updateTimer.cancel();
updateTimer = null;
}
}

Here's my code:
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_create_route);
SetupButton();
}
private void SetupButton()
{
Button createNewMessage = (Button) findViewById(R.id.button);
createNewMessage.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ListenForNewMessage();
}
});
}
private void ListenForNewMessage()
{
final SpeechRecognizer newDeliverySpeech = SpeechRecognizer.createSpeechRecognizer(this);
RecognitionListener newDeliveryRecognitionListener = new RecognitionListener() {
#Override
public void onReadyForSpeech(Bundle params) {
Log.d("SpeechListening","onReadyForSpeech");
}
#Override
public void onBeginningOfSpeech() {
Log.d("SpeechListening","onBeginningOfSpeech");
}
#Override
public void onRmsChanged(float rmsdB) {
//do nothing
}
#Override
public void onBufferReceived(byte[] buffer) {
//do nothing
}
#Override
public void onEndOfSpeech() {
Log.d("SpeechListening","onEndOfSpeech");
}
#Override
public void onError(int error) {
//do nothing
}
#Override
public void onResults(Bundle results) {
ArrayList<String> userMessage;
userMessage = results.getStringArrayList(RESULTS_RECOGNITION);
PushNewDelivery(userMessage);
}
#Override
public void onPartialResults(Bundle partialResults) {
//do nothing
}
#Override
public void onEvent(int eventType, Bundle params) {
//do nothing
}
};
newDeliverySpeech.setRecognitionListener(newDeliveryRecognitionListener);
if (newDeliverySpeech.isRecognitionAvailable(getApplicationContext()))
{
Log.d("SpeechListening","started listening hopefully");
newDeliverySpeech.startListening(new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH));
}
}
}
The problem is, only the started listening hopefully is logged, the RecognitionListener never has onReadyForSpeech() or any of its methods called.
details
details
details
details
Can someone please tell me what I'm doing wrong here?

You are basically creating a new SpeechRecognizer object and register a new listener each time you click on the button. On top of that you create the SpeechRecognizer using the current Activity Context but you are actually using the Application context when calling: isRecognitionAvailable();
Try to create the SpeechRecognizer as a member object and register your listener when onCreate() is called. Also try to avoid using the Application context to avoid memory leaks.
Here is an example of how you should do it.
private SpeechRecognizer mDeliverySpeech;
private Intent mSpeechIntent;
private boolean mListening = false;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_create_route);
SetupButton();
SetupSpeechRecognizer();
mSpeechIntent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
mSpeechIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_PREFERENCE, "en");
mSpeechIntent.putExtra(RecognizerIntent.EXTRA_CALLING_PACKAGE, this.getPackageName());
mSpeechIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
mSpeechIntent.putExtra(RecognizerIntent.EXTRA_MAX_RESULTS, 3);
}
private void SetupButton()
{
Button createNewMessage = (Button) findViewById(R.id.button);
createNewMessage.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ListenForNewMessage();
}
});
}
private void SetupSpeechRecognizer()
{
mDeliverySpeech = SpeechRecognizer.createSpeechRecognizer(this);
RecognitionListener newDeliveryRecognitionListener = new RecognitionListener() {
#Override
public void onReadyForSpeech(Bundle params) {
Log.d("SpeechListening","onReadyForSpeech");
}
#Override
public void onBeginningOfSpeech() {
Log.d("SpeechListening","onBeginningOfSpeech");
}
#Override
public void onRmsChanged(float rmsdB) {
//do nothing
}
#Override
public void onBufferReceived(byte[] buffer) {
//do nothing
}
#Override
public void onEndOfSpeech() {
Log.d("SpeechListening","onEndOfSpeech");
}
#Override
public void onError(int error) {
//do nothing
}
#Override
public void onResults(Bundle results) {
ArrayList<String> userMessage;
userMessage = results.getStringArrayList(RESULTS_RECOGNITION);
PushNewDelivery(userMessage);
}
#Override
public void onPartialResults(Bundle partialResults) {
//do nothing
}
#Override
public void onEvent(int eventType, Bundle params) {
//do nothing
}
};
mDeliverySpeech.setRecognitionListener(newDeliveryRecognitionListener);
}
private void ListenForNewMessage()
{
if (mDeliverySpeech.isRecognitionAvailable(this) && !mListening)
{
Log.d("SpeechListening","started listening hopefully");
mListening = true;
mDeliverySpeech.startListening(mSpeechIntent);
new CountDownTimer(5000, 5000) {
public void onTick(long millisUntilFinished) {}
public void onFinish() {
mDeliverySpeech.stopListening();
mListening = false;
}
}.start();
}
}
Do not forget to properly handle the activity life cycle when working with listener to avoid memory leak.

I'd appreciate your help in interrupting an Android/Java sleep. What I have in my layout is a button, which if clicked, calls the Skip method and starts a new activity. FYI The same activity would be called anyway when the Sleep method terminates.
Here's my failing code:
public class Splash extends Activity {
private Thread timer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.splash_screen);
timer = new Thread() {
public void run() {
try {
sleep(5000);
} catch (Exception e) {
e.printStackTrace();
onPause();
return;
} finally {
onPause();
startActivity(new Intent("net.example.splashscreenexample.MainActivity"));
}
}
};
timer.start();
}
#Override
public void onPause() {
timer.interrupt();
super.onPause();
finish();
}
public void Skip() {
timer.interrupt();
startActivity(new Intent("net.example.splashscreenexample.MainActivity"));
}
Now Resolved!
I've now got it all working. In addition to #RocketSpock's suggestions there was also a stupid error in my code in that I'd failed to include the View view paramater into my Skip method call. So the fully working code now looks like this:
public class Splash extends Activity {
private Thread timer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.splash_screen);
timer = new Thread() {
public void run() {
synchronized (this) {
try {
sleep(5000);
} catch (Exception e) {
e.printStackTrace();
onPause();
return;
} finally {
onPause();
startActivity(new Intent(
"net.rogw.splashscreenexample.MainActivity"));
}
}
}
};
timer.start();
}
#Override
public void onPause() {
timer.interrupt();
super.onPause();
finish();
}
public void Skip(View view) {
synchronized (this) {
this.notify();
}
startActivity(new Intent("net.rogw.splashscreenexample.MainActivity"));
}
}

If you want to be able to interrupt it you should be using a wait.
public class Splash extends Activity {
private Thread timer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.splash_screen);
timer = new Thread() {
public void run() {
synchronized(this) {
try {
wait(5000);
} catch (Exception e) {
e.printStackTrace();
onPause();
return;
} finally {
onPause();
startActivity(new Intent("net.example.splashscreenexample.MainActivity"));
}
}
}
};
timer.start();
}
#Override
public void onPause() {
timer.interrupt();
super.onPause();
finish();
}
public void Skip() {
//You may need to replace this with the timer object
synchronized (this) {
//Informs the wait to interrupt.
this.notify();
}
startActivity(new Intent("net.example.splashscreenexample.MainActivity"));
}

I have a trouble with getting Activity(Nullpointerexception) after that I have rotate screen and received callback from AsyncTask to update my views of the fragment. If I wont change orientation then everything is OK(but not all the time, sometimes this bug appears)
My main activity:
public class MainActivity extends SherlockFragmentActivity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.pager_layout);
fm = getSupportFragmentManager();
fm.addOnBackStackChangedListener(this);
session = new SessionManager(getApplicationContext());
if (session.isAuthorizated()) {
disableTabs();
FragmentTransaction ft = fm.beginTransaction();
if (session.termsAndConditions()) {
ft.replace(android.R.id.content, new TermsAndConditionsFragment(), "terms-and-conditions").commit();
}
}
} else {
enableTabs();
mTabsAdapter = new TabsAdapter(this, mViewPager);
mTabsAdapter.addTab(actionBar.newTab().setText("Log in"), LoginFragment.class, null);
mTabsAdapter.addTab(actionBar.newTab().setText("Calculator"), CalculatorFragment.class, null);
}
}
That`s my fragment:
public class TermsAndConditionsFragment extends SherlockFragment implements OnClickListener, OnTouchListener, OnEditorActionListener, ValueSelectedListener, AsyncUpdateViewsListener {
private static final String TAG = "TermsAndConditionsFragment";
private TermsAndConditionsManager termsAndConditionsM;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
prepareData();
}
public void prepareData() {
if (getSherlockActivity() == null)
Log.d(TAG, "Activity is null");
termsAndConditionsM = new TermsAndConditionsManager(getSherlockActivity().getApplicationContext());
termsAndConditions = termsAndConditionsM.getTermsAndConditions();
...
// some stuff
...
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootView = init(inflater, container);
return rootView;
}
private View init(LayoutInflater inflater, ViewGroup container) {
rootView = inflater.inflate(R.layout.fragment_terms_and_conditions, container, false);
//bla bla bla
return rootView;
}
public void updateTermsAndConditionsView() {
//update views here
}
#Override
public void onClick(View v) {
ft = fm.beginTransaction();
switch (v.getId()) {
case R.id.etHowMuch:
d = NumberPaymentsPickerFragment.newInstance(getSherlockActivity(), Integer.valueOf(howMuch.replace("£", "")), 0);
d.setValueSelectedListener(this);
d.show(getFragmentManager(), Const.HOW_MUCH);
break;
}
}
#Override
public void onValueSelected() {
Bundle args = new Bundle();
...
ExecuteServerTaskBackground task = new ExecuteServerTaskBackground(getSherlockActivity());
task.setAsyncUpdateViewsListener(this);
task.action = ServerAPI.GET_TERMS_AND_CONDITIONS;
task.args = args;
task.execute();
}
#Override
public void onUpdateViews() {
prepareData();
updateTermsAndConditionsView();
}
}
My AsyncTask with callback:
public class ExecuteServerTaskBackground extends AsyncTask<Void, Void, Void> {
private static final String TAG = "ExecuteServerTaskBackground";
Activity mActivity;
Context mContext;
private AsyncUpdateViewsListener callback;
public ExecuteServerTaskBackground(Activity activity) {
this.mActivity = activity;
this.mContext = activity.getApplicationContext();
}
public void setAsyncUpdateViewsListener(AsyncUpdateViewsListener listener) {
callback = listener;
}
#Override
protected Void doInBackground(Void... params) {
ServerAPI server = new ServerAPI(mContext);
if (!args.isEmpty())
msg = server.serverRequest(action, args);
else
msg = server.serverRequest(action, null);
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
callback.onUpdateViews();
}
}
Why does it behave so? How can I get activity correctly if I change orientation.
EDIT:
As I understand correctly nullpointer appears after orientation changed and asynctask executed due to wrong reference between asyctask and Activity. Recreated activity doesnt have this reference thats why when I receive callback I use wrong activity reference which isn`t exist anymore. But how can I save current activity reference?
EDIT:
I have decided to try realize my task throughout Service and that`s what I have done.
Activity:
public class MainFragment extends Fragment implements ServiceExecutorListener, OnClickListener {
private static final String TAG = MainFragment.class.getName();
Button btnSend, btnCheck;
TextView serviceStatus;
Intent intent;
Boolean bound = false;
ServiceConnection sConn;
RESTService service;
ProgressDialog pd = new ProgressDialog();
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setRetainInstance(true);
intent = new Intent(getActivity(), RESTService.class);
getActivity().startService(intent);
sConn = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName name, IBinder binder) {
Log.d(TAG, "MainFragment onServiceConnected");
service = ((RESTService.MyBinder) binder).getService();
service.registerListener(MainFragment.this);
if (service.taskIsDone())
serviceStatus.setText(service.getResult());
bound = true;
}
public void onServiceDisconnected(ComponentName name) {
Log.d(TAG, "MainFragment onServiceDisconnected");
bound = false;
}
};
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.main_fragment, container, false);
serviceStatus = (TextView) rootView.findViewById(R.id.tvServiceStatusValue);
btnSend = (Button) rootView.findViewById(R.id.btnSend);
btnCheck = (Button) rootView.findViewById(R.id.btnCheck);
btnSend.setOnClickListener(this);
btnCheck.setOnClickListener(this);
return rootView;
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btnSend:
pd.show(getFragmentManager(), "ProgressDialog");
service.run(7);
service.run(2);
service.run(4);
break;
case R.id.btnCheck:
if (service != null)
serviceStatus.setText(String.valueOf(service.taskIsDone()) + service.getTasksCount());
break;
}
}
#Override
public void onStart() {
super.onStart();
Log.d(TAG, "Bind service");
getActivity().bindService(intent, sConn, 0);
}
#Override
public void onPause() {
super.onDestroy();
Log.d(TAG, "onDestroy: Unbind service");
if (!bound)
return;
getActivity().unbindService(sConn);
service.unregisterListener(this);
bound = false;
}
#Override
public void onComplete(String result) {
Log.d(TAG, "Task Completed");
pd.dismiss();
serviceStatus.setText(result);
}
}
Dialog:
public class ProgressDialog extends DialogFragment implements OnClickListener {
final String TAG = ProgressDialog.class.getName();
public Dialog onCreateDialog(Bundle savedInstanceState) {
setRetainInstance(true);
AlertDialog.Builder adb = new AlertDialog.Builder(getActivity())
.setTitle("Title!")
.setPositiveButton(R.string.yes, this)
.setNegativeButton(R.string.no, this)
.setNeutralButton(R.string.maybe, this)
.setCancelable(false)
.setMessage(R.string.message_text)
.setOnKeyListener(new OnKeyListener() {
#Override
public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
return true;
}
});
return adb.create();
}
public void onClick(DialogInterface dialog, int which) {
int i = 0;
switch (which) {
case Dialog.BUTTON_POSITIVE:
i = R.string.yes;
break;
case Dialog.BUTTON_NEGATIVE:
i = R.string.no;
break;
case Dialog.BUTTON_NEUTRAL:
i = R.string.maybe;
break;
}
if (i > 0)
Log.d(TAG, "Dialog 2: " + getResources().getString(i));
}
public void onDismiss(DialogInterface dialog) {
Log.d(TAG, "Dialog 2: onDismiss");
// Fix to avoid simple dialog dismiss in orientation change
if ((getDialog() != null) && getRetainInstance())
getDialog().setDismissMessage(null);
super.onDestroyView();
}
public void onCancel(DialogInterface dialog) {
super.onCancel(dialog);
Log.d(TAG, "Dialog 2: onCancel");
}
}
Service:
public class RESTService extends Service {
final String TAG = RESTService.class.getName();
MyBinder binder = new MyBinder();
ArrayList<ServiceExecutorListener> listeners = new ArrayList<ServiceExecutorListener>();
Handler h = new Handler();
RequestManager mRequest;
ExecutorService es;
Object obj;
int time;
StringBuilder builder;
String result = null;
public void onCreate() {
super.onCreate();
Log.d(TAG, "RESTService onCreate");
es = Executors.newFixedThreadPool(1);
obj = new Object();
builder = new StringBuilder();
}
public void run(int time) {
RunRequest rr = new RunRequest(time);
es.execute(rr);
}
class RunRequest implements Runnable {
int time;
public RunRequest(int time) {
this.time = time;
Log.d(TAG, "RunRequest create");
}
public void run() {
Log.d(TAG, "RunRequest start, time = " + time);
try {
TimeUnit.SECONDS.sleep(time);
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
Log.d(TAG, "RunRequest obj = " + obj.getClass());
} catch (NullPointerException e) {
Log.d(TAG, "RunRequest error, null pointer");
}
builder.append("result " + time + ", ");
result = builder.toString();
sendCallback();
}
}
private void sendCallback() {
h.post(new Runnable() {
#Override
public void run() {
for (ServiceExecutorListener listener : listeners)
listener.onComplete();
}
});
}
public boolean taskIsDone() {
if (result != null)
return true;
return false;
}
public String getResult() {
return result;
}
public void registerListener(ServiceExecutorListener listener) {
listeners.add(listener);
}
public void unregisterListener(ServiceExecutorListener listener) {
listeners.remove(listener);
}
public IBinder onBind(Intent intent) {
Log.d(TAG, "RESTService onBind");
return binder;
}
public boolean onUnbind(Intent intent) {
Log.d(TAG, "RESTService onUnbind");
return true;
}
public class MyBinder extends Binder {
public RESTService getService() {
return RESTService.this;
}
}
}

As you mention in your edit, the current Activity is destroyed and recreated on orientation change.
But how can I save current activity reference?
You shouldn't. The previous Activity is no longer valid. This will not only cause NPEs but also memory leaks because the AsyncTask might hold the reference to old Activity, maybe forever.
Solution is to use Loaders.

I'm new to Android and I'm trying to work through a tutorial on using a ProgressBar in conjunction with a Handler. Just a note, I am targeting API 11.
Here is my code with the errors I am getting inline:
public class HandlerDemo extends Activity {
ProgressBar bar;
Handler handler = new Handler() {
#Override
public void handleMessage() { // Shows "method must override or implement supertype method" on this line.
bar.incrementProgressBy(5);
}
#Override
public void close() {
}
#Override
public void flush() {
}
#Override
public void publish(LogRecord arg0) {
}
};
AtomicBoolean isRunning = new AtomicBoolean(false);
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_handler_demo);
bar = (ProgressBar)findViewById(android.R.id.progress);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_handler_demo, menu);
return true;
}
public void onStart() {
super.onStart();
bar.setProgress(0);
Thread background = new Thread(new Runnable() {
#Override
public void run() {
try {
for(int i = 0; i < 20 && isRunning.get(); i++) {
Thread.sleep(1000);
handler.sendMessage(handler.obtainMessage()); // Shows "Method is undefined for type Handler" on this line.
}
} catch(Throwable t) { }
}
});
isRunning.set(true);
background.start();
}
public void onStop() {
super.onStop();
isRunning.set(false);
}
}
Why am I getting these errors?

Your Handler import is wrong. It should be android.os.Handler