Develop Reference

Race condition on boolean written by callbacks and read within the activity

From an Android activity I'm sending http requests driven by the user pressing buttons on the UI.
I don't want multiple requests running at the same time (OutlookClient crashes).
My question is: is it possible to have race conditions due to the callbacks with the results writing the same boolean (using runOnUiTread) that is read before sending a new request?
Thanks
// Should this be either "volatile" or atomic ??
private boolean isThereAPendingRequest = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
genericClient = clientInitializer.create(this);
// ...
isThereAPendingRequest = true; // still have to login
Futures.addCallback(genericClient.logon(this, scopes), new FutureCallback<Boolean>() {
#Override
public void onSuccess(Boolean result) {
// ...
isThereAPendingRequest = false;
}
#Override
public void onFailure(#NonNull Throwable t) {
// ...
isThereAPendingRequest = false;
}
});
// ...
}
// ...
public void getBookings(View view){
if(isThereAPendingRequest){
Toast.makeText(getApplicationContext(), "There's already a pending request. Try in a few seconds.", Toast.LENGTH_LONG).show();
return;
}
isThereAPendingRequest = true;
Futures.addCallback( genericClient.getCalendarEvents(), new FutureCallback<List<List>>(){
#Override
public void onSuccess(final List<List> resultCalendars) {
Log.d("APP", "Success. Result: "+resultCalendars);
runOnUiThread(new Runnable() {
#Override
public void run() {
// ..
isThereAPendingRequest = false;
}
}
}
// ..
}
public void sendBooking(View view){
if(isThereAPendingRequest){
Toast.makeText(getApplicationContext(), "There's already a pending request. Try in a few seconds.", Toast.LENGTH_LONG).show();
return;
}
isThereAPendingRequest = true;
Futures.addCallback( genericClient.sendBooking( booker, title), new FutureCallback<List<String>>(){
#Override
public void onSuccess(final List<String> resultBooking) {
Log.d("APP", "Success. Result: "+resultBooking);
runOnUiThread(new Runnable() {
#Override
public void run() {
// ...
isThereAPendingRequest = false;
}
});
}
#Override
public void onFailure(Throwable t) {
Log.e( "APP", "Delete error. Cause: "+t.getLocalizedMessage() );
// ...
Toast.makeText(getApplicationContext(), "Fail!", Toast.LENGTH_LONG).show();
isThereAPendingRequest = false;
}
});
}catch(Exception ex){
// logger
isThereAPendingRequest = false;
}
}
UPDATE: this is one of the function called in the Futures..
public ListenableFuture<List<List>> getCalendarEvents(){
// logger
final SettableFuture<List<List>> future = SettableFuture.create();
DateTime now = new DateTime(DateTimeZone.UTC);
DateTime workDayEnd = new DateTime( now.getYear(), now.getMonthOfYear(), now.getDayOfMonth(), 23, 59, 0 );
Futures.addCallback(
mClient .getMe()
.getCalendarView()
.addParameter("startDateTime", now)
.addParameter("endDateTime", workDayEnd)
.read(),
new FutureCallback<OrcList<Event>>() {
#Override
public void onSuccess(final OrcList<Event> result) {
// ...
future.set(myList);
}
#Override
public void onFailure(#NonNull Throwable t) {
// ...
future.setException(t);
}
}
);
return future;
}

If getBookings and setBookings are both invoked on the UI thread all the time, you should be fine. You know that by the time isThereAPendingRequest is set to false, the request must have already completed and therefore you are safe to go. By the way, Futures.addCallback has an alternate signature that allows you to explicitly pass in an Executor, so if you use that you don't need to call runOnUiThread which reduces some code nesting.
However, if you intend to invoke these methods concurrently, I see at least one race condition that requires locks to prevent. More details on that if you're interested.
Edit for completeness:
The question states that your goal is to prevent two requests from running at the same time. The are two cases where that can happen:
isThereAPendingRequest==false, but there is actually a pending request. Your code so far is safe from this, since you only set it to false after the request has been completed. You don't even need volatile here.
getBookings and/or setBookings are called on different threads. What happens if they both reach if(isThereAPendingRequest) at the same time? They can simultaneously (and correctly) see that it is false, set it to true, then both independently send a request and cause you to crash.
You don't need to worry about (1), and (2) should not be a problem as long as you always invoke those methods on the same thread.

Simple SignalR Android Example Issue

I am basically trying to send a message from my android to my server and the server to send back a response to my android app. I followed THIS tutorial.
Just a simple exercise to introduce myself in to SignalR using Azure Web API and Android.
My Complete Server code in C#:
public class TestHub: Hub {
public void SendMessage(string name, string message) {
// Call the broadcastMessage method to update clients.
Clients.All.broadcastMessage(name, message);
}
public void SendClientMessage(CustomType obj) {
Clients.All.broadcastMessage("From Server", "Server got the message bro");
}
public class CustomType {
public string Name;
public int Id;
}
}
Complete Android Java code:
public class MainActivity extends AppCompatActivity {
Handler handler;
TextView statustext;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
handler = new Handler();
statustext = (TextView) findViewById(R.id.status);
Platform.loadPlatformComponent(new AndroidPlatformComponent());
// Change to the IP address and matching port of your SignalR server.
String host = "https://My-Service-name.azure-mobile.net/";
HubConnection connection = new HubConnection(host);
HubProxy hub = connection.createHubProxy("TestHub");
SignalRFuture < Void > awaitConnection = connection.start();
try {
awaitConnection.get();
} catch (InterruptedException e) {
} catch (ExecutionException e) {
}
hub.subscribe(this);
try {
hub.invoke("SendMessage", "Client", "Hello Server!").get();
hub.invoke("SendClientMessage",
new CustomType() {
{
Name = "Android Homie";
Id = 42;
}
}).get();
} catch (InterruptedException e) {
} catch (ExecutionException e) {
}
}
//I have no idea what the following method is for. Just followed the tutorial.. (blindly)
public void UpdateStatus(String status) {
final String fStatus = status;
handler.post(new Runnable() {
#Override
public void run() {
statustext.setText(fStatus);
}
});
}
public class CustomType {
public String Name;
public int Id;
}
}
Problems with this:
1. I get an exception:
java.util.concurrent.ExecutionException:
microsoft.aspnet.signalr.client.transport.NegotiationException: There
was a problem in the negotiation with the server
2. I feel like I haven't properly called the server from the Java code.
Should the URL be:
https://My-Service-name.azure-mobile.net/
or
https://My-Service-name.azure-mobile.net/api/signalr
Can someone clarify these doubts and help me set it up?

Can't create handler inside thread that has not called Looper.prepare(), while implementing IdlingResource

I’m attempting to write Espresso unit test that depends on a component that makes TCP/IP network connection to an external app in order to pass successfully.
The test failed to due the fact that the TCP/IP network took longer than the allowed by Espresso...
Therefore, we need to have TCP/IP code Class TCPConnectionTask implement IdlingResource:
However, I'm getting, this exception:
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:200)
at android.os.Handler.<init>(Handler.java:114)
at android.app.Activity.<init>(Activity.java:786)
at com.sample.QuicksetSampleActivity.<init>(QuicksetSampleActivity.java:82)
at com.unitTests.QuicksetSampleActivityTest.<init>(QuicksetSampleActivityTest.java:52)
I enclosed the TCPConnectionTask and called Looper.prepare() & also attempted Looper.prepareMainLooper() , with no success, see below (TCPConnectionTask):
/**
* Async task to connect to create TCPIPDataComm and connect to external IRB.
*
*/
public class TCPConnectionTask extends AsyncTask<String, Void, Void > implements IdlingResource {
String ip_user = null;
int port_user;
private ResourceCallback callback;
private boolean flag = false;
protected Void doInBackground(String... args) {
try {
Handler handler = new Handler(Looper.getMainLooper());
handler.post(
new Runnable() {
#Override
public void run() {
Looper.prepare();
//Looper.prepareMainLooper();
flag = true;
TCPIPDataComm tcp = new TCPIPDataComm(ip_user, port_user);
if(tcp != null){
tcp.open();
_TCPDataComm = tcp;
// we can enable the DataComm interface for simulation in UI app
int resultCode = 0;
try {
resultCode = QuicksetSampleApplication.getSetup().setDataCommInfo(
getAuthKey(), _TCPDataComm.getHostName(),
_TCPDataComm.getPortNumber());
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally {
//task completed
flag = false;
}
Log.d(QuicksetSampleActivity.LOGTAG,
"Setting DataComm Result = "
+ resultCode
+ " - "
+ ResultCode
.getString(resultCode));
}
}
}
);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public void setInfo(String ipValue, int portNumber)
{
ip_user = ipValue;
port_user = portNumber;
}
#Override
public String getName() {
return this.getClass().getName().toString();
}
#Override public boolean isIdleNow() {
if (flag && callback != null) {
callback.onTransitionToIdle();
}
return flag;
}
#Override public void registerIdleTransitionCallback(ResourceCallback callback) {
this.callback = callback;
}
}
Below is the relevant snippet of the unit test class, QuicksetSampleActivityTest:
#RunWith(AndroidJUnit4.class)
public class QuicksetSampleActivityTest extends ActivityInstrumentationTestCase2<QuicksetSampleActivity> {
private QuicksetSampleActivity newQuicksetSampleActivity = null;
private final String ip = "192.168.43.139";
private final int port = 9999;
private final int timeOutTime = 1000;
//This is the idling resource that takes time to complete due to network latency...
private QuicksetSampleActivity.TCPConnectionTask taskIdlingResource = null;
//const
public QuicksetSampleActivityTest() {
super(QuicksetSampleActivity.class);
//instantiation of idling resource that is used for TCP connection
taskIdlingResource = new QuicksetSampleActivity().new TCPConnectionTask();
}
#Before
public void setUp() throws Exception {
super.setUp();
injectInstrumentation(InstrumentationRegistry.getInstrumentation());
//open activity
newQuicksetSampleActivity = getActivity();
// Make sure Espresso does not time out
IdlingPolicies.setMasterPolicyTimeout(timeOutTime * 10, TimeUnit.MILLISECONDS);
IdlingPolicies.setIdlingResourceTimeout(timeOutTime * 10, TimeUnit.MILLISECONDS);
//register idling resource
Espresso.registerIdlingResources(taskIdlingResource);
}
#After
public void unregisterIntentServiceIdlingResource() {
//unregister idling resource
Espresso.unregisterIdlingResources(taskIdlingResource);
}
//The EditText GUI with the port & Ip was noe found using espresso, we need to set teh ip & port programmatically
public void setIpandPortToPcBridge() {
// Use TCPCommunicatuonTask interface
taskIdlingResource.setInfo(ip, port);
taskIdlingResource.execute();
}
//after TCP connection is made and/or tested
#Test
public void testActionBarMenuItemsIrDevicesAfterTCPConnectionFunctions() {
//we were not able to find the IP & Port fields so set them programmatically
setIpandPortToPcBridge();
//open action bar menu
Espresso.openActionBarOverflowOrOptionsMenu(InstrumentationRegistry.getTargetContext());
//test IR Devices/Functions menu item
Espresso.onData(Matchers.allOf(Matchers.instanceOf(MenuItem.class), MatcherUtility.menuItemWithTitle("IR Devices/Functions"))).perform(ViewActions.click());
//add new device will connect the app
Espresso.onView(ViewMatchers.withId(R.id.btAdd)).perform(ViewActions.click());
//DeviceFunctionsActivity is rendered
Espresso.onView(ViewMatchers.withText("IR Devices")).check(ViewAssertions.matches(ViewMatchers.withText("IR Devices")));
//find the 3 required buttons for this UI
//test START learning
//Espresso.onView(ViewMatchers.withText("Start")).check(ViewAssertions.matches(ViewMatchers.withText("Start")));
//click
//test CANCEL learning
//test TEST Learned IR
//Espresso.onView(ViewMatchers.withText("Test Learned IR")).check(ViewAssertions.matches(ViewMatchers.withText("Test Learned IR")));
//click
//test Delete Learn Code
// Espresso.onView(ViewMatchers.withText("Delete Learn Code")).check(ViewAssertions.matches(ViewMatchers.withText("Delete Learn Code")));
//click
//go back
//ViewActions.pressBack();
}
}
}
How can I resolve this exception, and run the Espresso IdlingResource successfully?

Try
getInstrumentation().runOnMainSync(new Runnable() {
#Override
public void run() {
// Your testActionBarMenuItemsIrDevicesAfterTCPConnectionFunctions() test body
}
});

Example of usage with ActivityTestRule:
getInstrumentation().runOnMainSync(new Runnable() {
#Override
public void run() {
mMusicPlayerActivityTestRule.getActivity()
.getSupportMediaController().registerCallback(
new MediaControllerCompat.Callback() {
#Override
public void onPlaybackStateChanged(PlaybackStateCompat state) {
super.onPlaybackStateChanged(state);
if (state.getState() == STATE_PLAYING) {
countDownLatch.countDown();
}
}
});
}});

Issue about using Async with an Android Client

I am currently creating a project that needs to have a simple async task to take care of a thread running behind the scenes. The user needs to login. I am using another class called PVAndroid Client that supplies useful methods and has an XML serializer form packets for me. I am completely new to working with threads or doing anything with servers, so this may be completely wrong or somewhat right.
I get the data the user entered: the ip address and port, their username (I split this into first and last name), their region they selected. I encrypt their password, and attempt to connect to the tcp using ip address and port number. I am trying to work in the async task but am kind of confused on what I should do. Can anyone guide me in the right direction and help me out?
Thank you I really appreciate it.
private TcpClient myTcpClient = null;
private UdpClient udpClient;
private static final String USERNAME_SHARED_PREFS = "username";
private static final String PASSWORD_SHARED_PREFS = "password";
private static final String IP_ADDRESS_SHARED_PREFS = "ipAddressPref";
private static final String PORT_SHARED_PREFS = "portNumberPref";
private String encryptedNameLoginActivity, encryptPassLoginActivity;
private EditText userText, passText;
private String getIpAddressSharedPrefs, getPortNumberPrefs;
private String getUserNameValue;
private String getPasswordValue;
private String fName, lName;
private SharedPreferences settings;
private Editor myEditor;
private boolean getCheckedRemember;
private boolean resultCheck = false;
private int portNum;
private Button submitButton;
private String userMACVARIABLE = "";
private String regionSelected, gridSelected;
private Spinner regSpinner, gridSpinner;
PVDCAndroidClient client;
private int userNum;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
client = new PVDCAndroidClient();
}
#Override
protected void onStart() {
super.onStart();
// Take care of getting user's login information:
submitButton = (Button) findViewById(R.id.submitButton);
userText = (EditText) findViewById(R.id.nameTextBox);
passText = (EditText) findViewById(R.id.passwordTextBox);
regSpinner = (Spinner) findViewById(R.id.regionSpinner);
// grid selected as well? sometime?
regSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View v,
int position, long rowId) {
regionSelected = regSpinner.getItemAtPosition(position)
.toString();
}
#Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
});
submitButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
settings = PreferenceManager
.getDefaultSharedPreferences(AndroidClientCompnt.this);
getIpAddressSharedPrefs = settings.getString(
IP_ADDRESS_SHARED_PREFS, "");
portNum = Integer.parseInt(settings.getString(
PORT_SHARED_PREFS, ""));
if (getIpAddressSharedPrefs.length() != 0 && portNum != 0) {
if (userText.length() != 0 && passText.length() != 0) {
try {
try {
// encrypting the user's password.
encryptPassLoginActivity = Secure.encrypt(passText
.toString());
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// first connect attempt.
myTcpClient = new TcpClient();
myTcpClient.connect(getIpAddressSharedPrefs,
portNum);
// here is where I want to call Async to do login
// or do whatever else.
UploadTask task = new UploadTask();
task.execute();
} catch (Exception e) {
Toast.makeText(getApplicationContext(),
"Could not connect.", Toast.LENGTH_LONG)
.show();
e.printStackTrace();
}
}
}
}
});
}
private class UploadTask extends AsyncTask<String, Integer, Void>
{
#Override
protected void onPreExecute() {
Toast.makeText(getApplicationContext(), "Loading...",
Toast.LENGTH_LONG).show();
}
#Override
protected Void doInBackground(String... names) {
resultCheck = myTcpClient.connect(getIpAddressSharedPrefs,
portNum);
if (resultCheck == true) {
while (myTcpClient.getUserNum() < 0) {
// num set? session? with proxy server?
}
String[] firstAndLast;
String spcDelmt = " ";
firstAndLast = userText.toString().split(spcDelmt);
fName = firstAndLast[0];
lName = firstAndLast[1];
// set up the tcp client to sent the information to the
// server.
client.login(fName, lName, encryptPassLoginActivity,regionSelected, 128, 128, 20);
} else {
Toast.makeText(getApplicationContext(),
"Connection not successful", Toast.LENGTH_LONG)
.show();
}
return null;
}
#Override
protected void onPostExecute(Void result) {
Toast.makeText(getApplicationContext(), "Connected",
Toast.LENGTH_LONG).show();
}
}
}

First
#Override
protected Void doInBackground(String...params) {
new Thread (new Runnable() {
// ...
}
}
Never do this again. There is no need to create new Thread in doInBackground method which actually running on background Thread. So remove it.
The advice to you is tricky because you need to read about Threads, work with Connection etc. So the best advice to you is to read some tutorials, examples of basic applications and read references. So you can start here:
Android TCP Client and Server Communication Programming–Illustrated with Example

I cannot see, where you are yoursing your Task, but I see that you are doing something weired inside doInBackground()! There is absolutely NO reason, to create your own Thread inside it.
remove that, and you could just use your Task like this:
UploadTask task = new UploadTask();
task.execute("someString", "anotherString", "addAsManyStringsYouNeed");
The docs from AsyncTask are very helpfull, too.

how to pass data between service and it's application in the right way?

i'm a newbie in android. In my app i create a many-to-many chat, and need to update from server a list of Messages. In order to do so, i created a service that updates every second from the server.
My problem is that i don't know how to pass data back to the application. I know that I should do it using intent and broadcast receiver, but in that I stuck with Bundle object that i have to serialize in order to pass it to the app, and it does not make sense to me, since this operation is not that efficient.
For now i'm using the ref to my application (i think it's not that good but don't know why), and after every update from server in the service i activate the application function, and updates it's fields directly. Moreover i think maybe my code will do some good for beginners as well :)
public class UpdateChatService extends Service {
private static final long DELAY_FOR_CHAT_TASK = 0;
private static final long PERIOD_FOR_CHAT_TASK = 1;
private static final TimeUnit TIME_UNIT_CHAT_TASK = TimeUnit.SECONDS;
//private Task retryTask; TODO: check this out
private ScheduledExecutorService scheduler;
private boolean timerRunning = false;
private long RETRY_TIME = 200000;
private long START_TIME = 5000;
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onCreate() {
super.onCreate();
scheduleChatUpdate();
}
private void scheduleChatUpdate() {
BiggerGameApp app = (BiggerGameApp) getApplication();
this.scheduler = Executors.newScheduledThreadPool(3);
this.scheduler.scheduleAtFixedRate(new UpdateChatTask(app),
DELAY_FOR_CHAT_TASK, PERIOD_FOR_CHAT_TASK,
TIME_UNIT_CHAT_TASK);
timerRunning = true;
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
if (!timerRunning) {
scheduleChatUpdate();
}
return super.onStartCommand(intent, flags, startId);
}
#Override
public void onDestroy() {
super.onDestroy();
if (scheduler != null) {
scheduler.shutdown();
}
timerRunning = false;
}
}
Here is the code of the asynchronous task the runs in the service.
Please tell me what i'm doing wrong, and how should pass data from the service to the application.
public void run() {
try {
if (this.app.getLastMsgFromServer() == null) {
this.app.setLastMsgFromServer(new Message(new Player(DEFAULT_EMAIL), "", -1));
this.app.getLastMsgFromServer().setMessageId(-1);
}
Gson gson = new GsonBuilder()
.registerTypeAdapter(DateTime.class, new DateTimeTypeConverter())
.create();
ServerHandler serverHandler = new ServerHandler();
String jsonString = gson.toJson(this.app.getLastMsgFromServer());
// Sending player to servlet in server
String resultString = serverHandler.getResultFromServlet(jsonString, "GetListOfMessages");
if (resultString.contains("Error")) {
return;
}
// Parsing answer
JSONObject json = new JSONObject(resultString);
Status status = null;
String statusString = json.getString("status");
if (statusString == null || statusString.length() == 0)
return;
status = Status.valueOf(statusString);
if (Status.SUCCESS.equals(status)) {
ArrayList<Message> tempChat = null;
JSONArray jsonList = json.getJSONArray("data");
MyJsonParser jsonParser = new MyJsonParser();
tempChat = jsonParser.getListOfMessagesFromJson(jsonList.toString());
if (tempChat != null && tempChat.size() != 0) {
// After getting the chat from the server, it saves the last msg
// For next syncing with the server
this.app.setLastMsgFromServer(tempChat.get(LAST_MSG_INDEX));
tempChat.addAll(this.app.getChat());
if (tempChat.size() > SIZE_OF_USER_CHAT) {
tempChat = (ArrayList<Message>) tempChat.subList(0, SIZE_OF_USER_CHAT - 1);
}
this.app.setChat(tempChat);
this.app.updateViews(null);
}
}
return;

Is the Service local only (I'm going to assume "yes")?
Communication with a local-only service can be done by passing an instance of android.os.Binder back, as shown below:
public class UpdateChatService extends Service {
public static final class UpdateChat extends Binder {
UpdateChatService mInstance;
UpdateChat(UpdateChatService instance) {
mInstance = instance;
}
public static UpdateChat asUpdateChat(IBinder binder) {
if (binder instanceof UpdateChat) {
return (UpdateChat) binder;
}
return null;
}
public String pollMessage() {
// Takes a message from the list or returns null
// if the list is empty.
return mInstance.mMessages.poll();
}
public void registerDataSetObserver(DataSetObserver observer) {
mInstance.mObservable.registerObserver(observer);
}
public void unregisterDataSetObserver(DataSetObserver observer) {
mInstance.mObservable.unregisterObserver(observer);
}
}
private ScheduledExecutorService mScheduler;
private LinkedList<String> mMessages;
private DataSetObservable mObservable;
#Override
public IBinder onBind(Intent intent) {
return new UpdateChat(this);
}
#Override
public void onCreate() {
super.onCreate();
mObservable = new DataSetObservable();
mMessages = new LinkedList<String>();
mScheduler = Executors.newScheduledThreadPool(3);
mScheduler.scheduleAtFixedRate(new UpdateChatTask(), 0, 1, TimeUnit.SECONDS);
}
#Override
public void onDestroy() {
super.onDestroy();
mScheduler.shutdownNow();
mObservable.notifyInvalidated();
}
class UpdateChatTask implements Runnable {
int mN = 0;
public void run() {
// This example uses a list to keep all received messages, your requirements may vary.
mMessages.add("Message #" + (++mN));
mObservable.notifyChanged();
}
}
}
This example could be used to feed an Activity (in this case a ListActivity) like this:
public class ChattrActivity extends ListActivity implements ServiceConnection {
LinkedList<String> mMessages;
ArrayAdapter<String> mAdapter;
UpdateChat mUpdateChat;
DataSetObserver mObserver;
Runnable mNotify;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mMessages = new LinkedList<String>();
mNotify = new Runnable() {
public void run() {
mAdapter.notifyDataSetChanged();
}
};
mAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, mMessages);
getListView().setAdapter(mAdapter);
// Bind to the Service if you do not need it to persist when this Activity
// dies - otherwise you must call #startService(..) before!
bindService(new Intent(this, UpdateChatService.class), this, BIND_AUTO_CREATE);
}
/**
* #see android.app.ListActivity#onDestroy()
*/
#Override
protected void onDestroy() {
super.onDestroy();
if (mUpdateChat != null) {
mUpdateChat.unregisterDataSetObserver(mObserver);
unbindService(this);
}
}
public void onServiceConnected(ComponentName name, IBinder service) {
mUpdateChat = UpdateChat.asUpdateChat(service);
mObserver = new DataSetObserver() {
#Override
public void onChanged() {
String message;
while ((message = mUpdateChat.pollMessage()) != null) {
mMessages.add(message);
}
runOnUiThread(mNotify);
}
#Override
public void onInvalidated() {
// Service was killed - restart or handle this error somehow.
}
};
// We use a DataSetObserver to notify us when a message has been "received".
mUpdateChat.registerDataSetObserver(mObserver);
}
public void onServiceDisconnected(ComponentName name) {
mUpdateChat = null;
}
}
If you need to communicate across processes you should look into implementing an AIDL interface - but for "local" versions this pattern works just fine & doesn't involve abusing the global Application instance.

You can use a static memory shared between your service and rest of application (activities). If you do not plan to expose this service to external apps, then sharing static memory is better than serializing/deserializing data via bundles.
Bundles based approach is encouraged for components that are to be exposed to outside world. A typical app usually has just the primary activity exposed in app manifest file.

If your don't pulibc your service , the static memory and the callback function can do.
If not , you can send broadcast.