I have one doubt about using services. I have a service that initializes an object, is it a bad practice to pass an instance of the service to the object so it can be used for that object? A simplified object would be:
public class MyService extends Service {
MyObject myObject = new MyObject(this);
...
}
public MyObject {
private MyService myService;
public MyObject(MyService myService) {
this.myService = myService;
}
...
private void exampleMethod() {
myService.method();
}
}
What do you think? Is it a bad practice? How could I solve that issue without passing the service's instance?
The fact is that I want to split the code in two classes because the features are different, the websocket is connected from the service class, but the methods to parse/send events through the websocket are in the second class. I want to do this way in order to avoid having one class with 2000 lines of code, and by splitting the code by features. The service handles the websocket connection, while the other class handles the other features. As everything is asynchronous, the second class needs an instance of the service class. For instance: if an error is received and parsed (on the second class), this second class must call the service class to update its status and do a reconnection.
EDIT:
I'm thinking about implementing the following solution:
public class MyService extends Service {
MyObject myObject = new MyObject() {
protected void onSuccess() {
...
}
};
...
}
public abstract class MyObject {
public MyObject() {
}
protected abstract void onSuccess();
...
private void exampleMethod() {
...
onSuccess()
}
}
The more I think about it, the better solution I think it is. What do you think?
Thank you very much in advance!
This makes no sense at all. I suggest you to use a interface if you need to pass a callback to a dao (the websocket controller). The thing is that you should use your service to implement your websocket controller.
Please add the websocket code, so we can suggest more changes.
EDIT:
public interface onGetData {
public void onSuccess(Object response) // here you pass the obj type you need in your service
public void onError(Object error) // same, but if things fail
}
public class MyService extends Service implements onGetData {
#Override
public void OnCreate() {
MyObject myObject = new MyObject(this);
}
#Override
public void onSuccess(Object response) {
}
#Override
public void onError(Object error) {
}
}
public MyObject {
private OnGetData onGetData ;
public MyObject(OnGetData onGetData) {
this.onGetData = onGetData;
}
private void onRequestSuccess(Object response) {
onGetData.onSuccess(response)
}
private void onRequestError(Object error) {
onGetData.onError(error)
}
}
Related
I am trying to implement an architecture similar to the one presented at the Android Developer Summit 2015: https://github.com/yigit/dev-summit-architecture-demo. My application has a simple class that handles the network requests. The class uses Retrofit 2 for the requests. I am also using Dagger 2 for dependency injection.
I am trying to achieve something very simple. My activity tells a controller to fetch data. The controller then makes a call to my REST client to perform a network request. When the request completes successfully I want to broadcast an event to my Activity so that it can update the UI. However, the event is not being broadcast.
I am using the LocalBroadcastManager to broadcast events. My activity registers/unregisters for broadcasts in the onResume/onPause methods. My REST client has an instance of the application context which is provided through dependency injection. The REST client uses the application context to send the broadcast.
My first suspicion was that the broadcasts were not being sent because the network requests are executed on a worker thread whereas the activity is expecting broadcasts on the main thread. However, this type of scenario shouldn't be a problem if the Android documentation is correct.
This is my activity.
public class BaseActivity extends AppCompatActivity {
private ApplicationComponent mApplicationComponent;
private EventBroadcastReceiver mEventBroadcastReceiver = new EventBroadcastReceiver();
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mApplicationComponent = getMovieManagerApplication().getApplicationComponent();
}
#Override
protected void onResume() {
super.onResume();
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("now_playing");
LocalBroadcastManager.getInstance(this).registerReceiver(mEventBroadcastReceiver, intentFilter);
}
#Override
protected void onPause() {
super.onPause();
LocalBroadcastManager.getInstance(this).unregisterReceiver(mEventBroadcastReceiver);
}
protected MovieManagerApplication getMovieManagerApplication() {
return (MovieManagerApplication) getApplication();
}
protected ApplicationComponent getApplicationComponent() {
return mApplicationComponent;
}
protected void update(Intent intent) {
}
private class EventBroadcastReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
update(intent);
}
}
}
And this is my REST client.
public class MovieRestClient extends BaseRestClient implements Callback<MovieResponse> {
#Inject
public MovieApiService mMovieApiService;
#Inject
public Context mApplicationContext;
public MovieRestClient(ApplicationComponent applicationComponent) {
super(applicationComponent);
getApplicationComponent().inject(this);
}
#Override
public void onResponse(Response<MovieResponse> response) {
if (response.isSuccess()) {
Parcelable parcelable = Parcels.wrap(response.body());
MovieResponse movieResponse = Parcels.unwrap(parcelable);
Intent intent = new Intent("now_playing");
intent.putExtra(MovieResponse.class.getName(), parcelable);
LocalBroadcastManager.getInstance(mApplicationContext).sendBroadcast(intent);
}
}
#Override
public void onFailure(Throwable t) {
}
public void getNowPlaying() {
mMovieApiService.getNowPlaying(API_KEY).enqueue(this);
}
public void getPopular() {
mMovieApiService.getPopular(API_KEY).enqueue(this);
}
public void getTopRated() {
mMovieApiService.getTopRated(API_KEY).enqueue(this);
}
public void getUpcoming() {
mMovieApiService.getUpcoming(API_KEY).enqueue(this);
}
}
Any help would be greatly appreciated.
An Activity contains a Fragment which in turn contains a child Fragment, which requests a Service. The app tries to implement dobjanschi rest architecture.
When the Service is done working it has to propagate operation result. I tried using a PendingIntent but it seems to only be caught by the activity, while I need the child fragment to get notified. Could you suggest anything? Binder? greenRobot Eventbus? RxJava (which I already have in the project)?
Thanks.
RxJava
A simple way con be to use a Singleton to wrap a synchronized ´PublishSubject´
* Singleton
*
* to send an event use EventBusRx.getInstance().topic1.onNext("completed");
*/
public class EventBusRx {
private static EventBusRx ourInstance = new EventBusRx();
public static EventBusRx getInstance() {
return ourInstance;
}
private EventBusRx() {}
/**
* Use of multiple topics can be usefull
* SerializedSubject avoid concurrency issues
*/
public final Subject<String, String> topic1 = new SerializedSubject<>(PublishSubject.create());
public final Subject<Integer, Integer> topic2 = new SerializedSubject<>(PublishSubject.create());
}
And You can send events from service
EventBusRx.getInstance().topic1.onNext("completed");
and respond to event in fragments or whenever you want
public class MyFragment extends Fragment {
// [...]
Subscription subscription_topic1;
#Override
public void onResume() {
super.onResume();
subscription_topic1 = EventBusRx.getInstance().topic2
.subscribeOn(AndroidSchedulers.mainThread()) // or on other sheduler
.subscribe(new Action1<Integer>() {
#Override
public void call(Integer integer) {
// update ui
}
});
}
#Override
public void onPause() {
// important to avoid memory leaks
subscription_topic1.unsubscribe();
super.onPause();
}
}
do not forget to unsubcribe the Subscription
The idea is similar to Roger'one use a singleton but enforce ThreadSafety wrapping PublishSubject.
there is no need for Observable.switchOnNext(subject)
EventBus Libraries
greenRobot Eventbus and Otto are nice and has the same functionality, but the disadvantage is that they make the connection more smoky (expecialy EventBus) . If you already use rx i think is better to stay with it
Here is an insipring article about the topic
Implementing an Event Bus With RxJava
LocalBroadcast
The classic way to do this is to use LocalBroadcastManager but in my aopinion they are a pain
I would suggest using an Event Bus for this sort of thing. It will allow you to send messages to components within your system, without requiring creating special handlers.
Otto is a popular open source library for this, and there are others. http://square.github.io/otto/
Try this way hope it help you.
For Example:
YourService
public class MyService extends Service{
public static MyServiceListener getMyServiceListener() {
return MyService.myServiceListener;
}
public static void setMyServiceListener(MyServiceListener myServiceListener) {
MyService.myServiceListener = myServiceListener;
}
private static MyServiceListener myServiceListener;
public interface MyServiceListener{
void onResult(String response);
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onCreate() {
super.onCreate();
}
#Override
public void onStart(Intent intent, int startId) {
super.onStart(intent, startId);
executeYourTask();
}
private void executeYourTask(){
String result = "SomeResultMaybeFromServer";
if(getMyServiceListener()!=null){
getMyServiceListener().onResult(result);
}
}
}
YourFragment
public class MyFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = null; // some view
// Start service
MyService.setMyServiceListener(new MyService.MyServiceListener() {
#Override
public void onResult(String response) {
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() {
// To handle memory/window leaks
}
});
}
});
return v;
}
}
I'm currently developing a Bus based solely on RxJava. Since you already have RxJava on your project, you can use it for this. You should use a BehaviorSubject and Observable.switchOnNext().
For example:
private BehaviorSubject<Observable<Whatever>> subject = BehaviorSubject.create();
public void post(){
subject.onNext(...);
}
public Observable<Whatever> subscribe(){
return Observable.switchOnNext(subject);
}
You should have this as part of a Singleton so the same BehaviorSubject is used. All you have to do is post() from one fragment and subscribe() on the other one or in any other interested fragment or activity. You can have as many subscriptions as you want, plus if you implement it correctly then the last emitted Observable will survive orientation changes.
More info on BehaviorSubject can be found here: https://github.com/ReactiveX/RxJava/wiki/Subject
I'm currently using this Pub/Sub pattern with rxjava and enum class.
public enum Events {
public static PublishSubject <Object> myEvent = PublishSubject.create ();
}
//where you want to publish something
Events.myEvent.onNext(myObject);
//where you want to receive an event
Events.myEvent.subscribe (...);
I would use event bus, which is based on rx.
Make this as a sigletone and subscribe on particular class type.
public class RxBus {
private static final RxBus sBus = new RxBus();
private final Subject<Object, Object> mBus = new SerializedSubject<>(PublishSubject.create());
private RxBus() {
}
public static RxBus getInstance() {
return sBus;
}
public void send(Object o) {
mBus.onNext(o);
}
public Observable<Object> observe() {
return mBus;
}
#SuppressWarnings("unchecked")
public <T> Observable<T> observe(Class<T> c) {
return mBus.filter(o -> c.isAssignableFrom(o.getClass())).map(o -> (T) o);
}
}
usage:
class Message { public String result};
send a message:
Message m = new Message();
m.result = "Hello world";
RxBus.getInstance().send(m);
subscribe on a particular class type:
RxBus.getInstance().observe(Message.class).subscribe(msg -> Log.e(TAG, "Message was caught : " + msg));
I'm looking at retrofit for my networking layer. Is there any way to tell if a particular async request is running at any given moment?
For example, I'd like to know if a request is running so that I can update the user interface at various times. I could do this myself by keeping variables around to track state, but wondering if there's something already in the library for this.
Here is what I would normally do when needing a way to keep track of running requests:
First, using retrofit, as soon as you make the request, you can do the following:
Use EventBus library to post an event to your activity or fragment. Now, this can be done inside onSuccess() method of your Callback or onError() method of the same.
In your activity or fragment's onEvent(EventClassName event) method, you can simply check a variable like [isRunning] from your event to make sure that if the event is still running, you update the UI accordingly and if not, do what you need to do respectively.
When the request is completed, obviously isRunning will be false and you can then update the UI as expected by the user.
I am recommending EventBus here simply because it is much easier to decouple your application code with it; you can send different events that notify the activity of the different statuses of your requests and then update your UI that way.
You can find EventBus here
I hope this helps!
What I personally ended up doing in this case was that I was running the example with Retrofit, Android Priority Jobqueue (from yigit's fork) and Otto eventbus.
public enum SingletonBus {
INSTANCE;
private Bus bus;
private Handler handler = new Handler(Looper.getMainLooper());
private SingletonBus() {
this.bus = new Bus(ThreadEnforcer.ANY);
}
public <T> void postToSameThread(final T event) {
bus.post(event);
}
public <T> void postToMainThread(final T event) {
handler.post(new Runnable() {
#Override
public void run() {
bus.post(event);
}
});
}
public <T> void register(T subscriber) {
bus.register(subscriber);
}
public <T> void unregister(T subscriber) {
bus.unregister(subscriber);
}
}
public interface Interactor {
void injectWith(PresenterComponent presenterComponent);
}
public interface SendCertificateRequestInteractor
extends Interactor {
interface Listener {
void onSuccessfulEvent(SuccessfulEvent e);
void onFailureEvent(FailureEvent e);
}
class SuccessfulEvent
extends EventResult<CertificateBO> {
public SuccessfulEvent(CertificateBO certificateBO) {
super(certificateBO);
}
}
class FailureEvent
extends EventResult<Throwable> {
public FailureEvent(Throwable throwable) {
super(throwable);
}
}
void sendCertificateRequest(String username, String password);
}
Pay attention to the Job here:
public class SendCertificateRequestInteractorImpl
implements SendCertificateRequestInteractor {
private Presenter presenter;
private boolean isInjected = false;
#Inject
public JobManager jobManager;
public SendCertificateRequestInteractorImpl(Presenter presenter) {
this.presenter = presenter;
}
#Override
public void sendCertificateRequest(String username, String password) {
if(!isInjected) {
injectWith(presenter.getPresenterComponent());
isInjected = true;
}
InteractorJob interactorJob = new InteractorJob(presenter, username, password);
long jobId = jobManager.addJob(interactorJob); //this is where you can get your jobId for querying the status of the task if you want
}
#Override
public void injectWith(PresenterComponent presenterComponent) {
presenterComponent.inject(this);
}
public static class InteractorJob
extends Job {
private final static int PRIORITY = 1;
private final static String TAG = InteractorJob.class.getSimpleName();
private String username;
private String password;
#Inject
public MyService myService;
public InteractorJob(Presenter presenter, String username, String password) {
super(new Params(PRIORITY).requireNetwork());
presenter.getPresenterComponent().inject(this);
this.username = username;
this.password = password;
}
#Override
public void onAdded() {
// Job has been saved to disk.
// This is a good place to dispatch a UI event to indicate the job will eventually run.
// In this example, it would be good to update the UI with the newly posted tweet.
}
#Override
public void onRun()
throws Throwable {
String certificate = myService.getCertificate(username, password);
SingletonBus.INSTANCE.postToMainThread(new SuccessfulEvent(certificate));
}
#Override
protected void onCancel() {
// Job has exceeded retry attempts or shouldReRunOnThrowable() has returned false.
Log.e(TAG, "Cancelled job.");
}
#Override
protected boolean shouldReRunOnThrowable(Throwable throwable) {
// An error occurred in onRun.
// Return value determines whether this job should retry running (true) or abort (false).
Log.e(TAG, "Failed to execute job.", throwable);
SingletonBus.INSTANCE.postToMainThread(new FailureEvent(throwable));
return false;
}
}
}
And then
#Subscribe
#Override
public void onSuccessfulEvent(SendCertificateRequestInteractor.SuccessfulEvent e) {
String certificate = e.getResult();
//do things
}
#Subscribe
#Override
public void onFailureEvent(SendCertificateRequestInteractor.FailureEvent e) {
Throwable throwable = e.getResult();
//handle error
}
More about android priority jobqueue here.
This way, technically the async handling is referred to the job queue, while Retrofit itself is using the synchronous interface. It works well as long as you don't need to access the headers of the response. Although to be fair, I was also keeping track of whether the job was running with a boolean instead of the job manager and the id as well..
Also, I haven't figured out how to use dependency injection properly with persisted jobs; nor do I really know how they intended to make that work. Of course, it'd work if it was using the application scoped component rather than a supplied presenter scoped one, but that is irrelevant.
You'll probably need to customize this solution to your own scenario, and use only what you actually need.
I seem to be having one of two issues here. Either an error like:
java.lang.IllegalStateException: Event bus [Bus "default"] accessed from non-main thread Looper
Or, if I've managed to "address" that, I simply never receive the event in my subscriber.
Currently, I have a class, cobbled from a few sources, sub-classing Bus:
public class MainThreadBus extends Bus {
private static Bus _bus;
private Handler _handler = new Handler(Looper.getMainLooper());
public MainThreadBus() {
if (_bus == null) {
_bus = new Bus();
}
}
#Override public void register(Object obj) {
_bus.register(obj);
}
#Override public void unregister(Object obj) {
_bus.unregister(obj);
}
#Override public void post(final Object event) {
if (Looper.myLooper() == Looper.getMainLooper()) {
_bus.post(event);
} else {
_handler.post(new Runnable() {
#Override public void run() {
_bus.post(event);
}
});
}
}
}
Which is used in an Activity like this:
#Subscribe
public void requestProgressAvailable(RESTRequestProgress progress) {
processProgress(progress);
}
#Override
protected void onResume() {
super.onResume();
_bus = new MainThreadBus();
_bus.register(this);
}
#Override
protected void onPause() {
super.onPause();
_bus = new MainThreadBus();
_bus.unregister(this);
}
And publishing from an IntentService like this:
_bus = new MainThreadBus();
_bus.post(request.createRESTRequestProgress(RESTRequest.STATUS_STARTED));
And the messages are not received. An alternate configuration had me receiving the thread error, so I'm going with this, for now.
So, what am I missing, or doing wrong?
EDIT: Thanks to Andy below for pointing out that my code wasn't acting as I thought it was. The code above now reflects modifications based on that feedback.
Aside from the fact this implementation isn't a Singleton, when getting this error, you can use the threadEnforcer.ANY option in the constructor:
private static final Bus BUS = new Bus(ThreadEnforcer.ANY);
The problem is that your code is not interacting with the same bus instance. Instead of creating a new MainThreadBus in each case, you should access the same bus, for example a singleton obtained from a factory or via injection.
I have a Service that creates AsyncTasks for downloading files. In activities, we create Runnables or Threads that we pass to Activity.runOnUiThread(). I can't access that method from a service, so how do I use AsyncTask correctly, (do heavy work without blocking the UI Thread)?
If your service is only called from your application, and you can make it a singleton, then try this:
public class FileDownloaderService extends Service implements FileDownloader {
private static FileDownloaderService instance;
public FileDownloaderService () {
if (instance != null) {
throw new IllegalStateException("This service is supposed to be a singleton");
}
}
public static FileDownloaderService getInstance() {
// TODO: Make sure instance is not null!
return instance;
}
#Override
public void onCreate() {
instance = this;
}
#Override
public IBinder onBind(#SuppressWarnings("unused") Intent intent) {
return null;
}
#Override
public void downloadFile(URL from, File to, ProgressListener progressListener) {
new Thread(new Runnable() {
#Override
public void run() {
// Perform the file download
}
}).start();
}
}
Now you can directly call methods on your service. So just call downloadFile() to put the service to work.
About your real question of how to update the UI. Notice that this method receives a ProgressListener instance. It could look like this:
public interface ProgressListener {
void startDownloading();
void downloadProgress(int progress);
void endOfDownload();
void downloadFailed();
}
Now you just update the UI from the activity (not from the service, which remains unaware of how the UI looks like).