Get Reactive - Devoxx

The RxJava hype is still in full swing and almost everything gets Rxified. At least since the stable RxAndroid 1.0 release it’s time to take RxAndroid seriously!

In this session you will learn what RxJava is about, how to use it on Android and how RxAndroid can be used to build maintainable Android Apps from networking with Retrofit2 to UI with the new RxBinding and RxLifecycle libraries powered by MVP.

If you haven’t had the time to Get Reactive, we’ll provide a quick introduction why you should use RxAndroid in your current and next projects.

Transcript

1. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   Get Reactive
   

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2. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   +Wolfram Rittmeyer
   @rittmeyerw
   +Pascal Welsch
   @passsy
   

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3. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   Reactive Extensions
   

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4. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   RxJava – a library for composing
   asynchronous and event-based
   programs using observable sequences
   for the Java VM.
   https://github.com/ReactiveX/RxJava
   

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5. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   Reactive Extensions
   

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6. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   Simple Observable
   Observable countObservable =

   Observable.from(Arrays.asList(new Integer[]{2, 3, 5, 7}))

   .filter(n -> n % 2 != 0)

   .count()

   .map(n -> String.format("%d item(s)", n));
   

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7. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   Simple Subscriber
   countObservable.subscribe(new Subscriber() {

   @Override

   public void onCompleted() {

   Log.d("get_reactive", "Done!");

   }

   @Override

   public void onError(Throwable e) {

   Log.e("get_reactive", "Yikes!", e);

   }

   @Override

   public void onNext(String s) {

   Log.d("get_reactive", s);

   }

   });
   

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8. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   Simple Subscriber
   countObservable.subscribe(new Subscriber() {

   @Override

   public void onCompleted() {

   Log.d("get_reactive", "Done!");

   }

   @Override

   public void onError(Throwable e) {

   Log.e("get_reactive", "Yikes!", e);

   }

   @Override

   public void onNext(String s) {

   Log.d("get_reactive", s);

   }

   });
   

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9. @rittmeyerw, @passsy
   #Devoxx #GetReactive
   RxJava in Detail
   

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10. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Creating Observables
    • Basic
    • Observable.from()
    • Observable.just()
    • Observable.range()
    • Timing based
    • Observable.interval()
    • Observable.timer()
    • Custom
    • Observable.create()
    

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11. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Creating Observables
    Observable.create(new Observable.OnSubscribe() {

    public void call(Subscriber super Integer> s) {

    try {

    Random r = new Random();

    for (int i = 0; i < 10; i++) {

    s.onNext(r.nextInt());

    }

    s.onCompleted();

    }

    catch (Throwable t) {

    s.onError(t);

    }

    }

    });
    

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12. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Creating Observables
    Observable.create(new Observable.OnSubscribe() {

    public void call(Subscriber super Integer> s) {

    try {

    Random r = new Random();

    for (int i = 0; i < 10; i++) {

    s.onNext(r.nextInt());

    }

    s.onCompleted();

    }

    catch (Throwable t) {

    s.onError(t);

    }

    }

    });
    

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13. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Creating Observables
    Observable.create(new Observable.OnSubscribe() {

    public void call(Subscriber super Integer> s) {

    try {

    Random r = new Random();

    for (int i = 0; i < 10; i++) {

    if (!s.isUnsubscribed()) {

    s.onNext(r.nextInt());

    }

    else {

    break;

    }

    }

    // ...
    

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14. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Consuming Observables
    • subscribe() overloaded
    • Be careful to not leak anything
    • anonymous inner classes
    • forgetting to unsubscribe
    

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15. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Processing Chain
    • Transformers
    • map, flatMap, scan
    • Filters
    • filter, throttle, take, skip
    • Conditions
    • amb, skipWhile, takeWhile
    • Combination
    • concat, zip, combineLatest
    • Aggregate
    • count, reduce, toList, toMap
    

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16. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    flatMap
    

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17. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    combineLatest
    

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18. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    zip
    

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19. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Backpressure
    • Observable to fast for consumer
    • Can happen anywhere in the chain
    • Some possible actions:
    • Throttle
    • Buffer
    • request(n) upstream items
    

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20. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Off the Main thread
    • Schedulers
    • subscribeOn()
    • Schedulers.io()
    • Schedulers.computation()
    • Schedulers.newThread()
    • Schedulers.fromExecutor()
    • observeOn
    • AndroidSchedulers.mainThread()
    

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21. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Error Handling
    • Observable.onErrorResumeNext()
    • Observable.onErrorReturn()
    • yourObserver.onError()
    

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22. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Testing Observables
    • Create special cases
    • Observable.error()
    • Observable.empty()
    • Observable.never()
    • Use TestSubscriber
    

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23. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Debugging Observables
    • Side effect operators
    • doOnNext()
    • doOnSubscribe()
    • …
    • Hooks
    • RxJavaObservableExecutionHook
    • RxJavaSchedulersHook
    • RxJavaErrorHandler
    

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24. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    RxAndroid
    

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25. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    What is RxAndroid?
    // RxAndroid contains the AndroidScheduler (main thread)

    // few releases

    compile 'io.reactivex:rxandroid:1.0.1'
    

    

    // additionally add specific (latest) version of RxJava

    compile 'io.reactivex:rxjava:1.0.14'
    

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26. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Reactive Android UI
    

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27. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Make Listeners Reactive
    // typical Android widget listener
    final Button myButton = (Button)
    findViewById(R.id.myButton);

    myButton.setOnClickListener(new View.OnClickListener() {

    @Override

    public void onClick(final View v) {

    triggerAction();

    }

    });
    

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28. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Make Listeners Reactive
    final Observable myButtonClickObservable =

    Observable.create(subscriber -> {

    myButton.setOnClickListener(v -> {

    if (!subscriber.isUnsubscribed()) {

    subscriber.onNext(v);

    }

    });

    });

    

    myButtonClickObservable

    .subscribe(v -> triggerAction());
    unsubscribing not handled!
    lamda for
    Observable.OnSubscribe
    

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29. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Make Listeners Reactive
    final Observable myButtonClickObservable =

    Observable.create(subscriber -> {

    myButton.setOnClickListener(v -> {

    if (!subscriber.isUnsubscribed()) {

    subscriber.onNext(null);

    }

    });

    });

    

    myButtonClickObservable

    .delay(100, TimeUnit.MILLISECONDS)

    .observeOn(Schedulers.io())

    .subscribe(v -> triggerAction());
    

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30. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    RxBinding
    compile 'com.jakewharton.rxbinding:rxbinding:0.3.0'
    RxView.clicks(myButton)

    .subscribe(v -> triggerAction());
    Others and more
    RxView, RxTextView, RxAdapter, RxAdapterView, RxAutoCompleteTextView,
    RxCheckedTextView, RxCompoundButton, RxMenuItem, RxSeekBar, RxViewGroup,
    RxProgressBar, RxRadioGroup, RxRatingBar, RxRecyclerView, RxRecyclerViewAdapter,
    RxSearchView, RxToolbar, ...
    

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31. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    compile 'com.jakewharton.rxbinding:rxbinding:0.3.0'
    RxView.clicks(myButton)

    .subscribe(v -> triggerAction());
    Others and more
    RxView, RxTextView, RxAdapter, RxAdapterView, RxAutoCompleteTextView,
    RxCheckedTextView, RxCompoundButton, RxMenuItem, RxSeekBar, RxViewGroup,
    RxProgressBar, RxRadioGroup, RxRatingBar, RxRecyclerView, RxRecyclerViewAdapter,
    RxSearchView, RxToolbar, ...
    RxBinding
    :rxbinding-support-v4
    :rxbinding-appcompat-v7
    :rxbinding-design
    :rxbinding-recyclerview-v7
    :rxbinding-leanback-v17
    

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32. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Combine UI events
    

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33. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    The login view
    TextView username_tv = (TextView) findViewById(R.id.username);

    TextView password_tv = (TextView) findViewById(R.id.password);

    

    Observable rxUsername = RxTextView.textChanges(username_tv);
    Observable rxPassword = RxTextView.textChanges(password_tv);
    too easy...
    

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34. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Build a registration view!
    TextView username_tv = (TextView) findViewById(R.id.username);

    TextView password_tv = (TextView) findViewById(R.id.password);
    // optional field

    TextView fullName_tv = (TextView) findViewById(R.id.fullName);
    

    Observable rxUsername = RxTextView.textChanges(username_tv);
    Observable rxPassword = RxTextView.textChanges(password_tv);
    Observable rxFullName = RxTextView.textChanges(fullName_tv);
    Observable.combineLatest(

    rxUsername, rxPassword, rxFullName, RegistrationModel::new)
    

    .filter(RegistrationModel::isValid)

    .subscribe(LoginActivity::enableSubmitButton);
    never called when fullName not entered
    

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35. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    combineLatest
    

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36. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Build a registration view!
    TextView username_tv = (TextView) findViewById(R.id.username);

    TextView password_tv = (TextView) findViewById(R.id.password);
    // optional field

    TextView fullName_tv = (TextView) findViewById(R.id.fullName);

    

    Observable rxUsername = RxTextView.textChanges(username_tv);
    Observable rxPassword = RxTextView.textChanges(password_tv);
    Observable rxFullName = RxTextView.textChanges(fullName_tv)

    .mergeWith(Observable.just(""));
    Observable.combineLatest(

    rxUsername, rxPassword, rxFullName, RegistrationModel::new)
    // triggers now without entering a fullName

    .filter(RegistrationModel::isValid)

    .subscribe(LoginActivity::enableSubmitButton);
    emits "" after subscribe
    

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37. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    network requests triggered
    

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38. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    GitHub repository
    search
    Using Retrofit 2 for the
    network calls
    

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39. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    the Android Way
    searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {

    @Override

    public boolean onQueryTextChange(final String query) {

    if (!TextUtils.isEmpty(query)) {

    mGitApiService.searchRepositories(query).enqueue(callback);
    }

    return true;

    }

    

    @Override

    public boolean onQueryTextSubmit(final String query) {

    return false;

    }

    });
    

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40. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    the Android Way
    Callback callback
    = new Callback() {

    @Override public void onFailure(final Throwable t) {

    showEmptyErrorView(t.getMessage());

    }

    

    @Override
    public void onResponse(
    Response response, Retrofit retrofit) {

    if (response.isSuccess()) {

    showRepositories(response.body().getItems());

    } else {

    try {

    showEmptyErrorView(response.errorBody().string());

    } catch (IOException e) {

    showEmptyErrorView(response.message());
    // [\)\]\}]*
    

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41. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    the RxBeginner solution
    RxSearchView.queryTextChanges(searchView)

    .filter(charSequence -> !TextUtils.isEmpty(charSequence))

    .flatMap(charSequence -> {

    return mGitApiService
    .searchRepositoriesObservable(charSequence.toString())

    .subscribeOn(Schedulers.io());

    })

    .observeOn(AndroidSchedulers.mainThread())

    .subscribe(response -> {

    showRepositories(response.getItems());

    }, throwable -> {

    showEmptyErrorView(throwable.getMessage());

    });
    

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42. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    The RxBeginner solution
    RxSearchView.queryTextChanges(searchView)

    .filter(charSequence -> !TextUtils.isEmpty(charSequence))

    .flatMap(charSequence -> {

    return searchRepositories(charSequence);

    })

    .observeOn(AndroidSchedulers.mainThread())

    .subscribe(response -> {

    showRepositories(response.getItems());

    }, throwable -> {

    showEmptyErrorView(throwable.getMessage());

    });
    

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43. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    keep order with concatMap
    RxSearchView.queryTextChanges(searchView)

    .filter(charSequence -> !TextUtils.isEmpty(charSequence))

    .concatMap(charSequence -> {

    return searchRepositories(charSequence);

    })

    .observeOn(AndroidSchedulers.mainThread())

    .subscribe(response -> {

    showRepositories(response.getItems());

    }, throwable -> {

    showEmptyErrorView(throwable.getMessage());

    });
    

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44. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    without backpressure (1/3)
    11-12 04:24:48.897 V: searching:
    11-12 04:24:48.916 V: empty view
    11-12 04:24:49.581 V: searching: d
    11-12 04:24:49.598 V: requesting d
    11-12 04:24:49.624 D: --> GET /search/repositories?q=d HTTP/1.1
    11-12 04:24:49.741 V: searching: de
    11-12 04:24:49.743 V: requesting de
    11-12 04:24:49.910 V: searching: dev
    11-12 04:24:50.026 V: searching: devo
    11-12 04:24:50.155 V: searching: devox
    11-12 04:24:50.307 V: searching: devoxx
    11-12 04:24:50.667 D: 11-12 04:24:50.778 V: got data
    11-12 04:24:50.779 D: --> GET /search/repositories?q=de HTTP/1.1
    11-12 04:24:50.793 V: requesting dev
    

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45. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    without backpressure (2/3)
    11-12 04:24:50.307 V: searching: devoxx
    11-12 04:24:50.667 D: 11-12 04:24:50.778 V: got data
    11-12 04:24:50.779 D: --> GET /search/repositories?q=de HTTP/1.1
    11-12 04:24:50.793 V: requesting dev
    11-12 04:24:51.218 D: 11-12 04:24:51.223 V: got data
    11-12 04:24:51.223 D: --> GET /search/repositories?q=dev HTTP/1.1
    11-12 04:24:51.243 V: requesting devo
    11-12 04:24:51.728 D: 11-12 04:24:51.734 V: got data
    11-12 04:24:51.741 V: requesting devox
    11-12 04:24:51.741 D: --> GET /search/repositories?q=devo HTTP/1.1
    11-12 04:24:52.067 D: 11-12 04:24:52.077 V: got data
    

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46. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    without backpressure (3/3)
    11-12 04:24:51.741 V: requesting devox
    11-12 04:24:51.741 D: --> GET /search/repositories?q=devo HTTP/1.1
    11-12 04:24:52.067 D: 11-12 04:24:52.077 V: got data
    11-12 04:24:52.078 D: --> GET /search/repositories?q=devox HTTP/
    1.1
    11-12 04:24:52.096 V: requesting devoxx
    11-12 04:24:52.360 D: 11-12 04:24:52.369 V: got data
    11-12 04:24:52.369 D: --> GET /search/repositories?q=devoxx HTTP/
    1.1
    11-12 04:24:52.663 D: 11-12 04:24:52.670 V: got data
    2.3s until the response is visible
    

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47. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    handle backpressure
    RxSearchView.queryTextChanges(searchView)

    .filter(charSequence -> !TextUtils.isEmpty(charSequence))
    .throttleLast(100, TimeUnit.MILLISECONDS)

    .debounce(200, TimeUnit.MILLISECONDS)

    .onBackpressureLatest()

    .concatMap(charSequence -> {

    return searchRepositories(charSequence);

    })

    .observeOn(AndroidSchedulers.mainThread())

    .subscribe(response -> {

    showRepositories(response.getItems());

    }, throwable -> {

    showEmptyErrorView(throwable.getMessage());

    });
    prevents request for
    every character
    only one query waiting
    while request running
    

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48. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    with throttleLast and debounce
    11-12 04:21:35.661 V: searching:
    11-12 04:21:35.875 V: empty view
    11-12 04:21:37.098 V: searching: d
    11-12 04:21:37.261 V: searching: de
    11-12 04:21:37.430 V: searching: dev
    11-12 04:21:37.572 V: searching: devo
    11-12 04:21:37.740 V: searching: devox
    11-12 04:21:37.903 V: searching: devoxx
    11-12 04:21:38.177 V: requesting devoxx
    11-12 04:21:38.186 D: --> GET /search/repositories?q=devoxx HTTP/
    1.1
    11-12 04:21:39.024 D: 11-12 04:21:39.131 V: got data
    1.3s until the response is visible
    

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49. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    request while typing
    11-12 04:32:37.580 V: searching:
    11-12 04:32:37.875 V: empty view
    11-12 04:32:38.355 V: searching: d
    11-12 04:32:38.521 V: searching: de
    11-12 04:32:38.573 V: requesting d
    11-12 04:32:38.582 D: --> GET /search/repositories?q=d HTTP/1.1
    11-12 04:32:38.706 V: searching: dev
    11-12 04:32:38.882 V: searching: devo
    11-12 04:32:39.147 V: searching: devox
    11-12 04:32:39.172 V: requesting devo
    11-12 04:32:39.313 V: searching: devoxx
    11-12 04:32:39.379 D: 11-12 04:32:39.457 V: searching: devoxx
    11-12 04:32:39.692 V: searching: devoxx t
    11-12 04:32:39.784 V: searching: devoxx ta
    

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50. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    with throttleLast and debounce
    11-12 04:32:39.964 V: searching: devoxx tal
    11-12 04:32:39.972 V: got data
    11-12 04:32:39.975 D: --> GET /search/repositories?q=devo HTTP/1.1
    11-12 04:32:40.000 V: requesting devoxx
    11-12 04:32:40.089 V: searching: devoxx talk
    11-12 04:32:40.185 V: searching: devoxx talks
    11-12 04:32:40.264 D: 11-12 04:32:40.270 V: got data
    11-12 04:32:40.271 D: --> GET /search/repositories?q=devoxx%20
    HTTP/1.1
    11-12 04:32:40.346 V: searching: devoxx talks
    11-12 04:32:40.506 V: searching: devoxx talks a
    11-12 04:32:40.574 D: 11-12 04:32:40.582 V: got data
    11-12 04:32:40.612 V: searching: devoxx talks ab
    

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51. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    with throttleLast and debounce
    11-12 04:32:40.574 D: 11-12 04:32:40.582 V: got data
    11-12 04:32:40.612 V: searching: devoxx talks ab
    11-12 04:32:40.705 V: searching: devoxx talks abo
    11-12 04:32:40.831 V: searching: devoxx talks abou
    11-12 04:32:40.977 V: searching: devoxx talks about
    11-12 04:32:41.278 V: requesting devoxx talks about
    11-12 04:32:41.279 D: --> GET /search/repositories?q=devoxx
    %20talks%20about HTTP/1.1
    11-12 04:32:41.451 D: 11-12 04:32:41.452 V: got data
    

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52. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    handle error
    RxSearchView.queryTextChanges(searchView)

    .filter(charSequence -> !TextUtils.isEmpty(charSequence))
    .throttleLast(100, TimeUnit.MILLISECONDS)

    .debounce(200, TimeUnit.MILLISECONDS)

    .onBackpressureLatest()

    .concatMap(charSequence -> {

    return searchRepositories(charSequence);

    })

    .observeOn(AndroidSchedulers.mainThread())

    .subscribe(response -> {

    showRepositories(response.getItems());

    }, throwable -> {

    showEmptyErrorView(throwable.getMessage());

    });
    1. error not handled
    2. handled here
    3. completes Observable
    with error
    -> no more emits!
    

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53. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    handle error
    private Observable
    searchRepositories(CharSequence charSequence) {

    return mGitApiService
    .searchRepositoriesObservable(charSequence.toString())

    .subscribeOn(Schedulers.io())

    .onErrorResumeNext(throwable -> {

    // handle error somehow, change UI

    return Observable.empty();

    });

    } Observable
    completes without error
    and without result
    rx.Single doesn’t support
    this error handling :(
    

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54. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    Mock network requests
    // retrofit 2 interface
    @GET("/search/repositories")

    Observable>
    searchRepositoriesObservable(@Query("q") String name);
    // implementation
    @Override

    public Observable>
    searchRepositoriesObservable(final String name) {

    GitHubResponse response =
    new GitHubResponse<>(testRepo1, testRepo2, testRepoN);

    return Observable.just(response)

    .delay(1000, TimeUnit.MILLISECONDS);

    }
    

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55. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    cancel requests
    Call unsubscribe in #onStop();
    mSearchViewSubscription.unsubscribe();
    or use github.com/trello/RxLifecycle for it
    Use a Presenter (MVP) to continue the request during a
    configuration change
    Recommendation: Mosby or Nucleus
    github.com/sockeqwe/mosby github.com/konmik/nucleus
    

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56. @rittmeyerw, @passsy
    #Devoxx #GetReactive
    +Wolfram Rittmeyer
    @rittmeyerw
    +Pascal Welsch
    @passsy
    Don’t forget to subscribe to our social media streams
    (no error handling required)
    

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