Async Android

NYC Android Developers Meetup, June 2015

Transcript

2. Async Android Jamie McDonald
3. @Override public void onCreate() { super.onCreate(); Log.i(TAG, “Hi from the main thread!”); } Main Thread title, date, 01 of 10
4. ANR title, date, 01 of 10
5. ANR title, date, 01 of 10 I/Choreographer﹕ Skipped 480 frames! The application may be doing too much work on its main thread.
6. @UiThread public void updateUi(String title) { textView.setText(title); } @WorkerThread public void showTitle() { textView.setText(SlowStuff.loadTitle()); } Tools title, date, 01 of 10
7. @UiThread public void updateUi(String title) { textView.setText(title); } @WorkerThread public void showTitle() { textView.setText(SlowStuff.loadTitle()); } Tools title, date, 01 of 10
8. new Thread() { public void run() { final String result = SlowStuff.blocking(); new Handler().post(new Runnable() { @Override public void run() { updateUi(result); } }); } }.start(); Thread title, date, 01 of 10
9. class LooperThread extends Thread { private Handler handler; public void run() { Looper.prepare(); handler = new Handler() { public void handleMessage(Message msg) { // Process messages here } }; Looper.loop(); } } Looper title, date, 01 of 10
10. IntentService title, date, 01 of 10 public class BackgroundService extends IntentService { public BackgroundService() { super("BackgroundWork"); } @Override protected void onHandleIntent(Intent intent) { SlowStuff.blocking(); } } startService(new Intent(this, BackgroundService.class));
11. new AsyncTask<Void, Void, String>() { @Override protected String doInBackground(Void... params) { return SlowStuff.blocking(); } @Override protected void onPostExecute(String s) { updateUi(s); } }.execute(); AsyncTask title, date, 01 of 10
12. title, date, 01 of 10 “Painless threading” - The year 2009
13. new AsyncTask<Void, Void, Result>() { [...] @Override protected void onPostExecute(Result result) { if (result.isSuccess()) { doNextAsyncStep(result.getValue()); } else { // ??? } } }.execute(); Callback Hell title, date, 01 of 10
14. Execution Order title, date, 01 of 10 SERIAL SERIAL THREAD POOL
15. class DataLoader extends AsyncTaskLoader<String> { public BackgroundLoader(Context context) { super(context); } @Override protected void onStartLoading() { forceLoad(); } @Override public String loadInBackground() { return SlowStuff.blocking(); } } Loader title, date, 01 of 10
16. getLoaderManager().initLoader(LOADER_ID, null, new LoaderManager.LoaderCallbacks<String>() { @Override public Loader<String> onCreateLoader(int id, Bundle args) { return new DataLoader(MainActivity.this); } @Override public void onLoadFinished(Loader<String> loader, String text) { updateUi(text); } @Override public void onLoaderReset(Loader<String> loader) { loader.reset(); } }); Loader title, date, 01 of 10
17. Enter RxJava!
18. RxJava title, date, 01 of 10 “RxJava tries to be very lightweight. [...] focused on just the Observable abstraction and related higher-order functions”
19. Observer Pattern title, date, 01 of 10
20. Streams title, date, 01 of 10
21. public Observable<String> observable() { return Observable.create((subscriber) -> { subscriber.onNext(blocking()); subscriber.onCompleted(); }); } Observable title, date, 01 of 10
22. class MySubscriber extends DefaultSubscriber<String> { @Override public void onNext(String text) { updateUi(text); } @Override public void onError(Throwable e) { displayError(e); } } Subscriber title, date, 01 of 10
23. SlowStuff.observable() .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe(new MySubscriber()); Schedulers title, date, 01 of 10
24. title, date, 01 of 10 Thread IntentService AsyncTask Loader RxJava Main thread callbacks Configuration changes Error handling Composability Flexible scheduling
25. Operators title, date, 01 of 10 flatMap map filter doOnNext onErrorResumeNext distinct cache zip retry ...
26. FlatMap title, date, 01 of 10
27. trackOps.loadWaveformUrl(urn) .flatMap(url -> imageOps.renderWaveform(url)) .onErrorResumeNext(imageOps.defaultWaveform()) [...] .subscribe(new WaveformSubscriber()); FlatMap title, date, 01 of 10
28. OnErrorResumeNext title, date, 01 of 10
29. public final class EventQueue { static final Queue<StateTransition> PLAYBACK_STATE; static final Queue<ProgressEvent> PLAYBACK_PROGRESS; static final Queue<PlayableEvent> PLAYABLE_CHANGED; [...] } Event Bus title, date, 01 of 10
31. title, date, 01 of 10
32. Subtitle title, date, 01 of 10 eventBus.queue(EventQueue.PLAYABLE_CHANGE) .filter(PlayableEvent.IS_TRACK_FILTER) .doOnNext(updateLikeCount) .observeOn(AndroidSchedulers.mainThread()) Only listen to interesting events
33. Subtitle Respond to state without storing it title, date, 01 of 10 Observable.combineLatest( eventBus.queue(EventQueue.PLAY_QUEUE_TRACK), eventBus.queue(EventQueue.PLAYER_UI), combineStates) .doOnNext(setTrackHasBeenSeen)
34. Downsides title, date, 01 of 10 Debugging Testing long call chains Learning curve Boilerplate Config changes Backpressure Where & when to use it?
35. *£#%@£$?? title, date, 01 of 10
36. More title, date, 01 of 10 RxAndroid Not RxAndroid Retrofit Retrolambda
37. soundcloud.com/jobs Thank you, NYC!