Droidcon ES 16': How to fail going offline

Architecture proposal to work offline using mainly android components and a single dataflow

Transcript

1. HOW TO FAIL
   GOING
   OFFLINE
   @droidpl
   javier.pedro@mobgen.com
   javierdepedrolopez@gmail.com
   

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2. Javier de Pedro López
   Strengths
   Experience
   Senior Android Developer
   3 Years professionally
   2 Different companies
   Free time
   architecture
   Design Patterns
   Gradle
   Code quality
   @droidpl
   javier.pedro@mobgen.com
   javierdepedrolopez@gmail.com
   

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3. This talk
   Try & try & fail
   Architecture
   proposal
   Use case
   Show me the
   code
   

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4. TRY & TRY & FAIL
   Section 1
   

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5. Try & try & fail
   Pojos
   Services
   Sync Adapters
   Why I did investigate?
   • I work on an SDK similar to
   firebase
   • Should work offline
   • Should have a simple API
   • Should be reliable and user
   friendly
   Why This matters?
   

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6. Try & try & fail
   Why This matters?
   Pojos
   Services
   Sync Adapters
   Why I did investigate?
   • Offline improves user experience
   • No loading times (most of the cases)
   • App always accesible
   • Just like magic

   • Makes your app less error prone

   • Forces the developer to think more mobile

   • Say no to: “you always have a good internet
   connection”
   

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7. Try & try & fail
   Why This matters?
   Pojos
   Services
   Sync Adapters
   Why I did investigate?
   Views/MVP/
   Interactors
   Using POJOS
   Database
   Callback
   Network
   Callback
   Pojo
   Callback
   

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8. Try & try & fail
   Why This matters?
   Pojos
   Services
   Sync Adapters
   Why I did investigate?
   Using POJOS
   • Action cancellation
   • Lifecycle management
   • Single responsibility principle broken
   • Messy thread management
   • Hard to read code

   • Fast to implement
   

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9. Try & try & fail
   Why This matters?
   Pojos
   Services
   Sync Adapters
   Why I did investigate?
   Views/MVP/
   Interactors
   Using Services
   Service
   ResultReceiver/Binder
   Threading
   Database
   Sync
   Network
   Sync
   Pojo
   Callback
   

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10. Try & try & fail
    Why This matters?
    Pojos
    Services
    Sync Adapters
    Why I did investigate?
    Problems using Services
    • Action cancellation is still a pain
    • Easy to leak memory

    • Easy to split in many services
    • Export to other apps
    • Easier to handle threading
    • Possibility to have many processes
    • Simplified callback system
    

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11. Try & try & fail
    Why This matters?
    Pojos
    Services
    Sync Adapters
    Why I did investigate?
    Views/
    MVP/
    Interactors
    Using Sync Adapters
    Network
    Sync
    Sync
    adapter
    Sync
    trigger
    Database
    (content
    provider)
    Sync
    Content
    observer
    

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12. Try & try & fail
    Why This matters?
    Pojos
    Services
    Sync Adapters
    Why I did investigate?
    Problems using Services
    • Hard disconnection errors
    • Sync adapter documentation
    • Sync adapter configuration (many files)
    • Too linked to accounts

    • Uses system tools
    • Content change notifications
    • All the benefits from services
    

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13. ARCHITECTURE PROPOSAL
    Section 2
    

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14. ARCHITECTURE PROPOSAL
    ACT LOCALLY
    SYNC GLOBALLY
    

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15. Loaders
    Architecture
    proposal
    Job schedulers
    All together
    Read
    Write
    Loaders
    Repositories Views/
    MVP/
    Interactors
    Loader
    inits
    provides
    data
    gets notified
    android
    lifecycle
    asks for
    data
    Data
    source
    

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16. Loader states
    Architecture
    proposal
    Job schedulers
    All together
    Read
    Write
    Loaders
    Repositories
    Started Stopped Reset
    Can load
    Can observe
    Can deliver
    Can load
    Can observe
    Can deliver
    Can load
    Can observe
    Can deliver
    Stop/Reset Start/Reset Start
    

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17. Job schedulers
    Architecture
    proposal
    Job schedulers
    Loaders
    All together
    Read
    Write
    Repositories
    Pojo
    notifies
    notifies
    System
    Scheduler
    schedule
    job
    Preconditions
    check
    Sync
    Service
    trigger
    met
    Sync task
    run task
    

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18. Repositories
    Architecture
    proposal
    Job schedulers
    Loaders
    All together
    Read
    Write
    Repositories
    Data
    Repository
    notifies
    Database
    Repository
    Read
    Write
    Other sources
    Network
    repository
    Read
    Write
    

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19. Architecture
    proposal
    Job schedulers
    Loaders
    Overall diagram
    All together
    Read
    Write
    Repositories
    Data
    Repository
    Notifies
    Asks for
    data
    Loader
    Inits
    Provides
    data
    System
    Scheduler
    Schedule sync
    Sync
    Service
    Sync task
    Conditions
    met
    Run task
    Changes data
    Read
    Write
    Read
    Write
    Views/
    MVP/
    Interactors
    Start
    App SDK
    write
    

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20. Architecture
    proposal
    Job schedulers
    Loaders
    All together
    Read
    Write
    Repositories
    SDK
    Loader
    Loader
    Loader
    Overall diagram
    App Layer
    Android
    SDK
    Entry
    Entry
    Entry
    Entry
    

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21. Architecture
    proposal
    Job schedulers
    Loaders
    Read diagram
    All together
    Read
    Write
    Repositories
    

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22. Architecture
    proposal
    Job schedulers
    Loaders
    Write diagram
    All together
    Read
    Write
    Repositories
    online
    

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23. USE CASE
    Section 3
    

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24. Use case
    Online sample
    Models
    offline Sample
    Articles and comments
    

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25. Use case
    Online sample
    Models
    offline Sample
    

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26. Use case
    Online sample
    Models
    offline Sample
    

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27. SHOW ME THE CODE
    Section 4
    

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28. Classes
    PostActivity PostLoader PostRepository
    PostDAO
    CommentDAO
    PostService
    SyncService
    SynchronizeTask
    write
    

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29. Post Activity: init
    private PostRepository mRepository;
    private Executor mExecutor;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mRepository = DemosApplication.instance()
    .demoSdk()
    .postRepository();
    mExecutor = Executors.newSingleThreadExecutor();
    startLoading();
    PostLoader.init(getSupportLoaderManager(), this);
    }
    Views
    

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30. Post Activity: load data
    @Override
    public Loader> onCreateLoader(int id, Bundle args) {
    return new PostLoader(this, DemosApplication.instance().demoSdk());
    }
    @Override
    public void onLoadFinished(Loader> loader, List data) {
    stopLoading();
    setAdapter(data);
    }
    @Override
    public void onLoaderReset(@NonNull Loader> loader) {
    //Do nothing
    }
    Views
    

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31. Post Activity: Refresh
    @Override
    public void onRefresh() {
    startLoading();
    PostLoader.getLoader(getSupportLoaderManager()).forceLoad();
    }
    Views
    

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32. Post Activity: Create post
    @Override
    public void onPostCreated(@NonNull final Post post) {
    startLoading();
    mExecutor.execute(() -> {
    try {
    mRepository.localCreate(post);
    } catch (RepositoryException e) {
    showError();
    }
    });
    }
    Views
    

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33. Post Activity: Delete post
    @Override
    public void onDeleted(@NonNull final Post post) {
    startLoading();
    mExecutor.execute(() -> {
    try {
    mRepository.localDelete(post);
    } catch (RepositoryException e) {
    showError();
    }
    });
    }
    Views
    

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34. post loader
    @Override
    public List loadInBackground() {
    setData(mDemoSdk.postRepository().posts());
    return getData();
    }
    @Override
    public void registerListener() {
    if (mObserver == null) {
    mObserver = SyncService.listenForUpdates(this);
    }
    }
    @Override
    public void unregisterListener() {
    if (mObserver != null) {
    SyncService.removeUpdateListener(this, mObserver);
    }
    }
    loader
    

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35. Post repository: all posts
    @WorkerThread
    public List posts() {
    Response> postsResponse = mPostService.posts().execute();
    if (postsResponse.isSuccessful()) {
    List posts = postsResponse.body();
    mPostDao.deleteAll();
    mPostDao.save(posts);
    }
    return mPostDao.posts();
    }
    datasource
    

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36. Post repository: Save
    @WorkerThread
    public void localCreate(@NonNull Post post) {
    mPostDao.save(post);
    SyncService.triggerSync(mContext);
    }
    @WorkerThread
    public void remoteCreate(@NonNull Post post) {
    Response postResponse = mPostService.create(Post.builder(post)
    .internalId(null)
    .needsSync(false)
    .build()).execute();
    if (postResponse.isSuccessful()) {
    mPostDao.save(Post.builder(postResponse.body())
    .internalId(post.internalId())
    .build());
    }
    }
    datasource
    

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37. Post repository: DELETE
    @WorkerThread
    public void localDelete(@NonNull Post post) {
    long now = new Date().getTime();
    if (post.isNew() && post.isStoredLocally()) {
    mPostDao.delete(post.internalId());
    SyncService.notifyChange(mContext);
    } else {
    mPostDao.save(Post.builder(post)
    .deletedAt(now)
    .updatedAt(now)
    .needsSync(true).build());
    SyncService.triggerSync(mContext);
    }
    }
    @WorkerThread
    public void remoteDelete(@NonNull Post post) {
    if (mPostService.deletePost(post.id()).execute().isSuccessful() && post.isStoredLocally()) {
    for (Comment comment : mCommentDao.comments(post.internalId())) {
    remoteDelete(comment);
    }
    mPostDao.delete(post.internalId());
    }
    }
    datasource
    

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38. Sync service: trigger
    public static void triggerSync(@NonNull Context context) {
    SyncService.notifyChange(context);
    ComponentName component = new ComponentName(context, SyncService.class);
    JobInfo info = new JobInfo.Builder(SYNC_SERVICE_ID, component)
    .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
    .build();
    getScheduler(context).schedule(info);
    }
    sync
    

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39. Sync service: Listen for updates
    public static BroadcastReceiver listenForUpdates(@NonNull Loader loader) {
    IntentFilter filter = new IntentFilter(CHANGE_SYNC_INTENT_ACTION);
    SyncServiceReceiver receiver = new SyncServiceReceiver(loader);
    LocalBroadcastManager.getInstance(loader.getContext())
    .registerReceiver(receiver, filter);
    return receiver;
    }
    public static void removeUpdateListener(@NonNull Loader loader,
    @NonNull BroadcastReceiver observer) {
    LocalBroadcastManager.getInstance(loader.getContext())
    .unregisterReceiver(observer);
    }
    public static void notifyChange(@NonNull Context context) {
    LocalBroadcastManager.getInstance(context).sendBroadcast(getCompletionIntent());
    }
    sync
    

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40. Sync service: Do the JOB
    @Override
    public boolean onStartJob(JobParameters params) {
    DemoSdk sdk = DemoSdk.Factory.instance();
    boolean willExecute = true;
    if (sdk != null) {
    mRunningSyncTask = new SynchronizeTask(sdk, this);
    mRunningSyncTask.execute(params);
    } else {
    willExecute = false;
    }
    return willExecute;
    }
    sync
    @Override
    public boolean onStopJob(JobParameters params) {
    boolean reschedule = false;
    if (mRunningSyncTask != null) {
    mRunningSyncTask.cancel(true);
    reschedule = true;
    }
    return reschedule;
    }
    

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41. Sync task: Sync
    @Override
    protected JobParameters doInBackground(JobParameters... params) {
    syncPosts();
    syncComments();
    return params[0];
    }
    sync
    private void syncPosts() {
    List posts = mSdk.postRepository().localPendingPosts();
    for (Post post : posts) {
    if (post.isNew()) {
    mSdk.postRepository().remoteCreate(post);
    } else if (post.isDeleted()) {
    mSdk.postRepository().remoteDelete(post);
    }
    }
    }
    

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42. Sync task: NOTIFY
    @Override
    protected void onPostExecute(JobParameters jobParameters) {
    super.onPostExecute(jobParameters);
    SyncService.notifyChange(mSyncService);
    mSyncService.jobFinished(jobParameters, mNeedsResync);
    }
    sync
    

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43. And there you go! your app works offline
    

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44. SOURCE Code available
    https://github.com/droidpl/offline-architecture
    @droidpl
    

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45. Conclusions
    Offline matters
    because
    UX matters
    It is part of the
    architecture
    Not so much
    effort with the
    right choice
    Unique
    dataflow
    Don’t reinvent
    the wheel
    - Android has it -
    

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46. ……………………
    We are hiring!
    Ask
    

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47. ……………………
    Q&A
    

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48. ……………………
    Thank you!
    

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