Understanding Architecture of Nick Butcher's Plaid App - Part-2

FilterAdapter

Adapter for showing list of data sources in Drawer.

Note that there are only three items in the list that need authorization

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private boolean isAuthorisedDribbbleSource(Source source) { return source.key.equals(SourceManager.SOURCE_DRIBBBLE_FOLLOWING) || source.key.equals(SourceManager.SOURCE_DRIBBBLE_USER_LIKES) || source.key.equals(SourceManager.SOURCE_DRIBBBLE_USER_SHOTS); }

Two important interfaces this class implements

•   FilterAuthoriser

    The whole purpose of this authorizer callback is if you select any items in the drawer that
     require Dribble login , then this Callback would be invoked and HomeActivity will call the
     Dribble login activity 

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public interface FilterAuthoriser { void requestDribbbleAuthorisation(View sharedElement, Source forSource); }

 

 Constructor :

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public FilterAdapter(@NonNull Context context, @NonNull List<Source> filters, @NonNull FilterAuthoriser authoriser) { <- This is an interface , so that the list items which this.context = context.getApplicationContext(); require this authorization , we can call this callback this.filters = filters; provided by initializer this.authoriser = authoriser; setHasStableIds(true); }

This is how its called from onCreate () in HomeActivity

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filtersAdapter = new FilterAdapter(this, SourceManager.getSources(this), new FilterAdapter.FilterAuthoriser() { @Override public void requestDribbbleAuthorisation(View sharedElemeent, Source forSource) { Intent login = new Intent(HomeActivity.this, DribbbleLogin.class); login.putExtra(FabDialogMorphSetup.EXTRA_SHARED_ELEMENT_START_COLOR, ContextCompat.getColor(HomeActivity.this, R.color.background_dark)); ActivityOptions options = ActivityOptions.makeSceneTransitionAnimation(HomeActivity.this, sharedElemeent, getString(R.string.transition_dribbble_login)); startActivityForResult(login, getAuthSourceRequestCode(forSource), options.toBundle()); } });

•  FiltersChangedListener

   Selection / Unselection of these items in the drawer are reported to HomeActivity using this
   listener.

 public interface FiltersChangedListener {

        void onFiltersChanged(Source changedFilter);

        void onFilterRemoved(Source removed);

    }

And helper method to set this listener

public void addFilterChangedListener(FiltersChangedListener listener) {

        if (listeners == null) {

            listeners = new ArrayList<>();

        }

        listeners.add(listener);

    }

Question is how is HomeActivity notified of these changes ,  

 

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filtersAdapter.addFilterChangedListener(filtersChangedListener); private FilterAdapter.FiltersChangedListener filtersChangedListener = new FilterAdapter.FiltersChangedListener() { @Override public void onFiltersChanged(Source changedFilter) { if (!changedFilter.active) { adapter.removeDataSource(changedFilter.key); } checkEmptyState(); } @Override public void onFilterRemoved(Source removed) { adapter.removeDataSource(removed.key); checkEmptyState(); } };