Pull to refresh on discovery feed (#443)

* Added swipe to refresh WITH TESTS.
Created a swipe refresher for BaseFragments. A little copy pasta.

* Cleaning up some copy pasta.

* android x updates

* Added event tracking and updated tests.

app/src/main/java/com/kickstarter/libs/Koala.java

@@ -82,6 +82,14 @@ public void trackDiscoveryFilterSelected(final @NonNull DiscoveryParams params)
     this.client.track("Discover Modal Selected Filter", KoalaUtils.discoveryParamsProperties(params));
   }
 
+  public void trackDiscoveryRefreshTriggered() {
+    this.client.track(KoalaEvent.TRIGGERED_REFRESH, new HashMap<String, Object>() {
+      {
+        put("type", "swipe");
+      }
+    });
+  }
+
   /**
    * Tracks a project show event.
    *

app/src/main/java/com/kickstarter/libs/KoalaEvent.java

@@ -46,6 +46,7 @@ private KoalaEvent() {}
   public static final String SIGNUP_NEWSLETTER_TOGGLE = "Signup Newsletter Toggle";
   public static final String STARRED_PROJECT = "Starred Project";
   public static final String SWITCHED_PROJECTS = "Switched Projects";
+  public static final String TRIGGERED_REFRESH = "Triggered Refresh";
   public static final String TWO_FACTOR_AUTH_CONFIRM_VIEW = "Two-factor Authentication Confirm View";
   public static final String TWO_FACTOR_AUTH_RESEND_CODE = "Two-factor Authentication Resend Code";
   public static final String UNSTARRED_PROJECT = "Unstarred Project";

app/src/main/java/com/kickstarter/libs/SwipeRefresher.java

@@ -25,7 +25,7 @@ public SwipeRefresher(final @NonNull BaseActivity<? extends ActivityViewModel> a
     final @NonNull Func0<Observable<Boolean>> isRefreshing) {
 
     // Iterate through colors in loading spinner while waiting for refresh
-    layout.setColorSchemeResources(R.color.ksr_green_500, R.color.ksr_green_700, R.color.ksr_green_800);
+    setColorSchemeResources(layout);
 
     // Emits when user has signaled to refresh layout
     RxSwipeRefreshLayout.refreshes(layout)
@@ -39,4 +39,36 @@ public SwipeRefresher(final @NonNull BaseActivity<? extends ActivityViewModel> a
       .observeOn(AndroidSchedulers.mainThread())
       .subscribe(layout::setRefreshing);
   }
+
+  /**
+   *
+   * @param fragment Fragment to bind lifecycle events for.
+   * @param layout Layout to subscribe to for refresh events, send signals when no longer refreshing.
+   * @param refreshAction Action to call when a refresh event is emitted, likely a viewModel input.
+   * @param isRefreshing Observable that emits events when the refreshing status changes.
+   */
+  public SwipeRefresher(final @NonNull BaseFragment<? extends FragmentViewModel> fragment,
+    final @NonNull SwipeRefreshLayout layout,
+    final @NonNull Action0 refreshAction,
+    final @NonNull Func0<Observable<Boolean>> isRefreshing) {
+    setColorSchemeResources(layout);
+
+
+    // Emits when user has signaled to refresh layout
+    RxSwipeRefreshLayout.refreshes(layout)
+      .compose(fragment.bindToLifecycle())
+      .subscribe(__ -> refreshAction.call());
+
+    // Emits when the refreshing status changes. Hides loading spinner when feed is no longer refreshing.
+    isRefreshing.call()
+      .filter(refreshing -> !refreshing)
+      .compose(fragment.bindToLifecycle())
+      .observeOn(AndroidSchedulers.mainThread())
+      .subscribe(layout::setRefreshing);
+  }
+
+  private void setColorSchemeResources(final @NonNull SwipeRefreshLayout layout) {
+    // Iterate through colors in loading spinner while waiting for refresh
+    layout.setColorSchemeResources(R.color.ksr_green_500, R.color.ksr_green_700, R.color.ksr_green_800);
+  }
 }

app/src/main/java/com/kickstarter/ui/fragments/DiscoveryFragment.java

@@ -14,6 +14,7 @@
 import com.kickstarter.libs.BaseFragment;
 import com.kickstarter.libs.RecyclerViewPaginator;
 import com.kickstarter.libs.RefTag;
+import com.kickstarter.libs.SwipeRefresher;
 import com.kickstarter.libs.qualifiers.RequiresFragmentViewModel;
 import com.kickstarter.libs.utils.AnimationUtils;
 import com.kickstarter.libs.utils.ViewUtils;
@@ -37,6 +38,7 @@
 import androidx.annotation.Nullable;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
+import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import butterknife.Bind;
 import butterknife.ButterKnife;
 
@@ -54,6 +56,7 @@ public final class DiscoveryFragment extends BaseFragment<DiscoveryFragmentViewM
   protected @Bind(R.id.discovery_empty_view) View emptyView;
   protected @Bind(R.id.discovery_hearts_container) View heartsContainer;
   protected @Bind(R.id.discovery_recycler_view) RecyclerView recyclerView;
+  protected @Bind(R.id.discovery_swipe_refresh_layout) SwipeRefreshLayout swipeRefreshLayout;
 
   public DiscoveryFragment() {}
 
@@ -76,6 +79,9 @@ public DiscoveryFragment() {}
     this.recyclerView.setAdapter(adapter);
     final LinearLayoutManager layoutManager = new LinearLayoutManager(this.recyclerView.getContext());
     this.recyclerView.setLayoutManager(layoutManager);
+    new SwipeRefresher(
+      this, this.swipeRefreshLayout, this.viewModel.inputs::refresh, this.viewModel.outputs::isFetchingProjects
+    );
     this.recyclerViewPaginator = new RecyclerViewPaginator(this.recyclerView, this.viewModel.inputs::nextPage);
 
     this.viewModel.outputs.activity()

app/src/main/java/com/kickstarter/viewmodels/DiscoveryFragmentViewModel.java

@@ -31,7 +31,6 @@
 import com.kickstarter.ui.viewholders.ActivitySampleProjectViewHolder;
 import com.kickstarter.ui.viewholders.DiscoveryOnboardingViewHolder;
 
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
@@ -44,6 +43,7 @@
 import static com.kickstarter.libs.rx.transformers.Transformers.combineLatestPair;
 import static com.kickstarter.libs.rx.transformers.Transformers.neverError;
 import static com.kickstarter.libs.rx.transformers.Transformers.takePairWhen;
+import static com.kickstarter.libs.rx.transformers.Transformers.takeWhen;
 import static com.kickstarter.libs.utils.BooleanUtils.isTrue;
 
 public interface DiscoveryFragmentViewModel {
@@ -61,6 +61,9 @@ interface Inputs extends DiscoveryAdapter.Delegate {
     /** Call when params from Discovery Activity change. */
     void paramsFromActivity(final DiscoveryParams params);
 
+    /** Call when the projects should be refreshed. */
+    void refresh();
+
     /**  Call when we should load the root categories. */
     void rootCategories(final List<Category> rootCategories);
   }
@@ -69,6 +72,9 @@ interface Outputs {
     /**  Emits an activity for the activity sample view. */
     Observable<Activity> activity();
 
+    /** Emits a boolean indicating whether projects are being fetched from the API. */
+    Observable<Boolean> isFetchingProjects();
+
     /** Emits a list of projects to display.*/
     Observable<List<Pair<Project, DiscoveryParams>>> projectList();
 
@@ -118,10 +124,15 @@ public ViewModel(final @NonNull Environment environment) {
         (__, params) -> params
       );
 
+      final Observable<DiscoveryParams> startOverWith = Observable.merge(
+        selectedParams,
+        selectedParams.compose(takeWhen(this.refresh))
+      );
+
       final ApiPaginator<Project, DiscoverEnvelope, DiscoveryParams> paginator =
         ApiPaginator.<Project, DiscoverEnvelope, DiscoveryParams>builder()
           .nextPage(this.nextPage)
-          .startOverWith(selectedParams)
+          .startOverWith(startOverWith)
           .envelopeToListOfData(DiscoverEnvelope::projects)
           .envelopeToMoreUrl(env -> env.urls().api().moreProjects())
           .loadWithParams(this.apiClient::fetchProjects)
@@ -130,6 +141,10 @@ public ViewModel(final @NonNull Environment environment) {
           .concater(ListUtils::concatDistinct)
           .build();
 
+      paginator.isFetching()
+        .compose(bindToLifecycle())
+        .subscribe(this.isFetchingProjects);
+
       final Observable<Pair<Project, RefTag>> activitySampleProjectClick = this.activitySampleProjectClick
         .map(p -> Pair.create(p, RefTag.activitySample()));
 
@@ -215,14 +230,10 @@ public ViewModel(final @NonNull Environment environment) {
         .filter(ObjectUtils::isNotNull)
         .compose(bindToLifecycle())
         .subscribe(p -> this.koala.trackViewedUpdate(p, KoalaContext.Update.ACTIVITY_SAMPLE));
-    }
 
-    private List<Pair<Project, DiscoveryParams>> combineProjectsAndParams(final @NonNull List<Project> projects, final @NonNull DiscoveryParams params) {
-      final ArrayList<Pair<Project, DiscoveryParams>> projectAndParams = new ArrayList<>(projects.size());
-      for (int i = 0; i < projects.size(); i++) {
-        projectAndParams.add(Pair.create(projects.get(i), params));
-      }
-      return projectAndParams;
+      this.refresh
+        .compose(bindToLifecycle())
+        .subscribe(v -> this.koala.trackDiscoveryRefreshTriggered());
     }
 
     private boolean activityHasNotBeenSeen(final @Nullable Activity activity) {
@@ -261,10 +272,12 @@ private void saveLastSeenActivityId(final @Nullable Activity activity) {
     private final PublishSubject<Void> nextPage = PublishSubject.create();
     private final PublishSubject<DiscoveryParams> paramsFromActivity = PublishSubject.create();
     private final PublishSubject<Project> projectCardClicked = PublishSubject.create();
+    private final PublishSubject<Void> refresh = PublishSubject.create();
     private final PublishSubject<List<Category>> rootCategories = PublishSubject.create();
 
     private final BehaviorSubject<Activity> activity = BehaviorSubject.create();
     private final BehaviorSubject<Void> heartContainerClicked = BehaviorSubject.create();
+    private final BehaviorSubject<Boolean> isFetchingProjects = BehaviorSubject.create();
     private final BehaviorSubject<List<Pair<Project, DiscoveryParams>>> projectList = BehaviorSubject.create();
     private final Observable<Boolean> showActivityFeed;
     private final Observable<Boolean> showLoginTout;
@@ -301,6 +314,9 @@ private void saveLastSeenActivityId(final @Nullable Activity activity) {
     @Override public void projectCardViewHolderClicked(final @NonNull Project project) {
       this.projectCardClicked.onNext(project);
     }
+    @Override public void refresh() {
+      this.refresh.onNext(null);
+    }
     @Override public void rootCategories(final @NonNull List<Category> rootCategories) {
       this.rootCategories.onNext(rootCategories);
     }
@@ -323,6 +339,9 @@ private void saveLastSeenActivityId(final @Nullable Activity activity) {
     @Override public @NonNull Observable<Activity> activity() {
       return this.activity;
     }
+    @Override public @NonNull Observable<Boolean> isFetchingProjects() {
+      return this.isFetchingProjects;
+    }
     @Override public @NonNull Observable<List<Pair<Project, DiscoveryParams>>> projectList() {
       return this.projectList;
     }

app/src/main/res/layout/fragment_discovery.xml

@@ -4,11 +4,18 @@
   android:layout_width="match_parent"
   android:layout_height="match_parent">
 
-  <androidx.recyclerview.widget.RecyclerView
-    android:id="@+id/discovery_recycler_view"
+  <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
+    android:id="@+id/discovery_swipe_refresh_layout"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
-    tools:listitem="@layout/project_card_view" />
+    android:layout_height="wrap_content">
+
+    <androidx.recyclerview.widget.RecyclerView
+      android:id="@+id/discovery_recycler_view"
+      android:layout_width="match_parent"
+      android:layout_height="match_parent"
+      tools:listitem="@layout/project_card_view" />
+
+  </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
 
   <LinearLayout
     android:id="@+id/discovery_empty_view"

app/src/test/java/com/kickstarter/viewmodels/DiscoveryFragmentViewModelTest.java

@@ -65,6 +65,23 @@ private void setUpInitialHomeAllProjectsParams() {
     this.vm.inputs.rootCategories(CategoryFactory.rootCategories());
   }
 
+  @Test
+  public void testRefresh() {
+    setUpEnvironment(environment());
+
+    // Load initial params and root categories from activity.
+    setUpInitialHomeAllProjectsParams();
+
+    // Should emit current fragment's projects.
+    this.hasProjects.assertValues(true);
+    this.koalaTest.assertValues("Discover List View");
+
+    //Page is cleared and refreshed
+    this.vm.inputs.refresh();
+    this.hasProjects.assertValues(true, false, true);
+    this.koalaTest.assertValues("Discover List View", "Triggered Refresh");
+  }
+
   @Test
   public void testProjectsEmitWithNewCategoryParams() {
     setUpEnvironment(environment());