Add ViewObservables.listViewScroll(AbsListView).

rxandroid/src/main/java/rx/android/events/OnListViewScrollEvent.java

@@ -0,0 +1,85 @@
+/**
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package rx.android.events;
+
+import android.widget.AbsListView;
+
+public class OnListViewScrollEvent {
+    public final AbsListView listView;
+    public final int scrollState;
+    public final int firstVisibleItem;
+    public final int visibleItemCount;
+    public final int totalItemCount;
+
+    public OnListViewScrollEvent(
+        AbsListView listView, int scrollState, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
+        this.listView = listView;
+        this.scrollState = scrollState;
+        this.firstVisibleItem = firstVisibleItem;
+        this.visibleItemCount = visibleItemCount;
+        this.totalItemCount = totalItemCount;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        OnListViewScrollEvent that = (OnListViewScrollEvent) o;
+
+        if (firstVisibleItem != that.firstVisibleItem) {
+            return false;
+        }
+        if (scrollState != that.scrollState) {
+            return false;
+        }
+        if (totalItemCount != that.totalItemCount) {
+            return false;
+        }
+        if (visibleItemCount != that.visibleItemCount) {
+            return false;
+        }
+        if (!listView.equals(that.listView)) {
+            return false;
+        }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = listView.hashCode();
+        result = 31 * result + scrollState;
+        result = 31 * result + firstVisibleItem;
+        result = 31 * result + visibleItemCount;
+        result = 31 * result + totalItemCount;
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "OnListViewScrollEvent{" +
+            "listView=" + listView +
+            ", scrollState=" + scrollState +
+            ", firstVisibleItem=" + firstVisibleItem +
+            ", visibleItemCount=" + visibleItemCount +
+            ", totalItemCount=" + totalItemCount +
+            '}';
+    }
+}

rxandroid/src/main/java/rx/android/observables/ViewObservable.java

@@ -14,6 +14,7 @@
 package rx.android.observables;
 
 import android.view.View;
+import android.widget.AbsListView;
 import android.widget.AdapterView;
 import android.widget.CompoundButton;
 import android.widget.TextView;
@@ -22,9 +23,11 @@
 import rx.android.events.OnCheckedChangeEvent;
 import rx.android.events.OnClickEvent;
 import rx.android.events.OnItemClickEvent;
+import rx.android.events.OnListViewScrollEvent;
 import rx.android.events.OnTextChangeEvent;
 import rx.android.operators.OperatorAdapterViewOnItemClick;
 import rx.android.operators.OperatorCompoundButtonInput;
+import rx.android.operators.OnSubscribeListViewScroll;
 import rx.android.operators.OperatorTextViewInput;
 import rx.android.operators.OperatorViewClick;
 
@@ -58,4 +61,13 @@ public static Observable<OnItemClickEvent> itemClicks(final AdapterView<?> adapt
         return Observable.create(new OperatorAdapterViewOnItemClick(adapterView));
     }
 
+    /**
+     * Returns an observable that emits all the scroll events from the provided ListView.
+     * Note that this will replace any listeners previously set through
+     * {@link android.widget.AbsListView#setOnScrollListener(android.widget.AbsListView.OnScrollListener)} unless those
+     * were set by this method or {@link rx.android.operators.OnSubscribeListViewScroll}.
+     */
+    public static Observable<OnListViewScrollEvent> listScrollEvents(final AbsListView listView) {
+        return Observable.create(new OnSubscribeListViewScroll(listView));
+    }
 }

rxandroid/src/main/java/rx/android/operators/OnSubscribeListViewScroll.java

@@ -0,0 +1,115 @@
+/**
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package rx.android.operators;
+
+import android.widget.AbsListView;
+import android.widget.AdapterView;
+import rx.Observable;
+import rx.Subscriber;
+import rx.android.events.OnListViewScrollEvent;
+import rx.android.observables.Assertions;
+import rx.android.subscriptions.AndroidSubscriptions;
+import rx.functions.Action0;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.WeakHashMap;
+
+public class OnSubscribeListViewScroll implements Observable.OnSubscribe<OnListViewScrollEvent> {
+
+    private final AbsListView listView;
+
+    public OnSubscribeListViewScroll(AbsListView listView) {
+        this.listView = listView;
+    }
+
+    @Override
+    public void call(final Subscriber<? super OnListViewScrollEvent> observer) {
+        Assertions.assertUiThread();
+
+        final CompositeOnScrollListener composite = CachedListeners.getFromViewOrCreate(listView);
+        final AbsListView.OnScrollListener listener = new AbsListView.OnScrollListener() {
+            int currentScrollState = SCROLL_STATE_IDLE;
+
+            @Override
+            public void onScrollStateChanged(AbsListView view, int scrollState) {
+                this.currentScrollState = scrollState;
+            }
+
+            @Override
+            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
+                OnListViewScrollEvent event = new OnListViewScrollEvent(view, this.currentScrollState, firstVisibleItem,
+                    visibleItemCount, totalItemCount);
+                observer.onNext(event);
+            }
+        };
+
+        composite.addOnScrollListener(listener);
+        observer.add(AndroidSubscriptions.unsubscribeInUiThread(new Action0() {
+            @Override
+            public void call() {
+                composite.removeOnScrollListener(listener);
+            }
+        }));
+    }
+
+    private static class CompositeOnScrollListener implements AbsListView.OnScrollListener {
+
+        private final List<AbsListView.OnScrollListener> listeners = new ArrayList<AbsListView.OnScrollListener>();
+
+        public boolean addOnScrollListener(final AbsListView.OnScrollListener listener) {
+            return listeners.add(listener);
+        }
+
+        public boolean removeOnScrollListener(final AbsListView.OnScrollListener listener) {
+            return listeners.remove(listener);
+        }
+
+        @Override
+        public void onScrollStateChanged(AbsListView view, int scrollState) {
+            for (AbsListView.OnScrollListener listener : listeners) {
+                listener.onScrollStateChanged(view, scrollState);
+            }
+        }
+
+        @Override
+        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
+            for (AbsListView.OnScrollListener listener : listeners) {
+                listener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
+            }
+        }
+    }
+
+    private static class CachedListeners {
+
+        private static final Map<AdapterView<?>, CompositeOnScrollListener> sCachedListeners =
+            new WeakHashMap<AdapterView<?>, CompositeOnScrollListener>();
+
+        public static CompositeOnScrollListener getFromViewOrCreate(final AbsListView view) {
+            final CompositeOnScrollListener cached = sCachedListeners.get(view);
+            if (cached != null) {
+                return cached;
+            }
+
+            final CompositeOnScrollListener listener = new CompositeOnScrollListener();
+
+            sCachedListeners.put(view, listener);
+            view.setOnScrollListener(listener);
+
+            return listener;
+        }
+    }
+}

sample-app/src/main/java/rx/android/samples/ListFragmentActivity.java

@@ -1,12 +1,20 @@
 package rx.android.samples;
 
 import android.app.Activity;
-import android.app.ListFragment;
+import android.app.Fragment;
 import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
 import android.widget.ArrayAdapter;
-
+import android.widget.ListView;
+import android.widget.ProgressBar;
 import rx.Observable;
 import rx.Subscriber;
+import rx.android.events.OnListViewScrollEvent;
+import rx.android.observables.AndroidObservable;
+import rx.android.observables.ViewObservable;
+import rx.functions.Action1;
 
 import static rx.android.schedulers.AndroidSchedulers.mainThread;
 
@@ -30,7 +38,7 @@ protected void onCreate(Bundle savedInstanceState) {
     }
 
     @SuppressWarnings("ConstantConditions")
-    public static class RetainedListFragment extends ListFragment {
+    public static class RetainedListFragment extends Fragment {
 
         private ArrayAdapter<String> adapter;
 
@@ -39,18 +47,38 @@ public RetainedListFragment() {
         }
 
         @Override
-        public void onCreate(Bundle savedInstanceState) {
-            super.onCreate(savedInstanceState);
+        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+            View view = inflater.inflate(R.layout.list_fragment, container, false);
 
             adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1);
-            setListAdapter(adapter);
-            SampleObservables.numberStrings(1, 20, 250)
-                    .observeOn(mainThread())
-                    .lift(new BindAdapter())
-                    .subscribe();
+            ListView listView = (ListView) view.findViewById(android.R.id.list);
+            listView.setAdapter(adapter);
+
+            AndroidObservable.bindFragment(this, SampleObservables.numberStrings(1, 500, 100))
+                .observeOn(mainThread())
+                .lift(new BindAdapter())
+                .subscribe();
+
+            final ProgressBar progressBar = (ProgressBar) view.findViewById(android.R.id.progress);
+            AndroidObservable.bindFragment(this, ViewObservable.listScrollEvents(listView))
+                .subscribe(new Action1<OnListViewScrollEvent>() {
+                    @Override
+                    public void call(OnListViewScrollEvent event) {
+                        if (event.totalItemCount == 0) {
+                            return;
+                        }
+
+                        int progress =
+                            (int) ((100.0 * (event.firstVisibleItem + event.visibleItemCount)) / event.totalItemCount);
+                        progressBar.setProgress(progress);
+                    }
+                });
+
+            return view;
         }
 
         private final class BindAdapter implements Observable.Operator<String, String> {
+
             @Override
             public Subscriber<? super String> call(Subscriber<? super String> subscriber) {
                 return new Subscriber<String>() {

sample-app/src/main/res/layout/list_fragment.xml

@@ -1,18 +1,18 @@
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
-    <TextView
-        android:id="@android:id/empty"
+    <ProgressBar
+        android:id="@android:id/progress"
+        style="@android:style/Widget.Holo.ProgressBar.Horizontal"
         android:layout_width="match_parent"
-        android:layout_height="match_parent"
-        android:gravity="center"
-        android:text="Loading..."
-        android:visibility="gone" />
+        android:layout_height="48dp"
+        android:indeterminate="false" />
 
     <ListView
         android:id="@android:id/list"
         android:layout_width="match_parent"
-        android:layout_height="match_parent" />
+        android:layout_height="match_parent"
+        android:layout_marginTop="48dp" />
 
-</RelativeLayout>
+</FrameLayout>