Add full example for Activity + retained fragment + cache

Author: mttkay

rxjava-contrib/rxjava-android-samples/samples/src/main/AndroidManifest.xml

@@ -3,12 +3,13 @@
     package="com.netflix.rxjava.android.samples" >
 
     <application
+        android:name=".SamplesApplication"
         android:allowBackup="true"
         android:icon="@drawable/ic_launcher"
         android:theme="@style/AppTheme"
         android:label="@string/app_name">
         <activity
-            android:name=".SampleFragmentActivity">
+            android:name=".RetainedFragmentActivity">
 
             <intent-filter>
                 <category android:name="android.intent.category.LAUNCHER"/>

rxjava-contrib/rxjava-android-samples/samples/src/main/java/com/netflix/rxjava/android/samples/RetainedFragment.java

@@ -0,0 +1,105 @@
+package com.netflix.rxjava.android.samples;
+
+import android.app.Activity;
+import android.app.Fragment;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.Window;
+import android.widget.TextView;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import rx.Observable;
+import rx.Subscription;
+import rx.android.schedulers.AndroidSchedulers;
+import rx.functions.Action1;
+import rx.functions.Func1;
+import rx.subscriptions.Subscriptions;
+
+/**
+ * Problem:
+ * You have a data source (where that data is potentially expensive to obtain), and you want to
+ * emit this data into a fragment. However, you want to gracefully deal with rotation changes and
+ * not lose any data already emitted.
+ * <p/>
+ * Solution:
+ * Combine {@link android.app.Fragment#setRetainInstance(boolean)} with
+ * {@link rx.android.schedulers.AndroidSchedulers#mainThread()} and {@link rx.Observable#cache()}
+ */
+public class RetainedFragmentActivity extends Activity {
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
+        setTitle("Fake API call");
+        setContentView(R.layout.retained_fragment_activity);
+    }
+
+    @SuppressWarnings("ConstantConditions")
+    public static class RetainedFragment extends Fragment {
+
+        // in a production app, you don't want to have JSON parser code in your fragment,
+        // but we'll simplify a little here
+        private static final Func1<String, String> PARSE_JSON = new Func1<String, String>() {
+            @Override
+            public String call(String json) {
+                try {
+                    JSONObject jsonObject = new JSONObject(json);
+                    return String.valueOf(jsonObject.getInt("result"));
+                } catch (JSONException e) {
+                    throw new RuntimeException(e);
+                }
+            }
+        };
+
+        private Observable<String> strings;
+        private Subscription subscription = Subscriptions.empty();
+
+        public RetainedFragment() {
+            setRetainInstance(true);
+        }
+
+        @Override
+        public void onCreate(Bundle savedInstanceState) {
+            super.onCreate(savedInstanceState);
+
+            // simulate fetching a JSON document with a latency of 2 seconds
+            strings = SampleObservables.fakeApiCall(2000).map(PARSE_JSON)
+                    .observeOn(AndroidSchedulers.mainThread())
+                    .cache();
+        }
+
+        @Override
+        public void onDestroyView() {
+            subscription.unsubscribe();
+            super.onDestroyView();
+        }
+
+        @Override
+        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+            getActivity().setProgressBarIndeterminateVisibility(true);
+            return inflater.inflate(R.layout.retained_fragment, container, false);
+        }
+
+        @Override
+        public void onViewCreated(final View view, Bundle savedInstanceState) {
+            super.onViewCreated(view, savedInstanceState);
+
+            final TextView textView = (TextView) view.findViewById(android.R.id.text1);
+
+            // (re-)subscribe to the sequence, which either emits the cached result or simply re-
+            // attaches the subscriber to wait for it to arrive
+            subscription = strings.subscribe(new Action1<String>() {
+                @Override
+                public void call(String result) {
+                    textView.setText(result);
+                    getActivity().setProgressBarIndeterminateVisibility(false);
+                }
+            });
+        }
+    }
+}

rxjava-contrib/rxjava-android-samples/samples/src/main/java/com/netflix/rxjava/android/samples/RetainedFragmentActivity.java

@@ -3,6 +3,7 @@
 import android.os.SystemClock;
 
 import rx.Observable;
+import rx.Subscriber;
 import rx.functions.Action1;
 import rx.functions.Func1;
 import rx.schedulers.Schedulers;
@@ -12,18 +13,30 @@ public class SampleObservables {
     /**
      * Emits numbers as strings, where these numbers a generated on a background thread.
      */
-    public static Observable<String> numberStrings() {
-        return Observable.range(1, 10).map(new Func1<Integer, String>() {
+    public static Observable<String> numberStrings(int from, int to, final long delay) {
+        return Observable.range(from, to).map(new Func1<Integer, String>() {
             @Override
             public String call(Integer integer) {
                 return integer.toString();
             }
         }).doOnNext(new Action1<String>() {
             @Override
             public void call(String s) {
-                SystemClock.sleep(1000);
+                SystemClock.sleep(delay);
             }
         }).subscribeOn(Schedulers.newThread());
     }
 
+    public static Observable<String> fakeApiCall(final long delay) {
+        return Observable.create(new Observable.OnSubscribe<String>() {
+            @Override
+            public void call(Subscriber<? super String> subscriber) {
+                // simulate I/O latency
+                SystemClock.sleep(delay);
+                final String fakeJson = "{\"result\": 42}";
+                subscriber.onNext(fakeJson);
+                subscriber.onCompleted();
+            }
+        }).subscribeOn(Schedulers.io());
+    }
 }

rxjava-contrib/rxjava-android-samples/samples/src/main/java/com/netflix/rxjava/android/samples/SampleFragmentActivity.java

@@ -0,0 +1,13 @@
+package com.netflix.rxjava.android.samples;
+
+import android.app.Application;
+import android.os.StrictMode;
+
+public class SamplesApplication extends Application {
+
+    @Override
+    public void onCreate() {
+        super.onCreate();
+        StrictMode.enableDefaults();
+    }
+}

rxjava-contrib/rxjava-android-samples/samples/src/main/java/com/netflix/rxjava/android/samples/SampleObservables.java

@@ -2,13 +2,13 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    tools:context="com.netflix.rxjava.android.samples.SampleFragmentActivity">
+    tools:context="com.netflix.rxjava.android.samples.RetainedFragmentActivity">
 
     <fragment
         android:tag="retained_fragment"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:name="com.netflix.rxjava.android.samples.RetainedFragment"
+        android:name="com.netflix.rxjava.android.samples.RetainedFragmentActivity$RetainedFragment"
         tools:layout="@layout/retained_fragment" />
 
 </RelativeLayout>

rxjava-contrib/rxjava-android-samples/samples/src/main/java/com/netflix/rxjava/android/samples/SamplesApplication.java

@@ -0,0 +1,7 @@
+<menu xmlns:android="http://schemas.android.com/apk/res/android">
+    
+    <item android:id="@+id/action_settings"
+        android:title="@string/action_settings"
+        android:orderInCategory="100"
+        android:showAsAction="never" />
+</menu>