cherrypick from ics-mr1 docs: source for nw app Change-Id: If50f407a0e56fa802fe9beedaa650e3a131872b2

Change-Id: I55d8668f4065129c844ada239f268a6621df4780

13 files changed, 750 insertions, 0 deletions

diff --git a/samples/training/network-usage/AndroidManifest.xml b/samples/training/network-usage/AndroidManifest.xml
new file mode 100644
index 0000000..4b96d14
--- /dev/null
+++ b/samples/training/network-usage/AndroidManifest.xml
@@ -0,0 +1,48 @@
+<!--
+  Copyright (C) 2012 The Android Open Source Project
+
+  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.
+  -->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.android.networkusage"
+    android:versionCode="1"
+    android:versionName="1.0" >
+
+    <uses-sdk android:minSdkVersion="4"
+        android:targetSdkVersion="14" />
+
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+
+    <application
+        android:icon="@drawable/ic_launcher"
+        android:label="@string/app_name" >
+
+        <activity
+            android:name="com.example.networkusage.NetworkActivity"
+            android:label="@string/app_name" >
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+        <activity android:label="SettingsActivity" android:name=".SettingsActivity">
+             <intent-filter>
+                <action android:name="android.intent.action.MANAGE_NETWORK_USAGE" />
+                <category android:name="android.intent.category.DEFAULT" />
+          </intent-filter>
+        </activity>
+    </application>
+</manifest>
diff --git a/samples/training/network-usage/README.txt b/samples/training/network-usage/README.txt
new file mode 100644
index 0000000..cc9a7a0
--- /dev/null
+++ b/samples/training/network-usage/README.txt
@@ -0,0 +1,14 @@
+README
+======
+
+This Network Usage sample app does the following:
+
+-- Downloads an XML feed from StackOverflow.com for the most recent posts tagged "android".
+
+-- Parses the XML feed, combines feed elements with HTML markup, and displays the resulting HTML in the UI.
+
+-- Lets users control their network data usage through a settings UI. Users can choose to fetch the feed
+   when any network connection is available, or only when a Wi-Fi connection is available.
+
+-- Detects when there is a change in the device's connection status and responds accordingly. For example, if
+   the device loses its network connection, the app will not attempt to download the feed.
diff --git a/samples/training/network-usage/res/drawable-hdpi/ic_launcher.png b/samples/training/network-usage/res/drawable-hdpi/ic_launcher.png
new file mode 100644
index 0000000..8074c4c
--- /dev/null
+++ b/samples/training/network-usage/res/drawable-hdpi/ic_launcher.png
diff --git a/samples/training/network-usage/res/drawable-ldpi/ic_launcher.png b/samples/training/network-usage/res/drawable-ldpi/ic_launcher.png
new file mode 100644
index 0000000..1095584
--- /dev/null
+++ b/samples/training/network-usage/res/drawable-ldpi/ic_launcher.png
diff --git a/samples/training/network-usage/res/drawable-mdpi/ic_launcher.png b/samples/training/network-usage/res/drawable-mdpi/ic_launcher.png
new file mode 100644
index 0000000..a07c69f
--- /dev/null
+++ b/samples/training/network-usage/res/drawable-mdpi/ic_launcher.png
diff --git a/samples/training/network-usage/res/layout/main.xml b/samples/training/network-usage/res/layout/main.xml
new file mode 100644
index 0000000..8498934
--- /dev/null
+++ b/samples/training/network-usage/res/layout/main.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="fill_parent"
+    android:layout_height="fill_parent"
+    android:orientation="vertical" >
+
+<WebView  xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/webview"
+    android:layout_width="fill_parent"
+    android:layout_height="fill_parent"
+/>
+</LinearLayout>
diff --git a/samples/training/network-usage/res/menu/mainmenu.xml b/samples/training/network-usage/res/menu/mainmenu.xml
new file mode 100644
index 0000000..17d44db
--- /dev/null
+++ b/samples/training/network-usage/res/menu/mainmenu.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  Copyright (C) 2012 The Android Open Source Project
+
+  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.
+  -->
+
+<menu xmlns:android="http://schemas.android.com/apk/res/android">
+     <item android:id="@+id/settings"
+          android:title="@string/settings" />
+    <item android:id="@+id/refresh"
+          android:title="@string/refresh" />
+</menu>
diff --git a/samples/training/network-usage/res/values/arrays.xml b/samples/training/network-usage/res/values/arrays.xml
new file mode 100644
index 0000000..2e8b8a7
--- /dev/null
+++ b/samples/training/network-usage/res/values/arrays.xml
@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  Copyright (C) 2012 The Android Open Source Project
+
+  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.
+  -->
+
+<resources>
+    <string-array name="listArray">
+        <item>Only when on Wi-Fi</item>
+        <item>On any network</item>
+    </string-array>
+    <string-array name="listValues">
+        <item>Wi-Fi</item>
+        <item>Any</item>
+    </string-array>
+</resources>
diff --git a/samples/training/network-usage/res/values/strings.xml b/samples/training/network-usage/res/values/strings.xml
new file mode 100644
index 0000000..d7c702f
--- /dev/null
+++ b/samples/training/network-usage/res/values/strings.xml
@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  Copyright (C) 2012 The Android Open Source Project
+
+  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.
+  -->
+
+<resources>
+
+    <string name="app_name">NetworkUsage</string>
+
+    <!--  Menu items -->
+    <string name="settings">Settings</string>
+    <string name="refresh">Refresh</string>
+
+    <!--  NetworkActivity -->
+    <string name="page_title">Newest StackOverflow questions tagged \'android\'</string>
+    <string name="updated">Last updated:</string>
+    <string name="lost_connection">Lost connection.</string>
+    <string name="wifi_connected">Wi-Fi reconnected.</string>
+    <string name="connection_error">Unable to load content. Check your network connection.</string>
+    <string name="xml_error">Error parsing XML.</string>
+
+</resources>
diff --git a/samples/training/network-usage/res/xml/preferences.xml b/samples/training/network-usage/res/xml/preferences.xml
new file mode 100644
index 0000000..801ba79
--- /dev/null
+++ b/samples/training/network-usage/res/xml/preferences.xml
@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  Copyright (C) 2012 The Android Open Source Project
+
+  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.
+  -->
+
+<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
+    <ListPreference
+        android:title="Download Feed"
+        android:summary="Network connectivity required to download the feed."
+        android:key="listPref"
+        android:defaultValue="Wi-Fi"
+        android:entries="@array/listArray"
+        android:entryValues="@array/listValues"
+     />
+    <CheckBoxPreference
+        android:title="Show Summaries"
+        android:defaultValue="false"
+        android:summary="Show a summary for each link."
+        android:key="summaryPref" />
+</PreferenceScreen>
diff --git a/samples/training/network-usage/src/com/example/android/networkusage/NetworkActivity.java b/samples/training/network-usage/src/com/example/android/networkusage/NetworkActivity.java
new file mode 100644
index 0000000..b7ed331
--- /dev/null
+++ b/samples/training/network-usage/src/com/example/android/networkusage/NetworkActivity.java
@@ -0,0 +1,321 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * 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 com.example.android.networkusage;
+
+import android.app.Activity;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.SharedPreferences;
+import android.net.ConnectivityManager;
+import android.net.NetworkInfo;
+import android.os.AsyncTask;
+import android.os.Bundle;
+import android.preference.PreferenceManager;
+import android.view.Menu;
+import android.view.MenuInflater;
+import android.view.MenuItem;
+import android.webkit.WebView;
+import android.widget.Toast;
+
+import com.example.android.networkusage.R;
+import com.example.android.networkusage.StackOverflowXmlParser.Entry;
+
+import org.xmlpull.v1.XmlPullParserException;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import java.util.List;
+
+
+/**
+ * Main Activity for the sample application.
+ *
+ * This activity does the following:
+ *
+ * o Presents a WebView screen to users. This WebView has a list of HTML links to the latest
+ *   questions tagged 'android' on stackoverflow.com.
+ *
+ * o Parses the StackOverflow XML feed using XMLPullParser.
+ *
+ * o Uses AsyncTask to download and process the XML feed.
+ *
+ * o Monitors preferences and the device's network connection to determine whether
+ *   to refresh the WebView content.
+ */
+public class NetworkActivity extends Activity {
+    public static final String WIFI = "Wi-Fi";
+    public static final String ANY = "Any";
+    private static final String URL =
+            "http://stackoverflow.com/feeds/tag?tagnames=android&sort=newest";
+
+    // Whether there is a Wi-Fi connection.
+    private static boolean wifiConnected = false;
+    // Whether there is a mobile connection.
+    private static boolean mobileConnected = false;
+    // Whether the display should be refreshed.
+    public static boolean refreshDisplay = true;
+
+    // The user's current network preference setting.
+    public static String sPref = null;
+
+    // The BroadcastReceiver that tracks network connectivity changes.
+    private NetworkReceiver receiver = new NetworkReceiver();
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        // Register BroadcastReceiver to track connection changes.
+        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
+        receiver = new NetworkReceiver();
+        this.registerReceiver(receiver, filter);
+    }
+
+    // Refreshes the display if the network connection and the
+    // pref settings allow it.
+    @Override
+    public void onStart() {
+        super.onStart();
+
+        // Gets the user's network preference settings
+        SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
+
+        // Retrieves a string value for the preferences. The second parameter
+        // is the default value to use if a preference value is not found.
+        sPref = sharedPrefs.getString("listPref", "Wi-Fi");
+
+        updateConnectedFlags();
+
+        // Only loads the page if refreshDisplay is true. Otherwise, keeps previous
+        // display. For example, if the user has set "Wi-Fi only" in prefs and the
+        // device loses its Wi-Fi connection midway through the user using the app,
+        // you don't want to refresh the display--this would force the display of
+        // an error page instead of stackoverflow.com content.
+        if (refreshDisplay) {
+            loadPage();
+        }
+    }
+
+    @Override
+    public void onDestroy() {
+        super.onDestroy();
+        if (receiver != null) {
+            this.unregisterReceiver(receiver);
+        }
+    }
+
+    // Checks the network connection and sets the wifiConnected and mobileConnected
+    // variables accordingly.
+    private void updateConnectedFlags() {
+        ConnectivityManager connMgr =
+                (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
+
+        NetworkInfo activeInfo = connMgr.getActiveNetworkInfo();
+        if (activeInfo != null && activeInfo.isConnected()) {
+            wifiConnected = activeInfo.getType() == ConnectivityManager.TYPE_WIFI;
+            mobileConnected = activeInfo.getType() == ConnectivityManager.TYPE_MOBILE;
+        } else {
+            wifiConnected = false;
+            mobileConnected = false;
+        }
+    }
+
+    // Uses AsyncTask subclass to download the XML feed from stackoverflow.com.
+    // This avoids UI lock up. To prevent network operations from
+    // causing a delay that results in a poor user experience, always perform
+    // network operations on a separate thread from the UI.
+    private void loadPage() {
+        if (((sPref.equals(ANY)) && (wifiConnected || mobileConnected))
+                || ((sPref.equals(WIFI)) && (wifiConnected))) {
+            // AsyncTask subclass
+            new DownloadXmlTask().execute(URL);
+        } else {
+            showErrorPage();
+        }
+    }
+
+    // Displays an error if the app is unable to load content.
+    private void showErrorPage() {
+        setContentView(R.layout.main);
+
+        // The specified network connection is not available. Displays error message.
+        WebView myWebView = (WebView) findViewById(R.id.webview);
+        myWebView.loadData(getResources().getString(R.string.connection_error),
+                "text/html", null);
+    }
+
+    // Populates the activity's options menu.
+    @Override
+    public boolean onCreateOptionsMenu(Menu menu) {
+        MenuInflater inflater = getMenuInflater();
+        inflater.inflate(R.menu.mainmenu, menu);
+        return true;
+    }
+
+    // Handles the user's menu selection.
+    @Override
+    public boolean onOptionsItemSelected(MenuItem item) {
+        switch (item.getItemId()) {
+        case R.id.settings:
+                Intent settingsActivity = new Intent(getBaseContext(), SettingsActivity.class);
+                startActivity(settingsActivity);
+                return true;
+        case R.id.refresh:
+                loadPage();
+                return true;
+        default:
+                return super.onOptionsItemSelected(item);
+        }
+    }
+
+    // Implementation of AsyncTask used to download XML feed from stackoverflow.com.
+    private class DownloadXmlTask extends AsyncTask<String, Void, String> {
+
+        @Override
+        protected String doInBackground(String... urls) {
+            try {
+                return loadXmlFromNetwork(urls[0]);
+            } catch (IOException e) {
+                return getResources().getString(R.string.connection_error);
+            } catch (XmlPullParserException e) {
+                return getResources().getString(R.string.xml_error);
+            }
+        }
+
+        @Override
+        protected void onPostExecute(String result) {
+            setContentView(R.layout.main);
+            // Displays the HTML string in the UI via a WebView
+            WebView myWebView = (WebView) findViewById(R.id.webview);
+            myWebView.loadData(result, "text/html", null);
+        }
+    }
+
+    // Uploads XML from stackoverflow.com, parses it, and combines it with
+    // HTML markup. Returns HTML string.
+    private String loadXmlFromNetwork(String urlString) throws XmlPullParserException, IOException {
+        InputStream stream = null;
+        StackOverflowXmlParser stackOverflowXmlParser = new StackOverflowXmlParser();
+        List<Entry> entries = null;
+        String title = null;
+        String url = null;
+        String summary = null;
+        Calendar rightNow = Calendar.getInstance();
+        DateFormat formatter = new SimpleDateFormat("MMM dd h:mmaa");
+
+        // Checks whether the user set the preference to include summary text
+        SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
+        boolean pref = sharedPrefs.getBoolean("summaryPref", false);
+
+        StringBuilder htmlString = new StringBuilder();
+        htmlString.append("<h3>" + getResources().getString(R.string.page_title) + "</h3>");
+        htmlString.append("<em>" + getResources().getString(R.string.updated) + " " +
+                formatter.format(rightNow.getTime()) + "</em>");
+
+        try {
+            stream = downloadUrl(urlString);
+            entries = stackOverflowXmlParser.parse(stream);
+        // Makes sure that the InputStream is closed after the app is
+        // finished using it.
+        } finally {
+            if (stream != null) {
+                stream.close();
+            }
+        }
+
+        // StackOverflowXmlParser returns a List (called "entries") of Entry objects.
+        // Each Entry object represents a single post in the XML feed.
+        // This section processes the entries list to combine each entry with HTML markup.
+        // Each entry is displayed in the UI as a link that optionally includes
+        // a text summary.
+        for (Entry entry : entries) {
+            htmlString.append("<p><a href='");
+            htmlString.append(entry.link);
+            htmlString.append("'>" + entry.title + "</a></p>");
+            // If the user set the preference to include summary text,
+            // adds it to the display.
+            if (pref) {
+                htmlString.append(entry.summary);
+            }
+        }
+        return htmlString.toString();
+    }
+
+    // Given a string representation of a URL, sets up a connection and gets
+    // an input stream.
+    private InputStream downloadUrl(String urlString) throws IOException {
+        URL url = new URL(urlString);
+        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
+        conn.setReadTimeout(10000 /* milliseconds */);
+        conn.setConnectTimeout(15000 /* milliseconds */);
+        conn.setRequestMethod("GET");
+        conn.setDoInput(true);
+        // Starts the query
+        conn.connect();
+        InputStream stream = conn.getInputStream();
+        return stream;
+    }
+
+    /**
+     *
+     * This BroadcastReceiver intercepts the android.net.ConnectivityManager.CONNECTIVITY_ACTION,
+     * which indicates a connection change. It checks whether the type is TYPE_WIFI.
+     * If it is, it checks whether Wi-Fi is connected and sets the wifiConnected flag in the
+     * main activity accordingly.
+     *
+     */
+    public class NetworkReceiver extends BroadcastReceiver {
+
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            ConnectivityManager connMgr =
+                    (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
+            NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
+
+            // Checks the user prefs and the network connection. Based on the result, decides
+            // whether
+            // to refresh the display or keep the current display.
+            // If the userpref is Wi-Fi only, checks to see if the device has a Wi-Fi connection.
+            if (WIFI.equals(sPref) && networkInfo != null
+                    && networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {
+                // If device has its Wi-Fi connection, sets refreshDisplay
+                // to true. This causes the display to be refreshed when the user
+                // returns to the app.
+                refreshDisplay = true;
+                Toast.makeText(context, R.string.wifi_connected, Toast.LENGTH_SHORT).show();
+
+                // If the setting is ANY network and there is a network connection
+                // (which by process of elimination would be mobile), sets refreshDisplay to true.
+            } else if (ANY.equals(sPref) && networkInfo != null) {
+                refreshDisplay = true;
+
+                // Otherwise, the app can't download content--either because there is no network
+                // connection (mobile or Wi-Fi), or because the pref setting is WIFI, and there
+                // is no Wi-Fi connection.
+                // Sets refreshDisplay to false.
+            } else {
+                refreshDisplay = false;
+                Toast.makeText(context, R.string.lost_connection, Toast.LENGTH_SHORT).show();
+            }
+        }
+    }
+}
diff --git a/samples/training/network-usage/src/com/example/android/networkusage/SettingsActivity.java b/samples/training/network-usage/src/com/example/android/networkusage/SettingsActivity.java
new file mode 100644
index 0000000..73b72d2
--- /dev/null
+++ b/samples/training/network-usage/src/com/example/android/networkusage/SettingsActivity.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * 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 com.example.android.networkusage;
+
+import android.content.SharedPreferences;
+import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
+import android.os.Bundle;
+import android.preference.PreferenceActivity;
+import com.example.android.networkusage.R;
+
+/**
+ * This preference activity has in its manifest declaration an intent filter for
+ * the ACTION_MANAGE_NETWORK_USAGE action. This activity provides a settings UI
+ * for users to specify network settings to control data usage.
+ */
+public class SettingsActivity extends PreferenceActivity
+        implements
+            OnSharedPreferenceChangeListener {
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        // Loads the XML preferences file.
+        addPreferencesFromResource(R.xml.preferences);
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+
+        // Registers a callback to be invoked whenever a user changes a preference.
+        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
+    }
+
+    @Override
+    protected void onPause() {
+        super.onPause();
+
+        // Unregisters the listener set in onResume().
+        // It's best practice to unregister listeners when your app isn't using them to cut down on
+        // unnecessary system overhead. You do this in onPause().
+        getPreferenceScreen()
+                .getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
+    }
+
+    // Fires when the user changes a preference.
+    @Override
+    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
+        // Sets refreshDisplay to true so that when the user returns to the main
+        // activity, the display refreshes to reflect the new settings.
+        NetworkActivity.refreshDisplay = true;
+    }
+}
diff --git a/samples/training/network-usage/src/com/example/android/networkusage/StackOverflowXmlParser.java b/samples/training/network-usage/src/com/example/android/networkusage/StackOverflowXmlParser.java
new file mode 100644
index 0000000..6a01098
--- /dev/null
+++ b/samples/training/network-usage/src/com/example/android/networkusage/StackOverflowXmlParser.java
@@ -0,0 +1,169 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * 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 com.example.android.networkusage;
+
+import android.util.Xml;
+
+import org.xmlpull.v1.XmlPullParser;
+import org.xmlpull.v1.XmlPullParserException;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This class parses XML feeds from stackoverflow.com.
+ * Given an InputStream representation of a feed, it returns a List of entries,
+ * where each list element represents a single entry (post) in the XML feed.
+ */
+public class StackOverflowXmlParser {
+    private static final String ns = null;
+
+    // We don't use namespaces
+
+    public List<Entry> parse(InputStream in) throws XmlPullParserException, IOException {
+        try {
+            XmlPullParser parser = Xml.newPullParser();
+            parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
+            parser.setInput(in, null);
+            parser.nextTag();
+            return readFeed(parser);
+        } finally {
+            in.close();
+        }
+    }
+
+    private List<Entry> readFeed(XmlPullParser parser) throws XmlPullParserException, IOException {
+        List<Entry> entries = new ArrayList<Entry>();
+
+        parser.require(XmlPullParser.START_TAG, ns, "feed");
+        while (parser.next() != XmlPullParser.END_TAG) {
+            if (parser.getEventType() != XmlPullParser.START_TAG) {
+                continue;
+            }
+            String name = parser.getName();
+            // Starts by looking for the entry tag
+            if (name.equals("entry")) {
+                entries.add(readEntry(parser));
+            } else {
+                skip(parser);
+            }
+        }
+        return entries;
+    }
+
+    // This class represents a single entry (post) in the XML feed.
+    // It includes the data members "title," "link," and "summary."
+    public static class Entry {
+        public final String title;
+        public final String link;
+        public final String summary;
+
+        private Entry(String title, String summary, String link) {
+            this.title = title;
+            this.summary = summary;
+            this.link = link;
+        }
+    }
+
+    // Parses the contents of an entry. If it encounters a title, summary, or link tag, hands them
+    // off
+    // to their respective &quot;read&quot; methods for processing. Otherwise, skips the tag.
+    private Entry readEntry(XmlPullParser parser) throws XmlPullParserException, IOException {
+        parser.require(XmlPullParser.START_TAG, ns, "entry");
+        String title = null;
+        String summary = null;
+        String link = null;
+        while (parser.next() != XmlPullParser.END_TAG) {
+            if (parser.getEventType() != XmlPullParser.START_TAG) {
+                continue;
+            }
+            String name = parser.getName();
+            if (name.equals("title")) {
+                title = readTitle(parser);
+            } else if (name.equals("summary")) {
+                summary = readSummary(parser);
+            } else if (name.equals("link")) {
+                link = readLink(parser);
+            } else {
+                skip(parser);
+            }
+        }
+        return new Entry(title, summary, link);
+    }
+
+    // Processes title tags in the feed.
+    private String readTitle(XmlPullParser parser) throws IOException, XmlPullParserException {
+        parser.require(XmlPullParser.START_TAG, ns, "title");
+        String title = readText(parser);
+        parser.require(XmlPullParser.END_TAG, ns, "title");
+        return title;
+    }
+
+    // Processes link tags in the feed.
+    private String readLink(XmlPullParser parser) throws IOException, XmlPullParserException {
+        String link = "";
+        parser.require(XmlPullParser.START_TAG, ns, "link");
+        String tag = parser.getName();
+        String relType = parser.getAttributeValue(null, "rel");
+        if (tag.equals("link")) {
+            if (relType.equals("alternate")) {
+                link = parser.getAttributeValue(null, "href");
+                parser.nextTag();
+            }
+        }
+        parser.require(XmlPullParser.END_TAG, ns, "link");
+        return link;
+    }
+
+    // Processes summary tags in the feed.
+    private String readSummary(XmlPullParser parser) throws IOException, XmlPullParserException {
+        parser.require(XmlPullParser.START_TAG, ns, "summary");
+        String summary = readText(parser);
+        parser.require(XmlPullParser.END_TAG, ns, "summary");
+        return summary;
+    }
+
+    // For the tags title and summary, extracts their text values.
+    private String readText(XmlPullParser parser) throws IOException, XmlPullParserException {
+        String result = "";
+        if (parser.next() == XmlPullParser.TEXT) {
+            result = parser.getText();
+            parser.nextTag();
+        }
+        return result;
+    }
+
+    // Skips tags the parser isn't interested in. Uses depth to handle nested tags. i.e.,
+    // if the next tag after a START_TAG isn't a matching END_TAG, it keeps going until it
+    // finds the matching END_TAG (as indicated by the value of "depth" being 0).
+    private void skip(XmlPullParser parser) throws XmlPullParserException, IOException {
+        if (parser.getEventType() != XmlPullParser.START_TAG) {
+            throw new IllegalStateException();
+        }
+        int depth = 1;
+        while (depth != 0) {
+            switch (parser.next()) {
+            case XmlPullParser.END_TAG:
+                    depth--;
+                    break;
+            case XmlPullParser.START_TAG:
+                    depth++;
+                    break;
+            }
+        }
+    }
+}