Katie McCormick | 2f8cc17 | 2012-03-16 17:47:55 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2012 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except |
| 5 | * in compliance with the License. You may obtain a copy of the License at |
| 6 | * |
| 7 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | * |
| 9 | * Unless required by applicable law or agreed to in writing, software distributed under the License |
| 10 | * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express |
| 11 | * or implied. See the License for the specific language governing permissions and limitations under |
| 12 | * the License. |
| 13 | */ |
| 14 | |
| 15 | package com.example.android.networkusage; |
| 16 | |
| 17 | import android.app.Activity; |
| 18 | import android.content.BroadcastReceiver; |
| 19 | import android.content.Context; |
| 20 | import android.content.Intent; |
| 21 | import android.content.IntentFilter; |
| 22 | import android.content.SharedPreferences; |
| 23 | import android.net.ConnectivityManager; |
| 24 | import android.net.NetworkInfo; |
| 25 | import android.os.AsyncTask; |
| 26 | import android.os.Bundle; |
| 27 | import android.preference.PreferenceManager; |
| 28 | import android.view.Menu; |
| 29 | import android.view.MenuInflater; |
| 30 | import android.view.MenuItem; |
| 31 | import android.webkit.WebView; |
| 32 | import android.widget.Toast; |
| 33 | |
| 34 | import com.example.android.networkusage.R; |
| 35 | import com.example.android.networkusage.StackOverflowXmlParser.Entry; |
| 36 | |
| 37 | import org.xmlpull.v1.XmlPullParserException; |
| 38 | |
| 39 | import java.io.IOException; |
| 40 | import java.io.InputStream; |
| 41 | import java.net.HttpURLConnection; |
| 42 | import java.net.URL; |
| 43 | import java.text.DateFormat; |
| 44 | import java.text.SimpleDateFormat; |
| 45 | import java.util.Calendar; |
| 46 | import java.util.List; |
| 47 | |
| 48 | |
| 49 | /** |
| 50 | * Main Activity for the sample application. |
| 51 | * |
| 52 | * This activity does the following: |
| 53 | * |
| 54 | * o Presents a WebView screen to users. This WebView has a list of HTML links to the latest |
| 55 | * questions tagged 'android' on stackoverflow.com. |
| 56 | * |
| 57 | * o Parses the StackOverflow XML feed using XMLPullParser. |
| 58 | * |
| 59 | * o Uses AsyncTask to download and process the XML feed. |
| 60 | * |
| 61 | * o Monitors preferences and the device's network connection to determine whether |
| 62 | * to refresh the WebView content. |
| 63 | */ |
| 64 | public class NetworkActivity extends Activity { |
| 65 | public static final String WIFI = "Wi-Fi"; |
| 66 | public static final String ANY = "Any"; |
| 67 | private static final String URL = |
| 68 | "http://stackoverflow.com/feeds/tag?tagnames=android&sort=newest"; |
| 69 | |
| 70 | // Whether there is a Wi-Fi connection. |
| 71 | private static boolean wifiConnected = false; |
| 72 | // Whether there is a mobile connection. |
| 73 | private static boolean mobileConnected = false; |
| 74 | // Whether the display should be refreshed. |
| 75 | public static boolean refreshDisplay = true; |
| 76 | |
| 77 | // The user's current network preference setting. |
| 78 | public static String sPref = null; |
| 79 | |
| 80 | // The BroadcastReceiver that tracks network connectivity changes. |
| 81 | private NetworkReceiver receiver = new NetworkReceiver(); |
| 82 | |
| 83 | @Override |
| 84 | public void onCreate(Bundle savedInstanceState) { |
| 85 | super.onCreate(savedInstanceState); |
| 86 | |
| 87 | // Register BroadcastReceiver to track connection changes. |
| 88 | IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION); |
| 89 | receiver = new NetworkReceiver(); |
| 90 | this.registerReceiver(receiver, filter); |
| 91 | } |
| 92 | |
| 93 | // Refreshes the display if the network connection and the |
| 94 | // pref settings allow it. |
| 95 | @Override |
| 96 | public void onStart() { |
| 97 | super.onStart(); |
| 98 | |
| 99 | // Gets the user's network preference settings |
| 100 | SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this); |
| 101 | |
| 102 | // Retrieves a string value for the preferences. The second parameter |
| 103 | // is the default value to use if a preference value is not found. |
| 104 | sPref = sharedPrefs.getString("listPref", "Wi-Fi"); |
| 105 | |
| 106 | updateConnectedFlags(); |
| 107 | |
| 108 | // Only loads the page if refreshDisplay is true. Otherwise, keeps previous |
| 109 | // display. For example, if the user has set "Wi-Fi only" in prefs and the |
| 110 | // device loses its Wi-Fi connection midway through the user using the app, |
| 111 | // you don't want to refresh the display--this would force the display of |
| 112 | // an error page instead of stackoverflow.com content. |
| 113 | if (refreshDisplay) { |
| 114 | loadPage(); |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | @Override |
| 119 | public void onDestroy() { |
| 120 | super.onDestroy(); |
| 121 | if (receiver != null) { |
| 122 | this.unregisterReceiver(receiver); |
| 123 | } |
| 124 | } |
| 125 | |
| 126 | // Checks the network connection and sets the wifiConnected and mobileConnected |
| 127 | // variables accordingly. |
| 128 | private void updateConnectedFlags() { |
| 129 | ConnectivityManager connMgr = |
| 130 | (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); |
| 131 | |
| 132 | NetworkInfo activeInfo = connMgr.getActiveNetworkInfo(); |
| 133 | if (activeInfo != null && activeInfo.isConnected()) { |
| 134 | wifiConnected = activeInfo.getType() == ConnectivityManager.TYPE_WIFI; |
| 135 | mobileConnected = activeInfo.getType() == ConnectivityManager.TYPE_MOBILE; |
| 136 | } else { |
| 137 | wifiConnected = false; |
| 138 | mobileConnected = false; |
| 139 | } |
| 140 | } |
| 141 | |
| 142 | // Uses AsyncTask subclass to download the XML feed from stackoverflow.com. |
| 143 | // This avoids UI lock up. To prevent network operations from |
| 144 | // causing a delay that results in a poor user experience, always perform |
| 145 | // network operations on a separate thread from the UI. |
| 146 | private void loadPage() { |
| 147 | if (((sPref.equals(ANY)) && (wifiConnected || mobileConnected)) |
| 148 | || ((sPref.equals(WIFI)) && (wifiConnected))) { |
| 149 | // AsyncTask subclass |
| 150 | new DownloadXmlTask().execute(URL); |
| 151 | } else { |
| 152 | showErrorPage(); |
| 153 | } |
| 154 | } |
| 155 | |
| 156 | // Displays an error if the app is unable to load content. |
| 157 | private void showErrorPage() { |
| 158 | setContentView(R.layout.main); |
| 159 | |
| 160 | // The specified network connection is not available. Displays error message. |
| 161 | WebView myWebView = (WebView) findViewById(R.id.webview); |
| 162 | myWebView.loadData(getResources().getString(R.string.connection_error), |
| 163 | "text/html", null); |
| 164 | } |
| 165 | |
| 166 | // Populates the activity's options menu. |
| 167 | @Override |
| 168 | public boolean onCreateOptionsMenu(Menu menu) { |
| 169 | MenuInflater inflater = getMenuInflater(); |
| 170 | inflater.inflate(R.menu.mainmenu, menu); |
| 171 | return true; |
| 172 | } |
| 173 | |
| 174 | // Handles the user's menu selection. |
| 175 | @Override |
| 176 | public boolean onOptionsItemSelected(MenuItem item) { |
| 177 | switch (item.getItemId()) { |
| 178 | case R.id.settings: |
| 179 | Intent settingsActivity = new Intent(getBaseContext(), SettingsActivity.class); |
| 180 | startActivity(settingsActivity); |
| 181 | return true; |
| 182 | case R.id.refresh: |
| 183 | loadPage(); |
| 184 | return true; |
| 185 | default: |
| 186 | return super.onOptionsItemSelected(item); |
| 187 | } |
| 188 | } |
| 189 | |
| 190 | // Implementation of AsyncTask used to download XML feed from stackoverflow.com. |
| 191 | private class DownloadXmlTask extends AsyncTask<String, Void, String> { |
| 192 | |
| 193 | @Override |
| 194 | protected String doInBackground(String... urls) { |
| 195 | try { |
| 196 | return loadXmlFromNetwork(urls[0]); |
| 197 | } catch (IOException e) { |
| 198 | return getResources().getString(R.string.connection_error); |
| 199 | } catch (XmlPullParserException e) { |
| 200 | return getResources().getString(R.string.xml_error); |
| 201 | } |
| 202 | } |
| 203 | |
| 204 | @Override |
| 205 | protected void onPostExecute(String result) { |
| 206 | setContentView(R.layout.main); |
| 207 | // Displays the HTML string in the UI via a WebView |
| 208 | WebView myWebView = (WebView) findViewById(R.id.webview); |
| 209 | myWebView.loadData(result, "text/html", null); |
| 210 | } |
| 211 | } |
| 212 | |
| 213 | // Uploads XML from stackoverflow.com, parses it, and combines it with |
| 214 | // HTML markup. Returns HTML string. |
| 215 | private String loadXmlFromNetwork(String urlString) throws XmlPullParserException, IOException { |
| 216 | InputStream stream = null; |
| 217 | StackOverflowXmlParser stackOverflowXmlParser = new StackOverflowXmlParser(); |
| 218 | List<Entry> entries = null; |
| 219 | String title = null; |
| 220 | String url = null; |
| 221 | String summary = null; |
| 222 | Calendar rightNow = Calendar.getInstance(); |
| 223 | DateFormat formatter = new SimpleDateFormat("MMM dd h:mmaa"); |
| 224 | |
| 225 | // Checks whether the user set the preference to include summary text |
| 226 | SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this); |
| 227 | boolean pref = sharedPrefs.getBoolean("summaryPref", false); |
| 228 | |
| 229 | StringBuilder htmlString = new StringBuilder(); |
| 230 | htmlString.append("<h3>" + getResources().getString(R.string.page_title) + "</h3>"); |
| 231 | htmlString.append("<em>" + getResources().getString(R.string.updated) + " " + |
| 232 | formatter.format(rightNow.getTime()) + "</em>"); |
| 233 | |
| 234 | try { |
| 235 | stream = downloadUrl(urlString); |
| 236 | entries = stackOverflowXmlParser.parse(stream); |
| 237 | // Makes sure that the InputStream is closed after the app is |
| 238 | // finished using it. |
| 239 | } finally { |
| 240 | if (stream != null) { |
| 241 | stream.close(); |
| 242 | } |
| 243 | } |
| 244 | |
| 245 | // StackOverflowXmlParser returns a List (called "entries") of Entry objects. |
| 246 | // Each Entry object represents a single post in the XML feed. |
| 247 | // This section processes the entries list to combine each entry with HTML markup. |
| 248 | // Each entry is displayed in the UI as a link that optionally includes |
| 249 | // a text summary. |
| 250 | for (Entry entry : entries) { |
| 251 | htmlString.append("<p><a href='"); |
| 252 | htmlString.append(entry.link); |
| 253 | htmlString.append("'>" + entry.title + "</a></p>"); |
| 254 | // If the user set the preference to include summary text, |
| 255 | // adds it to the display. |
| 256 | if (pref) { |
| 257 | htmlString.append(entry.summary); |
| 258 | } |
| 259 | } |
| 260 | return htmlString.toString(); |
| 261 | } |
| 262 | |
| 263 | // Given a string representation of a URL, sets up a connection and gets |
| 264 | // an input stream. |
| 265 | private InputStream downloadUrl(String urlString) throws IOException { |
| 266 | URL url = new URL(urlString); |
| 267 | HttpURLConnection conn = (HttpURLConnection) url.openConnection(); |
| 268 | conn.setReadTimeout(10000 /* milliseconds */); |
| 269 | conn.setConnectTimeout(15000 /* milliseconds */); |
| 270 | conn.setRequestMethod("GET"); |
| 271 | conn.setDoInput(true); |
| 272 | // Starts the query |
| 273 | conn.connect(); |
| 274 | InputStream stream = conn.getInputStream(); |
| 275 | return stream; |
| 276 | } |
| 277 | |
| 278 | /** |
| 279 | * |
| 280 | * This BroadcastReceiver intercepts the android.net.ConnectivityManager.CONNECTIVITY_ACTION, |
| 281 | * which indicates a connection change. It checks whether the type is TYPE_WIFI. |
| 282 | * If it is, it checks whether Wi-Fi is connected and sets the wifiConnected flag in the |
| 283 | * main activity accordingly. |
| 284 | * |
| 285 | */ |
| 286 | public class NetworkReceiver extends BroadcastReceiver { |
| 287 | |
| 288 | @Override |
| 289 | public void onReceive(Context context, Intent intent) { |
| 290 | ConnectivityManager connMgr = |
| 291 | (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); |
| 292 | NetworkInfo networkInfo = connMgr.getActiveNetworkInfo(); |
| 293 | |
| 294 | // Checks the user prefs and the network connection. Based on the result, decides |
| 295 | // whether |
| 296 | // to refresh the display or keep the current display. |
| 297 | // If the userpref is Wi-Fi only, checks to see if the device has a Wi-Fi connection. |
| 298 | if (WIFI.equals(sPref) && networkInfo != null |
| 299 | && networkInfo.getType() == ConnectivityManager.TYPE_WIFI) { |
| 300 | // If device has its Wi-Fi connection, sets refreshDisplay |
| 301 | // to true. This causes the display to be refreshed when the user |
| 302 | // returns to the app. |
| 303 | refreshDisplay = true; |
| 304 | Toast.makeText(context, R.string.wifi_connected, Toast.LENGTH_SHORT).show(); |
| 305 | |
| 306 | // If the setting is ANY network and there is a network connection |
| 307 | // (which by process of elimination would be mobile), sets refreshDisplay to true. |
| 308 | } else if (ANY.equals(sPref) && networkInfo != null) { |
| 309 | refreshDisplay = true; |
| 310 | |
| 311 | // Otherwise, the app can't download content--either because there is no network |
| 312 | // connection (mobile or Wi-Fi), or because the pref setting is WIFI, and there |
| 313 | // is no Wi-Fi connection. |
| 314 | // Sets refreshDisplay to false. |
| 315 | } else { |
| 316 | refreshDisplay = false; |
| 317 | Toast.makeText(context, R.string.lost_connection, Toast.LENGTH_SHORT).show(); |
| 318 | } |
| 319 | } |
| 320 | } |
| 321 | } |