10/27/17. Network Connec1on. Outline. Connect to the Internet. Connect to the Internet. Perform Network Operations. Perform Network Operations

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1 Connecting to the Internet Outline Network Connec1on CS443 Mobile Applica1ons Instructor: Bo Sheng Perform network operations Manage network usage Parsing data 1 2 Connect to the Internet Permissions in the manifest file <uses-permission android:name="android.permission.internet" /> <uses-permission android:name="android.permission.access_network_state" /> Create an HTTP client Common approach for Android apps to send and receive data HttpURLConnection client: support HTTPS, streaming data, configurable timeouts, IPV6, Connect to the Internet Check the network connection Before your app attempts to connect to the network Using getactivenetworkinfo() and isconnected() getsystemservice(context.connectivity_service); NetworkInfo networkinfo = connmgr.getactivenetworkinfo(); if (networkinfo!= null && networkinfo.isconnected()) { // fetch data else { // display error URL url = new URL(" HttpURLConnection urlconnection = (HttpURLConnection) url.openconnection(); 3 4 Start a separate thread Network operations can involve unpredictable delays E.g., using AsyncTask doinbackground : network connection and operation onpostexecute : update the UI 1. The app passes the specified URL to the AsyncTask. 2. The AsyncTask method doinbackground() calls the downloadurl() method. 3. The downloadurl() method takes a URL string as a parameter and uses it to create a URL object. 4. The URL object is used to establish an HttpURLConnection. 5. The HttpURLConnection object fetches the web page content as an InputStream. 6. The InputStream is passed to the readit() method, which converts the stream to a string. 7. Finally, the AsyncTask's onpostexecute() method displays the string in the main activity's UI. Obtain a new HttpURLConnection by calling URL.openConnection() Prepare the request: set up the parameters of the HttpURLConnection, e.g., Timeout parameters conn.setreadtimeout(10000 /* milliseconds */); conn.setconnecttimeout(15000 /* milliseconds */); Request method: GET, POST, PUT, 5 6 1

Response header from the server: content type/length, encoding conn.connect(); int response = conn.getresponsecode(); Log.

2 Connection is initiated when HttpURLConnection.connect() is called Apps are not always required to explicitly call connect method Some operations such as getinputstream will implicitly perform the connection when necessary. Response header from the server: content type/length, encoding conn.connect(); int response = conn.getresponsecode(); Log.d(DEBUG_TAG, "The response is: " + response); An int representing the three digit HTTP Status-Code:1xx: Informational, 2xx: Success, 3xx: Redirection, 4xx: Client Error, 5xx: Server Error Response body from the server: handled by regular input stream with getinputstream() InputStream in = new BufferedInputStream(urlConnection.getInputStream()); readstream(in); Disconnect: Once the response body has been read, the HttpURLConnection should be closed by calling disconnect(). Disconnecting releases the resources held by a connection so they may be closed or reused. 7 8 URL url = new URL(" HttpURLConnection conn = (HttpURLConnection) url.openconnection(); getsystemservice(context.connectivity_service); NetworkInfo networkinfo = connmgr.getactivenetworkinfo(); if (networkinfo!= null && networkinfo.isconnected()) { conn.setreadtimeout(10000 /* milliseconds */); conn.setconnecttimeout(15000 /* milliseconds */); conn.connect(); InputStream in = new BufferedInputStream(conn.getInputStream()); readstream(in); else { // display error Post content: upload data to a web server Configure the connection for output using setdooutput(true) Call either setfixedlengthstreamingmode(int) when the body length is known in advance, or setchunkedstreamingmode(int) when it is not. urlconnection.setdooutput(true); urlconnection.setchunkedstreamingmode(0); OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream()); writestream(out); InputStream in = new BufferedInputStream(urlConnection.getInputStream()); readstream(in); 9 10 HW2 Convert the InputStream to a target data type InputStream is = urlconnection.getinputstream(); Bitmap bitmap = BitmapFactory.decodeStream(is); Reader reader = new InputStreamReader(is, "UTF-8"); char[] buffer = new char[len]; reader.read(buffer); return new String(buffer); Thread 1 Start from the beginning While(true){... sleep(3000); if(count<4){ randomly pick a tile to place X ; count++; updateui; Ac1vity Int count=0; GridView Array={, X,, O, Start onclick Thread 2 While(cur!=dest){... move to the next tile; updateui(); if passed a X { clear the tile; count--; pause;

3 Fine-grained control of network resources User specific settings, such as How often your app syncs data? Perform network operations only when on WiFi? Transfer data while roaming? Types of network connection (WiFi or cellular) Check the network state before performing network operations ConnectivityManager: Answers queries about the state of network connectivity. Notify applications when network connectivity changes Monitor network connections (Wi-Fi, GPRS, UMTS, etc.) Send broadcast intents when network connectivity changes Attempt to "fail over" to another network when connectivity to a network is lost Provide an API that allows applications to query the coarse-grained or fine-grained state of the available networks Provide an API that allows applications to request and select networks for their data traffic ConnectivityManager: Answers queries about the state of network connectivity. Notify applications when network connectivity changes NetworkInfo: Describes the status of a network interface of a given type (currently either Mobile or Wi-Fi) getsystemservice(context.connectivity_service); NetworkInfo networkinfo = connmgr.getnetworkinfo(connectivitymanager.type_wifi); boolean iswificonn = networkinfo.isconnected(); networkinfo = connmgr.getnetworkinfo(connectivitymanager.type_mobile); boolean ismobileconn = networkinfo.isconnected(); Log.d(DEBUG_TAG, "Wifi connected: " + iswificonn); Log.d(DEBUG_TAG, "Mobile connected: " + ismobileconn); ConnectivityManager: Answers queries about the state of network connectivity. Notify applications when network connectivity changes NetworkInfo: Describes the status of a network interface of a given type (currently either Mobile or Wi-Fi) isavailable() and isconnected() : Always check isconnected() before performing network operations, since it handles cases like flaky mobile networks, airplane mode, and restricted background data getactivenetworkinfo(): returns a NetworkInfo instance representing the first connected network interface it can find, or null if none of the interfaces is connected public boolean isonline() { getsystemservice(context.connectivity_service); NetworkInfo networkinfo = connmgr.getactivenetworkinfo(); return (networkinfo!= null && networkinfo.isconnected()); For example: allow users to upload videos only when the device is connected to a Wi-Fi network; sync (or not) depending on specific criteria such as network availability, time interval, Required permissions android.permission.internet Allows applications to open network socket android.permission.access_network_state Allows applications to access information about networks

4 10/27/17 MANAGE_NETWORK_USAGE Intent Filter: shows settings for managing the network data usage of a specific application. If you app includes an activity that offers options to control data usage <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> Settings A Preference object represents a single setting Key-value pairs are stored in a default SharedPreferences file PreferenceActivity or PreferenceFragment Different types of preferences CheckBoxPreference ListPreference EditTextPreference Define Preferences in XML Implement a preferences activity A subclass of PreferenceActivity Implement public void onsharedpreferencechanged( ){ // 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; Respond to preference changes Fetch the preferences settings in public void onstart () { super.onstart(); SharedPreferences sharedprefs = PreferenceManager.getDefaultSharedPreferences(this); spref = sharedprefs.getstring("listpref", "Wi-Fi"); updateconnectedflags(); if(refreshdisplay){ loadpage(); Respond to preference changes Get the current network state public void updateconnectedflags() { 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; Respond to preference changes Check the network preference public void loadpage() { if (((spref.equals(any)) && (wificonnected mobileconnected)) ((spref.equals(wifi)) && (wificonnected))) { // AsyncTask subclass new DownloadXmlTask().execute(URL); else { showerrorpage();

Choose a parser (XmlPullParser) via Xml.newPullParser() Analyze the feed <entry> <id>http://stackoverflow.com/q/9439999</id> <re:rank scheme="http://stackoverflow.

5 Choose a parser (XmlPullParser) via Xml.newPullParser() Analyze the feed <entry> <id> <re:rank scheme=" <title type="text">where is my data file?</title> <category scheme=" term="android"/> <category scheme=" term="file"/> <author> <name>cliff2310</name> <uri> </author> <link rel="alternate" href=" /> <published> t00:30:54z</published> <updated> t00:30:54z</updated> <summary type="html"> <p>i have an Application that requires a data file...</p> </summary> </entry> Instantiate the parser via Xml.newPullParser() Data fed by an InputStream Start parsing with nexttag() public List 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(); Read the feed Look for elements tagged entry Return a List containing the entries private List readfeed(xmlpullparser parser) throws XmlPullParserException, IOException { List entries = new ArrayList(); parser.require(xmlpullparser.start_tag, ns, "feed"); while (parser.next()!= XmlPullParser.END_TAG) { if (parser.geteventtype()!= XmlPullParser.START_TAG) { continue; String name = parser.getname(); if (name.equals("entry")) { entries.add(readentry(parser)); else { skip(parser); return entries; Parse each entry A "read" method for each tag you're interested in. For example, readentry(), readtitle(), and so on. 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); Read a user input (city s name or zip code) 2. Display the temperature 3. Display the weather icon openweathermap.org References Query examples q=boston,ma&appid=f9a0da d1453d0faa23006c2d9 4. Show the map of the city zip=02125,us&appid=f9a0da d1453d0faa23006c2d

6 Main steps Get the user input and form the http URL Then, download the data from the server Analyze/parse the returned data Temperature Icon file name Latitude, longitude Download the icon file Parse JSON data {"coord":{"lon":-71.06,"lat":42.36, "weather":[{"id":800,"main":"clear","descrip1on":"sky is clear","icon":"01d"], "base":"sta1ons", "main":{"temp":294.73,"pressure":1008,"humidity":60,"temp_min": ,"temp_max":297.15, "visibility":16093,"wind":{"speed":4.1,"deg":250,"clouds":{"all":1,"dt": ,"sys":{"type":1,"id":1801,"message": ,"country":"US","sunrise": ,"sunset": ,"id": ,"name":"Boston","cod":200 JSONObject jobj=new JSONObject(stringInput); jobj.getstring( base ), jobj.getjsonobject( coord ); Settings Use preference fragments public static class SettingsFragment extends PreferenceFragment public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate);... // Load the preferences from an XML resource addpreferencesfromresource(r.xml.preferences); public class SettingsActivity extends Activity protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); // Display the fragment as the main content. getfragmentmanager().begintransaction().replace(android.r.id.content, new SettingsFragment()).commit(); 33 6

Software Engineering Large Practical: Accessing remote data and XML parsing. Stephen Gilmore School of Informatics October 8, 2017

Software Engineering Large Practical: Accessing remote data and XML parsing Stephen Gilmore School of Informatics October 8, 2017 Contents 1. Android system permissions 2. Getting a network connection