cosc 4730

Brief return SocketsAnd HttpClient (and with AsyncTask)

DownloadManager

Android

• Networking is based on standard Java SE methods– And get the BufferedReader/PrintWriter– Most Java SE network code works with almost no

modifications.

typical Android network code.try {

InetAddress serverAddr = InetAddress.getByName(host);//make the connectionSocket socket = new Socket(serverAddr, port);String message = "Hello from Client android emulator";

try {//receive a messagePrintWriter out = new PrintWriter( new BufferedWriter( new

OutputStreamWriter(socket.getOutputStream())), true);out.println(message);//send a message nowBufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

String str = in.readLine(); } catch(Exception e) {

//error!

} finally { socket.close(); in.close(); out.close(); } } catch (Exception e) { //unable to connect }

Android Client Code

• Making a connection, the code is pretty straight forward

String hostname = “localhost”; // remote machineInt port = 3012; //remote port number

//make the connectionInetAddress serverAddr = InetAddress.getByName(hostname);Socket socket = new Socket(serverAddr, port);//now we have a connection to the server

Android Server Code

• Again pretty straight forwardInt port = 3012; //this is the local port number//create the server socketServerSocket serverSocket = new ServerSocket(port);//wait for a client to connectSocket socket = serverSocket.accept();//now we have a connection to the client.

Reading and writing.

• This works for both client and server.• Once we have the socket connection, we need to get the

read and write part of the socket.//Write sidePrintWriter out = new PrintWriter( new BufferedWriter( new OutputStreamWriter( socket.getOutputStream())),true);

– Note the true, turns on autoflush.

//Read side.BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

PrintWriter

• Networking is normally a text based protocol.– So while there are many function to send int, long,

etc. I’m ignoring them.– out.print(String) and out.println(String)• They both do the same thing, send a line of text.

println will add an end of line marker.• This is important for the read side.

BufferedReader

• The read method reads a single character and returns it as a int.– Second version uses a length and char[].

• readLine() returns line of text as a string. It stops at the end of line marker.– Back to the print and println methods for the writer.

• There is a ready() methods that return true or false. True if there is a data to be read, false other. Using the read() and ready() allows to prevent blocking reads. – Example: if (in.read()) { read() } else { do something else}

Lastly.

• Don’t forget to close everything when you are done with the network.

in.close(); out.close();socket.close();

Android example code

• There is a TCPclient and TCPServ examples for the android– For the sever code you will need to tell the

emulator to accept the port number– In android-sdk-windows\tools directory, run the

following dos command• adb forward tcp:3012 tcp:3012

– assuming you are using port 3012

Android notes

• You will need to put – <uses-permission android:name=

"android.permission.INTERNET" /> – In the AndroidManifest.xml file

• At this point you should be able to use it in both the simulator and on the phone.

Last Note.

• You must connect your phone to UW’s UWyo wireless network to talk to a local cosc machine.– See http://

www.uwyo.edu/askit/displaydoc.asp?askitdocid=1769&parentid=1 for help.

AndroidManifest.xml<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.cosc4730.TCPclient" android:versionCode="1" android:versionName="1.0"> <uses-permission android:name="android.permission.INTERNET" /> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".TCPclient" android:label="@string/app_name">

<intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>

</application> <uses-sdk android:minSdkVersion="10" android:targetSdkVersion="20"/></manifest>

Networking

• Android networking is built on standard Java SE – So use the same network code you learned earlier.

– See the source code example, Android TCPclient and TCPserv for examples that run on the Android platform.

simulator

• For server code, you need to tell the simulator to accept the port number

• In android-sdk-windows\tools directory, run the following dos command– adb forward tcp:3012 tcp:3012• assuming you are using port 3012

References

• Android dev site of course – http://developer.android.com/intl/zh-CN/

reference/android/net/package-summary.html• Socket programming tutorial.

http://www.anddev.org/socket_programming-t325-s30.html

Main thread and network.

• Networking can take some time and should not be done on the main thread– Ie it can lock up the drawing.

• As of v11 (honeycomb)– It will force close if you attempt networking on the

main thread.• It must be done in a thread

– Or a AsyncTask

HTTPCLIENT

HttpClient

• This is a modified version of Apache’s HttpClient– http://hc.apache.org/httpclient-3.x/– Used a lot with the J2EE space

Use

• Create an HttpClient• Instantiate a new HTTP method– PostMethod or GetMethod

• Set HTTP parameter names/values• Execute the HTTP call using the HttpClient• Process the HTTP response.

Example get

HttpClient client = new DefaultHttpClient();HttpGet request = new HttpGet();request.setURI(new URI("http://www.uwyo.edu/"));HttpResponse response = client.execute(request);

• To add parameters to a getHttpGet method = new HttpGet( "http://www.com/do.php?key=valueGoesHere");HttpResponse response = client.execute(method);

Example Post

• HttpClient client = new DefaultHttpClient();• HttpPost request = new

HttpPost("http://somewebsite/do.php");• List<NameValuePair> postParameters = new

ArrayList<NameValuePair>();• postParameters.add(new BasicNameValuePair("one",

"valueGoesHere"));• UrlEncodedFormEntity formEntity = new

UrlEncodedFormEntity(postParameters);• request.setEntity(formEntity);• HttpResponse response = client.execute(request);

ASYNCTASKA second look.

AsyncTask

• Networking can’t be used on the main thread, so an AsyncTask can be ideal for short networking tasks, say file downloads or other things.– otherwise you should use threads and handlers.

AsyncTask download Example private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> { protected Long doInBackground(URL... urls) { int count = urls.length; long totalSize = 0; for (int i = 0; i < count; i++) { totalSize += Downloader.downloadFile(urls[i]); publishProgress((int) ((i / (float) count) * 100)); // Escape early if cancel() is called if (isCancelled()) break; } return totalSize; } //background thread

protected void onProgressUpdate(Integer... progress) { setProgressPercent(progress[0]); } //UI thread

protected void onPostExecute(Long result) { showDialog("Downloaded " + result + " bytes"); } //UI thread }• Once created, a task is executed very simply:new DownloadFilesTask().execute(url1, url2, url3);

URL is pamaters to doInBackground

Integer is the value for publishProgress and onProgressUpdate

And Long is the return value and parameter to onPostExecute

The call, uses URL to create the “list” used in doInBackground

Rest of the examples

• See the GitHub page pages for the rest of the source code for the examples.

• HttpClientDemo uses threads• HttpClientDemo2 uses AsyncTask

DOWNLOADMANGER (API 9+)

DownloadManager

• The download manager is a system service that handles long-running HTTP downloads.– Clients may request that a URI be downloaded to a

particular destination file. • The download manager will conduct the download

in the background, taking care of HTTP interactions and retrying downloads after failures or across connectivity changes and system reboots.

• Note that the application must have the INTERNET permission to use this class.

How it works• Get the service via getSystemServiceDownloadManager downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);• Make a request via the request methodsDownloadManager.Request request = new DownloadManager.Request(URI)long download_id = downloadManager.enqueue(request);• Setup a broadcastReciever to receive an broadcast when it’s

done.– The downloadmanager uses the download_id number, so you need to

store it for use in the receiver.• The intent will contain the id number for the file downloaded, so you know

which one (when downloading more then one at a time.)

DownloadManager.Request(URI)

• Request has a lot of parameters you can set– .setAllowedNetworkTypes( DownloadManager.Request.NETWOR

K_WIFI | DownloadManager.Request.NETWORK_MOBILE)• All networks by default

– setDescription( String)– setTitle (CharSequence title)

• Sets the title and description for the notification line if enabled

– setShowRunningNotification (boolean)• Show notification, true. Deprecated for api 11+• setNotificationVisibility (int visibility)

– VISIBILITY_HIDDEN, VISIBILITY_VISIBLE, VISIBILITY_VISIBLE_NOTIFY_COMPLETED.

– If hidden, this requires the permission android.permission.DOWNLOAD_WITHOUT_NOTIFICATION.A note, setShowRunningNotification(false) didn’t work on 4.1.x

DownloadManager.Request(URI) (2)

• setDestinationInExternalFilesDir (String dirType, String subPath)– dirType is the directory type to pass to

getExternalStoragePublicDirectory(String)– subPath is the path within the external directory, including the

destination filename– Example:– .setDestinationInExternalPublicDir(Environment.DIRECTORY_D

OWNLOADS, "nasapic.jpg");• allowScanningByMediaScanner ()

– If setting above, add this so the media scanner is called as well.

Receiver• Set to receive DownloadManager.ACTION_DOWNLOAD_COMPLETE

• Since we don’t allows want to get download notifications, we set this on up dyanamically in onResume/OnPause

IntentFilter intentFilter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);registerReceiver(downloadReceiver, intentFilter);

• Where downloadReceiver is our methodunregisterReceiver(downloadReceiver);

DownloaderManager.Query

• In the receiver, we deal with the query methods to find out the status of the download– Successful or failure– Based on the download_id (which we can get from

the intent or keep from the enqueue method)– We filter and get a Cursor with the information

DownloaderManager.Query (2)

DownloadManager.Query query = new DownloadManager.Query();query.setFilterById(intentdownloadId);Cursor cursor = downloadManager.query(query);• The example code shows you how to get the

columns and information out of the cursor, including a file, so you can read the downloaded file.

Example code

• DownloadDemo– MainActivity has two buttons. One downloads

and shows the notification, the second doesn’t– MainActivityORG stores the download_id in

preferences, instead of a variable.

References (downloadManager)

• http://developer.android.com/reference/android/app/DownloadManager.html

• http://stackoverflow.com/questions/7239996/android-downloadmanager-api-opening-file-after-download

• http://blog.vogella.com/2011/06/14/android-downloadmanager-example/

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