The Suggest Example layout (cont ed)

Transcription

1 Using Web Services 5COSC005W MOBILE APPLICATION DEVELOPMENT Lecture 7: Working with Web Services Android provides a full set of Java-standard networking APIs, such as the java.net package containing among others the HttpURLConnection class. Dr Dimitris C. Dracopoulos Example: Use the Suggest web service to create an application which autocompletes phrases by making suggestions. Dimitris C. Dracopoulos 1/39 Dimitris C. Dracopoulos 2/39 The Suggest Example The layout of the main activity res/layout/activity main.xml: <? xml version =" 1.0 " encoding ="utf -8"?> < LinearLayout xmlns:android =" http: // schemas. android. com / apk / res / android " android: layout_ height =" fill_ parent " android: orientation =" vertical " android:padding ="10 dip " > < TextView android: layout_ height =" wrap_ content " android:text / original_label " /> < EditText android:id ="@+id/ original_text " android: layout_ height =" wrap_ content " android: hint / original_ hint " android: inputtype =" textnosuggestions " android:padding ="10 dip " android:textsize ="18 sp" /> < TextView android: layout_ height =" wrap_ content " android:text / result_label " /> Dimitris C. Dracopoulos 3/39 The Suggest Example layout (cont ed) < ListView android:id ="@+id/ result_list " android:layout_height ="0dp" android: layout_ weight =" 1" / > < TextView android:id ="@+id/ eband_text " android: layout_ height =" wrap_ content " android:gravity =" bottom right " android:text / eband " /> </ LinearLayout > Dimitris C. Dracopoulos 4/39

2 Specifying special permissions Add this to the AndroidManifest.xml: <uses - permission android: name =" android. permission. INTERNET " / > The main activity MainActivity.java: package org. example. suggest ; import... // look up the imports in the textbook or autoimport public class MainActivity extends Activity { private EditText origtext ; private ListView sugglist ; private TextView ebandtext ; private Handler ; private ExecutorService ; private ; private <? > ; private List < String > items ; private ArrayAdapter < String > adapter ; public void oncreate ( Bundle savedinstancestate ) { super. oncreate ( savedinstancestate ); Dimitris C. Dracopoulos 5/39 setcontentview ( R. layout. activity_ main ); initthreading (); findviews (); setlisteners (); setadapters (); Dimitris C. Dracopoulos 6/39 private void findviews () { origtext = ( EditText ) findviewbyid ( R. id. original_ text ); sugglist = ( ListView ) findviewbyid ( R. id. result_ list ); ebandtext = ( TextView ) findviewbyid ( R. id. eband_ text ); /* * Setup user interface event handlers */ private void setlisteners () { // Define listener text change TextWatcher textwatcher = new TextWatcher () { public void beetextchanged ( CharSequence s, int start, int count, int after ) { /* Do nothing */ public void ontextchanged ( CharSequence s, int start, int bee, int count ) { queueupdate (1000 /* milliseconds */ ); public void aftertextchanged ( Editable s) { /* Do nothing */ ; // Set listener on the original text field origtext. addtextchangedlistener ( textwatcher ); // Define listener clicking on an item OnItemClickListener clicklistener = new OnItemClickListener () public void onitemclick ( AdapterView <? > parent, View view, int position, long id) { String query = ( String ) parent. getitematposition ( position ); dosearch ( query ); ; // Set listener on the suggestion list sugglist. setonitemclicklistener ( clicklistener ); // Make website link clickable ebandtext. setmovementmethod ( LinkMovementMethod. getinstance ()); Dimitris C. Dracopoulos 7/39 Dimitris C. Dracopoulos 8/39

3 initthreading() method private void dosearch ( String query ) { Intent intent = new Intent ( Intent. ACTION_ WEB_ SEARCH ); intent. putextra ( SearchManager. QUERY, query ); startactivity ( intent ); /* * Set up adapter list view. */ private void setadapters () { items = new ArrayList < String >(); adapter = new ArrayAdapter < String >( this, android. R. layout. simple_list_item_1, items ); sugglist. setadapter ( adapter ); Dimitris C. Dracopoulos 9/39 Dimitris C. Dracopoulos 10/39 initthreading() method initthreading() method Dimitris C. Dracopoulos 11/39 Dimitris C. Dracopoulos 12/39

4 initthreading() method initthreading() method Dimitris C. Dracopoulos 13/39 Dimitris C. Dracopoulos 14/39 initthreading() method Dimitris C. Dracopoulos 15/39 Dimitris C. Dracopoulos 16/39

5 new new Dimitris C. Dracopoulos 17/39 Dimitris C. Dracopoulos 18/39 new new Dimitris C. Dracopoulos 19/39 Dimitris C. Dracopoulos 20/39

6 remove Dimitris C. Dracopoulos 21/39 Dimitris C. Dracopoulos 22/39 cancel Dimitris C. Dracopoulos 23/39 Dimitris C. Dracopoulos 24/39

7 cancel cancel Dimitris C. Dracopoulos 25/39 Dimitris C. Dracopoulos 26/39 new new Dimitris C. Dracopoulos 27/39 Dimitris C. Dracopoulos 28/39

8 Threading the task: private void initthreading () { = new Handler (); = Executors. newsinglethreadexecutor (); // This task gets suggestions and updates the screen = new () { public void run () { // Get text to suggest String original = origtext. gettext (). tostring (). trim (); // Cancel previous suggestion if there was one if (!= null ). cancel ( true ); ; // Check to make sure there is text to work on if ( original. length ()!= 0) { // Let user know we re doing something settext (R. string. working ); // Begin suggestion now but don t wait it try { SuggestTask = new SuggestTask ( MainActivity. this, // reference to activity original // original text ); =. submit ( ); catch ( RejectedExecutionException e) { // Unable to start new task settext (R. string. error ); Dimitris C. Dracopoulos 29/39 Dimitris C. Dracopoulos 30/39 /* * Request an update to start after a short delay */ private void queueupdate ( long delaymillis ) { // Cancel previous update if it hasn t started yet. removecallbacks ( ); // Start an update if nothing happens after a few milliseconds. postdelayed (, delaymillis ); Dimitris C. Dracopoulos 31/39 /* * Modify list on the screen ( called from another thread ) */ public void setsuggestions ( List < String > suggestions ) { guisetlist ( sugglist, suggestions ); /* * All changes to the GUI must be done in the GUI thread */ private void guisetlist ( final ListView view, final List < String > list ) {. post ( new () { public void run () { setlist ( list ); ); /* * Display a list */ private void setlist ( List < String > list ) { adapter. clear (); adapter. addall ( list ); /* * Display a message */ private void settext ( int id) { adapter. clear (); adapter. add ( getresources (). getstring (id )); Dimitris C. Dracopoulos 32/39

9 The strings.xml < resources > < string name =" app_name ">Suggest </ string > < string name =" action_settings ">Settings </ string > < string name =" original_ hint " > Enter partial text </ string > < string name =" original_ label " > Original text: </ string > < string name =" result_label ">Suggestions: </ string > < string name =" working ">Working... </ string > < string name =" error ">( Web service error )</ string > < string name =" interrupted " >( Web service interrupted ) </ string > < string name =" no_results ">(No suggestions )</ string > < string name =" eband " > Example from <a href =" http: // pragprog. com / book / eband4 ">Hello, Android </a> by Ed Burnette </ string > </ resources > Dimitris C. Dracopoulos 33/39 The Suggest task (SuggestTask.java file: package org. example. suggest ; import java. io. IOException ; import java. net. HttpURLConnection ; import java. net. URL ; import java. net. URLEncoder ; import java. util. LinkedList ; import java. util. List ; import org. xmlpull.v1. XmlPullParser ; import org. xmlpull. v1. XmlPullParserException ; import android. util. Log ; import android. util. Xml ; public class SuggestTask implements { private static final String TAG = " SuggestTask "; private final MainActivity suggest ; private final String original ; SuggestTask ( MainActivity context, String original ) { this. suggest = context ; this. original = original ; Dimitris C. Dracopoulos 34/39 private List < String > dosuggest ( String original ) { List < String > messages = new LinkedList < String >(); String error = null ; HttpURLConnection con = null ; Log.d(TAG, " dosuggest (" + original + ")"); public void run () { // Get suggestions the original text List < String > suggestions = dosuggest ( original ); suggest. setsuggestions ( suggestions ); try { // Check if task has been interrupted if ( Thread. interrupted ()) throw new InterruptedException (); // Build RESTful query Google API String q = URLEncoder. encode ( original, "UTF -8"); URL url = new URL ( " http :// google. com / complete / search? output = toolbar &q=" + q); con = ( HttpURLConnection ) url. openconnection (); con. setreadtimeout (10000 /* milliseconds */ ); con. setconnecttimeout (15000 /* milliseconds */ ); con. setrequestmethod (" GET "); con. addrequestproperty (" Referer ", " http :// www. pragprog. com / book / eband4 "); con. setdoinput ( true ); Dimitris C. Dracopoulos 35/39 Dimitris C. Dracopoulos 36/39

10 // Start the query con. connect (); // Check if task has been interrupted if ( Thread. interrupted ()) throw new InterruptedException (); // Read results from the query XmlPullParser parser = Xml. newpullparser (); parser. setinput ( con. getinputstream (), null ); int eventtype = parser. geteventtype (); while ( eventtype!= XmlPullParser. END_ DOCUMENT ) { String name = parser. getname (); if ( eventtype == XmlPullParser. START_ TAG && name. equalsignorecase (" suggestion ")) { ( int i = 0; i< parser. getattributecount (); i ++) { if ( parser. getattributename ( i). equalsignorecase ( " data ")) { messages. add ( parser. getattributevalue (i )); eventtype = parser. next (); Dimitris C. Dracopoulos 37/39 catch ( IOException e) { Log.e(TAG, " IOException ", e); error = suggest. getresources (). getstring ( R. string. error ) + " " + e. tostring (); catch ( XmlPullParserException e) { Log.e(TAG, " XmlPullParserException ", e); error = suggest. getresources (). getstring ( R. string. error ) + " " + e. tostring (); catch ( InterruptedException e) { Log.d(TAG, " InterruptedException ", e); error = suggest. getresources (). getstring ( R. string. interrupted ); finally { if ( con!= null ) { con. disconnect (); Dimitris C. Dracopoulos 38/39 // If there was an error, return the error by itself if ( error!= null ) { messages. clear (); messages. add ( error ); // Print something if we got nothing if ( messages. size () == 0) { messages. add ( suggest. getresources (). getstring ( R. string. no_results )); // All done Log. d( TAG, " -> returned " + messages ); return messages ; Dimitris C. Dracopoulos 39/39