August 2011

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Implementing Search activities

<div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on">Most Android phones have a<strong> search</strong> button. this button is used to search contacts,applications or anything on the phone. We can make use of the search functionality in our apps.<br /><br />In this post we're going to see how to implement search functionality to search for entries stored in a databaseand display them in a ListView.</div><div closure_uid_ghg7ej="237"><br /></div><div closure_uid_ghg7ej="237"><span style="font-size: large;">Creating database:</span></div></div>our database has two tables: <strong>Countries</strong> and <strong>Names:</strong><br /><pre class="brush:java" closure_uid_ghg7ej="312">public class DBHelper extends SQLiteOpenHelper {<br /><br /> public DBHelper(Context context) {<br />  super(context, "DemoDB", null, 1);<br /> }<br /><br /> @Override<br /> public void onCreate(SQLiteDatabase db) {<br />  StringBuilder builder=new StringBuilder();<br />  // countries table<br />  builder.append("CREATE TABLE Countries ");<br />  builder.append("(_id INTEGER PRIMARY KEY AUTOINCREMENT,");<br />  builder.append("NAME TEXT) ");<br />  db.execSQL(builder.toString());<br />  // Names table<br />  // Virtual table for full text search<br />  builder.setLength(0);<br />  builder.append("CREATE VIRTUAL TABLE NAMES USING FTS3");<br />  builder.append("(");<br />  builder.append("name TEXT) ");  <br />  db.execSQL(builder.toString());<br />  builder=new StringBuilder();<br /><br />  //dummy  data<br />  InsertData(db);<br /><br /> }<br /><br />  void InsertData(SQLiteDatabase db)<br />  {<br />   ContentValues cv=new ContentValues();<br />   cv.put("NAME","USA");<br />   db.insert("Countries", "NAME", cv);<br />   cv.put("NAME","UK");<br />   db.insert("Countries", "NAME", cv);<br />   cv.put("NAME","Spain");<br />   db.insert("Countries", "NAME", cv);<br />   cv.put("NAME","ITALY");<br />   db.insert("Countries", "NAME", cv);<br />   cv.put("NAME","Germany");<br />   db.insert("Countries", "NAME", cv);<br /><br />    cv=new ContentValues();<br />    cv.put("name","John");<br />    db.insert("NAMES", "name", cv);<br />    cv.put("name","Jack");<br />    db.insert("NAMES", "name", cv);<br />    cv.put("name","Ann");<br />    db.insert("NAMES", "name", cv);<br />    cv.put("name","Adam");<br />    db.insert("NAMES", "name", cv);<br />    cv.put("name","Sarah");<br />    db.insert("NAMES", "name", cv);<br /><br />  }<br /><br /> @Override<br /> public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {<br />  // TODO Auto-generated method stub<br /><br /> }<br />}</pre></div>notice that the <strong>Names </strong>table is a <strong>VIRTUAL </strong>table. we created it as virtual to make use of <strong>Full Text Search (FTS3)</strong> feature in SQLite. this feature makes queries faster than that in regular tables.</div>then we add two functions to retrieve all rows from both tables:<br /><pre class="brush:java">/**<br />  * Return all countries<br />  * @return<br />  */<br /> public ArrayListgetCountries(){<br />  ArrayList countries=new ArrayList();<br />  SQLiteDatabase db=this.getReadableDatabase();<br />  Cursor c=db.rawQuery("select * from Countries", null);<br />  while(c.moveToNext()){<br />   String country=c.getString(1);<br />   countries.add(country);<br />  }<br />  c.close();<br />  return countries;<br /> }<br />/**<br />  * Return all names<br />  * @return<br />  */<br /><br /> public ArrayListgetNames(){<br />  ArrayList names=new ArrayList();<br />  Cursor c=this.getReadableDatabase().rawQuery("select * FROM Names", null);<br />  while(c.moveToNext()){<br />   String name=c.getString(0);<br />   names.add(name);<br />  }<br />  c.close();<br />  return names;<br /> }</pre></div>and another two functions to retrieve data based on a <strong>search string</strong>:<br /><pre class="brush:java">/**<br />  * Return all countries based on a search string<br />  * @return<br />  */<br /> public ArrayListgetCountriesSearch(String query){<br />  ArrayList countries=new ArrayList();<br />  SQLiteDatabase db=this.getReadableDatabase();<br />  Cursor c=db.rawQuery("select * from Countries where NAME LIKE '%"+query+"%'", null);<br />  while(c.moveToNext()){<br />   String country=c.getString(1);<br />   countries.add(country);<br />  }<br />  c.close();<br />  return countries;<br /> }<br />/**<br />  * Return all names based on a search string<br />  * we use the MATCH keyword to make use of the full text search<br />  * @return<br />  */<br /> public ArrayListgetNamesSearch(String query){<br />  ArrayList names=new ArrayList();<br />  Cursor c=this.getReadableDatabase().rawQuery("select * FROM Names WHERE name MATCH '"+query+"'", null);<br />  while(c.moveToNext()){<br />   String name=c.getString(0);<br />   names.add(name);<br />  }<br />  c.close();<br />  return names;<br /> }</pre></div><br /><span style="font-size: large;">Implementing The activity:</span></div>then we will create our activity that has a list view like this:<br /><pre class="brush:xml" closure_uid_ghg7ej="313" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><?xml version="1.0" encoding="utf-8"?><br /><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"<br />    android:orientation="vertical"<br />    android:layout_width="fill_parent"<br />    android:layout_height="fill_parent"<br />    ><br /><ListView<br />android:layout_width="fill_parent"<br />    android:layout_height="fill_parent"<br />    android:id="@+id/list"/><br /></LinearLayout></pre></div><div closure_uid_ghg7ej="251" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br /></div><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: center;"><a href="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/Search%20Activity/search.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320px" src="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/Search%20Activity/search.bmp" /></a></div></div>we load data from database like this:<br /><pre class="brush:java">public void onCreate(Bundle savedInstanceState) {<br />        super.onCreate(savedInstanceState);<br />        setContentView(R.layout.main);<br />        list=(ListView)findViewById(R.id.list);<br /><br />            DBHelper helper=new DBHelper(this);<br />            ArrayList items=helper.getNames();<br />            ArrayAdapter adapter=new ArrayAdapter(this, android.R.layout.simple_list_item_1,items);<br />            list.setAdapter(adapter);<br />}</pre></div><div closure_uid_ghg7ej="315"><br /></div><div closure_uid_ghg7ej="315"><span style="font-size: large;">Handling the search dialog:</span></div></div>In order to handle the search dialog ourselves we need to create a xml file with search configurations such as the search dialog title, voice search capabilities, content provider for auto complete and so on. we create a file with the name <strong>searchable.xml</strong> in <strong>res/xml</strong>directory:<br /><pre class="brush:xml"><?xml version="1.0" encoding="utf-8"?><br /><searchable xmlns:android="http://schemas.android.com/apk/res/android"<br />    android:label="@string/app_name"<br />    android:hint="@string/hint"  ><br /></searchable></pre></div>the <strong>android:hint</strong> attribute denotes a string that acts as a water mark on the search text box.<br />then we need to add an <strong>Intent Filter</strong> in out app's <strong>AndroidManifest.xml</strong> file to our activity to handle the search dialog:<br /><pre class="brush:xml"><activity android:name=".MainActivty"<br />                  android:label="@string/app_name"><br />            <intent-filter><br />                <action android:name="android.intent.action.MAIN" /><br />                <category android:name="android.intent.category.LAUNCHER" /><br />            </intent-filter><br />             <intent-filter><br />            <action android:name="android.intent.action.SEARCH" /><br />        </intent-filter><br />        <meta-data android:name="android.app.searchable"<br />                   android:resource="@xml/searchable"/><br />        </activity></pre><br /></div><div closure_uid_ghg7ej="317"><span style="font-size: large;">Understanding the Search process:</span></div></div><br />when you press the search button, type some text and click on search the activit's <strong>onSearchRequested()</strong> function is called, then an Intent with the action <strong>Intent.ACTION_SEARCH</strong> is created and you activity is re-created with this intent.<br /><br />the search intent has you search string as a string extra with the name <strong>SearchManager.QUERY</strong>. also it can carry a <strong>bundle </strong>of other extras with the name <strong>SearchManager.APP_DATA</strong>.</div><br /><span style="font-size: large;">what if the device doesn't have a Search button:</span></div>not all Android devices have a search button, so we can start the search dialog manually by calling the activity's <strong>onSearchRequested()</strong> from a button or a menu item:<br /><pre class="brush:java">@Override<br />     public boolean onCreateOptionsMenu(Menu menu) {<br />     menu.add("Search").setOnMenuItemClickListener(new OnMenuItemClickListener() {<br /><br />   @Override<br />   public boolean onMenuItemClick(MenuItem item) {<br />                                //launch the search dialog<br />    onSearchRequested();<br />    return true;<br />   }<br />  });<br />     return true;<br />    }</pre></div><div closure_uid_ghg7ej="322"><br /></div><div closure_uid_ghg7ej="322"><span style="font-size: large;">Adding extras to the search dialog:</span></div></div>we can pass some extra data as a bundle with our search dialog or an initial search string by overriding the activity's <strong>onSearchRequested()</strong>:<br /><pre class="brush:java">@Override<br />    public boolean onSearchRequested() {<br />     Bundle bundle=new Bundle();<br />  bundle.putString("extra", "exttra info");<br />  // search initial query<br />  startSearch("Country", false, bundle, false);<br />  return true;<br />    }</pre></div><br /><span style="font-size: large;">Handling the search query:</span></div><div closure_uid_ghg7ej="324"><br /></div><div closure_uid_ghg7ej="324">we said before that the search query is passed as a <strong>String extra</strong> when our activity is re-created. so we can handle the searcgh string in our <strong>onCreate()</strong> like this:</div><pre class="brush:java" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">@Override<br />    public void onCreate(Bundle savedInstanceState) {<br />        super.onCreate(savedInstanceState);<br />        setContentView(R.layout.main);<br />        list=(ListView)findViewById(R.id.list);<br /><br />        DBHelper helper=new DBHelper(this);<br />        Intent intent=getIntent();<br />        // if the activity is created from search<br />         if(intent.getAction().equals(Intent.ACTION_SEARCH)){<br />          // get search query<br />          String query=intent.getStringExtra(SearchManager.QUERY);<br />          ArrayList items=helper.getNamesSearch(query);<br />          //get extras, just for demonstration<br />          Bundle bundle=intent.getBundleExtra(SearchManager.APP_DATA);<br />             String info=bundle.getString("extra");<br />          Log.v("extra", info);<br />          //bind the list<br />                ArrayAdapter adapter=new ArrayAdapter(this, android.R.layout.simple_list_item_1,items);<br />                list.setAdapter(adapter);<br />         }<br />        //activity created normally<br />        else{<br />         ArrayList items=helper.getNames();<br />            ArrayAdapter adapter=new ArrayAdapter(this, android.R.layout.simple_list_item_1,items);<br />            list.setAdapter(adapter);<br />        }<br />        helper.close();<br />    }</pre></div><div closure_uid_ghg7ej="368" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br /></div><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: center;"><a href="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/Search%20Activity/search2.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320px" src="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/Search%20Activity/search2.bmp" /></a></div></div><br />we just extract the search string and any other extras and perform our search logic based on the search string.<br />and that's was all about implementing search</div>

Most Android phones have a search button. this button is used to search contacts,applications or anything on the phone. We can make use of...

<div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on"><div dir="ltr" style="text-align: left;" trbidi="on">In this post we will see how can a client application call the methods of a service defined in another application. this is achieved through <strong>Android Interface Definition Language (AIDL). </strong><br /><br /><strong></strong>AIDL is a java like language that enables you to define an interface that both the application defining the service and the client application implement it.<br /><br /><div closure_uid_siyhg3="239"><div closure_uid_siyhg3="260">the interface defines the functions that are needed to be called in the client application.</div></div><div closure_uid_siyhg3="232"><br /></div><div closure_uid_siyhg3="232"><span style="font-size: large;">Defining the AIDL file:</span></div>AIDL syntax is similar to that of Java, we can use the following data types in AIDL:<br /><ol><li>primitive data types: int, long, char, boolean,....</li><li>String.</li><li>CharSequence.</li><li>List (ArrayList,Vector,...).</li></ol><br /><ol><li>the AIDL file is defined as follows:<br />open a notepad file and paste the following code in it:<br /><pre class="brush:java">package com.mina.servicedemo;<br /><br />// service interface<br />interface IRemoteService {<br />    //sample method<br />    String sayHello(String message);<br />}</pre>take care of the package name <strong>com.mina.servicedemo</strong>.<br />we defined a methods <strong>sayHello(String message)</strong> that returns a string.</li><li>save the file with the name<strong> IRemoteService</strong> and change it's extension to <strong>.aidl</strong>.</li><li>copy the file to the <strong>src</strong> folder of your project.</li><li>once you save and build the file, Android generates an interface java file with the name <strong>IRemoteService.java</strong> in the <strong>gen</strong> folder if the project.</li></ol><br /></div><div closure_uid_siyhg3="243"><span style="font-size: large;">Defining the Service:</span></div>now we want our service to expose this interface to client applications, so we return an implementation of the service in the <strong>onBind()</strong> method of our service:<br /><pre class="brush:java">package com.mina.servicedemo;<br /><br />import com.mina.servicedemo.IRemoteService.Stub;<br /><br />import android.app.Service;<br />import android.content.Intent;<br />import android.os.IBinder;<br />import android.os.RemoteException;<br />import android.widget.Toast;<br /><br />public class DemoService extends Service {<br /><br /> @Override<br /> public IBinder onBind(Intent arg0) {<br />  return mBinder;<br /> }<br /><br /> // implementation of the aidl interface<br /> private final IRemoteService.Stub mBinder=new Stub() {<br /><br />  @Override<br />  public String sayHello(String message) throws RemoteException {<br />   return "Hello "+message;<br /><br />  }<br /> };<br /><br /> }<br />}</pre></div>the last thing to do in the service is to make its <strong>exported</strong> attribute in the <strong>AndroidManifest.xml</strong> file set to true like this:<br /><pre class="brush:xml"><service android:name="DemoService" android:exported="true"></service></pre>our app structure can be like this:<br /><div class="separator" style="clear: both; text-align: center;"><a href="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/AIDL/aidl.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/AIDL/aidl.bmp" /></a></div><div closure_uid_siyhg3="248"><br /></div><div closure_uid_siyhg3="259"><span style="font-size: large;">Consuming the service at the client application:</span></div>now to our client application where we want to invoke methods from our service. the client application is a separate application with a different package name than that where the service is defined.<br /><br />the client application needs a reference to the AIDL interface defined in the original applcation, this is done through the following steps:<br /><ol><li>in the client applicatio create a package with the same package name of that the service is defined in: <strong>com.mina.servicedemo.</strong></li><li>copy the AIDL file in this package.</li><li closure_uid_siyhg3="261" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">save and build and a new file called IRemoteService.java is generated. your app structure should be like this: </li></ol><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: center;"><a href="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/AIDL/aidl2.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://dl.dropbox.com/u/2624328/Android%20Pro/2011/August/AIDL/aidl2.bmp" /></a></div>and we invoke the servcice methods in our activity like this:<br /><pre class="brush:java">package com.mina.serviceclient;<br /><br />import com.mina.servicedemo.IRemoteService;<br /><br />import android.app.Activity;<br />import android.content.ComponentName;<br />import android.content.Context;<br />import android.content.Intent;<br />import android.content.ServiceConnection;<br />import android.os.Bundle;<br />import android.os.IBinder;<br />import android.os.RemoteException;<br />import android.util.Log;<br /><br />public class MainActivity extends Activity {<br /><br /> IRemoteService mRemoteService;<br /><br />    /** Called when the activity is first created. */<br />    @Override<br />    public void onCreate(Bundle savedInstanceState) {<br />        super.onCreate(savedInstanceState);<br />        setContentView(R.layout.main);<br /><br />        Intent serviceIntent=new Intent();<br />        serviceIntent.setClassName("com.mina.servicedemo", "com.mina.servicedemo.DemoService");<br />        boolean ok=bindService(serviceIntent, mServiceConnection,Context.BIND_AUTO_CREATE);<br />        Log.v("ok", String.valueOf(ok));<br />    }<br /><br />    private ServiceConnection mServiceConnection=new ServiceConnection() {<br /><br />  @Override<br />  public void onServiceDisconnected(ComponentName name) {<br />   // TODO Auto-generated method stub<br /><br />  }<br /><br />  @Override<br />  public void onServiceConnected(ComponentName name, IBinder service) {<br />   // get instance of the aidl binder<br />   mRemoteService = IRemoteService.Stub.asInterface(service);<br />   try {<br />    String message=mRemoteService.sayHello("Mina");<br />    Log.v("message", message);<br />   } catch (RemoteException e) {<br />    Log.e("RemoteException", e.toString());<br />   }<br /><br />  }<br /> };<br />}</pre></div>and that's was all about calling remote services with AIDL.

In this post we will see how can a client application call the methods of a service defined in another application. this is achieved through...

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