Mahesh's........

Customized Tabs in android.

2012-06-19T03:25:00.001-07:00

Hello friends, every one of get a situation to make an application using Tabs, Some of use activities in place of tabs, Its generally become a large code,
This follows the simpler code for customized tabs.....

Create a new project and attach the below code in Activity file and create 2 more xml files in layout folder and name them as 1.tabhost.xml 2.tabs_bg.xml

package com.mahesh.android.tabs;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TabHost;
import android.widget.TabHost.TabSpec;
public class CustomTabActivity extends Activity {
// private TabHost mTabHost;
//
// private void setupTabHost() {
//  mTabHost = (TabHost) findViewById(android.R.id.tabhost);
//  mTabHost.setup();
// }
/** Called when the activity is first created. */
@Override

  /////////////////////////////////////////////
  public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main);
   TabHost tabHost=(TabHost)findViewById(R.id.tabHost);
   tabHost.setup();
   TabSpec spec1=tabHost.newTabSpec("Tab 1");
   spec1.setContent(R.id.tab1);
   spec1.setIndicator("Tab 1");
   TabSpec spec2=tabHost.newTabSpec("Tab 2");
   spec2.setIndicator("Tab 2");
   spec2.setContent(R.id.tab2);
   TabSpec spec3=tabHost.newTabSpec("Tab 3");
   spec3.setIndicator("Tab 3");
   spec3.setContent(R.id.tab3);

   TabSpec spec4=tabHost.newTabSpec("Tab 4");
   spec4.setIndicator("Tab 4");
   spec4.setContent(R.id.tab4);

   tabHost.addTab(spec1);
   tabHost.addTab(spec2);
   tabHost.addTab(spec3);
   tabHost.addTab(spec4);
   }
  /////////////////////////////////////////////////////

}

Now we have a look in main.xml file
add this piece of code in your xml

xml version="1.0" encoding="utf-8"?>

<TabHost android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@+id/tabHost"

xmlns:android=http://schemas.android.com/apk/res/android>

<TabWidget

android:layout_width="fill_parent"

android:layout_height="match_parent"

android:id="@android:id/tabs"/>

<FrameLayout

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@android:id/tabcontent">

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:id="@+id/tab1"

android:orientation="vertical"

android:paddingTop="130px">

<TextView

android:layout_width="fill_parent"

android:layout_height="100px"

android:text="This is tab1"

android:id="@+id/txt1"/>

</LinearLayout>

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@+id/tab2"

android:orientation="vertical"

android:paddingTop="130px">

<TextView

android:layout_width="fill_parent"

android:layout_height="100px"

android:text="This is tab 2"

android:id="@+id/txt2"/>

</LinearLayout>

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@+id/tab3"

android:orientation="vertical"

android:paddingTop="130px">

<TextView

android:layout_width="fill_parent"

android:layout_height="100px"

android:text="This is tab 3"

android:id="@+id/txt3"/>

</LinearLayout>

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@+id/tab4"

android:orientation="vertical"

android:paddingTop="130px">

<TextView

android:layout_width="fill_parent"

android:layout_height="100px"

android:text="This is tab 4"

android:id="@+id/txt4"/>

</LinearLayout>

</FrameLayout>

</TabHost>

Now have a look on tabhost.xml file, heres the following code

xml version="1.0" encoding="utf-8"?>

<TabHost android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@+id/tabHost"

xmlns:android=http://schemas.android.com/apk/res/android>

<TabWidget

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:id="@android:id/tabs"/>

<FrameLayout

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@android:id/tabcontent">

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:id="@+id/tab1"

android:orientation="vertical"

android:paddingTop="60px">

<TextView

android:layout_width="fill_parent"

android:layout_height="100px"

android:text="This is tab1"

android:id="@+id/txt1"/>

</LinearLayout>

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@+id/tab2"

android:orientation="vertical"

android:paddingTop="60px">

<TextView

android:layout_width="fill_parent"

android:layout_height="100px"

android:text="This is tab 2"

android:id="@+id/txt2"/>

</LinearLayout>

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:id="@+id/tab3"

android:orientation="vertical"

android:paddingTop="60px">

<TextView

android:layout_width="fill_parent"

android:layout_height="100px"

android:text="This is tab 3"

android:id="@+id/txt3"/>

</LinearLayout>

</FrameLayout>
</TabHost>

and finally the last xml file tabs_bg.xml

xml version="1.0" encoding="utf-8"?>

LinearLayout xmlns:android=http://schemas.android.com/apk/res/android

android:id="@+id/tabsLayout" android:layout_width="fill_parent"

android:layout_height="fill_parent" android:background="@drawable/tab_bg_selector"

android:padding="10dip" android:gravity="center" android:orientation="vertical">

<TextView android:id="@+id/tabsText" android:layout_width="wrap_content"

android:layout_height="wrap_content" android:text="Title"

android:textSize="15dip" android:textColor="@drawable/tab_text_selector" />

LinearLayout>

A vegetarian leaks.

2012-06-17T22:45:00.001-07:00

A vegetarian leaks.

Google maps tutorial in android

2012-06-17T08:42:00.002-07:00

Come on guys now lets see how to use Google maps in Android,

 
 //GMapsActivity .java//

package com.mahesh.android.googlemaps;

import java.util.List;

import android.graphics.drawable.Drawable;

import android.os.Bundle;

import com.google.android.maps.GeoPoint;

import com.google.android.maps.MapActivity;

import com.google.android.maps.MapController;

import com.google.android.maps.MapView;

import com.google.android.maps.Overlay;

import com.google.android.maps.OverlayItem;

public class GMapsActivity extends MapActivity {

    private MapView mapView;

    private static final int latitudeE6 = 37985339;

    private static final int longitudeE6 = 23716735;

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        mapView = (MapView) findViewById(R.id.map_view);       

        mapView.setBuiltInZoomControls(true);

        List<overlay> mapOverlays = mapView.getOverlays();

        Drawable drawable = this.getResources().getDrawable(R.drawable.icon);

        CustomItemizedOverlay itemizedOverlay = 

             new CustomItemizedOverlay(drawable, this);

        GeoPoint point = new GeoPoint(latitudeE6, longitudeE6);

        OverlayItem overlayitem = 

             new OverlayItem(point, "Hello", "I'm in Athens, Greece!");

        itemizedOverlay.addOverlay(overlayitem);

        mapOverlays.add(itemizedOverlay);

        MapController mapController = mapView.getController();

        mapController.animateTo(point);

        mapController.setZoom(6);

    }

    @Override

    protected boolean isRouteDisplayed() {

        return false;

    }

}

 
 //CustomItemizedOverlay .java//

package com.mahesh.android.googlemaps;

import java.util.ArrayList;

import android.app.AlertDialog;

import android.content.Context;

import android.graphics.drawable.Drawable;

import com.google.android.maps.ItemizedOverlay;

import com.google.android.maps.OverlayItem;

public class CustomItemizedOverlay extends ItemizedOverlay<OverlayItem> {

   private ArrayList<OverlayItem> mapOverlays = new ArrayList<OverlayItem>();

   private Context context;

   public CustomItemizedOverlay(Drawable defaultMarker) {

        super(boundCenterBottom(defaultMarker));

   }

   public CustomItemizedOverlay(Drawable defaultMarker, Context context) {

        this(defaultMarker);

        this.context = context;

   }

   @Override

   protected OverlayItem createItem(int i) {

      return mapOverlays.get(i);

   }

   @Override

   public int size() {

      return mapOverlays.size();

   }

   @Override

   protected boolean onTap(int index) {

      OverlayItem item = mapOverlays.get(index);

      AlertDialog.Builder dialog = new AlertDialog.Builder(context);

      dialog.setTitle(item.getTitle());

      dialog.setMessage(item.getSnippet());

      dialog.show();

      return true;

   }

   public void addOverlay(OverlayItem overlay) {

      mapOverlays.add(overlay);

       this.populate();

   }

}

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout

 xmlns:android="http://schemas.android.com/apk/res/android"

 android:orientation="vertical"

 android:layout_width="fill_parent"

 android:layout_height="fill_parent">

 <com.google.android.maps.MapView

  xmlns:android="http://schemas.android.com/apk/res/android"

  android:id="@+id/map_view"

  android:layout_width="fill_parent"

  android:layout_height="fill_parent"

  android:clickable="true"

  android:enabled="true"

  android:apiKey="API-KEY-HERE" />

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

      package="com.javacodegeeks.android.googlemaps"

      android:versionCode="1"

      android:versionName="1.0">

    <application android:icon="@drawable/icon" android:label="@string/app_name">

        <activity android:name=".GMapsActivity"

                  android:label="@string/app_name">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

      <uses-library android:name="com.google.android.maps" />

    </application>

    <uses-permission android:name="android.permission.INTERNET"/>

</manifest>

Parsing Xml data and deploying into list view in android

2012-06-17T07:41:00.002-07:00

In this part we will talk a bit about importing and parsing XML data into a Android ListView. We will cover the following points:

Make a HTTP request to get the data from the webservice
Parse a XML document and read the contents
Make a custom ListView with the data from the webservice

On the bottom you can download the source code. But lets runÂ throughÂ the some important parts first. So lets start on the top:

The HTTP request

We will use this URL: http://p-xr.com/xml.Â Its static, but you can make your own dynamic XML output by following this tutorial . The following code is the XML output:

 
<results count="6">

<result>

      <id>1</id>

      <name>Mark</name>

      <score>6958</score>

  </result>

  <result>

      <id>2</id>

      <name>Wesley</name>

      <score>4039</score>

  </result>

  <result>

      <id>3</id>

      <name>Roy</name>

      <score>3809</score>

  </result>

  <result>

      <id>4</id>

      <name>Mike</name>

      <score>1980</score>

  </result>

  <result>

      <id>5</id>

      <name>Tina</name>

      <score>24</score>

  </result>

  <result>

      <id>6</id>

      <name>Ike</name>

      <score>3</score>

  </result>

</results>

In Android its pretty simple to make a HTTP request:

public static String getXML(){

        String line = null;

        try {

            DefaultHttpClient httpClient = new DefaultHttpClient();

            HttpPost httpPost = new HttpPost("http://p-xr.com/xml");

            HttpResponse httpResponse = httpClient.execute(httpPost);

            HttpEntity httpEntity = httpResponse.getEntity();

            line = EntityUtils.toString(httpEntity);

        } catch (UnsupportedEncodingException e) {

            line = "<results status=\"error\"><msg>Can't connect to server</msg></results>";

        } catch (MalformedURLException e) {

            line = "<results status=\"error\"><msg>Can't connect to server</msg></results>";

        } catch (IOException e) {

            line = "<results status=\"error\"><msg>Can't connect to server</msg></results>";

        }

        return line;

}

A hard part is to actually read the XML So lets take a look there

Parse an XML document

To read an XML structure we will parse it to a Document. See the following code to learn how its done:

 
public Document XMLfromString(String xml){

    Document doc = null;

    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

        try {

        DocumentBuilder db = dbf.newDocumentBuilder();

        InputSource is = new InputSource();

            is.setCharacterStream(new StringReader(xml));

            doc = db.parse(is); 

        } catch (ParserConfigurationException e) {

            System.out.println("XML parse error: " + e.getMessage());

            return null;

        } catch (SAXException e) {

            System.out.println("Wrong XML file structure: " + e.getMessage());

            return null;

        } catch (IOException e) {

            System.out.println("I/O exeption: " + e.getMessage());

            return null;

        }

        return doc;

    }

Well Now we have got the data + we imported the XML structure into a Document. Lets see if we can put this into a nice ListView.

Make a custom ListView from the XML

Now we take what we learned and make a ListView with the data. The following script is a piece from the Activity and itÂ does the following:

Extends a ListActivity
A custom ListView with 2 lines in each list item
implementsÂ a onItemClick method

public class Main extends ListActivity {

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.listplaceholder);

        //Needed for the listItems

        ArrayList<hashmap<string, String="">> mylist = new ArrayList<hashmap<string, String="">>();

        //Get the xml string from the server

        String xml = XMLfunctions.getXML();

        Document doc = XMLfunctions.XMLfromString(xml);

        int numResults = XMLfunctions.numResults(doc);

        if((numResults <= 0)){

            Toast.makeText(Main.this, "Geen resultaten gevonden", Toast.LENGTH_LONG).show();

            finish();

        }

        NodeList nodes = doc.getElementsByTagName("result");

        //fill in the list items from the XML document

        for (int i = 0; i < nodes.getLength(); i++) {

            HashMap<string, String=""> map = new HashMap<string, String="">();  

            Element e = (Element)nodes.item(i);

            map.put("id", XMLfunctions.getValue(e, "id"));

            map.put("name", "Naam:" + XMLfunctions.getValue(e, "name"));

            map.put("Score", "Score: " + XMLfunctions.getValue(e, "score"));

            mylist.add(map);

        }       

        //Make a new listadapter

        ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.main,

                        new String[] { "name", "Score" },

                        new int[] { R.id.item_title, R.id.item_subtitle });

        setListAdapter(adapter);

        //Get the listView ( from: ListActivity )

        final ListView lv = getListView();

        lv.setTextFilterEnabled(true);

        lv.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                @SuppressWarnings("unchecked")

                HashMap<string, String=""> o = (HashMap<string, String="">) lv.getItemAtPosition(position);

                Toast.makeText(Main.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_LONG).show(); 

            }

        });

    }

}</string,></string,></string,></string,></hashmap<string,></hashmap<string,>

Have fun
Download: Source code / Eclipse project

Tutorial on Android Activity Life Cycle

2012-06-15T04:39:00.002-07:00

Activity Life Cycle(Android)

Let us understand the activity life cycle in android application . Activities in the system are managed as an activity stack. When a new activity is started, it is placed on the top of the stack and becomes the running activity — the previous activity always remains below it in the stack, and will not come to the foreground again until the new activity exits.

An activity has essentially four states:

If an activity in the foreground of the screen (at the top of the stack), it is active or running.
If an activity has lost focus but is still visible (that is, a new non-full-sized or transparent activity has focus on top of your activity), it is paused. A paused activity is completely alive (it maintains all state and member information and remains attached to the window manager), but can be killed by the system in extreme low memory situations.
If an activity is completely obscured by another activity, it is stopped. It still retains all state and member information, however, it is no longer visible to the user so its window is hidden and it will often be killed by the system when memory is needed elsewhere.
If an activity is paused or stopped, the system can drop the activity from memory by either asking it to finish, or simply killing its process. When it is displayed again to the user, it must be completely restarted and restored to its previous state.

The following diagram shows the important state paths of an Activity. The square rectangles represent callback methods you can implement to perform operations when the Activity moves between states. The colored ovals are major states the Activity can be in.

There are three key loops you may be interested in monitoring within your activity:

The entire lifetime of an activity happens between the first call to onCreate(Bundle) through to a single final call to onDestroy(). An activity will do all setup of “global” state in onCreate(), and release all remaining resources in onDestroy(). For example, if it has a thread running in the background to download data from the network, it may create that thread in onCreate() and then stop the thread in onDestroy().
The visible lifetime of an activity happens between a call to onStart() until a corresponding call to onStop(). During this time the user can see the activity on-screen, though it may not be in the foreground and interacting with the user. Between these two methods you can maintain resources that are needed to show the activity to the user. For example, you can register a BroadcastReceiver in onStart() to monitor for changes that impact your UI, and unregister it in onStop() when the user an no longer see what you are displaying. The onStart() and onStop() methods can be called multiple times, as the activity becomes visible and hidden to the user.
The foreground lifetime of an activity happens between a call to onResume() until a corresponding call to onPause(). During this time the activity is in front of all other activities and interacting with the user. An activity can frequently go between the resumed and paused states — for example when the device goes to sleep, when an activity result is delivered, when a new intent is delivered — so the code in these methods should be fairly lightweight.

The entire lifecycle of an activity is defined by the following Activity methods. All of these are hooks that you can override to do appropriate work when the activity changes state. All activities will implement onCreate(Bundle) to do their initial setup; many will also implement onPause() to commit changes to data and otherwise prepare to stop interacting with the user. You should always call up to your superclass when implementing these methods.


 public class Activity extends ApplicationContext {

     protected void onCreate(Bundle savedInstanceState);
protected void onStart();



     protected void onResume();
protected void onRestart();

     protected void onPause();



protected void onStop();

     protected void onDestroy();
 

}

Here is a short tutorial for explaining android activity life cycle ..

1. Download source code from this site

2. go File ->Import and select unzip version of source code folder .

3. Run and see at LogCat different states of your TestActivity .

If you do not how to use logCat, in last post we have covered running logcat and viewing states in android.

Code Example

package com.biplob.TestActivity;

import android.app.Activity;

import android.os.Bundle;

import android.util.Log;

public class TestActivity extends Activity {

/** Called when the activity is first created. */

private final static String TAG=”TestActivity”;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Log.i(TAG,”On Create”);

}

protected void onDestroy() {

// TODO Auto-generated method stub

super.onDestroy();

Log.i(TAG,”On Destroy”);

}

protected void onPause() {

// TODO Auto-generated method stub

super.onPause();

Log.i(TAG,”On Pause”);

}

protected void onRestart() {

// TODO Auto-generated method stub

super.onRestart();

Log.i(TAG,”On Restart”);

}

protected void onResume() {

// TODO Auto-generated method stub

super.onResume();

Log.i(TAG,”On Resume”);

}

protected void onStart() {

// TODO Auto-generated method stub

super.onStart();

Log.i(TAG,”On Start”);

}

protected void onStop() {

// TODO Auto-generated method stub

super.onStop();

Log.i(TAG,”On Stop”);

}

Unzip TestActivity project and import from eclipse(select File->Import …

Select Existing projects into workspace and click next button

Click on Browse button and give the path of TestActivity project folder.

Click Finish and now run it. Wait a moment ….You will get the following screen.

To see logcat message click DDMS from right top of eclipse click LogCat View .

You will get a screen like this.

Simple Music player code for Android.

2012-06-15T03:20:00.002-07:00

Simple Music player code for Android.
Here i want to write about my first experience in Android Dev.
This application just play embedded in application mp3 file. That’s all.
In first step i create a simple Android UI. Below you can see this:

 The source text (main.xml) of this UI is:

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout

android:id="@+id/widget31"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

xmlns:android="http://schemas.android.com/apk/res/android">

    <Button

        android:text="@string/play_str"

        android:textSize="15pt"

        android:textStyle="bold"

        android:id="@+id/ButtonPlayStop"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"/>

    <SeekBar

        android:id="@+id/SeekBar01"

        android:layout_height="wrap_content"

        android:layout_width="fill_parent"

        android:layout_below="@id/ButtonPlayStop"/>

</RelativeLayout>

In my simple mp3 media player i have few string constans, like “PLAY”, “PAUSE”, etc. The best practice is place this constats in special part of project. That part call values. In this part i Eclipse create for me strings.xml file and change it. Bellow you can see strings.xml content:

<?xml version="1.0" encoding="utf-8"?>

<resources>

    <string name="app_name">Android mp3 player</string>

    <string name="play_str">PLAY</string>

    <string name="pause_str">PAUSE</string>

</resources>

It’s very simple and useful practice.

Next i make changes in Activity file (Mp3player.java). Bellow i give you some comments about it:

package com.hrupin.mp3player;

import com.hrupin.mp3player.R;

import android.app.Activity;

import android.media.MediaPlayer;

import android.os.Bundle;

import android.os.Handler;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnClickListener;

import android.view.View.OnTouchListener;

import android.widget.Button;

import android.widget.SeekBar;

public class Mp3player extends Activity {

    private Button buttonPlayStop;

    private MediaPlayer mediaPlayer;

    private SeekBar seekBar;

    private final Handler handler = new Handler();

    public void onCreate(Bundle icicle) {

            super.onCreate(icicle);

            setContentView(R.layout.main);

  initViews();  

}

    private void initViews() {

        buttonPlayStop = (Button) findViewById(R.id.ButtonPlayStop);

        buttonPlayStop.setOnClickListener(new OnClickListener() {@Override public void onClick(View v) {buttonClick();}});

        mediaPlayer = MediaPlayer.create(this, R.raw.testsong_20_sec); 

        seekBar = (SeekBar) findViewById(R.id.SeekBar01);

        seekBar.setMax(mediaPlayer.getDuration());

    seekBar.setOnTouchListener(new OnTouchListener() {@Override public boolean onTouch(View v, MotionEvent event) {

            seekChange(v);

            return false; }

        });

    }

    public void startPlayProgressUpdater() {

        seekBar.setProgress(mediaPlayer.getCurrentPosition());

        if (mediaPlayer.isPlaying()) {

        Runnable notification = new Runnable() {

                public void run() {

                    startPlayProgressUpdater();

}

            };

            handler.postDelayed(notification,1000);

        }else{

         mediaPlayer.pause();

            buttonPlayStop.setText(getString(R.string.play_str));

            seekBar.setProgress(0);

        }

    } 

    // This is event handler thumb moving event

    private void seekChange(View v){

        if(mediaPlayer.isPlaying()){

            SeekBar sb = (SeekBar)v;

            mediaPlayer.seekTo(sb.getProgress());

     }

    }

    // This is event handler for buttonClick event

    private void buttonClick(){

        if (buttonPlayStop.getText() == getString(R.string.play_str)) {

            buttonPlayStop.setText(getString(R.string.pause_str));

            try{

                mediaPlayer.start();

                startPlayProgressUpdater();

            }catch (IllegalStateException e) {

                mediaPlayer.pause();

            }

        }else {

            buttonPlayStop.setText(getString(R.string.play_str));

            mediaPlayer.pause();

        }

    }

}

Types of Intents in android

2012-06-15T03:04:00.001-07:00

Types of Intents and Activities in Android....
However, just one more detail to be introduced as promised and that is -
There are 2 types of intents that Android understands.
1. Explicit Intent
2. Implicit Intent
In an Explicit intent, you actually specify the activity that is required to respond to the intent. In other words, you explicitly designate the target component. This is typically used for application internal messages.

In an Implicit intent (the main power of the android design), you just declare an intent and leave it to the platform to find an activity that can respond to the intent. Here, you do not declare the target component and hence is typically used for activating components of other applications seamlessly

There are 2 types activities

1. InvokingActivity
2. InvokedActivity

The InvokingActivity has a button "Invoke Next Activity" which when clicked explicitly calls the "InvokedActivity" class.
The relevant part of the code is here:

Button invokingButton = (Button)findViewById(R.id.invokebutton);
invokingButton.setOnClickListener(new OnClickListener() {

public void onClick(View v) {
Intent explicitIntent = new Intent(InvokingActivity.this,InvokedActivity.class);
startActivity(explicitIntent);
}
});

NOTE: The layout for InvokingActivity is defined in main.xml and for InvokedActivity in InvokedActivity.xml. The downloadable example can be opened in Eclipse Ganymede as an android project and can be executed.

Guys these are the basic Android interview questions

2012-06-15T02:40:00.003-07:00

What is Android?Android is a stack of software for mobile devices which includes an Operating System, middleware and some key applications. The application executes within its own process and its own instance of Dalvik Virtual Machine. Many Virtual Machines run efficiently by a DVM device. DVM executes Java languages byte code which later transforms into .dex format files.

What is an Activity?
A single screen in an application, with supporting Java code.

What is an Intent?
A class (Intent) which describes what a caller desires to do. The caller will send this intent to Android's intent resolver, which finds the most suitable activity for the intent. E.g. opening a PDF document is an intent, and the Adobe Reader apps will be the perfect activity for that intent (class).

What is a Sticky Intent?
sendStickyBroadcast() performs a sendBroadcast(Intent) known as sticky, i.e. the Intent you are sending stays around after the broadcast is complete, so that others can quickly retrieve that data through the return value of registerReceiver(BroadcastReceiver, IntentFilter). In all other ways, this behaves the same as sendBroadcast(Intent). One example of a sticky broadcast sent via the operating system is ACTION_BATTERY_CHANGED. When you call registerReceiver() for that action -- even with a null BroadcastReceiver -- you get the Intent that was last broadcast for that action. Hence, you can use this to find the state of the battery without necessarily registering for all future state changes in the battery.

How the nine-patch Image different from a regular bitmap? Alternatively, what is the difference between nine-patch Image vs regular Bitmap Image?
It is one of a resizable bitmap resource which is being used as backgrounds or other images on the device. The NinePatch class allows drawing a bitmap in nine sections. The four corners are unscaled; the middle of the image is scaled in both axes, the four edges are scaled into one axis.

What is a resource?
A user defined JSON, XML, bitmap, or other file, injected into the application build process, which can later be loaded from code.

How will you record a phone call in Android? or How to handle an Audio Stream for a call in Android?
Permission.PROCESS_OUTGOING_CALLS: Will Allow an application to monitor, modify, or abort outgoing calls. So using that permission we can monitor the Phone calls.

Does Android support the Bluetooth serial port profile?
Yes.

Can an application be started on powerup?
Yes.

What is the APK format?
The APK file is compressed AndroidManifest.xml file with extension .apk. It also includes the application code (.dex files), resource files, and other files which are compressed into a single .apk file.

How to Translate in Android?
The Google translator translates the data of one language into another language by using XMPP to transmit data. You can type the message in English and select the language which is understood by the citizens of the country in order to reach the message to the citizens.

Describe Briefly the Android Application Architecture
Android Application Architecture has the following components:

Services like Network Operation
Intent - To perform inter-communication between activities or services
Resource Externalization - such as strings and graphics
Notification signaling users - light, sound, icon, notification, dialog etc.
Content Providers - They share data between applications

What is needed to make a multiple choice list with a custom view for each row?
Multiple choice list can be viewed by making the CheckBox android:id value be “@android:id /text1". That is the ID used by Android for the CheckedTextView in simple_list_item_multiple_choice.

What dialog boxes are supported in android?Android supports 4 dialog boxes:

AlertDialog: An alert dialog box supports 0 to 3 buttons and a list of selectable elements, including check boxes and radio buttons. Among the other dialog boxes, the most suggested dialog box is the alert dialog box.
ProgressDialog: This dialog box displays a progress wheel or a progress bar. It is an extension of AlertDialog and supports adding buttons.
DatePickerDialog: This dialog box is used for selecting a date by the user.
TimePickerDialog: This dialog box is used for selecting time by the user.

General Android questions

The Activity life cycle is must. Different phases of Activity Life cycle. For example: when and how the activity comes to foreground?
Knowledge on AndroidManifest file, For example: Why do we need this file, What is the role of this file in Android app development.
Different Kinds of Intents
Different Kinds of Context
Different Storage Methods in android
Kinds of Log debugger and Debugger Configuration
How to debug the application on real device.
How do you ensure that the app design will be consistent across the different screen resolutions
Thread concepts also plus points as we deal with the treads more.
Can you able to build custom views and how?
How to create flexible layouts, For example to place English, Chinese fonts.
What is localization and how to achieve?
What are 9-patch images
How to avoid ANR status
How to do Memory management
Inter Process Communication (IPC)
What is onCreate(Bundle savedInstanceState), Have you used savedInstanceState when and why?
Fragments in an Activity
When to use a service
How to use a broadcast receiver and register it both in the manifest and in code
Intent filters
The types of flags to run an application
How to do data intensive calculations using threads
Passing large objects (that can't be passed via intents and shouldn't be serialized) via a service
Binding to a service and the service lifecycle
How to persist data (both savedInstanceState and more permanent ways)

Let us know if you have any other questions that should be added in the list. And don't forget to share!

Code Snippets:
————————
How to start a browser instance with some url ?

1Intent intent = new Intent(Intent.ACTION_VIEW);

2Uri u = Uri.parse("http://google.com");

3intent.setData(u);

4startActivity(intent);

//Function called when return from a sub activity.

1protected void onActivityResult(int requestCode, int resultCode, String data, Bundle extras) {

2}

//How to retrieve the device IMEI Number

1TelephonyManager mTelephonyMgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);

2imei = mTelephonyMgr.getDeviceId();

How to call a subactivity?

 
1Intent intent = new Intent(this, SubActivity.class);

2//to pass data

3addintent.putExtra(name, value);

4startActivityForResult(intent, int);

Android Developer

2012-06-15T02:28:00.001-07:00