Android Interview Questions

1. What is Android?

2. Explain about Android architecture.

3. How to create Android library? What its use?

4. What is ADB, DDMS? What are the Android tools till now you have used?

5. How the APK file will be generated?

6. What is the process to publish an APK in Google Play?

7. What is the role of Android Manifest file in the Application?

8. What are the Android Application components?

9. What is Activity?

10. What are the Activity lifecycle methods?

11. Explain the activity lifecycle methods flow for the following Activity navigation:

 A->B->C->Dialog->close dialog

12. startActivity() vs startActivityForResult().

13. What is ANR? How you will handle that?

14. How to save activity state?

15. What is Intent?

16. How many types of intents?

17. What is IntentFilter?

18. What are the actions to launch Browser, Camera, Compose Mail?

19. How to send object from one activity to another activity?

20. How to share data between applications?

21. How to create ContentProviders? what are the methods will be used to retrieve data?

22. Where you have used ContentProviders? Give me some examples.

23. What is Service?

24. Types of Services. (Bound vs Unbound)

25. Service lifecycle methods.

26. Local service vs Remote service

27. What is AIDL file? What are the uses?

28. Service vs IntentService

29. What is BroadcastReceivers? How many types (Synchronous/Ordered and Asynchronous).

30. StickyIntent

31. PendingIntent

32. In which thread/state application components lifecycle methods will run? 

33. Thread vs Process

34. Thread vs Handler vs AsyncTask. Which is efficient in which situations?

35. What is Error and Exceptions?

36. How many types of Exceptions?

37. What are the Exceptions you have faced in Android?

38. What is difference between sleep(), wait(), yield() in Threads?

39. What is Synchronization?

40. What are the disadvantages of Synchronization?

41. What is Collections?

42. List vs Set

43. ArrayList vs Vector

44. HashTable vs HashMap vs HashSet

45. OOPS concepts, Interface, abstract, static, final keywords, Serialization …….

46. What is GCM? Explain briefly about GCM architecture and its implementation.

47. How to create a notification.

48. Explain briefly about integration of Facebook, Twitter and LinkedIn

49. What is Google Analytics? Its implementation.

50. How to implement Google Map in Android Application.

51. How to draw the route on Map? Overlays….

52. How to get the device location in Android? 

53. What are different types of Location Providers?

54. What permissions needful to get the location?

55. What is the best way to load huge number of large size images in List? Explain in detail.

56. How you will handle OutOfMemory Error?

57. What are the different types of Storage mechanisms?

58. Where I have to write / How to alter a table in SQLite database of an application, which was already published in Google Play?

59. How to check network connection available or not?

60. What are diff between Rest and Soap services?

61. How you will send an 1MB image to server?

62. JSON and XML parsing

63. SAX vs DOM vs XMLPull parser. Which is efficient in which situations?

64. What is Localization and how to achieve it in Android? 

65. How to change device locale?

66. What’s your procedure to support Arabic language in Android 2.2 and 4.2? 

67. How you design/ what’s your procedure to create an app to support in all resolutions?

68. Px vs Sp vs Dp vs Dip

69. What is Nine-patch image?

70. What are different types of layouts? ‘Match_Parent’ vs ‘Wrap_Content’.

71. How you will handle screen orientation?

72. What are the launch modes in Android? Explain…

73. How to achieve following scenario.

Activity ‘Login’: tap on button (Finishes current page) --> shows Activity A: tap on button --> shows Activity B: tap on button --> shows Activity C: tap on button ………--> shows Activity Z: tap on ‘Logout’ button -->shows Login screen. 

*Need to show previous activity, if user taps back button.

74. Have you created any Custom Components (By creating custom xml attributes)? What are those?

75. Have you integrated any payment tools? What are those? Explain the process of data navigation in that. (Google in-app Billing, Amazon, Authorize.net, Paypal …)

76. What is Fragments? Explain in brief.

77. What is NFC? Explain in brief.

78. Did you ever use Action bars? If yes how?

79. Do you have any knowledge on ‘Widgets’? Why we need to create these?

80. Have you used any animations in your app? What are those and how to use?

81. Do you have any knowledge on OpenGL?

82. Have you heard ‘Volley’ library? Do you have any knowledge on it?

83. What is the latest version of Android? What are its features?

84. What is coming Android Version? Do you any idea about what features will be included? 

Follow the links to get more questions:

http://www.blendinfotech.com/android-interview-questions-and-answers-for-2-years-experience

http://www.javacodegeeks.com/2011/08/android-interview-questions-answers.html

http://www.durgasoft.com/Android%20Interview%20Questions.pdf

Posting message on Twitter

I have used twitter4j-core-3.0.3.jar and twitter4j-media-support-3.0.3.jar for posting.

1. Create an instance of TwitterApp class by passing context, consumerKey and secretKey.
2. For handling twitter login callbacks we need to create a class which implements TwDialogListener interface.
3. Before sharing on Twitter, we needs to check user twitter authentication using hasAccessToken(). If the token available means valid user otherwise we needs to show login page using authorize().
4. First time hasAccessToken() value will be null. So, authorize() will be called and internally(in TwitterApp class) it will get the authorization url by using consumerKey, secretKey and callbackUrl.
5. After retrieving authorization url, it will be loaded in Twitter dialog using webview.
6. By using custom webview client, shouldOverrideUrlLoading() - checks each url whether it is starting with callbackUrl. If we get url starts with callbackUrl means authorization process completed. At this time we need to store accessToken and necessary information in shared preferences for future use.
7. After storing all the necessary details, mTwLoginDialogListener's onComplete() will be called. Here we need to post message on Twitter.
8. Using updateStatus() of StatusUpdate class, we can post message on Twitter.

package com.android.sot;

import twitter4j.StatusUpdate;
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

import com.android.sot.twitter.TwitterApp;
import com.android.sot.twitter.TwitterApp.TwDialogListener;

public class TwitterShare extends Activity
{
private static final String TWITTER_CONSUMER_KEY = "Your twitter consumer key";
private static final String TWITTER_SECRET_KEY = "Your twitter secret key";

private Handler mHandler;
private TwitterApp mTwitter;
private ProgressDialog progressdialog;

@Override
protected void onCreate(Bundle savedInstanceState)
{
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_twitter_share);

  mHandler = new Handler();
    mTwitter = new TwitterApp(this, TWITTER_CONSUMER_KEY,TWITTER_SECRET_KEY);
  mTwitter.setListener(mTwLoginDialogListener);

  Button btnShare = (Button) findViewById(R.id.btnShare);
  btnShare.setOnClickListener(new OnClickListener()
  {
    @Override
      public void onClick(View v)
      {
        if (mTwitter.hasAccessToken())
        postMsgOnTwitter("Hi, This is from Android App");
        else
        mTwitter.authorize();
    }
  });
}

private TwDialogListener mTwLoginDialogListener = new TwDialogListener()
{
  @Override
             public void onComplete(String value)
             {
      postMsgOnTwitter("Hi, This is from Android App");
             }

  @Override
             public void onError(String value)
             {
            showToast("Twitter login failed");
                    mTwitter.resetAccessToken();
              }
      };
 
      private void postMsgOnTwitter(final String msg)
      {
    showProgressDialog("sending tweet..");

  new Thread(new Runnable()
  {
    @Override
      public void run()
      {
        StatusUpdate status = new StatusUpdate(msg);

        try
        {
          mTwitter.updateStatus(status);

          hideProgressDialog();

          showToast("Posted successfully.");
        }
        catch (Exception e)
        {
          hideProgressDialog();

          showToast("Failed to Tweet");
          e.printStackTrace();
        }
    }
  }).start();
}
 
  public void showToast(final String msg)
{
  mHandler.post(new Runnable()
  {
    @Override
    public void run()
    {
      Toast.makeText(TwitterShare.this, msg, Toast.LENGTH_SHORT).show();
    }
  });
}

     /** This will shows a progress dialog with loading text, this is useful to call when some other                          *functionality is taking place.
  */
  public void showProgressDialog(String msg)
  {
    runOnUiThread(new RunShowLoader(msg, false));
  }

  /**
  * Implementing Runnable for runOnUiThread(), This will show a progress dialog
  */
class RunShowLoader implements Runnable
{
  private String strMsg;
  private boolean isCancalable;

  public RunShowLoader(String strMsg, boolean isCancalable)
  {
    this.strMsg = strMsg;
    this.isCancalable = isCancalable;
  }

  @Override
  public void run()
  {
    try
    {
      if(progressdialog == null ||(progressdialog != null && !progressdialog.isShowing()))
      {
        progressdialog = ProgressDialog.show(TwitterShare.this, "", strMsg);
        progressdialog.setCancelable(isCancalable);
      }
    }
    catch(Exception e)
    {
      progressdialog = null;
      e.printStackTrace();
    }
  }
}

  /** For hiding progress dialog **/
public void hideProgressDialog()
{
  runOnUiThread(new Runnable()
  {
    @Override
    public void run()
    {
      try
      {
        if(progressdialog != null && progressdialog.isShowing())
        {
          progressdialog.dismiss();
        }
        progressdialog = null;
      }
      catch(Exception e)
      {
        e.printStackTrace();
      }
    }
  });
}
}

You can download the full source from here

Sending a video file via Bluetooth by directly opening the Bluetooth default page

try
{
Intent int_bluetooth= new Intent();
int_bluetooth.setAction(Intent.ACTION_SEND);
int_bluetooth.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
int_bluetooth.setType("video/*");
int_bluetooth.putExtra(Intent.EXTRA_STREAM, Uri.parse("file://mnt/sdcard/poi.3gp"));
int_bluetooth.setClassName("com.android.bluetooth", "com.android.bluetooth.opp.BluetoothOppLauncherActivity");

startActivity(int_bluetooth);
}
catch(ActivityNotFoundException e)
{
Log.e("Bluetooth", e.toString());
}

Inserting an image in to Gallery

Bitmap bmpImg = BitmapFactory.decodeFile("/sdcard/hi.png");
MediaStore.Images.Media.insertImage(getContentResolver(), bmpImg, null, null);

Dispatching touch event of one view to aother view

Button btnFirst = new Button(this);
btnFirst.setOnTouchListener(new OnTouchListener()
{
@Override
public boolean onTouch(View v, MotionEvent event)
{
Log.i("First Button","This is first button's onTouch()");
return false;
}
}));

Button btnSecond = new Button(this);
btnSecond.setOnTouchListener(new OnTouchListener()
{
@Override
public boolean onTouch(View v, MotionEvent event)
{
btnFirst.dispatchTouchEvent(event);
return false;
}
}));