Alert Dialog When User Press Back Button

Override  the following method  of Activity to add Key event into Android Application.

   @Override  
 public boolean onKeyDown(int keyCode, KeyEvent event) {  
   if ((keyCode == KeyEvent.KEYCODE_BACK)) {  
     AlertDialog.Builder alertbox = new AlertDialog.Builder(HomeActivity.this);  
     alertbox.setIcon(R.drawable.info_icon);  
     alertbox.setTitle("You Want To Exit Programm");  
     alertbox.setPositiveButton("Yes", new DialogInterface.OnClickListener() {  
       public void onClick(DialogInterface arg0, int arg1) {   
         // finish used for destroyed activity  
         finish();  
       }  
     });  
     alertbox.setNegativeButton("No", new DialogInterface.OnClickListener() {  
       public void onClick(DialogInterface arg0, int arg1) {  
           // Nothing will be happened when clicked on no button   
           // of Dialog     
      }  
     });  
     alertbox.show();  
   }  
   return super.onKeyDown(keyCode, event);  
 }