android: Can i use different class for different c

I have different screen to work in an android application. I'm using ViewFlipper for this. I decided to used different class for different view children

public main extends Activity{
{
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.sign_in);
    ViewFlipper viewFlipper = (ViewFlipper) findViewById(R.id.viewFlipper);

HomeScreen s = new HomeScreen(getApplicationContext(), getCurrentFocus(), viewFlipper);
  }
}

and this the Homescreen class is :-

public class HomeScreen {
private Button signIn;
private Button createAccount;
private View v;
private Context context;
private ViewFlipper viewflipper;

public HomeScreen(Context context,View v,ViewFlipper viewflipper ) {
 this.v=v;
 this.context = context;
 this.viewflipper = viewflipper;


 signIn = (Button) v.findViewById(R.id.button_sign_in_homeScreen);
 createAccount = (Button)v.findViewById(R.id.button_createAccount_homeScreen);
 signIn.setOnClickListener(new View.OnClickListener() {
 public void onClick(View v) {
   viewflipper.setDisplayedChild(1);
  }
 });   
}

but is shows run exception java.lang.RuntimeException: Unable to start activity ComponentInfo Can anyone please help me
is getCurrentFocus() is the correct way to get the view?

What i try to implement is

I need to use different class for defining, listening the controls of each child of view flipper
In the above example HomeScreen is one of my the child screen of view flipper
But the line v.findViewById is showing error i think that getCurrentFocus() is not the correct way to sent the view

I don't know weather i'm moving in the correct way? When i define and listen all the controls of all children of viewflipper in the Class where i define that viewflpper, that class become very big. That made me to think so..

Thanks...

U can perfrom animation using Intent to:

Step1: create anim folder under res directory in ur project.

Step2: create an slideleft.xml file

Step3: type the following code in that file

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:anim/accelerate_interpolator">
    <translate android:fromXDelta="100%p" android:toXDelta="0"
        android:duration="400" />
</set>

step 4: similarly create slideright.xml

step5: use the above code, but change the following

<translate android:fromXDelta="-100%p" android:toXDelta="0"
            android:duration="400" />

step 6:

 target.startAnimation(AnimationUtils.loadAnimation(HomeScreen.this, R.anim.slide_left));

perfroming fadein operation, just add the following code in fadein.xml file

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

<alpha xmlns:android="http://schemas.android.com/apk/res/android"
       android:interpolator="@android:anim/accelerate_interpolator"
       android:fromAlpha="0.0" android:toAlpha="1.0"
       android:duration="300" />

similarly for fade out too

<?xml version="1.0" encoding="UTF-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
       android:interpolator="@android:anim/accelerate_interpolator"
       android:fromAlpha="1.0" android:toAlpha="0.0"
       android:duration="300" />