How to prevent ViewFlipper from looping

I am developing an application in which I am using a ViewFlipper with a custom OnTouch implementation. In the ViewFlipper, I have about 20 images for the user to flip through. This works fine, but if I'm at the 20th image in the series and flip the screen, it returns to the first image.

I want to prevent the ViewFlipper from looping back to the first image. Instead, it should simply stop at the last image.

Here is my code:

import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.animation.AnimationUtils;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.Spinner;
import android.widget.ViewFlipper;

public class Activity1 extends Activity implements OnTouchListener{

    float downXValue;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Set main.XML as the layout for this Activity
        setContentView(R.layout.main);

        // Add these two lines
        LinearLayout layMain = (LinearLayout) findViewById(R.id.layout_main);
        layMain.setOnTouchListener((OnTouchListener) this); 

        // Add a few countries to the spinner
        Spinner spinnerCountries = (Spinner) findViewById(R.id.spinner_country);
        ArrayAdapter countryArrayAdapter = new ArrayAdapter(this,
                    android.R.layout.simple_spinner_dropdown_item,
                    new String[] { "Canada", "USA" });
        spinnerCountries.setAdapter(countryArrayAdapter);

    }

    public boolean onTouch(View arg0, MotionEvent arg1) {

        // Get the action that was done on this touch event
        switch (arg1.getAction())
        {
            case MotionEvent.ACTION_DOWN:
            {
                // store the X value when the user's finger was pressed down
                downXValue = arg1.getX();
                break;
            }

            case MotionEvent.ACTION_UP:
            {
                // Get the X value when the user released his/her finger
                float currentX = arg1.getX();            

                // going backwards: pushing stuff to the right
                if (downXValue < currentX)
                {
                    // Get a reference to the ViewFlipper
                     ViewFlipper vf = (ViewFlipper) findViewById(R.id.details);
                     // Set the animation
                      vf.setAnimation(AnimationUtils.loadAnimation(this, R.anim.push_left_out));
                      // Flip!
                      vf.showPrevious();
                }

                // going forwards: pushing stuff to the left
                if (downXValue > currentX)
                {
                    // Get a reference to the ViewFlipper
                    ViewFlipper vf = (ViewFlipper) findViewById(R.id.details);
                     // Set the animation
                     vf.setInAnimation(AnimationUtils.loadAnimation(this, R.anim.push_left_in));
                      // Flip!
                     vf.showNext();
                }
                break;
            }
        }

        // if you return false, these actions will not be recorded
        return true;
    }

}

And the XML layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/layout_main"
    >

    <ViewFlipper android:id="@+id/details"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">  


      <LinearLayout
               android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >

            <ImageView android:id="@+id/ImageView01" android:background="@drawable/two" 
            android:layout_x="1dip" android:layout_y="1dip" 
            android:layout_height="fill_parent" android:layout_width="fill_parent"></ImageView>
        </LinearLayout> 
         <LinearLayout
               android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >

            <ImageView android:id="@+id/ImageView01" android:background="@drawable/three" 
            android:layout_x="1dip" android:layout_y="1dip" 
            android:layout_height="fill_parent" android:layout_width="fill_parent"></ImageView>
        </LinearLayout> 
         <LinearLayout
               android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >

            <ImageView android:id="@+id/ImageView01" android:background="@drawable/four" 
            android:layout_x="1dip" android:layout_y="1dip" 
            android:layout_height="fill_parent" android:layout_width="fill_parent"></ImageView>
        </LinearLayout> 
         <LinearLayout
               android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >

            <ImageView android:id="@+id/ImageView01" android:background="@drawable/five" 
            android:layout_x="1dip" android:layout_y="1dip" 
            android:layout_height="fill_parent" android:layout_width="fill_parent"></ImageView>
        </LinearLayout> 
 <LinearLayout
               android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >

            <ImageView android:id="@+id/ImageView01" android:background="@drawable/six" 
            android:layout_x="1dip" android:layout_y="1dip" 
            android:layout_height="fill_parent" android:layout_width="fill_parent"></ImageView>
        </LinearLayout> 
         <LinearLayout
               android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >

            <ImageView android:id="@+id/ImageView01" android:background="@drawable/seven" 
            android:layout_x="1dip" android:layout_y="1dip" 
            android:layout_height="fill_parent" android:layout_width="fill_parent"></ImageView>
        </LinearLayout> 
         <LinearLayout
               android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >

            <ImageView android:id="@+id/ImageView01" android:background="@drawable/eight" 
            android:layout_x="1dip" android:layout_y="1dip" 
            android:layout_height="fill_parent" android:layout_width="fill_parent"></ImageView>
        </LinearLayout> 

    <ViewFlipper>
 </LinearLayout>

You know that there are 20 children in the viewflipper. Therefore make an if statement in the onclick that checks if the getDisplayedChild() is lower then 20. If it is 20 or higher then just dont call showNext().