Android : Update ImageView on listview click event

I am trying to get an image on my BikeActivity to update when a row is clicked in the Custom adapter but I am having trouble finding the code to do so and everything i've tried has resulted in the program crashing..

I want the ImageView iv to update on a listitem click and update with the image on that row in the array, any help is appreciated! Cheers.

    public class BikeActivity extends Activity {

    ListView lv;
    Context context;
    TextView tv;
    ImageView iv;
    ArrayList prgmName;
    public static int [] prgmImages={R.drawable.images1,R.drawable.images2,R.drawable.images3,R.drawable.images4,R.drawable.images5,R.drawable.images6};
    public static String[] bikes = new String[]{
        "Liteville 301,  Enduro",
                "Liteville 601,  Downhill",
                "Liteville 901,  Downhill",
                "Liteville Marathon, XC",
                "Liteville Werksmachine, Freeride",
                "Liteville AllMountain"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bike);

        context=this;

        lv=(ListView) findViewById(R.id.listView);
        lv.setAdapter(new CustomAdapter(this, bikes,prgmImages));
        iv=(ImageView) findViewById(R.id.imageView2);
        iv.setImageResource(R.drawable.images1);
        tv=(TextView) findViewById(R.id.textinfo);
        tv.setText(String.valueOf("BLAHBLAHTESTESTLDKSJHF:"));






    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {


        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_bike, menu);
        return true;
    }

}

Code for the custom adapter:

    public class CustomAdapter extends BaseAdapter{
    String [] result;
    Context context;
    int [] imageId;
    private static LayoutInflater inflater=null;
    public CustomAdapter(BikeActivity bikeActivity, String[] bikes, int[] prgmImages) {
    // TODO Auto-generated constructor stub
    result=bikes;
    context=bikeActivity;
    imageId=prgmImages;
    inflater = ( LayoutInflater )context.
            getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {

    return result.length;
}

@Override
public Object getItem(int position) {
    return position;
}

@Override
public long getItemId(int position) {
    // TODO Auto-generated method stub
    return position;
}

public class Holder
{
    TextView tv;
    ImageView img;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    final Holder holder=new Holder();
    View rowView;

    rowView = inflater.inflate(R.layout.list_item, null);
    holder.tv=(TextView) rowView.findViewById(R.id.textView1);
    holder.img=(ImageView) rowView.findViewById(R.id.imageView1);

    holder.tv.setText(result[position]);
    holder.img.setImageResource(imageId[position]);


    rowView.setOnClickListener(new OnClickListener() {


        @Override
        public void onClick(View v) {


         Toast.makeText(context, ""+result[position], Toast.LENGTH_LONG).show();
        }
    });

    return rowView;

}



}