اشکال در لیست ویو بسیار فوری

سلام من یک لیست ویو دارم که کاملا مطابق با آموزش های استاده فقط آیتم های UI فرق دارن اما وقتی اسکرول می کنم مقدار قبلیشونو از دست میدن !!!! تورو خدا کمکم کنید ....

 public class AdapterPiece extends ArrayAdapter<StructPiece> {

    public AdapterPiece(ArrayList<StructPiece> array) {
        super(G.context, R.layout.adapter_piece, array);
    }


    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder holder;
        StructPiece item = getItem(position);
        if (convertView == null) {
            convertView = G.inflater.inflate(R.layout.adapter_piece, parent, false);
            holder = new ViewHolder(convertView);
            convertView.setTag(holder);
        }
        else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.fill(this, item, position);
        return convertView;
    }


    private static class ViewHolder {

        public TextView itemNumber;
        public EditText edtnumber;
        public EditText edtLength;
        public EditText edtWidth;


        public ViewHolder(View view) {

            itemNumber = (TextView) view.findViewById(R.id.txtNumber);
            edtnumber = (EditText) view.findViewById(R.id.edtNumber);
            edtLength = (EditText) view.findViewById(R.id.edtLength);
            edtWidth = (EditText) view.findViewById(R.id.edtWidth);
        }


        public void fill(ArrayAdapter<StructPiece> adapter, final StructPiece item, int position) {

            edtLength.setText("" + item.Length);
            edtWidth.setText("" + item.width);
            edtnumber.setText("" + item.numOfPieces);
            itemNumber.setText("" + (position + 1));

            item.Length = Double.parseDouble(edtLength.getText().toString());
            item.width = Double.parseDouble(edtWidth.getText().toString());
            item.numOfPieces = Integer.parseInt(edtnumber.getText().toString());

        }
    }
}

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public class ActivityPieces extends Activity {

    public ArrayAdapter adapter;
    public static int   numberOfPieces = 0;


    @Override
    protected void onResume() {
        G.currentActivity = this;
        super.onResume();

        if (adapter != null) {
            adapter.notifyDataSetChanged();
        }
    }


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.form_pieces);

        Typeface btnFont = Typeface.createFromAsset(getAssets(), "mj_freehand.ttf");

        ListView listPieces = (ListView) findViewById(R.id.listPieces);
        Button btnAdd = (Button) findViewById(R.id.btnAdd);
        btnAdd.setTypeface(btnFont);

        adapter = new AdapterPiece(G.pieces);
        listPieces.setAdapter(adapter);

        btnAdd.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {

            }
        });

        for (int i = 0; i < 10; i++) {
            StructPiece piece = new StructPiece();
            G.pieces.add(piece);
            adapter.notifyDataSetChanged();
        }

    }
}