Android : How to search in an AlertDialog Android

I have got a cursor that gets data out of the database and puts it in an AlertDialog. I want to add a search filter in this AlertDialog. Thus if a key is pressed, it has to find all the products with that character. I've tried it with a TextWatcher but it didn't work. Can you please help me out.

public void onClickSelectBrands(View view) {
        builder=new AlertDialog.Builder(AddProduct.this);
        builder.setTitle("Brands");         
        input = new EditText(this);     
        input.addTextChangedListener(filterTextWatcher);

    builder.setView(input);

    cursor = DatabaseHelper.fetchAllData("Brands");

    builder.setCursor(cursor, new DialogInterface.OnClickListener() {

        @Override
        public void onClick(DialogInterface dialog, int position) {
            // TODO Auto-generated method stub
            bid = cursor.getString(cursor
                    .getColumnIndexOrThrow(DatabaseHelper.KEY_ID));
            String name = cursor.getString(1);
            brandName.setText(name);
        }
    }, DatabaseHelper.KEY_NAME);
    dialog=builder.create();
    dialog.show();
}

private TextWatcher filterTextWatcher = new TextWatcher() {

    public void afterTextChanged(Editable s) {
    }

    public void beforeTextChanged(CharSequence s, int start, int count,
            int after) {
    }

    public void onTextChanged(CharSequence s, int start, int before,
            int count) {
        ((Filterable) builder).getFilter().filter(s);
    }
};

@Override
public void onStop(){
    input.removeTextChangedListener(filterTextWatcher);
}