尝试从自定义列表视图中获取EditText的总值时是否为空指针异常？

Question

在这里，我尝试从自定义def sliding(string, k): return [string[i:i+k] for i in range(len(string)-k+1)] 获取EditText的值，并添加ListView的所有值。当列表项为3或小于3时，它运行良好但是当列表视图的项目是4或大于4时，它会抛出空指针异常。我认为它是由于ListView的不可见项而发生的....但是如何我能解决吗???

EditText

logcat的

etPayAmount.addTextChangedListener(new TextWatcher() {
    @Override
    public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {

    }

    @Override
    public void onTextChanged(CharSequence cs, int i, int i2, int i3) {

    }

    @Override
    public void afterTextChanged(Editable editable) {

            int count = lvRePayment.getCount();// count number of item in listview
            double sum = 0;
        Toast.makeText(getApplicationContext(),"child of listview: "+count,Toast.LENGTH_SHORT).show();
            for (int i = 0; i <count; i++) {
                LinearLayout layout = (LinearLayout) lvRePayment.getChildAt(i);// get child from first linear layout

                LinearLayout innerLayout = (LinearLayout) layout.getChildAt(1); // get child from inner linear layout

                if (innerLayout.getChildCount() > 1) {
                    EditText editText = (EditText) (innerLayout).getChildAt(1);
                    try {
                        double totalPayment = Double.parseDouble(editText.getText().toString());
                        sum += totalPayment;
                    }
                    catch (Exception e) {
                    }
                }
            }
            etTotalPay.setText(String.valueOf(sum));
            pay = sum;
            double balance = totalAmount - pay;
            etBalance.setText(String.valueOf(balance));

    }
});