Android编辑文本焦点在可扩展列表视图中输入内容后消失

Question

我的编辑文字有问题。我在子视图中为每个组编辑了文本，我可以动态添加新组，当我键入最初可以放入屏幕的组的编辑文本时，焦点仍然指向编辑文本，但是当我点击编辑文本以键入我需要向下滚动的那些组，在我键入任何第一个字符后，编辑文本焦点突然消失并随机指向这怎么可能发生？我希望这张照片足以让你理解。我的适配器代码：

@Override
    public View getGroupView(final int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {

        LayoutInflater inflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.personal_loan_list_group, null);

        TextView titleText = (TextView) convertView.findViewById(R.id.lblListHeader);
        Button deleteBtn = (Button) convertView.findViewById(R.id.deleteBtn);
        titleText.setText("Group" + " " + (groupPosition+1));
        deleteBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                customer.removePersonalLoan(groupPosition);
                notifyDataSetChanged();
            }
        });
        return convertView;
    }

    @Override
    public View getRealChildView(final int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.personal_loan_list_item, null);

        final CustomEditText installmentText = (CustomEditText) convertView.findViewById(R.id.installmentET);
        installmentText.setTag("amount");

        installmentText.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
            }

            @Override
            public void afterTextChanged(Editable s) {
                try {
                    installmentText.removeTextChangedListener(this);
                    installmentText.setText("999");
                    installmentText.addTextChangedListener(this);
                } catch (Exception ex) {
                    ex.printStackTrace();
                    installmentText.addTextChangedListener(this);
                }
            }
        });

        return convertView;
    }