android - 如何使用 InputFilter 实现数字分组输入掩码？

Question

我正在使用 InputFilter 类制作一个支持数字分组的屏蔽 EditText。例如，当用户插入“12345”时，我想在 EditText 中显示“12,345”。我该如何实现？

这是我的不完整代码:

        InputFilter IF = new InputFilter() {
        @Override
        public CharSequence filter(CharSequence source, int start, int end,
                Spanned dest, int dstart, int dend) {

            for (int i = start; i < end; i++) {
                if (!Character.isLetterOrDigit(source.charAt(i))) {
                    return "";
                }
            }
            if (dest.length() > 0 && dest.length() % 3 == 0)
            {
                return "," + source;
            }
            return null;
        }
    };
    edtRadius.setFilters(new InputFilter[] { IF });

还有其他方法可以实现这种输入掩码吗？

Answer 1

这是对@vincent 回复的改进。它添加了对删除格式为 1234 5678 9190 的数字中的空格的检查，因此当尝试删除空格时，它只是将光标后退字符移动到空格之前的数字。即使插入空格，它也会将光标保持在相同的相对位置。

    mTxtCardNumber.addTextChangedListener(new TextWatcher() {

        private boolean spaceDeleted;

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

        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            // check if a space was deleted
            CharSequence charDeleted = s.subSequence(start, start + count);
            spaceDeleted = " ".equals(charDeleted.toString());
        }

        public void afterTextChanged(Editable editable) {
            // disable text watcher
            mTxtCardNumber.removeTextChangedListener(this);

            // record cursor position as setting the text in the textview
            // places the cursor at the end
            int cursorPosition = mTxtCardNumber.getSelectionStart();
            String withSpaces = formatText(editable);
            mTxtCardNumber.setText(withSpaces);
            // set the cursor at the last position + the spaces added since the
            // space are always added before the cursor
            mTxtCardNumber.setSelection(cursorPosition + (withSpaces.length() - editable.length()));

            // if a space was deleted also deleted just move the cursor
            // before the space
            if (spaceDeleted) {
                mTxtCardNumber.setSelection(mTxtCardNumber.getSelectionStart() - 1);
                spaceDeleted = false;
            }

            // enable text watcher
            mTxtCardNumber.addTextChangedListener(this);
        }

        private String formatText(CharSequence text)
        {
            StringBuilder formatted = new StringBuilder();
            int count = 0;
            for (int i = 0; i < text.length(); ++i)
            {
                if (Character.isDigit(text.charAt(i)))
                {
                    if (count % 4 == 0 && count > 0)
                        formatted.append(" ");
                    formatted.append(text.charAt(i));
                    ++count;
                }
            }
            return formatted.toString();
        }
    });