android:inputType="numberDecimal"

/** 输入框小数的位数*/
private static final int DECIMAL_DIGITS = 1;

InputFilter lengthfilter = new InputFilter() {
  public CharSequence filter(CharSequence source, int start, int end,
                Spanned dest, int dstart, int dend) {
    // 删除等特殊字符，直接返回
    if ("".equals(source.toString())) {
      return null;
    }
    String dValue = dest.toString();
    String[] splitArray = dValue.split("//.");
    if (splitArray.length > 1) {
      String dotValue = splitArray[1];
      int diff = dotValue.length() + 1 - DECIMAL_DIGITS;
      if (diff > 0) {
        return source.subSequence(start, end - diff);
      }
    }
    return null;
  }
};
et_content.setFilters(new InputFilter[] { lengthfilter });