项目中一些细节东西

1 需要输入金额的时候，限制输入两位小数，以及小数点不能出现在第一位，只能输入一个小数点 

 amountInput.setFilters(new InputFilter[]{new InputFilter() {//设置输入两位小数
@Override
public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
if (source.equals(".") && dest.toString().length() == 0) {
return "0.";
}
if (dest.toString().contains(".")) {
int index = dest.toString().indexOf(".");
int mlength = dest.toString().substring(index).length();
if (mlength == 3) {
return "";
}
}
return null;
}

}});

2 监听银行卡号的输入，每四位一个空格

changeCardNumber.addTextChangedListener(new TextWatcher() {
    int beforeTextLength = 0;
    int onTextLength = 0;
    boolean isChanged = false;

    int location = 0;// 记录光标的位置
    private char[] tempChar;
    private StringBuffer buffer = new StringBuffer();
    int konggeNumberB = 0;

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count,
                                  int after) {
        beforeTextLength = s.length();
        if (buffer.length() > 0) {
            buffer.delete(0, buffer.length());
        }
        konggeNumberB = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == ' ') {
                konggeNumberB++;
            }
        }
    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before,
                              int count) {
        onTextLength = s.length();
        buffer.append(s.toString());
        if (onTextLength == beforeTextLength || onTextLength <= 3
                || isChanged) {
            isChanged = false;
            return;
        }
        isChanged = true;
    }

    @Override
    public void afterTextChanged(Editable s) {
        if (isChanged) {
            location = changeCardNumber.getSelectionEnd();
            int index = 0;
            while (index < buffer.length()) {
                if (buffer.charAt(index) == ' ') {
                    buffer.deleteCharAt(index);
                } else {
                    index++;
                }
            }

            index = 0;
            int konggeNumberC = 0;
            while (index < buffer.length()) {
                if ((index == 4 || index == 9 || index == 14 || index == 19)) {
                    buffer.insert(index, ' ');
                    konggeNumberC++;
                }
                index++;
            }

            if (konggeNumberC > konggeNumberB) {
                location += (konggeNumberC - konggeNumberB);
            }

            tempChar = new char[buffer.length()];
            buffer.getChars(0, buffer.length(), tempChar, 0);
            String str = buffer.toString();
            if (location > str.length()) {
                location = str.length();
            } else if (location < 0) {
                location = 0;
            }
            changeCardNumber.setText(str);
            Editable etable = changeCardNumber.getText();
            Selection.setSelection(etable, location);
            isChanged = false;
        }
    }
});

  用String.replace的方法获取到不带空格的字符串

3  不四舍五入的截取小数点后两位

DecimalFormat format=new DecimalFormat("#.00");
format.setRoundingMode(RoundingMode.FLOOR);
double tt=Double.parseDouble(format.format(num));