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));