作者：兜子

需求背景

我们需要做一个金额输入过滤器，限制小数点后只能输入两位数，以下解决方案，部分使用kotlin语言。

解决方案

  1. EditText的属性中先设置android:inputType=”numberDecimal”属性
  2. 新建一个类，继承DigitsKeyListener
  1. public class MoneyValueFilter extends DigitsKeyListener {
  3.     public MoneyValueFilter() {
  4.         super(false, true);
  5.     }
  7.     private int digits = 2;
  9.     public MoneyValueFilter setDigits(int d) {
  10.         digits = d;
  11.         return this;
  12.     }
  14.     @Override
  15.     public CharSequence filter(CharSequence source, int start, int end,
  16.                                Spanned dest, int dstart, int dend) {
  17.         CharSequence out = super.filter(source, start, end, dest, dstart, dend);
  20.         // if changed, replace the source
  21.         if (out != null) {
  22.             source = out;
  23.             start = 0;
  24.             end = out.length();
  25.         }
  27.         int len = end - start;
  29.         // if deleting, source is empty
  30.         // and deleting can't break anything
  31.         if (len == 0) {
  32.             return source;
  33.         }
  35.         //以点开始的时候，自动在前面添加0
  36.         if(source.toString().equals(".") && dstart == 0){
  37.             return "0.";
  38.         }
  39.         //如果起始位置为0,且第二位跟的不是".",则无法后续输入
  40.         if(!source.toString().equals(".") && dest.toString().equals("0")){
  41.             return "";
  42.         }
  44.         int dlen = dest.length();
  46.         // Find the position of the decimal .
  47.         for (int i = 0; i < dstart; i++) {
  48.             if (dest.charAt(i) == '.') {
  49.                 // being here means, that a number has
  50.                 // been inserted after the dot
  51.                 // check if the amount of digits is right
  52.                 return (dlen-(i+1) + len > digits) ?
  53.                         "" :
  54.                         new SpannableStringBuilder(source, start, end);
  55.             }
  56.         }
  58.         for (int i = start; i < end; ++i) {
  59.             if (source.charAt(i) == '.') {
  60.                 // being here means, dot has been inserted
  61.                 // check if the amount of digits is right
  62.                 if ((dlen-dend) + (end-(i + 1)) > digits)
  63.                     return "";
  64.                 else
  65.                     break;  // return new SpannableStringBuilder(source, start, end);
  66.             }
  67.         }
  70.         // if the dot is after the inserted part,
  71.         // nothing can break
  72.         return new SpannableStringBuilder(source, start, end);
  73.     }
  74. }
  1. 在代码中设置过滤器
  1.  etAbleWithdrawMoney.filters = arrayOf(MoneyValueFilter())