@Override
 public void onTextChanged(CharSequence s, int start, int before, int count) {
   String bankId = "";
   for (int i = 0; i < s.length(); i++) {
     if ((i + 1) % 4 == 0) {
       bankId += " ";
     }
     bankId += s.charAt(i);
   }
   bankcardnum.setText(bankId);
   Log.v(
       "TextWatcher-onTextChanged-->",
       " text="
           + s.toString()
           + " length="
           + s.length()
           + " start="
           + start
           + " before-"
           + before
           + " count="
           + count);
 }
        @Override
        public void afterTextChanged(Editable s) {
          Log.v("TextWatcher-afterTextChanged-->", s.toString() + "length" + s.length());
          // 输入的时候,只有一个光标,那么这两个值应该是相等的。。。
          editStart = et_user_ban.getSelectionStart();
          editEnd = et_user_ban.getSelectionEnd();

          // 限定EditText只能输入19个数字,并且达到19个的时候用红色显示
          if (charSequence.length() > 19) {
            Toast.makeText(AddBankCardActivity.this, "你输入的字数已经超过了限制,不能再输入!", Toast.LENGTH_SHORT)
                .show();
            // 默认光标在最前端,所以当输入第19个数字的时候,删掉(光标位置从11-1到11)的数字,这样就无法输入超过19个以后的数字
            s.delete(editStart - 1, editEnd);
            // 当输入超过第19个数字的时候,改变字体颜色为红色
          }
        }
 @Override
 public void beforeTextChanged(CharSequence ss, int start, int count, int after) {
   charSequence = ss;
   Log.v(
       "TextWatcher-beforeTextChanged-->",
       " text="
           + ss.toString()
           + " length="
           + ss.length()
           + " start="
           + start
           + " count-"
           + count
           + " after="
           + after);
 }