動態獲取第三個數

edt_pay_amount.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {

            }

            @Override
            public void afterTextChanged(Editable s) {
                if (s.length() > 0) {
                    if (s.charAt(0) == '.') {
                        s.insert(0, "0");
                    }
                    float realamount = Float.parseFloat(s.toString());
                    edt_zhao_amount.setText((realamount - PayInfo.getAmount()) + "");
                } else {
                    edt_zhao_amount.setText("");
                }
            }
        });
        根據實收金額獲取找零金額