对 TextFields 执行算术运算的事件监听器

Question

我对代码块的执行感到困惑。我有 4 个文本字段，每个文本字段是 quantity、price、vat 和 amount。

我想向 price 和 quantity 文本字段添加一个事件侦听器，以便每当我更改每个文本字段时，新的 vat 计算和新的 amount值会自动显示在各自的文本字段中。

我在想这样的事情：

    private void addEventListeners() {
        txtInvoiceQuantity.textProperty().addListener((ChangeListener) (observable, oldVal, newVal) -> calculateVATAmount((String) oldVal, (String) newVal));
    }

    private void calculateVATAmount(String oldVal, String newVal) {
 if (newVal.length() > oldVal.length()) {
            if (txtInvoiceQuantity.getText().length() > 0 && txtInvoicePrice.getText().length() > 0) {
                try {
                    double quantity = Double.parseDouble(newVal);
                    double price = Double.parseDouble(txtInvoicePrice.getText());
                    double vat = Double.parseDouble(lblVAT.getText()) / 100;
                    double vatamount = quantity * price * vat;
                    txtInvoiceVAT.setText(String.valueOf(vatamount));
                    double invoiceAmount = (price * quantity) + vatamount;
                    txtInvoiceAmount.setText(String.valueOf(invoiceAmount));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }

我显然不能使用 txtInvoiceQuantity 上的那个事件。那么我怎样才能改变 calculateVATAmount(oldVal,newVal) 让它做我想做的事呢？

如何将 oldVal 也考虑在内（以防用户按回 space）？

Answer 1

嗯，据我了解，您必须复制该代码块，因为您要从每个处理程序中的不同文本字段传递参数。

至于考虑旧值，只需删除 if(newVal.length() > oldVal.length()) {} 即可。它应该是这样的：

   private void quantityHandler(String oldVal, String newVal) {
            if (txtInvoiceQuantity.getText().length() > 0 && txtInvoicePrice.getText().length() > 0) {
                try {
                    double quantity = Double.parseDouble(newVal);
                    double price = Double.parseDouble(txtInvoicePrice.getText());
                    double vat = Double.parseDouble(lblVAT.getText()) / 100;
                    double vatamount = quantity * price * vat;
                    txtInvoiceVAT.setText(String.valueOf(round(vatamount,2)));
                    double invoiceAmount = (price * quantity) + vatamount;
                    txtInvoiceAmount.setText(String.valueOf(round(invoiceAmount,2)));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
    }
    private void priceHandler(String oldVal, String newVal) {
            if (txtInvoiceQuantity.getText().length() > 0 && txtInvoicePrice.getText().length() > 0) {
                try {
                    double quantity = Double.parseDouble(txtInvoiceQuantity.getText());
                    double price = Double.parseDouble(newVal);
                    double vat = Double.parseDouble(lblVAT.getText()) / 100;
                    double vatamount = quantity * price * vat;
                    txtInvoiceVAT.setText(String.valueOf(round(vatamount,2)));
                    double invoiceAmount = (price * quantity) + vatamount;
                    txtInvoiceAmount.setText(String.valueOf(round(invoiceAmount,2)));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
    }

由于您使用的是货币值，我找到了一种转换为指定小数位数的方法，请在此处找到它

Rounding to 2 decimal places

对 TextFields 执行算术运算的事件监听器

Event Listener to Performing Arithmetic Operations on TextFields

java

event-listener

listener

textfield