FocusEvent 没有得到 JFormattedTextField 的最后一个值，我怎样才能得到它?

2022-01-24 00:00:00 java swing jframe jformattedtextfield

我的 JFrame 对象上有两个 JFormattedTextField 对象.我想要这些 JFormattedTextField 对象的值的基本数学(加法).我希望它在焦点丢失第一个或第二个文本字段时发生.但是当focusLost()"时，事件并没有得到最后一个值，而是得到了前一个值.

I have two JFormattedTextField objects on my JFrame object. I want a basic Math (addition) by the values of these JFormattedTextField objects. I want it happen when focus lost either the first or the second textfield. But when "focusLost()", event doesn't get the last value, it gets the previous value.

例如；tf1 有 0，而 tf2 有 0.我将 2 写入 tf1，当 focusLost() 时，结果 (tf1+tf2) 仍然为 0.当我更改其中任何一个时，结果变成2(之前的值)

For example; tf1 has 0 and tf2 has 0 at first. I write 2 to tf1, and when focusLost(), result (tf1+tf2) become still 0. when I change any of them, the result becomes 2 (the previous value)

如何获取 focusLost 上的最后一个值?

How do I get the last values on focusLost?

这是我的代码:

JFormattedTextField tf1,tf2;
NumberFormat format=NumberFormat.getNumberInstance();
tf1=new JFormattedTextField(format);
tf1.addFocusListener(this);

tf2=new JFormattedTextField(format);
tf2.addFocusListener(this);

和focusLost():

public void focusLost(FocusEvent e) {
    if(tf1.getValue() == null) tf1.setValue(0); 
    if(tf2.getValue() == null) tf2.setValue(0);
    //because if I dont set, it throws nullPointerException for tf.getValue()

    BigDecimal no1 = new BigDecimal(tf1.getValue().toString());
    BigDecimal no2 = new BigDecimal(tf2.getValue().toString());
    System.out.println("total: " + (no1.add(no2)));
}

推荐答案

我认为你应该使用 PropertyChangeListener，参见 如何编写属性更改监听器.

I think you should use a PropertyChangeListener, see How to Write a Property Change Listener.

有一个使用JFormattedTextField的例子:

//...where initialization occurs:
double amount;
JFormattedTextField amountField;
...
amountField.addPropertyChangeListener("value",
                                      new FormattedTextFieldListener());
...
class FormattedTextFieldListener implements PropertyChangeListener {
    public void propertyChanged(PropertyChangeEvent e) {
        Object source = e.getSource();
        if (source == amountField) {
            amount = ((Number)amountField.getValue()).doubleValue();
            ...
        }
        ...//re-compute payment and update field...
    }
}

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