可以在键入JTextel时将其计算到JLabel中吗? [英] Is it possible to calculate JTextFields into a JLabel as they are being typed?

问题描述

是否可以在输入时计算一组JTextField并将结果设置为JLabel?

Is it possible to calculate a group of JTextFields as they are typed in and set the result to a JLabel?

例如:

int iCalc = 0;
JTextField x = new JTextField();
JTextField y = new JTextField();
JTextField z = new JTextField();

JLabel lCalc = new JLabel("Your total is: " + calc);

在我键入内容时，计算得到了calc.我输入x"12"并显示12. 并在y中我自动输入"10" 22.

As i am typing, calc gets calculated. I put in x "12" and 12 is shown. and in y i put "10" 22 is automatically typed in.. ect, ect.

为了自动"澄清，我不想使用按键侦听器(例如，将Tab键按下到下一个TextField)(除非绝对必要)，而且我也不想点击按钮来进行计算

To clarify "automatically" i don't want to use key listener (like pressing tab to for next TextField) (unless it is absolutely necessary) And I don't want to hit a button to do the calculations

这就像在字符串中键入Hello World一样:在键入时，标签将显示:"H"，"e"，"l" 等等，

Its much like typing Hello World into a String: as I Type the Label will show: "H", "e", "l" ect, ect.

希望我已经澄清了

推荐答案

您可以使用

You can use a DocumentListener for this purpose, add it to the Document of each JTextField in question and perform the addition operation in the insertUpdate(...) and removeUpdate(...) method of the DocumentListener interface.

这里是一个工作示例，以供进一步了解:

Here is one working example, for further insight :

import java.awt.*;
import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class DocumentListenerExample {

    private JPanel contentPane;
    private JPanel compPanel;
    private JTextField firstField;
    private JTextField secondField;
    private JTextField thirdField;
    private JLabel resultLabel;

    private static final String RESULT = "Result : ";
    private int result;

    private void displayGUI() {
        JFrame frame = new JFrame("Document Listener Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        contentPane = new JPanel(new GridBagLayout());
        compPanel = new JPanel(new BorderLayout(5, 5));

        JPanel fieldPanel = new JPanel(new GridLayout(3, 3, 5, 5));
        JLabel firstLabel = new JLabel("First Number : ", JLabel.CENTER);
        firstField = new JTextField(10);
        firstField.getDocument().addDocumentListener(
                                    new MyDocumentListener());
        JLabel secondLabel = new JLabel("Second Number : ", JLabel.CENTER);
        secondField = new JTextField(10);
        secondField.getDocument().addDocumentListener(
                                    new MyDocumentListener());
        JLabel thirdLabel = new JLabel("Third Number : ", JLabel.CENTER);
        thirdField = new JTextField(10);
        thirdField.getDocument().addDocumentListener(
                                    new MyDocumentListener());
        fieldPanel.add(firstLabel);
        fieldPanel.add(firstField);
        fieldPanel.add(secondLabel);
        fieldPanel.add(secondField);
        fieldPanel.add(thirdLabel);
        fieldPanel.add(thirdField);

        JPanel footerPanel = new JPanel();
        resultLabel = new JLabel((RESULT + "0"), JLabel.CENTER);
        footerPanel.add(resultLabel);

        compPanel.add(fieldPanel, BorderLayout.CENTER);
        compPanel.add(footerPanel, BorderLayout.PAGE_END);
        contentPane.add(compPanel);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private class MyDocumentListener implements DocumentListener {

        @Override
        public void changedUpdate(DocumentEvent de) {}

        @Override
        public void insertUpdate(DocumentEvent de) {
            calculateSum();
        }

        @Override
        public void removeUpdate(DocumentEvent de) {
            calculateSum();
        }

        private void calculateSum() {
            int first = 0, second = 0, third = 0;
            if (firstField.getDocument().getLength() > 0)
                first = Integer.parseInt(firstField.getText()); 
            if (secondField.getDocument().getLength() > 0)
                second = Integer.parseInt(secondField.getText());
            if (thirdField.getDocument().getLength() > 0)
                third = Integer.parseInt(thirdField.getText());
            result = first + second + third;
            resultLabel.setText(RESULT + result);
        }
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new DocumentListenerExample().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}

您可能还必须在Document上添加一个DocumentFilter，以仅允许将Digit放在JTextField内，而不是任何随机字符.这是一个相关的示例

You might have to add a DocumentFilter too to the Document to only allow putting Digit inside the JTextField, instead of any random character. Here is a related example

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