是否可以在输入一组 JTextField 时计算它们并将结果设置为 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);
当我打字时,calc 就会被计算出来。我输入 x“12”,然后显示 12。 在 y 中,我输入“10”22 会自动输入..等等。
为了“自动”澄清,我不想使用关键监听器(例如按 Tab 键进入下一个文本字段)(除非绝对必要)并且我不想点击按钮来进行计算
这很像在字符串中输入 Hello World:当我输入时,标签将显示:“H”、“e”、“l” 等等,等等
希望我说得足够清楚
最佳答案
您可以使用 DocumentListener为此,请将其添加到相关JTextField
的Document
中,并在insertUpdate(...) 和removeUpdate(... )
DocumentListener
接口(interface)的方法。
这里是一个工作示例,供您进一步了解:
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);
}
}
您可能还必须向 Document
添加一个 DocumentFilter,以仅允许将 Digit
放入 JTextField
中,而不是任何随机字符。这是相关的example
关于java - 是否可以在键入 JTextField 时将其计算到 JLabel 中?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18165573/