Question

将Java和Java Swing用于GUI。方案是，我希望用户以HH：MM：SS的格式在所需的时间（在JTextbox中）输入，并从该给定时间开始倒数几秒，直到达到零为止。目前，我正在使用计时器和timer.between函数。我从用户输入的时间创建一个Instant（），也使用Instant.now（）。瞬间是在创建的，但是倒数时钟并不是从用户输入时间开始倒数的，而是一些我无法弄清楚它们来自何处的随机数。其他人可以看到问题吗？

 javax.swing.Timer countDown = new javax.swing.Timer(1000, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                Duration countingDown = Duration.between(Instant.now(), userInputCountDown);
                autoShutOffTF.setText(String.format("%02d:%02d:%02d",
                        countingDown.toHours(),
                        countingDown.toMinutes() % 60,
                        countingDown.getSeconds() % 60));
            }
        });
        startButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                //Getting user input, parsing String in the form of HH:MM:SS 
                String countdownInput = autoShutOffTF.getText();

                String getHours = countdownInput.substring(0,2);
                int hours = Integer.parseInt(getHours);

                String getMins = countdownInput.substring(3,5);
                int mins = Integer.parseInt(getMins);

                String getSecs = countdownInput.substring(6,8);
                int seconds = Integer.parseInt(getSecs);

                //Creating a date instance, to get the current year, month and date
                Date date = new Date();
                Calendar calendar = Calendar.getInstance();
                calendar.setTime(date);
                int year = calendar.get(Calendar.YEAR);
                int month = calendar.get(Calendar.MONTH);
                int day = calendar.get(Calendar.DAY_OF_MONTH);

                //creating a new calendar with all of the data
                Calendar cal = Calendar.getInstance();
                cal.set(year, month, day, hours, mins, seconds);

                //creating a new instant with the new calendar with all of the data
                userInputCountDown = cal.toInstant();

                //starting timer
                countDown.start();
            }
        });

Answer 1

不要使用Date或Calendar，java.time API可以实现所需的功能。

看着这个...

Date date = new Date();
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
int year = calendar.get(Calendar.YEAR);
int month = calendar.get(Calendar.MONTH);
int day = calendar.get(Calendar.DAY_OF_MONTH);

//creating a new calendar with all of the data
Calendar cal = Calendar.getInstance();
cal.set(year, month, day, hours, mins, seconds);

您要根据小时/分钟/秒来创建新时间，但是让我担心的是，如果时间少于现在，会发生什么？这个“可能”就是您遇到的问题。

因此，您可能需要做的是验证时间是在当前时间之前还是之后，并相应地滚动显示日期-假设您要使用绝对时间（即创建一个从现在开始倒数到下午6点的计时器））

这个...

Duration countingDown = Duration.between(Instant.now(), userInputCountDown);

在我看来，userInputCountDown应该会在将来出现

以下示例采用了稍微不同的方法，因为它创建了一个“计时器”，该计时器将在当前时间（加上小时，分钟和秒）之后（基于输入）创建一个目标，并将其用作倒数的锚点。

例如，您可能会说“创建1小时”计时器。

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.time.Duration;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;

class Main {

    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JTextField targetHours;
        private JTextField targetMins;
        private JTextField targetSeconds;

        private Instant futureTime;
        private Timer timer;

        private JLabel countDown;

        public TestPane() {

            setLayout(new GridBagLayout());

            targetHours = new JTextField("00", 2);
            targetMins = new JTextField("00", 2);
            targetSeconds = new JTextField("00", 2);

            JPanel targetPane = new JPanel(new GridBagLayout());
            targetPane.add(targetHours);
            targetPane.add(new JLabel(":"));
            targetPane.add(targetMins);
            targetPane.add(new JLabel(":"));
            targetPane.add(targetSeconds);

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.insets = new Insets(8, 8, 8, 8);

            add(targetPane, gbc);

            JButton btn = new JButton("Start");
            btn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    futureTime = LocalDateTime.now()
                            .plusHours(Long.parseLong(targetHours.getText()))
                            .plusMinutes(Long.parseLong(targetMins.getText()))
                            .plusSeconds(Long.parseLong(targetSeconds.getText()))
                            .atZone(ZoneId.systemDefault()).toInstant();

                    if (timer != null) {
                        timer.stop();
                    }

                    countDown.setText("---");
                    timer = new Timer(500, new ActionListener() {
                        @Override
                        public void actionPerformed(ActionEvent e) {
                            Duration duration = Duration.between(Instant.now(), futureTime);
                            if (duration.isNegative()) {
                                timer.stop();
                                timer = null;
                                countDown.setText("00:00:00");
                            } else {
                                String formatted = String.format("%02d:%02d:%02d", duration.toHours(), duration.toMinutesPart(), duration.toSecondsPart());
                                countDown.setText(formatted);
                            }
                        }
                    });
                    timer.start();
                }
            });

            add(btn, gbc);

            countDown = new JLabel("---");
            add(countDown, gbc);
        }

    }

}

警告-我不对输入内容进行验证，因此您必须要小心。

相反，如果您想倒计时至某个特定时间点（即从现在开始倒计时至下午6点），那么您将需要使用LocalDateTime#withHour(Long)#withMinute(Long)#withSecond(Long)链。但是要当心，您必须验证时间是将来还是过去，并采取适当的措施，因为如果您想倒数到下午6点，但现在是晚上7点...实际上是什么意思：/？

从特定时间开始的Java计时器倒计时

1 个答案: