我必须制作一个倒计时程序,它还显示十分之一秒; 例如,从 10.0 秒倒计时开始,它应该显示 9.9s、9.8s、...0.0s
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
timer.start();
timer2.start();
}
Double timeLeft=5000; //5 seconds
Timer timer=new Timer(1,countDown);
Timer timer2=new Timer(1000,countDown2);
ActionListener countDown=new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
timeLeft--;
SimpleDateFormat df=new SimpleDateFormat("mm:ss:S");
jLabel1.setText(df.format(timeLeft));
if(timeLeft<=0)
{
timer.stop();
}
}
};
实际情况是需要超过 5 秒才能完成这 5 秒。
我将上面的代码与另一个计时器进行了比较
int timeLeft2=5;
ActionListener countDown2=new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
timeLeft2--;
jLabel2.setText(String.valueOf(timeLeft2));
if(timeLeft2<=0)
{
time2.stop();
}
}
};
他们得到的结果不同是很自然的吗?
最佳答案
滴答之间的时间(调用 actionPerfomed
的时间)是可变的,它只能保证至少为 n
毫秒
您应该尝试计算 Timer
启动时间与当前时间之间的差异,而不是依赖某个随着时间的推移而变得不可靠的计数器,例如...
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.text.SimpleDateFormat;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class CountDown {
public static void main(String[] args) {
new CountDown();
}
public CountDown() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private Timer timer;
private long startTime = -1;
private long duration = 5000;
private JLabel label;
public TestPane() {
setLayout(new GridBagLayout());
timer = new Timer(10, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (startTime < 0) {
startTime = System.currentTimeMillis();
}
long now = System.currentTimeMillis();
long clockTime = now - startTime;
if (clockTime >= duration) {
clockTime = duration;
timer.stop();
}
SimpleDateFormat df = new SimpleDateFormat("mm:ss:SSS");
label.setText(df.format(duration - clockTime));
}
});
timer.setInitialDelay(0);
addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
if (!timer.isRunning()) {
startTime = -1;
timer.start();
}
}
});
label = new JLabel("...");
add(label);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
}
关于Java Swing 定时器倒计时,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28337718/