Java 我不能启动计时器两次
我正在用Java制作计时器,我需要帮助。主类中添加了一个swing计时器。我有一个jFrame,它有两个面板,一个有jLabel,另一个有3个按钮,“开始”、“停止”和“重置”。当我点击开始,一切正常,当我停止,然后重置。但当我再次单击“开始”时,它会输出以下异常:Java 我不能启动计时器两次,java,swing,timer,Java,Swing,Timer,我正在用Java制作计时器,我需要帮助。主类中添加了一个swing计时器。我有一个jFrame,它有两个面板,一个有jLabel,另一个有3个按钮,“开始”、“停止”和“重置”。当我点击开始,一切正常,当我停止,然后重置。但当我再次单击“开始”时,它会输出以下异常: Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Timer already
Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Timer already cancelled.
at java.util.Timer.sched(Unknown Source)
at java.util.Timer.schedule(Unknown Source)
at org.stopwatch.Stopwatch.start(Stopwatch.java:71)
at org.stopwatch.Stopwatch$1.actionPerformed(Stopwatch.java:48)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
这是我的代码:
包org.stopwatch
import static javax.swing.UIManager.getSystemLookAndFeelClassName;
import static javax.swing.UIManager.setLookAndFeel;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Timer;
import java.util.TimerTask;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Stopwatch {
private static boolean running = false;
public static int time = 0;
public static Timer timer = new Timer();
public static JLabel leftLabel = new JLabel(time + "s");
public static final void main(String[] args) throws Exception {
setLookAndFeel(getSystemLookAndFeelClassName());
JFrame f = new JFrame();
f.setVisible(true);
f.setSize(1, 1);
f.setTitle("Секундомір");
f.setDefaultCloseOperation(3);
f.setLocationRelativeTo(null);
JPanel leftPanel = new JPanel();
f.add(leftPanel, BorderLayout.NORTH);
leftPanel.add(leftLabel);
JPanel buttonPanel = new JPanel();
f.add(buttonPanel, BorderLayout.SOUTH);
JButton startBtn = new JButton("Start");
JButton stopBtn = new JButton("Stop");
JButton resetBtn = new JButton("Reset");
buttonPanel.add(startBtn);
buttonPanel.add(stopBtn);
buttonPanel.add(resetBtn);
startBtn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent a) {
running = true;
start();
}
});
stopBtn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent a) {
running = false;
timer.cancel();
}
});
resetBtn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent a) {
if(!running) {
time = 0;
leftLabel.setText("0s");
}
}
});
f.pack();
}
public static void start() {
timer.schedule(new TimerTask() {
@Override
public void run() {
time++;
leftLabel.setText(time + "s");
}
}, 1000, 1000);
}
}
是的,它的行为完全符合记录。根据: 一旦计时器被终止,它的执行线程将正常终止,并且不能在其上安排更多的任务 并根据
计划的文件
方法:
IllegalStateException
-如果任务已计划或取消,则计时器被取消,或计时器线程终止
基本上,您需要在每个
start
操作上创建一个新的Timer
,或者不要取消现有的run
方法,将TimerTask
的run方法更改为在定时器逻辑停止时忽略操作。答案在错误消息中。它说你不能启动一个被取消的计时器。您必须使用new
操作符创建一个新的计时器
在start()
函数中执行此操作
timer=新定时器()代码>
如果您决定执行此操作,请不要忘记从声明中删除new
操作。您将在start()
函数中覆盖分配
公共静态定时器代码>
如果要存储两次运行之间的时间,则需要在使用新计时器覆盖计时器之前执行此操作。您应该在start()
上创建一个新计时器,并用“旧”计时器中的时间填充它
调用timer.cancel()时,请查看,然后计时器线程将停止!
您可以停止某些任务,但不能停止计时器!当计时器被取消时,你必须重新设置一个tiemr
你可以看看谢谢。我更新了启动方法中的计时器。现在开始工作了@user2564491为什么要使用java.util.Timer
?您应该为swing应用程序使用javax.swing.Timer
,如@peeskillet所示,如果java.util.Timer
满足他的需求,他肯定应该使用它。如果他需要计时器来更新GUI,那么他应该使用javax.swing.timer
。但是,情况正好相反-他的GUI正在更新计时器,在这种情况下,没有理由使用swing计时器。@peeskillet您似乎将更新GUI与在GUI中显示计时器混淆了。他的计时器不会触发事件、显示和隐藏元素以及执行其他GUI操作。显示时间与在计时器上触发事件不同。我们很清楚,setText()
是标签的函数,而不是计时器。如果这还不够清楚,想象一下您希望在GUI中显示一个整数。你会使用一些swing变量吗?