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主页 / 问题 / 1308051
Accepted
sus developer
sus developer
Asked:2022-07-23 17:31:59 +0000 UTC2022-07-23 17:31:59 +0000 UTC 2022-07-23 17:31:59 +0000 UTC

尝试第二次启动线程时出现 IllegalThreadStateException 错误

  • 772

一个简单的秒表,但是当我尝试第二次启动计算时间的线程时,会弹出 IllegalThreadStateException:

Exception in thread "JavaFX Application Thread" java.lang.IllegalThreadStateException
    at java.base/java.lang.Thread.start(Thread.java:792)
    at com.company.Stopwatch.lambda$start$0(Stopwatch.java:30)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics/javafx.scene.Node.fireEvent(Node.java:8889)
    at javafx.controls/javafx.scene.control.Button.fire(Button.java:203)
    at javafx.controls/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:208)
    at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3856)
    at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1851)
    at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2584)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:409)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:299)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:447)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:412)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:446)
    at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
    at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    at java.base/java.lang.Thread.run(Thread.java:832)

这是程序代码:

package com.company;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class Stopwatch extends Application {

    public static Label timeAmount = new Label("00:00:00"); // вывод времени
    private Button start = new Button("Start");
    private Button stop = new Button("Stop");

    private StackPane root;
    public static Scene stopwatchScene;

    private StopwatchThread stopwatch = new StopwatchThread("stopwatch");

    public static void main(String[] args){ Application.launch(args); }
    public void start(Stage stage){

        timeAmount.setStyle("-fx-font: 50 arial");

        start.setOnAction(event -> {
            stopwatch.start(); // запускаем новый класс

            start.setDisable(true);
            stop.setDisable(false);
        });

        stop.setOnAction(event -> {
            stopwatch.stop();

            start.setDisable(false);
            stop.setDisable(true);
        });
        stop.setDisable(true);

        StackPane.setAlignment(start, Pos.BOTTOM_CENTER);
        StackPane.setAlignment(stop, Pos.BOTTOM_CENTER);

        StackPane.setMargin(start, new Insets(0, 0, 0 , 50));
        StackPane.setMargin(stop, new Insets(0, 50, 0 , 0));

        root = new StackPane(timeAmount, start, stop); //распологаме элементы
        stopwatchScene = new Scene(root);

        stage.setScene(stopwatchScene);
        stage.setTitle("Stopwatch");
        stage.show();
        stage.setMinWidth(250);
        stage.setMinHeight(160);
        stage.setMaxHeight(150);
        stage.setResizable(false);
    }

    private static class StopwatchThread extends Thread { // класс с секундомером

        private byte sec = 0;
        private byte min = 0;
        private byte hours = 0;

        StopwatchThread(String name){super(name);}

        public void run(){

            while(true) { // костыль для подсчёта секунд
                if (sec == 59) {
                    if (min == 59) {
                        min = 0;
                        hours++;
                    } else {
                        sec = 0;
                        min++;
                    }
                } else {
                    sec++;
                }

                Runnable setTimeLeft = new Runnable() {
                    @Override
                    public void run() {
                        timeAmount.setText(hours + ":" + min + ":" + sec); // выводим время
                    }
                };
                Platform.runLater(setTimeLeft);

                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}
java
  • 1 1 个回答
  • 10 Views

1 个回答

  • Voted
  1. Best Answer
    Alexander Pavlov
    2022-07-23T21:23:58Z2022-07-23T21:23:58Z

    一般来说,我会做不同的事情,但如果你快速修复你的代码,那么

            private StopwatchThread stopwatch;
    
    ...
    
            start.setOnAction(event -> {
                stopwatch = new StopwatchThread("stopwatch"); // новый поток
                stopwatch.start(); 
                start.setDisable(true);
                stop.setDisable(false);
            });
    
            stop.setOnAction(event -> {
                stopwatch.setRunning(false);
                start.setDisable(false);
                stop.setDisable(true);
            });
    ...
    
     private static class StopwatchThread extends Thread {
            private boolean running = false;
    ...
            public synchronized void setRunning(boolean running) {
              this.running = running; 
              notify();
            }
    ...
            public synchronized void run(){
                running = true;
                while(running) { 
    ...    
                    try {
                        wait(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
    ...
    

    此外,使用计时器是不正确的,它sleep也wait不能保证延迟的准确性。距离很远,差距会太大。

    我会怎么做

    1. 变量volatile long startMs。
    2. 单击开始时,它会初始化startMs = System.currentMillis();
    3. 当您单击停止重置时startMs = 0
    4. 一些标准的 android 计时器,每 500 毫秒触发一次并检查startMs. 如果为 0,则计时器未运行。如果不是 0 那么
    Duration elapsed = Duration.ofMillis(System.currentMillis() - startMs);
    int hours = elapsed.toHours(); // 0 .. infinity
    int minutes = elapsed.toMinutesPart(); // 0..59
    int seconds = elapsed.toSecondsPart(); // 0..59
    
    • 0

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