我知道 Java 的实际模型是针对协作线程的,并且它不会强制线程终止。
由于 Thread.stop()
已被弃用(出于上面列出的原因)。我试图通过 BooleanProperty 监听器停止线程。
这是 MCVE:
TestStopMethod.java
package javatest;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.value.ObservableValue;
public class TestStopMethod extends Thread {
private BooleanProperty amIdead = new SimpleBooleanProperty(false);
public void setDeath() {
this.amIdead.set(true);
}
@Override
public void run() {
amIdead.addListener((ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue) -> {
System.out.println("I'm dead!!!");
throw new ThreadDeath();
});
for(;;);
}
}
WatchDog.java
package javatest;
import java.util.TimerTask;
public class Watchdog extends TimerTask {
TestStopMethod watched;
public Watchdog(TestStopMethod target) {
watched = target;
}
@Override
public void run() {
watched.setDeath();
//watched.stop(); <- Works but this is exactly what I am trying to avoid
System.out.println("You're dead!");
}
}
驱动程序.java
package javatest;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Driver {
public static void main(String[] args) {
try {
TestStopMethod mythread = new TestStopMethod();
Timer t = new Timer();
Watchdog w = new Watchdog(mythread);
t.schedule(w, 1000);
mythread.start();
mythread.join();
t.cancel();
System.out.println("End of story");
} catch (InterruptedException ex) {
Logger.getLogger(Driver.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
最佳答案
如果您更改属性值,则会在更改属性的同一线程上调用监听器(只需考虑一下您将/可以如何实现属性类)。所以在你的例子中 ThreadDeath
支持 Timer
的线程抛出错误例如,这并不是您真正想要的。
从外部(对该线程)终止线程的正确方法是设置一个标志,然后在线程的实现中定期轮询该标志。这实际上比听起来更棘手,因为必须从多个线程访问该标志,因此必须正确同步对它的访问。
幸运的是,有一些实用程序类可以帮助解决这个问题。 FutureTask
,例如,包装 Runnable
或Callable
并提供cancel()
和isCancelled()
方法。如果您使用 JavaFX,那么 javafx.concurrent API 提供 Callable
的一些实现和Runnable
这样做,并且还提供专门用于在 FX 应用程序线程上执行代码的功能。看看documentation for javafx.concurrent.Task举一些例子。
例如,您可以这样做:
package javatest;
public class TestStopMethod implements Runnable {
@Override
public void run() {
try {
synchronized(this) {
for(;;) {
wait(1);
}
}
} catch (InterruptedException exc) {
System.out.println("Interrupted");
}
}
}
看门狗.java:
package javatest;
import java.util.TimerTask;
import java.util.concurrent.Future;
public class Watchdog extends TimerTask {
Future<Void> watched;
public Watchdog(Future<Void> target) {
watched = target;
}
@Override
public void run() {
watched.cancel(true);
//watched.stop(); <- Works but this is exactly what I am trying to avoid
System.out.println("You're dead!");
}
}
驱动程序.java:
package javatest;
import java.util.*;
import java.util.concurrent.FutureTask;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Driver {
public static void main(String[] args) {
try {
FutureTask<Void> myTask = new FutureTask<>(new TestStopMethod(), null);
Timer t = new Timer();
Watchdog w = new Watchdog(myTask);
t.schedule(w, 1000);
Thread mythread = new Thread(myTask);
mythread.start();
mythread.join();
t.cancel();
System.out.println("End of story");
} catch (InterruptedException ex) {
Logger.getLogger(Driver.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
在 JavaFX 应用程序中,您可以这样做。请注意,如果您尝试在没有运行 FX 应用程序线程的情况下执行此操作,事情会变得很糟糕,因为 cancelled
FX 中的标志 Task
必须在该线程上更新。
package javatest;
import javafx.concurrent.Task;
public class TestStopMethod extends Task<Void> {
@Override
public Void call() {
System.out.println("Calling");
while (true) {
if (isCancelled()) {
System.out.println("Cancelled");
break ;
}
}
System.out.println("Exiting");
return null ;
}
}
看门狗.java:
package javatest;
import java.util.TimerTask;
import javafx.concurrent.Task;
public class Watchdog extends TimerTask {
Task<Void> watched;
public Watchdog(Task<Void> target) {
watched = target;
}
@Override
public void run() {
watched.cancel();
//watched.stop(); <- Works but this is exactly what I am trying to avoid
System.out.println("You're dead!");
}
}
驱动程序.java
package javatest;
import java.util.Timer;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.concurrent.Task;
import javafx.concurrent.Worker;
import javafx.scene.Scene;
import javafx.scene.control.TextArea;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
public class Driver extends Application {
@Override
public void start(Stage primaryStage) {
try {
TextArea console = new TextArea();
BorderPane root = new BorderPane(console);
Scene scene = new Scene(root, 600, 400);
primaryStage.setScene(scene);
primaryStage.show();
Task<Void> myTask = new TestStopMethod();
Timer t = new Timer();
Watchdog w = new Watchdog(myTask);
t.schedule(w, 1000);
Thread mythread = new Thread(myTask);
mythread.setDaemon(true);
myTask.stateProperty().addListener((obs, oldState, newState) -> {
console.appendText("State change "+oldState+" -> "+newState+"\n");
if (oldState == Worker.State.RUNNING) {
t.cancel();
console.appendText("End of Story\n");
}
});
mythread.start();
} catch (Exception ex) {
Logger.getLogger(Driver.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
关于java - 终止属性监听器中的线程 (JavaFX 8),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/26263152/