[英]create new thread inside actionPerformed and Event Dispatch Thread (EDT) issue
As stated from Sun that actionPerformed() from ActionListener is executed in EDT automatically so I've decided to create new thread inside actionPerformed() method and the problem is this thread is not running inside EDT. 正如Sun所说,来自ActionListener的actionPerformed()是在EDT中自动执行的,因此我决定在actionPerformed()方法中创建新线程,问题是该线程不在EDT中运行。 Can someone explain this? 有人可以解释吗? Thanks 谢谢
If you create a new thread from EDT that thread is different than the EDT. 如果从EDT创建新线程,则该线程与EDT不同。 Isn't that clear? 不清楚吗?
You are supposed to update controls via the EDT. 您应该通过EDT更新控件。
You can create your own background threads for heavy tasks but the update of the controls should be only via the EDT. 您可以为繁重的任务创建自己的后台线程,但是控件的更新只能通过EDT进行。 There are constructs for you to use to facilitate your code eg pass a Runnable
to be called by EDT via SwingUtilities invoke Runnable . 有结构供你使用,以方便您的代码,例如通过一个Runnable
于由EDT通过所谓的SwingUtilities调用Runnable接口 。 You should study about Concurrency in Swing 您应该学习Swing中的并发性
1) AWT or Swing GUI invoked and created EDT, this event is done by (maybe there are another) methods pack() and setVisible(true) 1)调用和创建EDT的AWT或Swing GUI,此事件由(可能还有其他)方法pack()和setVisible(true)完成
2) if all events waiting in EDT are done and EDT is empty then if (EventQueue.isDispatchThread()) { returns false, but EDT thread is there until current JVM instance exist 2)如果在EDT中等待的所有事件都已完成并且EDT为空,则如果(EventQueue.isDispatchThread()){返回false,但是EDT线程存在,直到当前的JVM实例存在
3) as mentioned for invoke EDT queue you can use invokeLater or invokeAndWait, notice invokeAndWait you can use only if isDispatchThread returns false, otherwise returns exceptions 3)如提到的调用EDT队列,您可以使用invokeLater或invokeAndWait,请注意invokeAndWait仅在isDispatchThread返回false时可以使用,否则返回异常
4) by calling Thread.sleep(int) from Swing Listener or its method can freeze and lock EDT, causing lost some event from event queue, 4)通过从Swing侦听器调用Thread.sleep(int)或其方法可以冻结并锁定EDT,从而导致事件队列中的某些事件丢失,
two codes example for testing isDispatchThread() and how to alive EDT from Java Objects 两个代码示例,用于测试isDispatchThread()以及如何从Java Objects激活EDT
import java.awt.EventQueue;
import java.lang.reflect.InvocationTargetException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;
public class IsThereEDT {
private ScheduledExecutorService scheduler;
private AccurateScheduledRunnable periodic;
private ScheduledFuture<?> periodicMonitor;
private int taskPeriod = 30;
private SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
private Date dateRun;
private JFrame frame1 = new JFrame("Frame 1");
public IsThereEDT() {
scheduler = Executors.newSingleThreadScheduledExecutor();
periodic = new AccurateScheduledRunnable() {
private final int ALLOWED_TARDINESS = 200;
private int countRun = 0;
private int countCalled = 0;
private int maxCalled = 10;
@Override
public void run() {
countCalled++;
if (countCalled < maxCalled) {
if (countCalled % 3 == 0) {
/*if (EventQueue.isDispatchThread()) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
//some stuff
}
});
} else {
try {
SwingUtilities.invokeAndWait(new Runnable() {
@Override
public void run() {
//some stuff
}
});
} catch (InterruptedException ex) {
Logger.getLogger(IsThereEDT.class.getName()).log(Level.SEVERE, null, ex);
} catch (InvocationTargetException ex) {
Logger.getLogger(IsThereEDT.class.getName()).log(Level.SEVERE, null, ex);
}
}*/
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
System.out.println("Push a new event to EDT");
frame1.repaint();
isThereReallyEDT();
}
});
} else {
if (this.getExecutionTime() < ALLOWED_TARDINESS) {
countRun++;
isThereReallyEDT(); // non on EDT
}
}
} else {
System.out.println("Terminating this madness");
System.exit(0);
}
}
};
periodicMonitor = scheduler.scheduleAtFixedRate(periodic, 0, taskPeriod, TimeUnit.SECONDS);
periodic.setThreadMonitor(periodicMonitor);
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
isThereReallyEDT();
frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame1.getContentPane().add(new JLabel("Hello in frame 1"));
frame1.pack();
frame1.setLocation(100, 100);
frame1.setVisible(true);
}
});
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
Logger.getLogger(IsThereEDT.class.getName()).log(Level.SEVERE, null, ex);
}
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JFrame frame2 = new JFrame("Frame 2");
frame2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame2.getContentPane().add(new JLabel("Hello in frame 2"));
frame2.pack();
frame2.setLocation(200, 200);
frame2.setVisible(true);
isThereReallyEDT();
}
});
}
private void isThereReallyEDT() {
dateRun = new java.util.Date();
System.out.println(" Time at : " + sdf.format(dateRun));
if (EventQueue.isDispatchThread()) {
System.out.println("EventQueue.isDispatchThread");
} else {
System.out.println("There isn't Live EventQueue.isDispatchThread, why any reason for that ");
}
if (SwingUtilities.isEventDispatchThread()) {
System.out.println("SwingUtilities.isEventDispatchThread");
} else {
System.out.println("There isn't Live SwingUtilities.isEventDispatchThread, why any reason for that ");
}
System.out.println();
}
public static void main(String[] args) {
IsThereEDT isdt = new IsThereEDT();
}
}
abstract class AccurateScheduledRunnable implements Runnable {
private ScheduledFuture<?> thisThreadsMonitor;
public void setThreadMonitor(ScheduledFuture<?> monitor) {
this.thisThreadsMonitor = monitor;
}
protected long getExecutionTime() {
long delay = -1 * thisThreadsMonitor.getDelay(TimeUnit.MILLISECONDS);
return delay;
}
}
and simpler code 和更简单的代码
. 。
. 。
import java.awt.EventQueue;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;
public class IsThereEDT {
private ScheduledExecutorService scheduler;
private AccurateScheduledRunnable periodic;
private ScheduledFuture<?> periodicMonitor;
private int taskPeriod = 30;
private SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
private Date dateRun;
private JFrame frame1 = new JFrame("Frame 1");
public IsThereEDT() {
scheduler = Executors.newSingleThreadScheduledExecutor();
periodic = new AccurateScheduledRunnable() {
private final int ALLOWED_TARDINESS = 200;
private int countRun = 0;
private int countCalled = 0;
private int maxCalled = 10;
@Override
public void run() {
countCalled++;
if (countCalled < maxCalled) {
if (countCalled % 3 == 0) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
System.out.println("Push a new event to EDT");
frame1.repaint();
isThereReallyEDT();
}
});
} else {
if (this.getExecutionTime() < ALLOWED_TARDINESS) {
countRun++;
isThereReallyEDT(); // non on EDT
}
}
} else {
System.out.println("Terminating this madness");
System.exit(0);
}
}
};
periodicMonitor = scheduler.scheduleAtFixedRate(periodic, 0, taskPeriod, TimeUnit.SECONDS);
periodic.setThreadMonitor(periodicMonitor);
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
isThereReallyEDT();
frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame1.getContentPane().add(new JLabel("Hello in frame 1"));
frame1.pack();
frame1.setLocation(100, 100);
frame1.setVisible(true);
}
});
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
Logger.getLogger(IsThereEDT.class.getName()).log(Level.SEVERE, null, ex);
}
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JFrame frame2 = new JFrame("Frame 2");
frame2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame2.getContentPane().add(new JLabel("Hello in frame 2"));
frame2.pack();
frame2.setLocation(200, 200);
frame2.setVisible(true);
isThereReallyEDT();
}
});
}
private void isThereReallyEDT() {
dateRun = new java.util.Date();
System.out.println(" Time at : " + sdf.format(dateRun));
if (EventQueue.isDispatchThread()) {
System.out.println("EventQueue.isDispatchThread");
} else {
System.out.println("There isn't Live EventQueue.isDispatchThread, why any reason for that ");
}
if (SwingUtilities.isEventDispatchThread()) {
System.out.println("SwingUtilities.isEventDispatchThread");
} else {
System.out.println("There isn't Live SwingUtilities.isEventDispatchThread, why any reason for that ");
}
System.out.println();
}
public static void main(String[] args) {
IsThereEDT isdt = new IsThereEDT();
}
}
abstract class AccurateScheduledRunnable implements Runnable {
private ScheduledFuture<?> thisThreadsMonitor;
public void setThreadMonitor(ScheduledFuture<?> monitor) {
this.thisThreadsMonitor = monitor;
}
protected long getExecutionTime() {
long delay = -1 * thisThreadsMonitor.getDelay(TimeUnit.MILLISECONDS);
return delay;
}
}
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