Question

EDT是什么时候开始的?

我猜是"一些SwingComponent. 可见的(真实)" 做的这个把戏, 但我不确定。

谢谢!

Answer 1

Q: When exactly is the EDT started? What line of code is responsible [f]of it?

Swing 的内部操作是 JVM 特有的。不同的 JVM 启动事件调度线索( EDT ), 依据不同的标准。通常 :

EDT从收到第一个AWTEvent 开始。

下面的堆叠轨迹再次确认此点。例如, 以下的main 方法。

public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setVisible(true);
}

在上述例子中,负责启动电子数据交换的代码线是 < code > frame. set Veabilable( true); 。

上述main 方法在两个不同的JVMs上实施。在 EventQuuee.init DispatchThread 放置了一个断点。当中断点被击中时,会发现以下的堆叠痕迹。

在 AWT-AppKit 线索上使用 Mac s JDK:

EventQueue.initDispatchThread() line: 906   
EventQueue.wakeup(boolean) line: 1109   
NativeMethodAccessorImpl.invoke0(Method, Object, Object[]) line: not available [native method]  
NativeMethodAccessorImpl.invoke(Object, Object[]) line: 39  
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25  
Method.invoke(Object, Object...) line: 597  
SunToolkit.wakeupEventQueue(EventQueue, boolean) line: 348  
PostEventQueue.postEvent(AWTEvent) line: 2137   
SunToolkit.postEvent(AppContext, AWTEvent) line: 583    
SunToolkit.executeOnEventHandlerThread(PeerEvent) line: 654 
SunToolkit.executeOnEventHandlerThread(Object, Runnable) line: 631  
EventFactoryProxy.windowMoved(CWindow) line: 89

在 main 线索上的窗口使用 Oracle s JDK:

java.awt.EventQueue.initDispatchThread() line: 861  
java.awt.EventQueue.postEventPrivate(java.awt.AWTEvent) line: 199   
java.awt.EventQueue.postEvent(java.awt.AWTEvent) line: 180  
javax.swing.RepaintManager.scheduleProcessingRunnable(sun.awt.AppContext) line: 1369    
javax.swing.RepaintManager.nativeAddDirtyRegion(sun.awt.AppContext, java.awt.Container, int, int, int, int) line: 548   
javax.swing.SwingPaintEventDispatcher.createPaintEvent(java.awt.Component, int, int, int, int) line: 45 
sun.awt.windows.WFramePeer(sun.awt.windows.WComponentPeer).postPaintIfNecessary(int, int, int, int) line: 741   
sun.awt.windows.WFramePeer(sun.awt.windows.WComponentPeer).handlePaint(int, int, int, int) line: 736    
sun.java2d.d3d.D3DScreenUpdateManager.repaintPeerTarget(sun.awt.windows.WComponentPeer) line: 274   
sun.java2d.d3d.D3DScreenUpdateManager.createScreenSurface(sun.awt.Win32GraphicsConfig, sun.awt.windows.WComponentPeer, int, boolean) line: 175  
...
sun.awt.windows.WToolkit.createFrame(java.awt.Frame) line: 383  
javax.swing.JFrame(java.awt.Frame).addNotify() line: 460    
javax.swing.JFrame(java.awt.Window).show() line: 859    
javax.swing.JFrame(java.awt.Component).show(boolean) line: 1584 
javax.swing.JFrame(java.awt.Component).setVisible(boolean) line: 1536   
javax.swing.JFrame(java.awt.Window).setVisible(boolean) line: 842   
Example.main(java.lang.String[]) line: 113

在Mac上,调用PostEventQueue.postEvent(AWTEvent) 。同样,在Windows上,调用java.awt.EventQueue.postEvent(java.awt.AWTEvent) 。两者最终都调用 EventQuue.init DispatchThread 。

例如,考虑以下main方法:

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            System.out.println("Start!");
        }
    });
}

使用 main 线索上的 Mac s JDK:

EventQueue.initDispatchThread() line: 906 [local variables unavailable] 
EventQueue.postEventPrivate(AWTEvent) line: 227 
EventQueue.postEvent(AWTEvent) line: 208    
EventQueue.invokeLater(Runnable) line: 1048 
SwingUtilities.invokeLater(Runnable) line: 1267 
Example.main(String[]) line: 31

在 main 线索上的窗口使用 Oracle s JDK:

java.awt.EventQueue.initDispatchThread() line: 861  
java.awt.EventQueue.postEventPrivate(java.awt.AWTEvent) line: 199   
java.awt.EventQueue.postEvent(java.awt.AWTEvent) line: 180  
java.awt.EventQueue.invokeLater(java.lang.Runnable) line: 999   
javax.swing.SwingUtilities.invokeLater(java.lang.Runnable) line: 1267

swindUtities.invokeLater 的呼叫负责启动 EDT。这里再次呼叫 EventQuue. post Event (AWTEvent) 。

Thoughts on My guess is that "someSwingComponent.setVisible(true)" does the trick, but I m not sure.

不只是调用 somes SwingComponent. set Veable( true) 来启动 EDT。例如,执行以下 main 方法不会创建 AWT-Event-Queue-0 线 :

public static void main(String[] args) {
    JLabel label = new JLabel();
    label.setVisible(true);
}

Resources

当然,网上有许多关于特殊和差别待遇的在线资源。

"The Event Dispatch Thread" from The Java Tutorials s "Lesson: Concurrency in Swing"
"Threads and Swing" from the Sun Developer Network
"Swing Threads" from the Java Glossary at mindprod.com
"How does the event dispatch thread work?" on Stack Overflow

Answer 2

任何AWT / Swing 集装箱从EDT开始使用,不安全的方式
Intial Thread 是最安全的方式
如果在目前的 EDT 中所有事件都完成, 那么是DisapatchThread 返回假
如果DissatchTread返回假的, 那么任何摇线安全方法都可以活过EDT, 最安全的方法就是从引用( ) 中引用最安全的方法。

测试的代码代码

import java.awt.Color;
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.getContentPane().setBackground(Color.red);
                                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;
    }
}

Answer 3

你们是对的,EDT不是在启动时直接启动的。我做了一些调试,这就是我找到的:

事件调度线索在某个部件请求访问事件队列时启动, 只需调用工具包. getEventQuue () 即可启动。这可以在调用 subject.show () () (与 subject. set Veabilable () 相同) 时完成, 但还有其他电话可以触发此初始化, 如 subp. repaint () 。一旦引用了事件队列, 可以在它上添加一个任务, 使用“ 事件队列 ”. postEvent () 。如果 EDT 存在, 并且如果它没有以 Init DispatchThread () 创建它, 此方法可以检查。

防止它开始的唯一办法是用“-Djava.awt.headless= true”的旗帜启动无头模式的JVM(它共同禁用了 AWT ) 。但是这基本上是你唯一可以与之进行低层次互动的。

元件的可视方法应该总是在 EDT 上引用( 就像您对 Swing / AWT 组件所做的任何其它修改一样 ) 。您通过告诉 Java 执行 EDT 代码来使用 EDT 。最简单的方法就是使用 SwingUplities. invokeLater () 。这安排了您从 EDT 上执行的线索( 您的可运行执行程序) 。这是您作为开发者应该与 EDT 进行的唯一一种互动。您不应该像中止或中止线一样, 与 EDT 有任何低级别的互动。

Q: When exactly is the EDT started? What line of code is responsible [f]of it?

Thoughts on My guess is that "someSwingComponent.setVisible(true)" does the trick, but I m not sure.

Resources

友情链接