为什么SwingWorker意外停止了？ [英] Why does SwingWorker stop unexpectedly?
问题描述
我想尝试一些使用 SwingWorker 的想法，因为我没有使用它太多。
这里是一个简短的 SSCCE 演示这个问题（我知道这里的人喜欢SSCCE）：
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class SwingWorkerTest
{
public static void main（String [] args）
{
SwingUtilities.invokeLater（new Runnable b
@Override
public void run（）
{
new MySwingWorker（500）.execute（）;
new MySwingWorker（900）.execute
new MySwingWorker（1200）.execute（）;
}
}）;
}
}
类MySwingWorker扩展SwingWorker< Void，Void>
{
private int ms;
public MySwingWorker（int ms）
{
this.ms = ms;
}
@Override
protected Void doInBackground（）
{
Thread t = Thread.currentThread（）;
for（int i = 0; i <50; i ++）
{
try
{
Thread.sleep
}
catch（InterruptedException e）
{
e.printStackTrace（）;
}
System.out.println（我的线程是+ ms +休眠在迭代+ i +：+ t.getName（）+ t.getId（）+））;
}
return null;
}
}
因此我的程序应该创建3个SwingWorkers打印一行然后在屏幕上睡眠指定的毫秒数，然后再次打印该行并再次睡眠等。我从Swing的线程创建 SwingWorker s，否则他们不会甚至开始。
所以预期输出是：
线程500休眠在迭代0：SwingWorker-pool-1-thread-1（15）
我是线程900休眠在迭代0：SwingWorker-pool-1-thread-2（16）
我在线程500睡眠在迭代1：SwingWorker-pool-1-thread-1（15）
我是线程1200睡眠在迭代0：SwingWorker-pool-1-thread-3（17）
我在线程500休眠在迭代2：SwingWorker-pool-1-thread-1（15）
我是线程900休眠在迭代1：SwingWorker-pool-1-thread-2（16）
我在线程与500睡眠在迭代3：SwingWorker-pool-1-thread-1（15）
我是线程1200睡眠在迭代1：SwingWorker-pool-1-thread-3 17）
我在线程500休眠在迭代4：SwingWorker-pool-1-thread-1（15）
我是线程900休眠在迭代2：SwingWorker-pool-1-thread- 2（16）
我在线程有500睡眠在迭代5：SwingWorker-pool-1-thread-1（15）
我是线程500睡眠在迭代6：SwingWorker-我的线程有900睡眠在迭代3：SwingWorker-pool-1-thread-2（16）
我是线程1200睡眠在迭代2：SwingWorker-pool- 1-thread-3（17）
我在线程500次睡眠在迭代7：SwingWorker-pool-1-thread-1（15）
............ 。
等等，总共150行（每个3个工人x 50次迭代）相反，我得到的输出是：
睡眠在迭代0：SwingWorker-pool-1-thread-1（15）
我是线程900睡眠在迭代0：SwingWorker-pool-1-thread-2（16）
我是线程在迭代1中有500个睡眠：SwingWorker-pool-1-thread-1（15）
它。只有3行。之后程序退出。 try catch 块中没有堆栈跟踪。
1）。工人有1200ms的睡眠吗？实际上，如果我用1000ms替换1200ms，那么这个工人也打印1行...是的，只有一个。很奇怪...
2）。为什么工人停止？ （我不会得到150行的东西）
我使用在Windows 7 64位的JRE 7 Update 11 64位运行此程序。
PS：我很确定这里提到的错误在这个版本的JRE中是固定的，因为我得到2个不同的值（15和16）作为打印在控制台上的线程ID。这是我怀疑的第一件事。
我相信你需要显示一个可视化的Swing顶级窗口， Swing事件线程活着。否则程序将由于缺少非守护线程而关闭。
编辑：
为了证明SwingWorker thread是一个Daemon线程，只是添加一行代码来测试它：
System.out.println ++（+ t.getId（）+））;+ ms +sleep in iteration
+ i +：+ t.getName
// **** added
System.out.println（Daemon ?:+ Thread.currentThread（）。isDaemon（））;
I wanted to try out some ideas using SwingWorker since I haven't used it too much. Instead, I ran into an issue and I can't figure out what's wrong.
Here's a short SSCCE that demonstrates this problem (I know people here like SSCCEs):
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class SwingWorkerTest
{
public static void main (String[] args)
{
SwingUtilities.invokeLater (new Runnable ()
{
@Override
public void run ()
{
new MySwingWorker (500).execute ();
new MySwingWorker (900).execute ();
new MySwingWorker (1200).execute ();
}
});
}
}
class MySwingWorker extends SwingWorker<Void, Void>
{
private int ms;
public MySwingWorker (int ms)
{
this.ms = ms;
}
@Override
protected Void doInBackground()
{
Thread t = Thread.currentThread ();
for (int i = 0; i < 50; i++)
{
try
{
Thread.sleep (ms);
}
catch (InterruptedException e)
{
e.printStackTrace ();
}
System.out.println ("I am thread with " + ms + " sleep in iteration " + i + ": " + t.getName () + " (" + t.getId () + ")");
}
return null;
}
}
So my program should create 3 SwingWorkers that print a line on the screen then sleep for the specified number of milliseconds and then print the line again and sleep again etc. I create the SwingWorkers from within Swing's thread because otherwise they wouldn't even start.
So the expected output is:
I am thread with 500 sleep in iteration 0: SwingWorker-pool-1-thread-1 (15)
I am thread with 900 sleep in iteration 0: SwingWorker-pool-1-thread-2 (16)
I am thread with 500 sleep in iteration 1: SwingWorker-pool-1-thread-1 (15)
I am thread with 1200 sleep in iteration 0: SwingWorker-pool-1-thread-3 (17)
I am thread with 500 sleep in iteration 2: SwingWorker-pool-1-thread-1 (15)
I am thread with 900 sleep in iteration 1: SwingWorker-pool-1-thread-2 (16)
I am thread with 500 sleep in iteration 3: SwingWorker-pool-1-thread-1 (15)
I am thread with 1200 sleep in iteration 1: SwingWorker-pool-1-thread-3 (17)
I am thread with 500 sleep in iteration 4: SwingWorker-pool-1-thread-1 (15)
I am thread with 900 sleep in iteration 2: SwingWorker-pool-1-thread-2 (16)
I am thread with 500 sleep in iteration 5: SwingWorker-pool-1-thread-1 (15)
I am thread with 500 sleep in iteration 6: SwingWorker-pool-1-thread-1 (15)
I am thread with 900 sleep in iteration 3: SwingWorker-pool-1-thread-2 (16)
I am thread with 1200 sleep in iteration 2: SwingWorker-pool-1-thread-3 (17)
I am thread with 500 sleep in iteration 7: SwingWorker-pool-1-thread-1 (15)
.............
and so on for a total of 150 lines (3 workers x 50 iterations for each)
Instead, the output I get is:
I am thread with 500 sleep in iteration 0: SwingWorker-pool-1-thread-1 (15)
I am thread with 900 sleep in iteration 0: SwingWorker-pool-1-thread-2 (16)
I am thread with 500 sleep in iteration 1: SwingWorker-pool-1-thread-1 (15)
And that's it. Just 3 lines. After this the program exits. There's no stacktrace anywhere from that try catch block.
1). Where is the worker with the 1200ms sleep ? Actually, if I replace 1200ms with 1000ms, then this worker also prints 1 line... yes, only one. Weird...
2). Why do the workers stop ? (and I don't get 150 lines of stuff)
I ran this program using JRE 7 Update 11 on Windows 7 64-bit.
PS: I'm pretty sure that the bug mentioned here was fixed in this version of JRE, since I do get 2 distinct values (15 and 16) as thread ID's printed on the console. This was the first thing I suspected.
I believe that you need to show a visualized Swing top level Window in order to keep the Swing event thread alive. Otherwise the program will shut down for lack of non-daemon threads.
Edit:
To prove that the SwingWorker thread is a Daemon thread, just add a line of code to test it:
System.out.println("I am thread with " + ms + " sleep in iteration "
+ i + ": " + t.getName() + " (" + t.getId() + ")");
// **** added
System.out.println("Daemon?: " + Thread.currentThread().isDaemon());
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