使用Java线程获取和发送消息 [英] Get and send messages with Java Threads

问题描述

我想创建一个线程，该线程运行，使用我提供的数据计算某些内容，并返回一些值或一个对象.该线程是Swing GUI的一部分.

I want to make a thread, which runs, computes something with the data i give it, and returns a few values, or an object. The thread is a part of a Swing GUI.

我的问题:如何创建一个在线程创建并返回对象(或想要返回的对象)时运行的方法?

My question: How can I make a method that runs when I make the thread, and returns an object (or whatever I want it to return)?

我的代码:

private void nextTurn () {
    // do something
    if (turn == white) {
        try {
            Engine e = new Engine(); // Engine is implemented by runnable
            e.start();
            Move m = e.getBestMove (board);
            // thread should work, next code should be excecuted immediately
        }
        catch (Exception e) {}
    }

    // end of Main class
}

这是我第一次使用Threads，我知道您应该尽可能避免使用它们，但是这次我的GUI需要它. Oracle网站上关于Threads的信息并没有帮助我.我可以制作一个具有不确定运行的多个线程的程序，但不能使其与函数一起使用.

This is the first time I am working with Threads, and I know you should avoid them if possible, but I need it this time for my GUI. The info on the Oracle site on Threads did not help me out. I am able to make a program with multiple Threads that runs indefinately, but I can't make it work with functions.

推荐答案

由于这是带有Swing GUI的，请考虑使用创建后台线程的SwingWorker对象(所有代码均在doInBackground方法中运行)，然后可以返回最终结果和/或中期结果.有关如何使用它的信息已在此处的教程中得到了很好的记录:

Since this is with a Swing GUI, consider using a SwingWorker object which creates a background thread (all the code run in the doInBackground method), and then can return a final result and/or interim results. Information on how to use this is well documented in the tutorials here:

Swing中的并发

SwingWorkers具有属性更改支持，因此将允许侦听器通过PropertyChangeListener观察其状态(作为SwingWorker.StateValue).这是您的程序可以确定线程已完成其处理，获取返回结果并从那里进行的一种方法.

SwingWorkers have property change support and thus will allow listeners to observe its state (as a SwingWorker.StateValue) via a PropertyChangeListener. This is one way your program can determine that the thread has completed its processing, get the returned result and go from there.

在不相关的注释上，这不是您的生产代码吗?:

On an unrelated note, this isn't in your production code is it?:

catch (Exception e) {}

如果是这样，您可能会想解决此问题，因为被忽略的异常会在很长一段时间内咬住您.

If so, you will likely want to fix this as ignored exceptions can bite you in the tail big time.

例如

  if (turn == white) {
     try {
        final SwingWorker<Move, Void> mySwingWorker = new SwingWorker<Move, Void>() {
           @Override
           protected Move doInBackground() throws Exception {
              Engine e = new Engine(); // Engine is implemented by runnable
              e.start();
              Move m = e.getBestMove(board);                  
              return m;
           }
        };

        mySwingWorker.addPropertyChangeListener(new PropertyChangeListener() {
           public void propertyChange(PropertyChangeEvent evt) {
              if (StateValue.DONE == mySwingWorker.getState()) {
                 try {
                    Move m = mySwingWorker.get();

                    // TODO: insert code to run on the EDT after move determined

                 } catch (InterruptedException e) {
                    e.printStackTrace();
                 } catch (ExecutionException e) {
                    e.printStackTrace();
                 }
              }
           }
        });
        mySwingWorker.execute();

     } catch (Exception e) {
        e.printStackTrace();
     }
  }

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