java - 取消/强制停止通过 SwingWorker 执行的输入和输出流

Question

我想停止通过 SwingWorker doInBackground 执行的输入和输出流。每当我取消任务时，它仍然会创建文件(请参阅下面的代码)。任务很简单，“对于指定的每个文件名(String)，输出具有给定名称的文件”(类似的东西)。

我在单独的包/类中编写了 IO 流。所以代码是这样的:

public class ResourceFileExtract(String outputFile) {
  InputStream inputStream = null;
  OutputStream outputStream = null;
  try {
    inputStream = getClass().getResourceAsStream("/resources/someFile");
    outputStream = new FileOutputStream(outputFile);
    byte[] bytes = new byte[1024];
    int numbers;
    while ((numbers = inputStream.read(bytes)) > 1) {
      outputStream.write(bytes, 0, length)
    }
    outputStream.flush();
    outputStream.close();
    inputStream.close();
  } /* Other codes here */
}

SwingWorker 设置。

private class BackgroundTask extends SwingWorker<Integer, String> {
  @Override
  protected Integer doInBackground() {
    /* Some codes here */
    if (!isCancelled()) {
       for (/* Loop statement */) {
         try {
           // Input and Output stream called from a class...
           ResourceFileExtract fileExtract = new ResourceFileExtract(specifiedOutputName);
           System.out.println("Done (file extracted successfully)");
         } catch (IOException ex) {
           System.out.println("Error (unable to read resource file)");
           return 0;
         }
       }
    } else {
      // These texts are not printed in console...
      System.out.println("Cancelled (I/O streaming stopped)");
      return 0;
    }
    return 0;
  }
}

SwingWorker 执行方式:

JButton start = new JButton("Start");
start.addActionListener(new ActionListener() {
  @Override
  public void actionPerformed(ActionEvent evt) {
    BackgroundTask bgTask = new BackgroundTask();
    bgTask.execute();
  }
});

并取消:

JButton stop = new JButton("Stop");
stop.addActionListener(new ActionListener() {
  @Override
  public void actionPerformed(ActionEvent evt) {
    bgTask.cancel(true);
  }
});

在调试程序时，取消消息不会打印在控制台中，这意味着每当我点击取消按钮时任务都不会被取消，并且仍然使用成功消息创建输出文件。我怎样才能阻止这个呢？有什么帮助吗？

Answer 1

基本上，您的 ResourceFileExtract 类需要以某种方式取消，例如......

public class ResourceFileExtract {

    private String outputFile;
    private AtomicBoolean cancelled = new AtomicBoolean(false);

    public ResourceFileExtract(String outputFile) {
        this.outputFile = outputFile;
    }

    public void cancel() {
        cancelled.set(true);
    }

    public void extract() throws IOException {

        try (InputStream inputStream = getClass().getResourceAsStream("/resources/someFile");
                 OutputStream outputStream = new FileOutputStream(outputFile)) {
            byte[] bytes = new byte[1024];
            int numbers;
            while (!cancelled.get() && (numbers = inputStream.read(bytes)) > 1) {
                outputStream.write(bytes, 0, numbers);
            }
        } catch (IOException exp) {
            throw exp;
        }
    }
}

然后在您的 SwingWorker 中，您需要提供某种自己的“停止”方法(因为 cancel 是 final : P) 并且我不能保证会因为调用 cancel 本身而触发任何属性更改事件。

工作线程需要维护对由 doInBackground 方法创建的提取器的引用，以允许其成功触发提取器中的取消