Question

使用线程刷新SWT构建的图形用户界面是一个大问题。我已经研究了文档，但无法弄清楚任务是将文件夹的所有文件（仅文件，而不是子目录）复制到给定的目标文件夹在此过程中，我计算已经完成的文件的大小和剩余时间然后在每次迭代中，我都会尝试通过单步进度条和更改状态标签来显示此信息。

代码如下所示：

public class MyClass {
  private Display display;
  private ProgressBar progressBar;
  private Label statusLabel;

  private File inputFile;
  private File outputFolder;

  ...

  public void init(File inputFile, File outputFolder) {
    this.inputFile = inputFile;
    this.outputFolder = outputFolder;

    progressBar.setSelection(0);
    statusLabel.setText("");
  }

  private class CopyFileTask implements Runnable {
    @Override
    public void run() {
      long processedSize = 0L;
      long startTime = System.currentTimeMillis();
      long totalSize = 0L;

      try {
        File[] entries = inputFile.getParentFile().listFiles();

        for (File theEntry : entries) {
          if (theEntry.isFile()) {
            totalSize += theEntry.length();
          }
        }

        for (File theEntry : entries) {
          if (theEntry.isFile()) {
            String entryName = theEntry.getName();
            File file = new File(outputFolder, entryName);

            InputStream fis = new FileInputStream(theEntry);
            FileOutputStream fos = new FileOutputStream(file);

            try {
              byte[] buffer = new byte[1024];
              int len;

              while ((len = fis.read(buffer)) > 0) {
                fos.write(buffer, 0, len);
                processedSize += len;

                showProgressInfo(startTime, processedSize, totalSize);
              }
            } finally {
              try {
                fis.close();
                fos.close();
              } catch (IOException e) {
              }
            }
          }
        }
      } catch (Exception e) {
        Log.error(e);
      }
    }

    private void showProgressInfo(long startTimeMillis, long processedSize, long totalSize) {
      int percent = (int) ((double) processedSize / (double) totalSize * 100.0);
      progressBar.setSelection(percent);

      long elapsedTimeSeconds = (System.currentTimeMillis() - startTimeMillis) / 1000L;
      long remainingSize = totalSize - processedSize;
      long remainingTimeSeconds = (long) ((double) remainingSize
        / (double) processedSize * elapsedTimeSeconds);
      statusLabel.setText(formatFileSize(processedSize)
        + " of "
        + formatFileSize(totalSize)
        + " - Remaining: "
        + secondsToString(remainingTimeSeconds));
    }

    private String formatFileSize(long value) {
      // return value in Bytes, KB, MB, GB
    }

    private String secondsToString(long value) {
      // return value in MM:SS
    }
  }
}

我点击按钮开始这个过程：

startButton.addListener(SWT.Selection, new Listener() {
  @Override
  public void handleEvent(Event e) {
    display.asyncExec(new CopyFileTask());
  }    
});

现在我的问题是GUI在整个过程完成之前一直处于冻结状态，换句话说 - 标签和进度条只在最后刷新。

Answer 1

您应该从不同的线程中的selectionListener中开始更新：

startButton.addListener(SWT.Selection, new Listener() {

    @Override
    public void handleEvent(Event e) {
        Thread thread = new Thread(new CopyFileTask());
        thread.start();
    }
});

然后使用asyncExec（）将进度更新从当前线程发布到显示线程，例如：

...                         
final long tmpStartTime = startTime;
final long tmpProcessedSize = processedSize;
final long tmpTotalSize = totalSize;
Display.getDefault().asyncExec(new Runnable() {

    @Override
    public void run() {
        showProgressInfo(tmpStartTime, tmpProcessedSize, tmpTotalSize);
    }
});
...

asyncExec不适用于文件复制进度

1 个答案: