Question

我有一段下载文件的代码。这发生在SwingWorker doInBackground方法中。（参见下面的代码）file是一个File对象（temp dir），连接是一个URLConnection对象，它保存要下载的文件的url。（url.openConnection（））除了取消...

之外，下载在SwingWorker中正常工作

SwingWorker<Integer,Integer> swingWorker = new SwingWorker<Integer,Integer>() {

    int contentLength = 0;
    int bytesDownloaded = 0;

    double speed = 0;

    @Override
    protected Integer doInBackground() throws Exception {

    setStatus("Dowloading...");

    URL url = null;
    URLConnection connection = null;

    try {
        url = new URL(MainScreen.getUrl()); // Gets a URL entered earlier to dowload
        connection = url.openConnection();
    } catch (Exception ex) {
        ex.printStackTrace(System.err);
    }

    BufferedOutputStream outputStream = null;
    try {
        BufferedInputStream inputStream = new BufferedInputStream(connection.getInputStream());
        outputStream = new BufferedOutputStream(new FileOutputStream(doelBestand));

        contentLength = connection.getContentLength();

        long start = System.nanoTime();
        final double nanosPerSecond = 1000000000.0;
        final double bytesPerMB = 1024 * 1024;

        while(true) {
        int b = inputStream.read();
        bytesDownloaded += b;
        speed = nanosPerSecond / bytesPerMB * bytesDownloaded / (System.nanoTime() - start + 1);
        process();
        if (b == -1 || Thread.interrupted()) {
            break;
        }
        outputStream.write(b);
        }
    } catch (IOException ex) {
        ex.printStackTrace(System.err);
    } finally {
        try {
        if(outputStream != null) {
            outputStream.close();
        }
        } catch (IOException ex) { }
        try {
        if(connection != null) {
            connection.getInputStream().close();
        }
        } catch (IOException ex) {  }
    }
    return 100;
    }

    @Override
    protected void done() {
    progressBar.setIndeterminate(false);
    progressBar.setValue(100);
    lblPercent.setText("100 %");
    btnStartCancel.setEnabled(false);
    btnOpenFolder.setEnabled(true);
    chkCloseOnFinish.setEnabled(false);
    state = State.DONE;
    }

    protected void process() {
    DecimalFormat df = new DecimalFormat("0.##"); 
    if(speed > 0) {
        lblDownloadSpeed.setText(df.format(speed) + " mb/s");
    }

    if(contentLength > 0) {
        Integer percent = (int) (bytesDownloaded / (contentLength / 100.0));
        progressBar.setValue(percent);
        lblPercent.setText(percent + " %");
    } else {
        progressBar.setIndeterminate(true);
    }

    }
};

但是当用户按下“开始/取消”按钮时，程序的状态是“下载”。我正在调用swingWorker.cancel(true);方法。

switch(state) {
    case READY:
    state = State.DOWNLOADING;
    btnStartCancel.setText("Cancel");

    swingWorker.execute();
    break;
    case DOWNLOADING:
    swingWorker.cancel(true);
        progressBar.setIndeterminate(false);
    lblPercent.setText("Download was cancelled by the user.");
    btnStartCancel.setText("Start");
    btnStartCancel.setEnabled(true);
    break;
    case DONE:
    // Do nothing
    break;

}

但是isInterrupted()总是返回false，所以它继续运行线程，但是cancel函数确实返回true。

我也尝试了while(!isCancelled())，但这也会继续返回false。

还有一个问题，当它被取消时，它永远不会停止，所以它变成了一个无限的线程。（int b继续运行被添加，bytesDownloaded将增长和增长）。只要在没有取消的情况下完成下载（然后b将为-1）并且循环将中断，它就不是无限的。

如何确保swingWorker中止下载？

Java SwingWorker isInterrputed在取消后返回false

0 个答案: