java - 线程中断不起作用(Java Android)

Question

编辑: see here!

我有一个带有 Runnable 的线程，如下所示。它有一个我无法弄清楚的问题:我在线程上调用 interrupt() 的一半时间(以停止它)实际上并没有终止(InterruptedException 未被捕获)。

private class DataRunnable implements Runnable {
    @Override
    public void run() {
        Log.d(TAG, "DataRunnable started");
        while (true) {
            try {
                final String currentTemperature = HeatingSystem.get("currentTemperature");
                mView.post(() -> showData(currentTemperature));
            } catch (ConnectException e) {
                mView.post(() -> showConnectionMessage());
                break;
            }
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                break;
            }
        }
        Log.d(TAG, "DataRunnable terminated");
    }
}

问题出在执行长网络操作的 HeatingSystem.get(String) 方法。我猜想在那个方法的某个地方，中断标志被重置了，但我找不到什么语句会这样做(我没有在该方法涉及的所有类的引用中找到它，比如 HttpURLConnection ).方法如下(不是我写的)

/**
 * Retrieves all data except for weekProgram
 * @param attribute_name
 *            = { "day", "time", "currentTemperature", "dayTemperature",
 *            "nightTemperature", "weekProgramState" }; Note that
 *            "weekProgram" has not been included, because it has a more
 *            complex value than a single value. Therefore the funciton
 *            getWeekProgram() is implemented which return a WeekProgram
 *            object that can be easily altered.
 */
public static String get(String attribute_name) throws ConnectException,
        IllegalArgumentException {
    // If XML File does not contain the specified attribute, than
    // throw NotFound or NotFoundArgumentException
    // You can retrieve every attribute with a single value. But for the
    // WeekProgram you need to call getWeekProgram().
    String link = "";
    boolean match = false;
    String[] valid_names = {"day", "time", "currentTemperature",
            "dayTemperature", "nightTemperature", "weekProgramState"};
    String[] tag_names = {"current_day", "time", "current_temperature",
            "day_temperature", "night_temperature", "week_program_state"};
    int i;
    for (i = 0; i < valid_names.length; i++) {
        if (attribute_name.equalsIgnoreCase(valid_names[i])) {
            match = true;
            link = HeatingSystem.BASE_ADDRESS + "/" + valid_names[i];
            break;
        }
    }

    if (match) {
        InputStream in = null;
        try {
            HttpURLConnection connect = getHttpConnection(link, "GET");
            in = connect.getInputStream();

            /**
             * For Debugging Note that when the input stream is already used
             * with this BufferedReader, then after that the XmlPullParser
             * can no longer use it. This will cause an error/exception.
             *
             * BufferedReader inn = new BufferedReader(new
             * InputStreamReader(in)); String testLine = ""; while((testLine
             * = inn.readLine()) != null) { System.out.println("Line: " +
             * testLine); }
             */
            // Set up an XML parser.
            XmlPullParser parser = Xml.newPullParser();
            parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES,
                    false);
            parser.setInput(in, "UTF-8"); // Enter the stream.
            parser.nextTag();
            parser.require(XmlPullParser.START_TAG, null, tag_names[i]);

            int eventType = parser.getEventType();

            // Find the single value.
            String value = "";
            while (eventType != XmlPullParser.END_DOCUMENT) {
                if (eventType == XmlPullParser.TEXT) {
                    value = parser.getText();
                    break;
                }
                eventType = parser.next();
            }

            return value;
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            System.out.println("FileNotFound Exception! " + e.getMessage());
            // e.printStackTrace();
        } catch (XmlPullParserException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (in != null)
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }
    } else {
        // return null;
        throw new IllegalArgumentException("Invalid Input Argument: \""
                + attribute_name + "\".");
    }
    return null;
}

/**
 * Method for GET and PUT requests
 * @param link
 * @param type
 * @return
 * @throws IOException
 * @throws MalformedURLException
 * @throws UnknownHostException
 * @throws FileNotFoundException
 */
private static HttpURLConnection getHttpConnection(String link, String type)
        throws IOException, MalformedURLException, UnknownHostException,
        FileNotFoundException {
    URL url = new URL(link);
    HttpURLConnection connect = (HttpURLConnection) url.openConnection();
    connect.setReadTimeout(HeatingSystem.TIME_OUT);
    connect.setConnectTimeout(HeatingSystem.TIME_OUT);
    connect.setRequestProperty("Content-Type", "application/xml");
    connect.setRequestMethod(type);
    if (type.equalsIgnoreCase("GET")) {
        connect.setDoInput(true);
        connect.setDoOutput(false);
    } else if (type.equalsIgnoreCase("PUT")) {
        connect.setDoInput(false);
        connect.setDoOutput(true);
    }
    connect.connect();
    return connect;
}

有人知道上述方法中的什么可能导致问题吗？

当 interrupt() 在进入 Thread.sleep() 之前被调用时，Thread.sleep() 也会抛出 InterruptException : Calling Thread.sleep() with *interrupted status* set? .

我检查了Thread.sleep()是否在中断后到达，是到达了。

这就是 DataRunnable 的启动和中断方式(我总是得到“onPause called”日志):

@Override
public void onResume() {
    connect();
    super.onResume();
}

@Override
public void onPause() {
    Log.d(TAG, "onPause called");
    mDataThread.interrupt();
    super.onPause();
}

private void connect() {
    if (mDataThread != null && mDataThread.isAlive()) {
        Log.e(TAG, "mDataThread is alive while it shouldn't!"); // TODO: remove this for production.
    }
    setVisibleView(mLoading);
    mDataThread = new Thread(new DataRunnable());
    mDataThread.start();
}

Answer 1

这不是真正的答案，但我不知道该把它放在哪里。通过进一步调试，我认为我遇到了奇怪的行为，并且能够在测试类中重现它。现在我很好奇这是否真的是我怀疑的错误行为，以及其他人是否可以重现它。我希望把它写成答案是可行的。

(将其变成一个新问题，或者实际上只是提交错误报告会更好吗？)

下面是测试类，它必须在 Android 上运行，因为它是关于 getInputStream() 调用的，它在 Android 上的行为不同(不知道为什么)。在 Android 上，getInputStream() 将在中断时抛出 InterruptedIOException。下面的线程循环并在一秒钟后被中断。因此，当它被中断时，异常应该由 getInputStream() 抛出，并且应该使用 catch block 捕获。这有时可以正常工作，但大多数时候不会抛出异常!相反，只有中断标志被重置，因此从 interrupted==true 更改为 interrupted==false，然后被 if 捕获。 if 中的消息为我弹出。在我看来，这是错误的行为。

import java.net.HttpURLConnection;
import java.net.URL;

class InterruptTest {

InterruptTest() {
    Thread thread = new Thread(new ConnectionRunnable());
    thread.start();
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {}
    thread.interrupt();
}

private class ConnectionRunnable implements Runnable {
    @Override
    public void run() {
        while (true) {
            try {
                URL url = new URL("http://www.google.com");
                HttpURLConnection connect = (HttpURLConnection) url.openConnection();

                boolean wasInterruptedBefore = Thread.currentThread().isInterrupted();
                connect.getInputStream(); // This call seems to behave odd(ly?)
                boolean wasInterruptedAfter = Thread.currentThread().isInterrupted();

                if (wasInterruptedBefore == true && wasInterruptedAfter == false) {
                    System.out.println("Wut! Interrupted changed from true to false while no InterruptedIOException or InterruptedException was thrown");
                    break;
                }
            } catch (Exception e) {
                System.out.println(e.getClass().getName() + ": " + e.getMessage());
                break;
            }
            for (int i = 0; i < 100000; i += 1) { // Crunching
                System.out.print("");
            }
        }
        System.out.println("ConnectionThread is stopped");
    }
}
}