使主要方法等待较小的方法（java）

Question

我真的需要找到更好的方式来表达我的问题。 基本上我已经创建了一个程序，它从网页中获取信息并在屏幕上很好地显示它。

当用户关闭程序时，他们实际上是隐藏了它。

我还有另一种方法，它不断循环检查信息以查看是否已更新。 不幸的是，我遇到的问题是它循环速度很快，我只希望它每 40 秒左右检查一次信息。

我尝试的是在方法本身和程序的主体中插入等待（1000,1000）。但是这两个都会导致 IllegalMonitorStateException。

这是使线程正确等待的正确方法吗？或者，还有更好的方法？ 注意：我唯一的线程是主线程。

主要

class Marquee
{
public static void main(String[] args) throws InterruptedException
{
    MyFrame frame = new MyFrame();
    frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
    frame.setVisible(true);
    frame.setAlwaysOnTop(true);
    frame.setBackground(Color.BLACK);
    frame.setResizable(true);


    while(true)
    {
        // this doesnt work
        frame.wait(1000,1000);
        frame.notifyAll();

        frame.checkForNewUpdate();
        System.out.println("  ____________________________next line _______________________________");

    }
} 
}

检查更新

public String[] checkForNewUpdate()
{
    //setVisible(true);
    String tempUpdate = getEngineersUpdate();

    if (latestUpdate[0] != tempUpdate)
    {
        // do nothign 
        setVisible(false);
    }
    else if(latestUpdate[0]==tempUpdate)
    {
        latestUpdate[0] = tempUpdate;
        //show the page again
        setVisible(true);
    }
    else if(latestUpdate[0]!= "NULL")
    {   
        // do nothing
        //latestUpdate[0] = tempUpdate;
    }
    else
    {
        latestUpdate[0] = tempUpdate;
    }
    return latestUpdate;
}

1：我做错了什么得到这个异常

2：有没有其他方法可以让方法中的时间间隔

3：我是否必须将所有这些方法放到另一个线程中？请说不

---

// my constructor which I failed to mention has a timer in it. only i dont know hwo to use it

 class MyFrame extends JFrame implements ActionListener
{
private ActionListener listener;
private Timer t1;
private String [] latestUpdate = new String[1];


public MyFrame()
{
    Dimension d = Toolkit.getDefaultToolkit().getScreenSize();// gets the maximum size of the screen 
    setSize(d.width,(d.height/100)*10);//sets it to max. need to change this

    // this shit find the max size of screen and puts it bottom left
    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice defaultScreen = ge.getDefaultScreenDevice();
    Rectangle rect = defaultScreen.getDefaultConfiguration().getBounds();
    int x = (int)rect.getMinX();
    int y = (int)rect.getMaxY()-getHeight();
    setLocation(x,y-30);
    setTitle("ALERT::OUTAGE");
    MyPanel panel = new MyPanel();
    add(panel);
    listener = this;
    t1 = new Timer(50,listener);
    t1.start();
}

根据要求，这里是 getEngineersUpdate()

public String getEngineersUpdate()  //gets data from page and sets it to string.
{
    String update = "blank";

    final WebClient webClient = new WebClient();
    webClient.setJavaScriptEnabled(false);// javascript causes some serious problems.
    webClient.setCssEnabled(false);
    String forChecking;

    HtmlPage page;

    try 
    {

        URL outageURL = new URL("file:\\C:\\Users\\0vertone\\Desktop\\version control\\OUTAGE\\Outages.html"); //local drive at home


        page = webClient.getPage(outageURL);


        //All this crap can be gone if we just give the table an id
        Object[] dates = page.getByXPath("//span[@id='date']/text()").toArray();
        Object[] sites = page.getByXPath("//span[@id='site']/text()").toArray();
        Object[] issues = page.getByXPath("//span[@id='issue']/text()").toArray();
        System.out.println("" + dates[0].toString());
        System.out.println("" + sites[0].toString());
        System.out.println("" + issues[0].toString());

        update = (dates[0].toString() + "   " + sites[0].toString() + "   " +issues[0].toString());
        forChecking = dates[0].toString();




        /**some examples of the getCellAt() method*/
        //update = table.getCellAt(0,0).asText();   // This returns DATE/Time
        //update = table.getCellAt(1,0).asText();   // This return the actual date
        //update = table.getCellAt(0,1).asText();   // This returns, SITE/Sector
        //update = table.getCellAt(1,1).asText();   // This returns the actual site issue

    }
    catch (FailingHttpStatusCodeException a) 
    {
    System.out.println("Failing HTTP Status Execution");
    a.printStackTrace();
    } 
    catch (MalformedURLException b) 
    {
    System.out.println("Malformed URL");
    b.printStackTrace();
    } 
    catch (IOException c) 
    {
    System.out.println("IO PROBLEMS!");
    c.printStackTrace();
    }
webClient.closeAllWindows();
return update;
}

Answer 1

我已经更改了您的代码，因此它应该可以按您的预期工作。我不清楚 getEngineersUpdate() 的作用，所以我不能确定它是否会起作用，但我已经给了你一个开始。我已经包含了 2 个关于如何处理它的选项，并在 cmets 中进行了解释。您还可以看到如何在构造函数中正确使用 Timer。最后，我没有你的完整代码，所以我不得不组装一些东西来模拟它。

class Marquee {
    public static void main(String[] args) throws InterruptedException {
        MyFrame frame = new MyFrame();
        frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
        frame.setVisible(true);
        frame.setAlwaysOnTop(true);
        frame.setBackground(Color.BLACK);
        frame.setResizable(true);
    }
}



class MyFrame extends JFrame {
    private String [] latestUpdate = new String[1];
    private static final int DISPLAY_TIME = 3000;
    private Timer displayTimer;

    /*
     * Option #1:
     * Ideally, you'd have the thread that generates the "Engineers Update" messages call this
     * method. If you can't make this event based, then you should use option #2
     */
    public void newUpdate(String message) {
        setVisible(true);
        // change this to whatever you need to.
        text.setText(message);
        displayTimer.restart();
    }

    // I used this to test it
    private JTextField text;

    public MyFrame() {
        // gets the maximum size of the screen
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        //sets it to max. need to change this
        setSize(d.width, (d.height / 100) * 10);

        // this shit find the max size of screen and puts it bottom left
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice defaultScreen = ge.getDefaultScreenDevice();
        Rectangle rect = defaultScreen.getDefaultConfiguration().getBounds();
        int x = (int) rect.getMinX();
        int y = (int) rect.getMaxY() - getHeight();
        setLocation(x, y - 30);
        setTitle("ALERT::OUTAGE");

        //MyPanel panel = new MyPanel();
        //add(panel);
        text = new JTextField("Initial Text");
        add(text);

        // this creates a timer that when it goes off, will hide the frame
        displayTimer = new Timer(DISPLAY_TIME, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                setVisible(false);
            }
        });
        // sets the timer not to repeat
        displayTimer.setRepeats(false);

        //This code is for option #2:
        updateTimer = new Timer(UPDATE_INTERVAL, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                checkForNewUpdate();
            }
        });
        updateTimer.start();
    }

    // This is for option #2
    private static final int UPDATE_INTERVAL = 1000;
    private Timer updateTimer;

    /*
     * Option #2:
     * Not ideal, but this should work.
     */
    public String[] checkForNewUpdate() {
        // I don't know how getEngineersUpdate() works
        // which would have made it much easier to help you.
        String tempUpdate = getEngineersUpdate();

        // String comparison doesn't work like this in java.
        // you also had a sleeping NullPointerException here
        if (!tempUpdate.equals(latestUpdate[0])) {
            // this is when you have a new update, correct?
            newUpdate(tempUpdate);
            latestUpdate[0] = tempUpdate;
        } else if (tempUpdate.equals(latestUpdate[0])) {
            // it's the same update as last time, so do nothing
        } else if (tempUpdate.equals("NULL")) {
            // You need to handle this according to what getEngineersUpdate() does
        }
        return latestUpdate;
    }

    // This code is rigged to show how it would work
    private static int i = 0;
    private String getEngineersUpdate() {
        // 1 in 6 chance of returning "NULL"
        if (Math.random() * 6 - 1 < 0)
            return "NULL";

        // probability of 1 in 4 of generating a new update
        if(Math.random() * 4 - 1 < 0)
            return "UPDATE #"+i++;
        else
            return "UPDATE #"+i;
    }
}

Answer 2

1. 我认为您不能在 JFrame 上调用 wait()，但我不确定。
2. 您必须在同步块内调用wait()。 （以下示例）
3. Thread.sleep(1000l) 可以使用，如果它在线程中运行，但要查找类 Timer
4. 如果您创建一个检查更新的线程，那将是更好的设计。您可以使用某种事件侦听器通知 GUI (JFrame) 要显示的新日期。

看看Timer和Callable。

Answer 3

你应该创建另一个线程，你应该从这个线程调用 checkforNewUpdate 方法。并且不要忘记使用 SwingUtilities.invokeLater 方法在 checkforNewUpdate 方法中更新你的 UI。这是代码的一部分；

 public class Marque         { 

    private JFrame frame;
    class CheckForUpdate implements Runnable {

        public void run() {
            while(true) {
                checkForNewUpdate();
                try {
                    Thread.sleep(40000);
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                    throw new RuntimeException(e1);
                }                     }

        }

        public String[] checkForNewUpdate()     { 
            //your code
            // user interface interaction code
            SwingUtilities.invokeLater(new Runnable() {
                public void run() {
                    frame.setVisible(true);
                }
            });

        }
    }

    public Marque() {
        frame = new JFrame(); 
        //....frame related code
        new Thread(new CheckForUpdate()).start();


    }  
    public static void main(String[] arg) { 
        Marque marque = new Marque();


    }