Question

我正在编写一个涉及JFrame的代码和一个线程。线程应该从文本字段中获取文本并将其写入文本区域。我有4个按钮如下：

“开始”以启动主题。
停止线程的“停止”。
“暂停”暂停并继续线程。
和“退出”停止线程并退出程序。

我已经在frame的构造函数中创建了线程并实现了“run（）”函数，这里是：

WritingThread = new Thread(new Runnable() {
    @Override
    public void run() {
        String s = WrittenText.getText();
        while(true)
        {
            for(int i = 0; i < 4; i++)
            {
                for(int j = 0; j < s.length(); j++)
                {
                    WritingArea.append("" + s.charAt(j));
                    try {
                        Thread.sleep((int)ThreadSpeedSpinner.getValue());
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }   
                }
                WritingArea.append("\n");
            }   
            WritingArea.setText("");
        }
    }
});

这些是按钮：

JButton btnStart = new JButton("Start");
btnStart.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if(!WritingThread.isAlive())
            WritingThread.start();
    }
});
JButton btnStop = new JButton("Stop");
btnStop.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if(WritingThread.isAlive())
            WritingThread.stop();
    }
});
btnPause = new JButton("Pause");
btnPause.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if(!isPaused)
        {
            if(WritingThread.isAlive())
            {
                WritingThread.suspend();
                btnPause.setText("Continue");
                isPaused = true;
            }
        }
        else
        {
            WritingThread.resume();
            btnPause.setText("Pause");
        }
    }
});
JButton btnExit = new JButton("Exit");
btnExit.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        WritingThread.stop();
        System.exit(0);
    }
});

我出现两个问题：

当我使用stop()，suspend()或resume()时，我收到一条警告，说“不推荐使用Thread类型的方法”。

当我运行程序时，我启动线程，然后停止它，然后尝试启动它我有这个异常

Exception in thread "AWT-EventQueue-0" java.lang.IllegalThreadStateException
    at java.lang.Thread.start(Unknown Source)
    at com.HomeWork.HomeWork5$6.actionPerformed(HomeWork5.java:140)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$200(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

我不想直接回答，我想了解为什么我会收到这些错误，如果有任何资源我应该通过。附：我搜索了很多答案，并没有得到任何解释这个问题。感谢

Answer 1

线程获取对象的锁定。而多线程中最重要的部分是安全地交织线程，以便所有线程都可以使用资源（对象）。如果处理不当，则会导致死锁。

当您使用stop()时，您将终止线程。那个线程永远消失了。它可能导致已停止线程获取的对象处于不一致状态。

suspend()已弃用，因为一旦线程被挂起，其他线程将无法获取资源，因为挂起的线程持有锁。

下图描述了如何正确使用线程。使用sleep()，wait()和notify()有效地交错线程。

enter image description here

线程停止，暂停和恢复

1 个答案: