如何在单独的线程中调用（JAVA LIBRARY）的编码方法？

【问题标题】：How to call encode method of (JAVE LIBRARY) in a separate thread?如何在单独的线程中调用（JAVA LIBRARY）的编码方法？
【发布时间】：2015-11-21 23:24:40
【问题描述】：

我正在编写一个 java 应用程序来将音频文件从 mp3 转换为 mp3 或其他格式。我正在使用 JAVE 库。 Encoder 类的 encode 方法是一种阻塞方法。所以，我试图在一个单独的线程中运行它。它压缩成功，但它给出了空指针异常。

请告诉我在新线程中调用 encode 方法的正确方法。如何避免 IllegalStateException？

run 方法抛出 NPE

public class DayTwo extends JFrame implements ActionListener, Runnable
{

public static JFrame frame = new JFrame("Audio Compression Utility");

Thread myThread;

String[] bitRateValues = {"64000", "128000", "160000", "192000", "256000","320000"};
String samplingRateValues[] = {"44100", "48000","24000", "96000"};
String[] formatValues = {"wav", "mp3"};
JFileChooser sourceFileOpen = new JFileChooser();

String sourceStr = new String(), targetStr = new String() ;
 File source = null,target = null;

 Encoder encoder = new Encoder();
 EncodingAttributes attrs = new EncodingAttributes();
 AudioAttributes audio = new AudioAttributes();

 //After that i have declared JButtons , Jlabels etc..
 ...
  }

类的构造函数

DayTwo()
{
super("Audio Compression");
setLookAndFeel();
setBounds(50,50,850,650);
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
browseTargetFileBtn.setEnabled(false);

这是构造函数中的运行方法

myThread = new Thread(new Runnable()
        {
    public void run()
    {
        try
        {
            encoder.encode(source, target, attrs);
            JOptionPane.showMessageDialog(frame, "Success");
        }catch(Exception e)
        {
                 e.printStackTrace();
        }

    }
    });

这是“压缩”按钮的操作执行方法

ActionListener actionListenerObjectForCompression =new ActionListener()
{
      @Override public void actionPerformed(ActionEvent e) {
          try
          {  
                audio.setCodec("libmp3lame");
                audio.setBitRate( 96000 ); //96,000 = 96 kbit per sec
                audio.setSamplingRate(44100);

                attrs.setFormat("mp3");
                attrs.setAudioAttributes(audio);

                myThread.start();
          }
          catch(Exception je)
          {
             je.printStackTrace();
          }
          }
};

这是用户选择输出文件夹时“浏览”按钮的操作执行方法

ActionListener actionListenerObjectForTargetLocation = new ActionListener()
{
        @Override public void actionPerformed(ActionEvent e) 
        {
            JFileChooser targetFileOpen = new JFileChooser();
            if (targetFileOpen.showSaveDialog(null) == JFileChooser.APPROVE_OPTION)
            {

                targetStr = targetFileOpen.getSelectedFile().getPath();
                browseTargetFileTextField.setText(targetStr);
                target = new File(targetStr);
            }
        }
};

这是用户选择源文件时“浏览”按钮的操作执行方法

ActionListener actionListenerObjectForSelectFile = new ActionListener()
{

public void actionPerformed(ActionEvent e) 
{

    if (sourceFileOpen.showOpenDialog(null) == JFileChooser.APPROVE_OPTION)
    {
        browseTargetFileBtn.setEnabled(true);
        sourceStr = sourceFileOpen.getSelectedFile().getPath();
        browseTargetFileBtn.setEnabled(true);
        source = new  File(sourceStr);
        browseSourceFileTextField.setText(sourceFileOpen.getSelectedFile().getPath());
    }
}
};

主要方法：

public static void main(String[] args)
{
 DayTwo ob = new DayTwo();
}

}

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.text.JTextComponent.getSelectionStart(Unknown Source)
at javax.swing.text.PlainView.paint(Unknown Source)
at javax.swing.text.FieldView.paint(Unknown Source)
at javax.swing.plaf.basic.BasicTextUI$RootView.paint(Unknown Source)
at javax.swing.plaf.basic.BasicTextUI.paintSafely(Unknown Source)
at javax.swing.plaf.basic.BasicTextUI.paint(Unknown Source)
at javax.swing.plaf.basic.BasicTextUI.update(Unknown Source)
at javax.swing.JComponent.paintComponent(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JLayeredPane.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintToOffscreen(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
at javax.swing.RepaintManager.paint(Unknown Source)
at javax.swing.JComponent._paintImmediately(Unknown Source)
at javax.swing.JComponent.paintImmediately(Unknown Source)
at javax.swing.RepaintManager$4.run(Unknown Source)
at javax.swing.RepaintManager$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.access$1200(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at   java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.basic.BasicComboBoxUI.isPopupVisible(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsComboBoxUI.getXPComboBoxState(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsComboBoxUI.paintXPComboBoxBackground(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsComboBoxUI.paint(Unknown Source)
at javax.swing.plaf.ComponentUI.update(Unknown Source)
at javax.swing.JComponent.paintComponent(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintToOffscreen(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source)
at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
at javax.swing.RepaintManager.paint(Unknown Source)
at javax.swing.JComponent._paintImmediately(Unknown Source)
at javax.swing.JComponent.paintImmediately(Unknown Source)
at javax.swing.RepaintManager$4.run(Unknown Source)
at javax.swing.RepaintManager$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.access$1200(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.DefaultListCellRenderer.getListCellRendererComponent(Unknown Source)
at javax.swing.plaf.basic.BasicComboBoxUI.getDisplaySize(Unknown Source)
at javax.swing.plaf.basic.BasicComboBoxUI.getMinimumSize(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsComboBoxUI.getMinimumSize(Unknown Source)
at javax.swing.JComponent.getMinimumSize(Unknown Source)
at java.awt.GridLayout.minimumLayoutSize(Unknown Source)
at java.awt.Container.minimumSize(Unknown Source)
at java.awt.Container.getMinimumSize(Unknown Source)
at javax.swing.JComponent.getMinimumSize(Unknown Source)
at javax.swing.BoxLayout.checkRequests(Unknown Source)
at javax.swing.BoxLayout.preferredLayoutSize(Unknown Source)
at java.awt.Container.preferredSize(Unknown Source)
at java.awt.Container.getPreferredSize(Unknown Source)
at javax.swing.JComponent.getPreferredSize(Unknown Source)
at java.awt.FlowLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.validateInvalidComponents(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.BoxLayout.preferredLayoutSize(Unknown Source)
at java.awt.Container.preferredSize(Unknown Source)
at java.awt.Container.getPreferredSize(Unknown Source)
at javax.swing.JComponent.getPreferredSize(Unknown Source)
at java.awt.FlowLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.validateInvalidComponents(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.BoxLayout.preferredLayoutSize(Unknown Source)
at java.awt.Container.preferredSize(Unknown Source)
at java.awt.Container.getPreferredSize(Unknown Source)
at javax.swing.JComponent.getPreferredSize(Unknown Source)
at java.awt.FlowLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.validateInvalidComponents(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.BoxLayout.preferredLayoutSize(Unknown Source)
at java.awt.Container.preferredSize(Unknown Source)
at java.awt.Container.getPreferredSize(Unknown Source)
at javax.swing.JComponent.getPreferredSize(Unknown Source)
at java.awt.FlowLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.validateInvalidComponents(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.BoxLayout.preferredLayoutSize(Unknown Source)
at java.awt.Container.preferredSize(Unknown Source)
at java.awt.Container.getPreferredSize(Unknown Source)
at javax.swing.JComponent.getPreferredSize(Unknown Source)
at java.awt.FlowLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.validateInvalidComponents(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at   java.security.ProtectionDomain$JavaSecurityAccessImpl.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)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.BoxLayout.preferredLayoutSize(Unknown Source)
at java.awt.Container.preferredSize(Unknown Source)
at java.awt.Container.getPreferredSize(Unknown Source)
at javax.swing.JComponent.getPreferredSize(Unknown Source)
at java.awt.FlowLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.validateInvalidComponents(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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)

【问题讨论】：

  • 如果您询问有关引发异常的代码的问题并需要我们的帮助，您应始终发布完整的异常堆栈跟踪，并在代码中指出哪一行（哪些）引发了异常。否则我们就瞎了。
  • 首先，我会注意在 Swing 事件线程上运行我的 Swing 代码，并确保没有任何 Swing 代码从该线程运行，除了可能调用 repaint()但没什么。如果仍然卡住，并且您没有得到具体帮助，您可能需要创建并发布您的 minimal reproducible example。
  • 我的问题已经解决了。出现异常是因为我在运行方法中访问 UI 元素。谢谢

标签： java multithreading swing nullpointerexception illegalstateexception


【解决方案1】：

多线程问题的最佳解决方案是使用SwingWorker。
它基本上将工作划分为后台阶段，之后是 GUI 更新阶段。
一个基本的例子：

   class ProperDecoder extends SwingWorker<Object, Object> {
       @Override
       public Object doInBackground() {
           return decode();
       }

       @Override
       protected void done() {
           try {
               Object decoderResult = get();
               updateGUI();
           } catch (Exception ignore) {
             // catch errors
           }
       }
   }

   (new ProperDecoder()).execute();

【讨论】：

  • 这些都是不错的建议，1+，但我不确定它是否能解决 OP 的 NPE。
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