Question

我正在编写一个程序，可以将一组问题写入审阅文件，供另一个程序阅读。可能的答案输入底部的JTextFields。它有代码确保最后不会有多个空白的JTextField。当我输入答案时，在不同的点上会抛出一个StackOverflowError。

堆栈跟踪：

Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
    at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232)
    at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232)
    at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232)
    at java.awt.AWTEventMulticaster.keyPressed(AWTEventMulticaster.java:232)

和代码：现在缩短了!!!

package writer;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class MyPanel extends JPanel implements KeyListener
{
    private MutableQuestion current;
    private WriterPanel writer;
    private JPanel top=new JPanel(new BorderLayout()),answerPanel=new JPanel(new GridLayout(0,1));
    private JSplitPane split;
    private JTextField title=new JTextField();
    private JTextArea question=new JTextArea();
    private ArrayList<JTextField> answers=new ArrayList<JTextField>();
    public MyPanel()
    {
    super(new BorderLayout());
        this.add(title,BorderLayout.PAGE_START);
        split=new JSplitPane(JSplitPane.VERTICAL_SPLIT,true,new JScrollPane(question),new JScrollPane(answerPanel));
    split.setDividerLocation(150);
    this.add(split,BorderLayout.CENTER);
    answers.add(new JTextField());
    answerPanel.add(answers.get(0));
    answers.get(0).addKeyListener(this);
}
private void back(){}
private void fitTitle(){}
private void fixAnswers()
{
    //System.out.println(answers);
    while(answers.get(answers.size()-1).getText().equals("")&&answers.size()>1&&answers.get(answers.size()-2).getText().equals(""))
        removeAnswer(answers.size()-1);
    if(!answers.get(answers.size()-1).getText().equals(""))
    {
        answers.add(new JTextField());
        answerPanel.add(answers.get(answers.size()-1));
        answers.get(answers.size()-2).removeKeyListener(this);
        //answers.get(answers.size()-1);
        answerPanel.revalidate();
    }
    answers.get(answers.size()-1).addKeyListener(this);
}
private void removeAnswer(int i){}
public void keyTyped(KeyEvent e) 
{
    fixAnswers();
}
public void keyPressed(KeyEvent e) {}
public void keyReleased(KeyEvent e) {}
public void newQuestion(){}
public void loadQuestion(int i){}
public void saveQuestion(){}
public void loadQuestion(MutableQuestion q){}
public static void main(String[] args)
{
    JFrame j=new JFrame();
    j.setSize(600,600);
    j.add(new MyPanel());
    j.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    j.setVisible(true);
}

}

Answer 1

每次键入一个键时，都会调用初始侦听器（此＆＃39;）keyTyped方法，调用fixAnswers，最后一步，它会向JTextField添加另一个侦听器。您永远不会删除任何侦听器，因此最终您拥有比Java堆栈可以处理的更长的字符串。

你只需要一个听众。不要继续添加它们，我怀疑你的问题会消失。

Answer 2

AWTEventMulticaster中的无限递归通常是由您自己添加组件引起的。我无法看到你粘贴的代码会发生什么情况，但错误可能出现在代码的其他部分。

请参阅What causes an endless recursion in AWTEventMulticaster.mouseEntered()?。

Answer 3

下次发布问题时的建议：提供SSCCE。如果我们现在想运行你的代码，我们必须修复由于缺少类而导致的一堆编译错误，并提供自己的主要方法。 WriterPanel类似乎与错误完全无关。

此外，删除代码。您已经得出结论，错误在fixAnswers方法中。然后，我们无需为top面板和question提供代码。请参阅下面的精简版，可以重现问题。取消注释该行以修复错误。

package writer;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.WindowConstants;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;

public class SetPanel extends JPanel implements KeyListener {
  private JPanel answerPanel = new JPanel( new GridLayout( 0, 1 ) );
  private ArrayList<JTextField> answers = new ArrayList<JTextField>();

  public SetPanel(  ) {
    super( new BorderLayout() );
    this.add( new JScrollPane( answerPanel ), BorderLayout.CENTER );
    answers.add( new JTextField() );
    answerPanel.add( answers.get( 0 ) );
    answers.get( 0 ).addKeyListener( this );
  }

  private void fixAnswers() {
    while ( answers.get( answers.size() - 1 ).getText().equals( "" ) && answers.size() > 1 && answers.get( answers.size() - 2 ).getText().equals( "" ) )
      removeAnswer( answers.size() - 1 );
    if ( !answers.get( answers.size() - 1 ).getText().equals( "" ) ) {
      answers.add( new JTextField() );
      answerPanel.add( answers.get( answers.size() - 1 ) );
      answers.get( answers.size() - 2 ).removeKeyListener( this );
      answerPanel.revalidate();
    }
//    answers.get( answers.size() - 1 ).removeKeyListener( this );
    answers.get( answers.size() - 1 ).addKeyListener( this );
  }

  private void removeAnswer( int i ) {
    answers.remove( i );
    answerPanel.remove( i );
    answerPanel.revalidate();
  }

  @Override
  public void keyTyped( KeyEvent e ) {
  }

  @Override
  public void keyPressed( KeyEvent e ) {
    fixAnswers();
  }

  @Override
  public void keyReleased( KeyEvent e ) {

  }

  public static void main( String[] args ) {
    EventQueue.invokeLater(new Runnable() {
      @Override
      public void run() {
        JFrame testFrame = new JFrame( "TestFrame" );
        testFrame.add( new SetPanel() );
        testFrame.pack();
        testFrame.setDefaultCloseOperation( WindowConstants.EXIT_ON_CLOSE );
        testFrame.setVisible( true );
      }
    });
  }
}

KeyListener中出现意外的StackOverflowError

3 个答案: