java - "AWT-EventQueue-0"java.lang.NullPointerException 异常

Question

我想突出显示字符串中存在的模式。为此，我创建了一个模式数据库并将它们存储在一个数组中。现在我希望这些模式在 jtextpane 中以不同的颜色突出显示，并且我为此目的使用了 if else 条件，该条件将根据存储在其他数组列表中的字符串突出显示具有不同颜色的模式，但我遇到以下异常。

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.text.DefaultHighlighter.paint(DefaultHighlighter.java:72)
at javax.swing.plaf.basic.BasicTextUI.paintSafely(BasicTextUI.java:731)
at javax.swing.plaf.basic.BasicTextUI.paint(BasicTextUI.java:881)
at javax.swing.plaf.synth.SynthEditorPaneUI.paint(SynthEditorPaneUI.java:180)
at javax.swing.plaf.synth.SynthEditorPaneUI.update(SynthEditorPaneUI.java:168)
at javax.swing.JComponent.paintComponent(JComponent.java:778)
at javax.swing.JComponent.paint(JComponent.java:1054)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5219)

at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1452)
at javax.swing.RepaintManager.paint(RepaintManager.java:1249)
at javax.swing.JComponent._paintImmediately(JComponent.java:5167)
at javax.swing.JComponent.paintImmediately(JComponent.java:4978)
at javax.swing.RepaintManager$3.run(RepaintManager.java:808)
at javax.swing.RepaintManager$3.run(RepaintManager.java:796)
at java.security.AccessController.doPrivileged(Native Method)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:769)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:718)
at javax.swing.RepaintManager.access$1100(RepaintManager.java:62)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1677)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
atjava.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

这是我的代码。

  jTextPane2.setText(seq);

  for (int i = 0; i < mot.size(); i++) {
    if (mot.get(i) == "set") {
      myHighlightPainter = new MyHighlightPainter(Color.red);
    } else if (mot.get(i) == "get") {
      myHighlightPainter = new MyHighlightPainter(Color.green);
    }
    highlight(jTextPane2, pat.get(i));
  }// patterns arraylist
}

public void highlight(JTextComponent textComp, String pattern) {

  try {
    Highlighter hilite = textComp.getHighlighter();
    Document doc = textComp.getDocument();
    String text = doc.getText(0, doc.getLength());
    int pos = 0;

    // Search for pattern
    // see I have updated now its not case sensitive
    while ((pos = text.toUpperCase().indexOf(pattern.toUpperCase(), pos)) >= 0) {
      // Create highlighter using private painter and apply around pattern
      hilite.addHighlight(pos, pos + pattern.length(), myHighlightPainter);
      pos += pattern.length();
    }
  } catch (BadLocationException e) {
  }
}

如何解决这个问题？

Answer 1

在某些情况下，您的 myHighlightPainter 为 null。

DefaultHighlighter第72行

            Highlighter.HighlightPainter p = info.getPainter();
      -->   p.paint(g, info.getStartOffset(), info.getEndOffset(),a, component);