すべての種類のファイル (Microsoft メモ帳など) を読み込もうとしています。私が持っている SwingWorker は通常のテキストを問題なくロードできますが、mp3、pdf などのファイルをロードしようとすると、NullPointerException が発生します。
誰かが私のコードを見て、mp3、pdf などのファイルでこのエラーが発生し続ける理由を理解できますか? 私が言ったように、エラーなしで通常の.htmlプレーンテキストファイルをロードできます。
class Open extends SwingWorker<StringBuilder, Void>
{
File file;
JTextArea jta;
Open(File file, JTextArea jta)
{
this.file = file;
this.jta = jta;
}
@Override
protected StringBuilder doInBackground() throws Exception
{
BufferedReader br = null;
StringBuilder b = new StringBuilder();
try
{
br = new BufferedReader(new FileReader(file));
while(br.ready())
{
b.append(br.readLine() + "\n");
}
}
finally
{
try
{
br.close();
} catch (IOException e) { }
}
return b;
}
@Override
protected void done()
{
try {
jta.append(get().toString());
} catch (InterruptedException ex) {
Logger.getLogger(Open.class.getName()).log(Level.SEVERE, null, ex);
} catch (ExecutionException ex) {
Logger.getLogger(Open.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
これは、コードを次のように変更した後に得られるものです。
class Open extends SwingWorker<Void, String>
{
File file;
JTextArea jta;
Open(File file, JTextArea jta)
{
this.file = file;
this.jta = jta;
}
@Override
protected Void doInBackground() throws Exception
{
BufferedReader br = null;
try
{
br = new BufferedReader(new FileReader(file));
String line = br.readLine();
while(line != null)
{
publish(line);
line = br.readLine();
}
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
try
{
br.close();
} catch (IOException e) { }
}
return null;
}
@Override
protected void process(List<String> chunks)
{
for(String s : chunks)
jta.append(s + "\n");
}
}
これは、Netbeans の「スタック トレース」(だと思います) です。
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.util.Hashtable.put(Hashtable.java:394)
at sun.font.PhysicalStrike.getGlyphPoint(PhysicalStrike.java:112)
at sun.font.SunLayoutEngine.nativeLayout(Native Method)
at sun.font.SunLayoutEngine.layout(SunLayoutEngine.java:133)
at sun.font.GlyphLayout$EngineRecord.layout(GlyphLayout.java:648)
at sun.font.GlyphLayout.layout(GlyphLayout.java:447)
at sun.font.ExtendedTextSourceLabel.createGV(ExtendedTextSourceLabel.java:308)
at sun.font.ExtendedTextSourceLabel.getGV(ExtendedTextSourceLabel.java:294)
at sun.font.ExtendedTextSourceLabel.createCharinfo(ExtendedTextSourceLabel.java:563)
at sun.font.ExtendedTextSourceLabel.getCharinfo(ExtendedTextSourceLabel.java:492)
at sun.font.ExtendedTextSourceLabel.getLineBreakIndex(ExtendedTextSourceLabel.java:438)
at java.awt.font.TextMeasurer.calcLineBreak(TextMeasurer.java:308)
at java.awt.font.TextMeasurer.getLineBreakIndex(TextMeasurer.java:544)
at java.awt.font.LineBreakMeasurer.nextOffset(LineBreakMeasurer.java:340)
at java.awt.font.LineBreakMeasurer.nextLayout(LineBreakMeasurer.java:422)
at javax.swing.text.TextLayoutStrategy.sync(TextLayoutStrategy.java:298)
at javax.swing.text.TextLayoutStrategy.insertUpdate(TextLayoutStrategy.java:52)
at javax.swing.text.FlowView.loadChildren(FlowView.java:126)
at javax.swing.text.CompositeView.setParent(CompositeView.java:122)
at javax.swing.text.FlowView.setParent(FlowView.java:272)
at javax.swing.plaf.basic.BasicTextAreaUI$PlainParagraph.setParent(BasicTextAreaUI.java:222)
at javax.swing.text.CompositeView.replace(CompositeView.java:200)
at javax.swing.text.BoxView.replace(BoxView.java:164)
at javax.swing.text.View.updateChildren(View.java:1095)
at javax.swing.text.View.insertUpdate(View.java:679)
at javax.swing.plaf.basic.BasicTextUI$RootView.insertUpdate(BasicTextUI.java:1590)
at javax.swing.plaf.basic.BasicTextUI$UpdateHandler.insertUpdate(BasicTextUI.java:1849)
at javax.swing.text.AbstractDocument.fireInsertUpdate(AbstractDocument.java:185)
at javax.swing.text.AbstractDocument.handleInsertString(AbstractDocument.java:734)
at javax.swing.text.AbstractDocument.insertString(AbstractDocument.java:693)
at javax.swing.text.PlainDocument.insertString(PlainDocument.java:114)
at javax.swing.JTextArea.append(JTextArea.java:470)
at Open.process(main.java:313)
at javax.swing.SwingWorker$3.run(SwingWorker.java:391)
at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:95)
at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:860)
at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:95)
at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:870)
at javax.swing.Timer.fireActionPerformed(Timer.java:271)
at javax.swing.Timer$DoPostEvent.run(Timer.java:201)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
コードを次のように変更しました。
class Open extends SwingWorker<Void, String>
{
File file;
JTextArea jta;
Open(File file, JTextArea jta)
{
this.file = file;
this.jta = jta;
}
@Override
protected Void doInBackground() throws Exception
{
BufferedReader br = null;
try
{
br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
String line = br.readLine();
while(line != null)
{
publish(line);
line = br.readLine();
}
}
catch (Exception e) { e.printStackTrace(); }
finally
{
try
{
if(br != null)
br.close();
} catch (IOException e) { }
}
return null;
}
@Override
protected void process(List<String> chunks)
{
for(String s : chunks)
jta.append(s + "\n");
}
}
そして、私はまだNPEを受けています。