OutputStream.write()上出现空指针异常

Question

尝试使用itext写入pdf格式晚上一切都很好，但现在不行了。

我已经浏览了大约100次代码，但我仍然不明白问题出在哪里。

这是我的代码

public void writetopdf()
{
flag=1;

File f = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/pdf_report");
if(f.isDirectory())
Log.d("Main", "writetopdf: " + f.isDirectory());
else {
f.mkdir();
Log.d("Main", "writetopdf: " + f.isDirectory());
}
File pdf = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/pdf_report/" + title.getText().toString().trim() + ".pdf");
OutputStream output = null;
try {
output = new FileOutputStream(pdf);
} catch (FileNotFoundException e) {
e.printStackTrace();
}

try {
reader = new PdfReader( getResources().openRawResource(R.raw.hrgroup) );
} catch (IOException e) {
e.printStackTrace();
}

try {
stamper = new PdfStamper(reader, output);
} catch (DocumentException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
acroFields = stamper.getAcroFields();
Set<String> fldNames = acroFields.getFields().keySet();
for (String fldName : fldNames) {
Log.d("Main","some = " + fldName );
fieldnames.add(fldName);
}

try {
setthedata();
} catch (IOException | DocumentException e) {
e.printStackTrace();
}

stamper.setFormFlattening(true);
try {
stamper.close();
} catch (DocumentException | IOException e) {
e.printStackTrace();
}

Toast.makeText(Objects.requireNonNull(getActivity()).getApplicationContext(),"PDF Generated", Toast.LENGTH_LONG).show();

}

这是Logcat错误

java.lang.NullPointerException: Attempt to invoke virtual method 'void java.io.OutputStream.write(byte[], int, int)' on a null object reference
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
at java.io.BufferedOutputStream.write(BufferedOutputStream.java:126)
at java.io.FilterOutputStream.write(FilterOutputStream.java:97)
at com.itextpdf.text.pdf.OutputStreamCounter.write(OutputStreamCounter.java:104)
at com.itextpdf.text.pdf.PdfObject.toPdf(PdfObject.java:175)
at com.itextpdf.text.pdf.PdfDictionary.toPdf(PdfDictionary.java:148)
at com.itextpdf.text.pdf.PdfIndirectObject.writeTo(PdfIndirectObject.java:157)
at com.itextpdf.text.pdf.PdfWriter$PdfBody.write(PdfWriter.java:402)
at com.itextpdf.text.pdf.PdfWriter$PdfBody.add(PdfWriter.java:380)
at com.itextpdf.text.pdf.PdfWriter.addToBody(PdfWriter.java:869)
at com.itextpdf.text.pdf.PdfStamperImp.close(PdfStamperImp.java:433)
at com.itextpdf.text.pdf.PdfStamperImp.close(PdfStamperImp.java:408)
at com.itextpdf.text.pdf.PdfStamper.close(PdfStamper.java:230)
at com.example.aditya.pdf_report.GroupFragment.writetopdf(GroupFragment.java:245)
at com.example.aditya.pdf_report.GroupFragment.checkfill(GroupFragment.java:289)
at com.example.aditya.pdf_report.GroupFragment.onClick(GroupFragment.java:412)
at android.view.View.performClick(View.java:6312)
at android.view.View$PerformClick.run(View.java:24811)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:171)
at android.app.ActivityThread.main(ActivityThread.java:6649)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:824)

在245：我有stamper.close()

289：

writetopdf()

我已经尝试了一切，消除了所有可能的空指针异常问题，但不知怎么的，我仍然得到了它。

请帮忙

Answer 1

我打赌会发生FileNotFoundException。通过您实现的异常(非(处理：

OutputStream output = null;
try {
output = new FileOutputStream(pdf);
} catch (FileNotFoundException e) {
e.printStackTrace();
}

这给您留下了output的null参考！