NetworkOnMainThreadException从输入流中检索文件并将其打开为PDF

Question

下面的代码基本上是有用的......主要是.它适用于我正在测试的所有手机,但在客户端手机上失败,我无法使用.此代码的哪一部分可能导致NetworkOnMainThreadException？

这真的很直接.我在onPostExecute()中做的是:

1. 从onBackground()获取InputStream
2. 如果InputStream为null则中止,如果为null则中止.
3. 检查外部存储可用性,如果没有则中止.
4. 从InputStream创建文件
5. 检查PDF查看器是否可用,如果不可用则中止

6. 打开新创建的PDF

   @Override
   protected void onPostExecute(InputStream is) {
       super.onPostExecute(is);
       if (progressDialog.isShowing()) {
           progressDialog.dismiss();
       }
   
       if (is== null) {
           errorMessage = getString(R.string.error_server_communication);
           CustomDialogs.showErrorDialog( fragment.getActivity(), getString( R.string.error_title ), errorMessage );
           return;
       }
   
       //checking external storage avalibility
       if (!Tools.isWriteableExternalStorageAvalible()) {
           errorMessage = getString(R.string.error_no_external_storage);
           CustomDialogs.showErrorDialog( fragment.getActivity(), getString( R.string.error_title ), errorMessage );
           return;
       }               
   
       // opening pdf
       try {
           File directory = new File(Environment.getExternalStorageDirectory(), "MyApp");
           if (!directory.exists())
               directory.mkdirs();
   
           File file = new File(directory, "file.pdf");
   
           //usuwa poprzednio przechowywany wynik jesli taki byl
           if (file.exists()) 
               file.delete();
   
           file.createNewFile();                   
   
           // write the inputStream to a FileOutputStream
           OutputStream out = new FileOutputStream(file);
           out.write(IOUtils.toByteArray(is));
   
           is.close();
           out.flush();
           out.close();
   
           if (Tools.canDisplayPdf(fragment.getActivity())) {
               Intent intent = new Intent(Intent.ACTION_VIEW);
               intent.setDataAndType(Uri.fromFile(file), "application/pdf");
               startActivity( intent );
           } else {
               //user nie ma przegladarki pdf - komunikat
               errorMessage = getString(R.string.error_server_communication);
               CustomDialogs.showErrorDialog( fragment.getActivity(), getString( R.string.error_title ), errorMessage );
           }
   
       } catch (IOException e) {
           errorMessage = getString(R.string.error_server_communication);
           CustomDialogs.showErrorDialog( fragment.getActivity(), getString( R.string.error_title ), errorMessage );
       }
   }
   

还包括堆栈跟踪.还有一条线索.客户端正在使用SSL检索InputStream,而我不是.不幸的是,无法用SSL调试它.

12-05 21:34:02.648: E/AndroidRuntime(711): FATAL EXCEPTION: main
12-05 21:34:02.648: E/AndroidRuntime(711): android.os.NetworkOnMainThreadException
12-05 21:34:02.648: E/AndroidRuntime(711):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl$SSLInputStream.read(OpenSSLSocketImpl.java:668)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:103)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.http.impl.io.AbstractSessionInputBuffer.read(AbstractSessionInputBuffer.java:134)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:174)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:188)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.http.conn.EofSensorInputStream.read(EofSensorInputStream.java:178)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.commons.io.IOUtils.copyLarge(IOUtils.java:1383)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.commons.io.IOUtils.copy(IOUtils.java:1357)
12-05 21:34:02.648: E/AndroidRuntime(711):  at org.apache.commons.io.IOUtils.toByteArray(IOUtils.java:361)
12-05 21:34:02.648: E/AndroidRuntime(711):  at pl.luxmed.pp.activities.MedicalExaminationsActivity$OpenPdfAsyncTask.onPostExecute(MedicalExaminationsActivity.java:270)
12-05 21:34:02.648: E/AndroidRuntime(711):  at pl.luxmed.pp.activities.MedicalExaminationsActivity$OpenPdfAsyncTask.onPostExecute(MedicalExaminationsActivity.java:1)
12-05 21:34:02.648: E/AndroidRuntime(711):  at android.os.AsyncTask.finish(AsyncTask.java:631)
12-05 21:34:02.648: E/AndroidRuntime(711):  at android.os.AsyncTask.access$600(AsyncTask.java:177)
12-05 21:34:02.648: E/AndroidRuntime(711):  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
12-05 21:34:02.648: E/AndroidRuntime(711):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-05 21:34:02.648: E/AndroidRuntime(711):  at android.os.Looper.loop(Looper.java:137)
12-05 21:34:02.648: E/AndroidRuntime(711):  at android.app.ActivityThread.main(ActivityThread.java:4745)
12-05 21:34:02.648: E/AndroidRuntime(711):  at java.lang.reflect.Method.invokeNative(Native Method)
12-05 21:34:02.648: E/AndroidRuntime(711):  at java.lang.reflect.Method.invoke(Method.java:511)
12-05 21:34:02.648: E/AndroidRuntime(711):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-05 21:34:02.648: E/AndroidRuntime(711):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-05 21:34:02.648: E/AndroidRuntime(711):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

虽然您正在使用AsyncTask,但它的onPostExecute()方法是在UI线程上执行的(让您更新视图等).实际上,AsyncTask在单独的线程中执行的唯一方法是doInBackground(),因此您必须执行涉及I/O(磁盘,网络)的所有操作,仅在此方法中,否则您将获得异常.

请参阅此了解详情.