尝试上传到 Dropbox：NetworkOnMainThreadException？

Question

我已经为此奋斗了 6 个小时。 我遵循了 Dropbox 的“教程”（如果可以这样称呼的话，因为它们非常糟糕），玩过 DBRoulette 示例，并做了很多事情来让我的应用程序正常运行。

我的应用可以毫无问题地进行身份验证。但我无法上传任何内容，尽管完全按照教程的方式进行操作：

这是我的小sn-p代码（这是在手机上保存创建的笔记，然后上传到Dropbox）：

        saveBtn.setOnClickListener(new OnClickListener()
    {
        @Override
        public void onClick(View view)
        {
            try
            {
                //Create the directory if it doesn't exist. If it does exist the next two line won't do anything.
                File dropNotesDir = new File(Environment.getExternalStorageDirectory() + "/documents/AppData/Dropnotes/");
                dropNotesDir.mkdirs();
                //-----------------------------------------------------------------------------------------------
                String wholeNoteString = noteBody.getText().toString();
                //Now we create the title of the txt file. It will be the first line of the whole note. The name will get truncated to 32 characters
                //if it's too long.
                String noteTitle;
                if(wholeNoteString.indexOf("\n") >= 0) //New line character found.
                {
                    noteTitle = wholeNoteString.substring(0, wholeNoteString.indexOf("\n"));
                    if(noteTitle.length() >= 32)
                    {
                        noteTitle = wholeNoteString.substring(0, 32);
                    }
                }
                else
                {
                    if(wholeNoteString.length() >= 32)
                    {
                        noteTitle = wholeNoteString.substring(0, 32);
                    }else
                    {
                        noteTitle = wholeNoteString;
                    }
                }
                if(extras.getString("file-mode").equals("modify"))
                {
                    //We will need to delete the existing file if it does exist to save the new one.
                    File existing = new File(Environment.getExternalStorageDirectory() + "/documents/AppData/Dropnotes/" + extras.getString("noteTitle"));
                    existing.delete();
                }
                File newNote = new File(Environment.getExternalStorageDirectory() + "/documents/AppData/Dropnotes/" + noteTitle + ".txt");
                PrintWriter newNoteWriter = new PrintWriter(new FileOutputStream(newNote));
                newNoteWriter.print(noteBody.getText().toString());
                newNoteWriter.close();

                //TRYING TO UPLOAD TO DROPBOX HERE
                File fileToUpload = new File(Environment.getExternalStorageDirectory() + "/documents/AppData/Dropnotes/" + noteTitle + ".txt");
                FileInputStream file2Uis = new FileInputStream(fileToUpload);
                Entry newEntry = mDBApi.putFile("/" + noteTitle + ".txt", file2Uis, fileToUpload.length(), null, null);
                //END OF TRYING TO UPLOAD TO DROPBOX HERE

                Toast.makeText(view.getContext(), "Saved successfully", Toast.LENGTH_SHORT).show();
                finish();
            } catch (FileNotFoundException e)
            {
                Toast.makeText(view.getContext(), "File not found: " + e.getMessage(), Toast.LENGTH_SHORT).show();
                e.printStackTrace();
            } catch(Exception e)
            {
                Toast.makeText(view.getContext(), "Some bizarre exception occured: " + e.getClass().toString(), Toast.LENGTH_SHORT).show();
                e.printStackTrace();
            }
        }

    });

它给了我一个 NetworkOnMainThreadException，我不知道为什么。我正在尝试遵循标题为“上传文件”here 的部分。他们的 sn-p 让我感到困惑的是，他们甚至没有试图捕捉我被抛出的异常......

有什么帮助吗？我真的需要在下周五完成这项工作。

Answer 1

在 Honeycomb SDK 之前，允许在主线程上执行网络操作。但是，对于 Honeycomb，如果在主/UI 线程中尝试网络操作，则不再允许这样做，并且会抛出 NetworkOnMainThreadException。

您需要在不同的线程中执行网络操作。你可以看看AsyncTask 来实现同样的效果。

Answer 2

我的猜测是，由 StrictMode.ThreadPolicy 引起的错误。你不能在同一个 UI 线程中访问网络。

尝试在 oncreate 中将这些行添加到您的代码中

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build(); 
StrictMode.setThreadPolicy(policy);