如何从文档中选择pdf文件，将其存储在SQLite中，然后再次从SQLite中打开它？

Question

I want to pick .pdf file from mobile internal storage , save this file in sqlite as blob type. When i click on 'View' button then retrieve it from database and open it in pdf supported application.

Here i used this code for pick file

Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
                intent.setType("application/pdf");
                intent.addCategory(Intent.CATEGORY_OPENABLE);
                startActivityForResult(intent, 100);

code of onActivityResult

                Uri fileuri = data.getData();
                Log.d(TAG, "Document File Uri = " + fileuri);
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                FileInputStream fis;
                try
                {
                    fis = new FileInputStream(new File(fileuri.getPath()));
                    byte[] buf = new byte[1024];
                    int n;
                    while (-1 != (n = fis.read(buf)))
                        baos.write(buf, 0, n);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                byte[] byteFile = baos.toByteArray();

then this byteFile saved into database as a blob type. Now how can i retrieve and open it. Please help me

Answer 1

code of onActivityResult

A Uri is not a file. Only if the scheme of the Uri is file does your code work. Replace your FileInputStream with an InputStream , where you get that InputStream from getContentResolver().openInputStream(data.getData()) .

Also:

• Your app will crash a lot, as you will not have enough memory to hold the PDF

• Saving large files in BLOB columns is an anti-pattern in Android, as the SQLite APIs that we use do not handle large contents very well

• The user will not be happy with you, as you are doing this disk I/O on the main application thread, causing the UI of your app to freeze while that I/O is being performed

Now how can i retrieve and open it

Reverse the process:

• Get the byte[] from the database

• Save that byte[] to a file

• Use ACTION_VIEW and FileProvider.getUriForFile() to open the file in the user's chosen PDF viewer

Once again:

• Your app will crash a lot, due to running out of memory trying to load in a large BLOB

• Do the I/O on a background thread, so as not to freeze the UI

• Storing large BLOB values is an anti-pattern in Android

I strongly recommend that you not store the PDF as a BLOB in a database. Either:

• Use ACTION_OPEN_DOCUMENT and takePersistableUriPermission() instead of ACTION_GET_CONTENT , and save the Uri in the database, or

• Copy the PDF to a file, and store some identifier of the file in the database