在一个 CSV 文件中写入和读取两个列表

Question

我编写代码将房间数据库数据导出到 CSV 文件，并使用存储访问框架从中导入数据。它可以工作，但我的房间数据库有两个实体类，因此还有一个列表。

所以我想在同一个CSV文件里多写入和读取一个列表，这样用户就可以一键备份和恢复数据了

有办法吗？

谢谢。

出口：

 public void exportCSV() {
        Intent intent2 = new Intent(Intent.ACTION_CREATE_DOCUMENT);
        intent2.setType("text/csv");
        intent2.putExtra(Intent.EXTRA_TITLE, "db_backUp");
        startForExportResult.launch(intent2);
    }

进口：

public void importCSV() {
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.setType("text/*");
        intent.putExtra(Intent.EXTRA_TITLE, "db_backUp");
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        startForImportResult.launch(intent);
    }

ActivityResultLaunche:export

ActivityResultLauncher<Intent> startForExportResult = registerForActivityResult(
            new ActivityResultContracts.StartActivityForResult(), result -> {
                Intent intent = result.getData();
                if(intent != null){
                    Uri title = intent.getData();
                    recordList.clear();
                    db = Room.databaseBuilder(getContext().getApplicationContext(), DeckRoomDatabase.class, "deck_database")
                            .allowMainThreadQueries().build();
                    deckDao = db.deckDao();
                    List<Deck> decks = deckDao.getAllDecksForCSV();
                    recordList = (ArrayList<Deck>) decks;
                    if(title != null && result.getResultCode() == RESULT_OK){
                        try(BufferedWriter writer = new BufferedWriter(
                                new OutputStreamWriter(
                                        getContext().getContentResolver().openOutputStream(title)))){

                            for(int i = 0; i < recordList.size(); i++){
                                writer.append("" + recordList.get(i).getName());
                                writer.append(",");
                                writer.append("" + recordList.get(i).getListCount());
                                writer.append(",");
                                writer.append("" + recordList.get(i).getDateTime());
                                writer.append(",");
                                writer.append("" + recordList.get(i).getParameter());
                                writer.append("\n");
                            }
                            writer.flush();
                            writer.close();
                            Toast.makeText(this.getContext(), "Backup Export to:" + title.toString(), Toast.LENGTH_SHORT).show();
                        } catch (IOException e){
                            e.printStackTrace();
                            Toast.makeText(this.getContext(), "" + e.getMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                }
    });

ActivityResultLaunche:import

ActivityResultLauncher<Intent> startForImportResult = registerForActivityResult(
            new ActivityResultContracts.StartActivityForResult(), result -> {
                Intent intent = result.getData();
                if(intent != null){
                    Uri uri = intent.getData();
                    if(uri != null && result.getResultCode() == RESULT_OK){
                        try(BufferedReader reader = new BufferedReader(
                                new InputStreamReader(
                                        getContext().getContentResolver().openInputStream(uri)))){
                            String line;
                            while ((line = reader.readLine()) != null){
                                String[] nextLine = line.split(",", 4);
                                if(nextLine.length != 4) {
                                    continue;
                                }
                                    String name = nextLine[0];
                                    String listCount = nextLine[1];
                                    String dateTime = nextLine[2];
                                    String parameter = nextLine[3];

                                    deckDao.insertDeck(new Deck(name, Integer.parseInt(listCount), LocalDateTime.parse(dateTime),
                                            Integer.parseInt(parameter)));
                            }

                            Toast.makeText(this.getContext(), "Backup Restored...", Toast.LENGTH_SHORT).show();
                        }
                        catch (Exception e){
                            Toast.makeText(this.getContext(), "" + e, Toast.LENGTH_SHORT).show();
                        }
                    }
                }
            });