android - 将 SQLite 数据库导出到 android 中的 csv 文件

Question

我正在尝试将 SQLite 数据作为目录中的 CSV 文件导出到 android 中的 SD 卡。

所以我在下面尝试了这种方法，显然它只显示打印出的文本:

数据库的第一个表
日期、项目、金额、货币

在我的 DBHelper.java 中，我定义了如下函数:

public boolean exportDatabase() {
        DateFormat df = DateFormat.getDateInstance(DateFormat.SHORT, Locale.getDefault());

        /**First of all we check if the external storage of the device is available for writing.
         * Remember that the external storage is not necessarily the sd card. Very often it is
         * the device storage.
         */
        String state = Environment.getExternalStorageState();
        if (!Environment.MEDIA_MOUNTED.equals(state)) {
            return false;
        }
        else {
            //We use the Download directory for saving our .csv file.
            File exportDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
            if (!exportDir.exists())
            {
                exportDir.mkdirs();
            }

            File file;
            PrintWriter printWriter = null;
            try
            {
                file = new File(exportDir, "MyCSVFile.csv");
                file.createNewFile();
                printWriter = new PrintWriter(new FileWriter(file));

                /**This is our database connector class that reads the data from the database.
                 * The code of this class is omitted for brevity.
                 */
                SQLiteDatabase db = this.getReadableDatabase(); //open the database for reading

                /**Let's read the first table of the database.
                 * getFirstTable() is a method in our DBCOurDatabaseConnector class which retrieves a Cursor
                 * containing all records of the table (all fields).
                 * The code of this class is omitted for brevity.
                 */
                Cursor curCSV = db.rawQuery("select * from contacts", null);
                //Write the name of the table and the name of the columns (comma separated values) in the .csv file.
                printWriter.println("FIRST TABLE OF THE DATABASE");
                printWriter.println("DATE,ITEM,AMOUNT,CURRENCY");
                while(curCSV.moveToNext())
                {
                    Long date = curCSV.getLong(curCSV.getColumnIndex("date"));
                    String title = curCSV.getString(curCSV.getColumnIndex("title"));
                    Float amount = curCSV.getFloat(curCSV.getColumnIndex("amount"));
                    String description = curCSV.getString(curCSV.getColumnIndex("description"));

                    /**Create the line to write in the .csv file.
                     * We need a String where values are comma separated.
                     * The field date (Long) is formatted in a readable text. The amount field
                     * is converted into String.
                     */
                    String record = df.format(new Date(date)) + "," + title + "," + amount + "," + description;
                    printWriter.println(record); //write the record in the .csv file
                }

                curCSV.close();
                db.close();
            }

            catch(Exception exc) {
                //if there are any exceptions, return false
                return false;
            }
            finally {
                if(printWriter != null) printWriter.close();
            }

            //If there are no errors, return true.
            return true;
        }
    }
}

我的专栏是:

 public static final String DATABASE_NAME = "MyDBName.db";
 public static final String CONTACTS_TABLE_NAME = "contacts";
 public static final String CONTACTS_COLUMN_ID = "id";
 public static final String CONTACTS_COLUMN_TITLE = "title";
 public static final String CONTACTS_COLUMN_AMOUNT = "amount";
 public static final String CONTACTS_COLUMN_DESC = "description";

如果您需要更多代码，请告诉我。

Answer 1

感谢你们的建议让我得到这个答案:

private void exportDB() {

        DBHelper dbhelper = new DBHelper(getApplicationContext());
        File exportDir = new File(Environment.getExternalStorageDirectory(), "");
        if (!exportDir.exists())
        {
            exportDir.mkdirs();
        }

        File file = new File(exportDir, "csvname.csv");
        try
        {
            file.createNewFile();
            CSVWriter csvWrite = new CSVWriter(new FileWriter(file));
            SQLiteDatabase db = dbhelper.getReadableDatabase();
            Cursor curCSV = db.rawQuery("SELECT * FROM contacts",null);
            csvWrite.writeNext(curCSV.getColumnNames());
            while(curCSV.moveToNext())
            {
                //Which column you want to exprort
                String arrStr[] ={curCSV.getString(0),curCSV.getString(1), curCSV.getString(2)};
                csvWrite.writeNext(arrStr);
            }
            csvWrite.close();
            curCSV.close();
        }
        catch(Exception sqlEx)
        {
            Log.e("MainActivity", sqlEx.getMessage(), sqlEx);
        }
}