在 SQLite DatabaseErrorHandler 中需要做什么

Question

我一直致力于完善一个有效的 SQLite 数据库恢复。更具体地说，当数据库损坏时（我一直在使用包含 SQL 的文件并将其复制到数据库文件而不是数据库副本）。

我可以在没有处理程序的情况下使用 SQL 查看 sqlite_master 来处理此问题（没有表检测到损坏）。

当我在研究技术时遇到 DatabaseErrorHanlder，我想我会涉足 DatabaseErorHandler。

我已经到了触发 DataBaseErrorHandler 的阶段（处理程序中的日志被调用（由于第二次尝试读取而两次））。但是，与使用 null 而不是处理程序和应用程序崩溃相比，我报告的错误更多（好像让处理程序关闭 SQLite 的自动化，我相信，删除损坏的文件，因此任何调用处理程序重新创建它） .崩溃不是问题，因为很明显 SQLite 已试图绕过损坏，但似乎处理程序会阻止它执行其他操作。）

在没有处理程序的情况下运行会导致以下消息（首先由应用程序编写为路标）：-

11-03 16:36:13.414 10959-10959/? I/mjt.shopper: Thu Nov 03 16:36:13 AEDT 2016 Activity=dataBaseIntegrityCheck Method=MainDataHandling MSG=restore Database Integrity Check - IC Database created
11-03 16:36:13.415 10959-10959/? E/SQLiteLog: (26) file is encrypted or is not a database
11-03 16:36:13.416 10959-10959/? E/DefaultDatabaseErrorHandler: Corruption reported by sqlite on database: /data/data/mjt.shopper/databases/ICShopper
11-03 16:36:13.416 10959-10959/? E/DefaultDatabaseErrorHandler: deleting the database file: /data/data/mjt.shopper/databases/ICShopper

与我得到的处理程序一起运行（相同的路标 + 处理程序发出的路标）：-

11-03 16:58:23.923 12265-12265/? I/mjt.shopper: Thu Nov 03 16:58:23 AEDT 2016 Activity=dataBaseIntegrityCheck Method=MainDataHandling MSG=restore Database Integrity Check - IC Database created
11-03 16:58:23.925 12265-12265/? E/SQLiteLog: (26) file is encrypted or is not a database
11-03 16:58:23.925 12265-12265/? I/mjt.shopper: Thu Nov 03 16:58:23 AEDT 2016 Activity=MainDataHandling Method=dataBaseIntegrityCheck MSG=DB onCorruption error handler invoked
11-03 16:58:23.925 12265-12265/? E/SQLiteLog: (26) file is encrypted or is not a database
11-03 16:58:23.927 12265-12265/? E/SQLiteDatabase: Failed to open database '/data/data/mjt.shopper/databases/ICShopper'.
                                                   android.database.sqlite.SQLiteDatabaseCorruptException: file is encrypted or is not a database (code 26): , while compiling: PRAGMA journal_mode
.............
11-03 16:58:23.928 12265-12265/? E/SQLiteOpenHelper: Couldn't open ICShopper for writing (will try read-only):
                                                     android.database.sqlite.SQLiteDatabaseCorruptException: file is encrypted or is not a database (code 26): , while compiling: PRAGMA journal_mode
'''''''''''''
11-03 16:58:23.929 12265-12265/? E/SQLiteLog: (26) statement aborts at 1: [PRAGMA user_version;] file is encrypted or is not a database
11-03 16:58:23.930 12265-12265/? I/mjt.shopper: Thu Nov 03 16:58:23 AEDT 2016 Activity=MainDataHandling Method=dataBaseIntegrityCheck MSG=DB onCorruption error handler invoked
11-03 16:58:23.934 12265-12265/? D/AndroidRuntime: Shutting down VM
11-03 16:58:23.934 12265-12265/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                   Process: mjt.shopper, PID: 12265
                                                   android.database.sqlite.SQLiteDatabaseCorruptException: file is encrypted or is not a database (code 26)

DatabaseHelper 代码是：-

public class IntegrityCheckDBHelper extends SQLiteOpenHelper implements DatabaseErrorHandler{

    public static final String DATABASE_NAME = "IC"+ShopperDBHelper.DATABASE_NAME;
    public static final int DATABASE_CORRUPTED = 1;
    private static int databasestate = 0;
    private Context context;

    public IntegrityCheckDBHelper(Context context,
                                  String name,
                                  SQLiteDatabase.CursorFactory factory,
                                  int version, DatabaseErrorHandler errorHandler) {
        super(context, DATABASE_NAME,factory,1,errorHandler);
        this.context = context;

    };

    public void onCreate(SQLiteDatabase db) {};
    public void onUpgrade(SQLiteDatabase db, int oldversion, int newversion) {};
    public void onCorruption(SQLiteDatabase db) {
    }
    public boolean checkDB() {
        SQLiteDatabase icdb = this.getReadableDatabase();
        String icsqlstr = " PRAGMA quick_check";
        Cursor iccsr;
        iccsr = icdb.rawQuery(icsqlstr,null);
        return false;
    }
    public static void setDatabaseCorrupted() {
        databasestate = DATABASE_CORRUPTED;
    }
    public boolean isDatabaseCouurpted() {
        if(databasestate != 0) return false;
        return true;
    }
}

注意！这个帮助器专门用于检查恢复文件是否可以是用户（所以不需要onCreate/onUpgrade 做任何事情我认为）。

这是相关代码，即 dataBaseIntegrityCheck 方法（即从正在恢复的备份中创建一个数据库文件以检查备份是否创建了一个有效的数据库）：-

private boolean dataBaseIntegrityCheck() {

        final String THIS_METHOD = "dataBaseIntegrityCheck";
        String sqlstr_mstr = "SELECT name FROM sqlite_master WHERE type = 'table' AND name!='android_metadata' ORDER by name;";
        Cursor iccsr;
        boolean rv = true;
        DatabaseErrorHandler myerrorhandler = new DatabaseErrorHandler() {
            @Override
            public void onCorruption(SQLiteDatabase sqLiteDatabase) {
                mjtUtils.logMsg(mjtUtils.LOG_INFORMATIONMSG,"DB onCorruption error handler invoked",THIS_ACTIVITY,THIS_METHOD,true);
                dbcorrupted = true;
            }
        };
        mjtUtils.logMsg(mjtUtils.LOG_INFORMATIONMSG,"Restore Databae Integrity Check - Starting",THIS_METHOD,THIS_ACTIVITY,true);
        try {
            FileInputStream bkp = new FileInputStream(backupfilename);
            OutputStream ic = new FileOutputStream(icdbfilename);
            while ((copylength = bkp.read(buffer)) > 0) {
                ic.write(buffer, 0, copylength);
            }
            ic.close();
            bkp.close();

            mjtUtils.logMsg(mjtUtils.LOG_INFORMATIONMSG,"restore Database Integrity Check - IC Database created",THIS_METHOD,THIS_ACTIVITY,true);

            //Note SQLite will actually check for corruption and if so delete the file
            IntegrityCheckDBHelper icdbh = new IntegrityCheckDBHelper(this,null,null,1,myerrorhandler);

            //>>>>>>>>>>>>> Errors all point here (the getReadableDatabase)
            SQLiteDatabase icdb = icdbh.getReadableDatabase();

            if(dbcorrupted) {
                mjtUtils.logMsg(mjtUtils.LOG_INFORMATIONMSG,"DB corrupted",THIS_ACTIVITY,THIS_METHOD,true);
                return false;
            }

            //Check to see if there are any tables, if wrong file type shouldn't be any
            iccsr = icdb.rawQuery(sqlstr_mstr,null);
            if(iccsr.getCount() < 1) {
                errlist.add("Integrity Check extract from sqlite_master returned nothing - Propsoed file is corrupt or not a database file.");
                rv = false;
            }
            iccsr.close();
            icdb.close();

        } catch (IOException e) {
            e.printStackTrace();
            errlist.add("Integrity Check Failed Error Message was " + e.getMessage());
        }

        if(!rv) {
            // AlertDialog removed.
        }
        return rv;
    }

重申一下，问题主要是关于 DatabaseErrorHandler 以及我能做什么、不能做什么和/或应该做什么。

我发现的文档以及我看过的许多帖子似乎没有那么有用。

Answer 1

SQLiteDatabase.open()中的相关代码如下：

        try {
            openInner();
        } catch (SQLiteDatabaseCorruptException ex) {
            onCorruption();
            openInner();
        }

所以你的onCorruption()处理程序必须在它返回之前恢复数据库；这不能推迟到以后。

如果您实际上不想恢复您尝试打开的数据库，则使用 onCorrupt() 处理程序没有意义。