5

第一次更新 sqlite 数据库时，我的应用程序遇到了崩溃。重新加载应用程序，从那时起它就可以正常工作了。我猜这与 onUpgrade 函数有关。我似乎无法找到问题所在，非常感谢任何建议。提前致谢。

数据库助手：

public class DatabaseHelper extends SQLiteOpenHelper {

    private static String DB_PATH = "/data/data/jp.atomicideas.ne/databases/";
    private static String DB_NAME = "dataset";
    public static final int DB_VERSION = 2;
    private SQLiteDatabase myDataBase;
    private final Context myContext;
    public static final String EXPRESSION_TABLE = "expression";

    /**
     * Constructor
     * Takes and keeps a reference of the passed context in order to access
     * the assets and resources.
     * 
     * @param context
    */
    public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
        this.myContext = context;
    }

    /**
     * Creates an empty database on the system and rewrites with database from app
     * @throws IOException
    */
    public void createDataBase() throws IOException {
        boolean dbExist = checkDataBase();  
        // if the database already exists, do nothing
        if(dbExist){
            Log.v("DB Exists", "db exists");
            // by calling this method here, onUpgrade will be called on a writeable db, if version number is bumped
            this.getWritableDatabase();
        } 
        dbExist = checkDataBase();
        // if the database doesn't exist, copy the application's database to be used
        if(!dbExist) {
            this.getReadableDatabase();
            try {
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    /**
     * Check if the database already exists to avoid re-copying the file
     * @return true only if it exists, falls if it doesnt
    */
    private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;

        try {
            String mypath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(mypath, null, SQLiteDatabase.OPEN_READONLY);
        } catch(SQLiteException e) {
            // database does not exist yet
        }

        if(checkDB != null) {
            checkDB.close();
        }

        return checkDB != null ? true : false;
    }

    /**
     * Copies database from the local assets folder to the system folder
     * @throws IOException
    */
    private void copyDataBase() throws IOException {

        // Open the app database file as the input stream
        InputStream myInput = myContext.getAssets().open(DB_NAME);

        // Path to the empty temporary database to be replaced
        String outFileName = DB_PATH + DB_NAME;

        // Open the empty database file as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);

        // Transfer bytes from the input file to the output file
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }

        // Close the streams
        myOutput.flush();
        myOutput.close();
        myInput.close();

    }

    public void openDataBase() throws SQLException {

        // Open the database
        String myPath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    }

    @Override
    public synchronized void close() {
        if(myDataBase != null)
            myDataBase.close();
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        Toast.makeText(myContext, "onUpgrade called!", Toast.LENGTH_LONG).show();

        if (oldVersion < newVersion) {
            Log.v("Database Upgrade", "Database version higher, upgrading");
            myContext.deleteDatabase(DB_NAME);                          
        }
    }

}

这是 LogCat 输出：

06-28 20:52:07.638: V/DB Exists(26580): db exists
06-28 20:52:07.658: V/Database Upgrade(26580): Database version higher, upgrading
06-28 20:52:07.658: I/Database(26580): sqlite returned: error code = 1802, msg = statement aborts at 3: [PRAGMA user_version = 2] 
06-28 20:52:07.658: E/Database(26580): Failure 10 (disk I/O error) on 0x33a3f0 when executing 'PRAGMA user_version = 2'
06-28 20:52:07.658: I/Database(26580): sqlite returned: error code = 1, msg = statement aborts at 2: [ROLLBACK;] cannot rollback - no transaction is active
06-28 20:52:07.658: E/Database(26580): Failure 1 (cannot rollback - no transaction is active) on 0x33a3f0 when executing 'ROLLBACK;'
06-28 20:52:07.658: D/Database(26580): exception during rollback, maybe the DB previously performed an auto-rollback
06-28 20:52:07.668: D/AndroidRuntime(26580): Shutting down VM
06-28 20:52:07.668: W/dalvikvm(26580): threadid=1: thread exiting with uncaught exception (group=0x2aac8578)

和

06-28 20:52:07.678: E/AndroidRuntime(26580): Caused by: android.database.sqlite.SQLiteDiskIOException: disk I/O error: PRAGMA user_version = 2
4

1 回答 1

8

您不需要删除数据库，只需使用您已经定义的方法（copyDataBase）复制它，如下所示：

@Override  
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {  
    Toast.makeText(myContext, "onUpgrade called!", Toast.LENGTH_LONG).show();  
    if (oldVersion < newVersion) {  
        Log.v("Database Upgrade", "Database version higher, upgrading");  
        try { 
            copyDataBase(); 
        } catch (IOException e) { 
            throw new Error("Error upgrading database"); 
        } 
    } 
}
于 2012-06-28T12:52:35.460 回答