我有一个要添加列的数据库，我更改了静态数据库版本，但是当我在我的设备上运行该程序时，新列仍然不存在，所以我猜测我的 onUpdate 没有接到电话，我不确定为什么。

这是我创建数据库的方式

     private static class DatabaseHelper extends SQLiteOpenHelper 
    {
        DatabaseHelper(Context context) 
        {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) 
        {
            createTables(db);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, 
                              int newVersion) 
        {
            Log.w("CalendarDB", "Upgrading database from version " + oldVersion 
                  + " to "
                  + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS Events_Table");
            onCreate(db);
        }

        private void createTables(SQLiteDatabase db){
            db.execSQL("CREATE TABLE " + EVENTS_TABLE + "(" + ID + " integer primary key autoincrement, " +
                    EVENT + " TEXT, " + LOCATION + " TEXT, " + DESCRIPTION + " TEXT, " + DATE + " TEXT, " + START + " LONG, " + END + " TEXT, " + REAL_START_TIME + " TEXT," 
                    + REAL_END_TIME + " TEXT," + COLOR + " TEXT, " + BLINK + " TEXT, " + VIBRATE + " TEXT, " + RING_TONE_PATH + " TEXT, " + ICON + " TEXT, " + REMINDERS +
                    " TEXT, " + START_WITH_REMINDER + " TEXT, " + CALENDAR_ID + " TEXT, " + EVENT_ID + " TEXT);");
        }
    }

我还需要做些什么才能让 onUpdate 被调用吗？我尝试关注 this answer还是没有结果

最佳答案

为了升级 Android 中的数据库，您应该将 DATABASE_VERSION 递增 1，以便 SQLOpenHelper 知道它必须调用 onUpgrade 方法。

记住

这仅在您调用 getWritableDatabase() 时有效，否则它不会升级。如果您更改版本并调用 getReadableDatabase，它将显示异常

throw new SQLiteException("Can't upgrade read-only database from version " +
                        db.getVersion() + " to " + mNewVersion + ": " + path);

但是为什么？ 调用getWritableDatabase就知道了代码检查版本是否相同:

if (version != mNewVersion) {
                db.beginTransaction();
                try {
                    if (version == 0) {
                        onCreate(db);
                    } else {
                        if (version > mNewVersion) {
                            onDowngrade(db, version, mNewVersion);
                        } else {
                            onUpgrade(db, version, mNewVersion);
                        }
                    }
                    db.setVersion(mNewVersion);
                    db.setTransactionSuccessful();
                } finally {
                    db.endTransaction();
}
}

更新

事实证明，它应该与 getReadableDatabase() 一起使用，因为在代码中您也总是获得 WrittableDatabase。所以它应该适用于这两种方法，这里是 getReadableDatabase() 的文档:

Create and/or open a database. This will be the same object returned by getWritableDatabase() unless some problem, such as a full disk, requires the database to be opened read-only. In that case, a read-only database object will be returned. If the problem is fixed, a future call to getWritableDatabase() may succeed, in which case the read-only database object will be closed and the read/write object will be returned in the future.

关于android - 更新 sqlite 数据库版本？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/8627075/