android在sqlite資料庫的SQLiteOpenHelper中的onUpgrade裡判斷表是否存在

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private boolean tabbleIsExist(String tableName, SQLiteDatabase db) {            LogUtils.d("DatabaseHelper", "checking tabbleIsExist " + tableName);            boolean result = false;            if (tableName == null) {                return false;            }            Cursor cursor = null;            try {                String sql = "select count(*) as c from sqlite_master where type =‘table‘ and name =‘"                        + tableName.trim() + "‘ ";                cursor = db.rawQuery(sql, null);                if (cursor.moveToNext()) {                    int count = cursor.getInt(0);                    if (count > 0) {                        result = true;                    }                }            } catch (Exception e) {                LogUtils.e("DatabaseHelper", "error in tabbleIsExist:" + e.toString());            }            LogUtils.d("DatabaseHelper", "checking tabbleIsExist "                    + tableName + " " + result);            return result;        }