僅維護特定表的域數據遷移

Question

我想使用Realm migration來維護僅一個表的數據。像這裏一樣，我想維護Profile User表的數據並刪除表中的所有其餘部分。

這是我迄今爲止所做的。但數據庫中的所有內容都會被刪除。

initRealm()會從onCreate()

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的配置類

private class RealmMigrationClass implements RealmMigration { 
    @Override 
    public void migrate(DynamicRealm realm, long oldVersion, long newVersion) { 
     RealmSchema schema = realm.getSchema(); 
     if (oldVersion == 2) { 
      RealmObjectSchema profileUserSchema = schema.get("ProfileUser"); 
      profileUserSchema.addField("test", String.class); 
      oldVersion++; 
     } 
    } 
} 

Answer 1

這將刪除除從用戶配置類的所有數據稱爲

private void initRealm() { 
    Realm.init(this); 
    RealmConfiguration configuration = new RealmConfiguration.Builder() 
      .schemaVersion(3) 
      .name("sipradi") 
      .migration(new RealmMigrationClass()) 
      .build(); 
    Realm.setDefaultConfiguration(configuration); 
} 

private class RealmMigrationClass implements RealmMigration { 
    @Override 
    public void migrate(DynamicRealm realm, long oldVersion, long newVersion) { 
     RealmSchema schema = realm.getSchema(); 
     if (oldVersion == 2) { 
      RealmObjectSchema profileUserSchema = schema.get("ProfileUser"); 
      profileUserSchema.addField("test", String.class); 

      // Delete all other data than `ProfileUser` 
      for (RealmObjectSchema classSchema : schema.getAll()) { 
       if (classSchema.getClassName().equals("ProfileUser")) { 
        continue; 
       } 
       realm.delete(classSchema.getClassName()); 
      } 
      oldVersion++; 
     } 
    } 
}