RealmMigrationNeededException：需要迁移Realm，同时在现有数据库上添加新表，Android

Question

我正在使用 Realm gradle 版本“3.0.0”，我有两个表“Word”和“Favourite”，如下所示

现在我想添加第三个名为“历史”的表

为此我在下面的代码中完成了

@Override
    public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {
        final RealmSchema schema = realm.getSchema();

        if (oldVersion == 0) {
            RealmObjectSchema wordSchema = schema.get("Word");
            wordSchema.addField(DBHelper.COLUMN_NAME_PRONOUCE, String.class);
            wordSchema.addField(DBHelper.COLUMN_NAME_TYPE, String.class);
            oldVersion++;
        } if(oldVersion == 1){
            RealmObjectSchema favouriteSchema = schema.get("Favourite");
            favouriteSchema.addField(DBHelper.COLUMN_NAME_ID, String.class);
            favouriteSchema.addField(DBHelper.COLUMN_NAME_WORD, String.class);
            favouriteSchema.addField(DBHelper.COLUMN_NAME_OBJECT_ID, String.class);
            favouriteSchema.addField(DBHelper.COLUMN_NAME_PRONOUCE, String.class);
            favouriteSchema.addField(DBHelper.COLUMN_NAME_TYPE, String.class);
            favouriteSchema.addField(DBHelper.COLUMN_NAME_MEANING, String.class);
            oldVersion++;
        }
         if(oldVersion == 2){
                schema.create("History")
                .addField(DBHelper.COLUMN_NAME_ID, String.class)
                .addField(DBHelper.COLUMN_NAME_WORD, String.class)
                .addField(DBHelper.COLUMN_NAME_OBJECT_ID, String.class)
                .addField(DBHelper.COLUMN_NAME_PRONOUCE, String.class)
                .addField(DBHelper.COLUMN_NAME_TYPE, String.class)
                .addField(DBHelper.COLUMN_NAME_MEANING, String.class);
                oldVersion++;
            }
    }

但我遇到了错误，

io.realm.exceptions.RealmMigrationNeededException: Migration is required due to the following errors:
    - Property 'History.id' has been changed from 'string' to 'int'.
    - Property 'History.word' has been made required.
    - Property 'History.objectId' has been made required.
    - Property 'History.pronunciation' has been made required.
    - Property 'History.type' has been made required.
    - Property 'History.meaning' has been made required.

我之前没有创建任何历史表，为什么它说 History.id 已从 'string' 更改为 'int'？

如何正确添加历史表？

Answer 1

     if(oldVersion == 2){
            schema.create("History")
            .addField(DBHelper.COLUMN_NAME_ID, int.class)
            .addField(DBHelper.COLUMN_NAME_WORD, String.class, FieldAttribute.REQUIRED)
            .addField(DBHelper.COLUMN_NAME_OBJECT_ID, String.class, FieldAttribute.REQUIRED)
            .addField(DBHelper.COLUMN_NAME_PRONOUCE, String.class, FieldAttribute.REQUIRED)
            .addField(DBHelper.COLUMN_NAME_TYPE, String.class, FieldAttribute.REQUIRED)
            .addField(DBHelper.COLUMN_NAME_MEANING, String.class, FieldAttribute.REQUIRED);
            oldVersion++;
        }

在您的测试手机上，只需在之后卸载/重新安装应用程序，否则您需要升级架构版本并将字段更改为正确的类型。