Room - 架构导出目录未提供给注释处理器，因此我们无法导出架构

问题描述

我正在使用 Android 数据库组件室

I am using Android Database Component Room

我已经配置了一切，但是当我编译时，Android Studio 给了我这个警告:

I've configured everything, but when I compile, Android Studio gives me this warning:

模式导出目录没有提供给注解处理器，所以我们无法导出架构.您可以提供room.schemaLocation 注释处理器参数或设置exportSchema 为 false.

据我所知，这是数据库文件所在的位置

As I understand it is the location where DB file will be located

它如何影响我的应用程序?这里的最佳做法是什么?我应该使用默认位置(false 值)吗?

How can it affect my app? What is the best practice here? Should I use the default location (false value)?

推荐答案

根据 文档:

您可以设置注释处理器参数 (room.schemaLocation) 来告诉 Room 将架构导出到文件夹中.尽管这不是强制性的，但在您的代码库中包含版本历史记录是一个很好的做法，您应该将该文件提交到您的版本控制系统中(但不要随您的应用一起提供！).

因此，如果您不需要检查架构并且想要摆脱警告，只需将 exportSchema = false 添加到您的 RoomDatabase 中，如下所示.

So if you don't need to check the schema and you want to get rid of the warning, just add exportSchema = false to your RoomDatabase, as follows.

@Database(entities = { YourEntity.class }, version = 1, exportSchema = false)
public abstract class AppDatabase extends RoomDatabase {
   //...
}

如果您遵循下面的@mikejonesguy answer，您将遵循文档中提到的良好做法:).基本上，您将在 ../app/schemas/ 文件夹中获得一个 .json 文件.它看起来像这样:

If you follow @mikejonesguy answer below, you will follow the good practice mentioned in the docs :).Basically you will get a .json file in your ../app/schemas/ folder.And it looks something like this:

{
  "formatVersion": 1,
  "database": {
    "version": 1,
    "identityHash": "53db508c5248423325bd5393a1c88c03",
    "entities": [
      {
        "tableName": "sms_table",
        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT, `message` TEXT, `date` INTEGER, `client_id` INTEGER)",
        "fields": [
          {
            "fieldPath": "id",
            "columnName": "id",
            "affinity": "INTEGER"
          },
          {
            "fieldPath": "message",
            "columnName": "message",
            "affinity": "TEXT"
          },
          {
            "fieldPath": "date",
            "columnName": "date",
            "affinity": "INTEGER"
          },
          {
            "fieldPath": "clientId",
            "columnName": "client_id",
            "affinity": "INTEGER"
          }
        ],
        "primaryKey": {
          "columnNames": [
            "id"
          ],
          "autoGenerate": true
        },
        "indices": [],
        "foreignKeys": []
      }
    ],
    "setupQueries": [
      "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, "53db508c5248423325bd5393a1c88c03")"
    ]
  }
}

如果我的理解是正确的，每次数据库版本更新你都会得到这样一个文件，这样你就可以很容易地跟踪你的数据库的历史.

If my understanding is correct, you will get such a file with every database version update, so that you can easily follow the history of your db.

这篇关于Room - 架构导出目录未提供给注释处理器，因此我们无法导出架构的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！