Room无法验证数据完整性。我如何在不编写迁移步骤的情况下修复它？

Question

在交付到生产构建之前，我已经确保了以下几点

1. 增加数据库版本
@database注释行中有 exportschema=false
2. allowBackup在清单中变为false
3. 创建数据库时有.fallbacktoDestructiveMigration()
4. 创建数据库时有.fallbacktoDestructiveMigrationonDowngrade()
5. 创建数据库时有.EnableMultiInstanceInvalidation()

应用程序崩溃，出现以下StackTrace。

java.lang.IllegalStateException: Room cannot verify the data integrity. Looks like you've changed schema but forgot to update the version number. You can simply fix this by increasing the version number.

Fatal Exception: java.lang.RuntimeException: Exception while computing database live data.
   at androidx.room.RoomTrackingLiveData$1.run + 92(RoomTrackingLiveData.java:92)
   at java.util.concurrent.ThreadPoolExecutor.runWorker + 1167(ThreadPoolExecutor.java:1167)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run + 641(ThreadPoolExecutor.java:641)
   at java.lang.Thread.run + 764(Thread.java:764)

Caused by java.lang.IllegalStateException: A migration from 19 to 20 was required but not found. Please provide the necessary Migration path via RoomDatabase.Builder.addMigration(Migration ...) or allow for destructive migrations via one of the RoomDatabase.Builder.fallbackToDestructiveMigration* methods.
   at androidx.room.RoomOpenHelper.onUpgrade + 101(RoomOpenHelper.java:101)
   at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onUpgrade + 124(FrameworkSQLiteOpenHelper.java:124)
   at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked + 398(SQLiteOpenHelper.java:398)
   at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase + 298(SQLiteOpenHelper.java:298)
   at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase + 92(FrameworkSQLiteOpenHelper.java:92)
   at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase + 53(FrameworkSQLiteOpenHelper.java:53)
   at androidx.room.RoomDatabase.inTransaction + 452(RoomDatabase.java:452)
   at androidx.room.RoomDatabase.assertNotSuspendingTransaction + 275(RoomDatabase.java:275)
   at androidx.room.RoomDatabase.query + 304(RoomDatabase.java:304)
   at androidx.room.util.DBUtil.query + 54(DBUtil.java:54)
   at com.xxx.data.local.banner.BannerDao_Impl$4.call + 218(BannerDao_Impl.java:218)
   at com.xxx.data.local.banner.BannerDao_Impl$4.call + 215(BannerDao_Impl.java:215)
   at androidx.room.RoomTrackingLiveData$1.run + 90(RoomTrackingLiveData.java:90)
   at java.util.concurrent.ThreadPoolExecutor.runWorker + 1167(ThreadPoolExecutor.java:1167)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run + 641(ThreadPoolExecutor.java:641)
   at java.lang.Thread.run + 764(Thread.java:764)

Answer 1

我用下面的方法解决了房间迁移问题。

 Room.databaseBuilder(context, AppDatabase::class.java, "xxx.db")
        .fallbackToDestructiveMigration()
        .fallbackToDestructiveMigrationOnDowngrade()
        .fallbackToDestructiveMigrationFrom(16, 17, 18, 19)
        .build() 

必须添加fallbacktoDestructiveMigrationFrom()方法，该方法强制删除表并用新模式重新创建表。

因此，db版本的varargs（例如16、17、18、19)将为方法FallbacktoDestructiveMigrationFrom(...)的这些版本号重新创建db