Question

我有以下简单的数据库：

NameList.kt

@Entity(tableName = "name_list")
data class NameList(
        @PrimaryKey(autoGenerate = true)
        var id: Long = 0L,

        @ColumnInfo(name = "name")
        var name: String = "")

NameListDao.kt

@Dao
interface NameListDao{    
    @Insert
    fun insert(nameList: NameList)

    @Update
    fun update(nameList: NameList)

    @Query("SELECT * FROM name_list ORDER BY id DESC")
    fun getAll(): LiveData<List<NameList>>
}

NameListRepository.kt

class NameListRepository(private val nameListDao: NameListDao){
    val allNames: LiveData<List<NameList>> = nameListDao.getAll()
}

现在，当我通过添加/删除列（如

）来更改NameList.kt中的表时

@Entity(tableName = "name_list")
data class NameList(
        @PrimaryKey(autoGenerate = true)
        var id: Long = 0L,

        @ColumnInfo(name = "first_name")
        var firstName: String = "",

        @ColumnInfo(name = "last_name")
        var lastName: String = "")

在不删除/更改手机上的数据库的情况下，访问数据库时应用程序崩溃并显示以下错误消息：

E AndroidRuntime: java.lang.RuntimeException: Exception while computing database live data.
E AndroidRuntime:   at androidx.room.RoomTrackingLiveData$1.run(RoomTrackingLiveData.java:92)
E AndroidRuntime:   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
E AndroidRuntime:   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
E AndroidRuntime:   at java.lang.Thread.run(Thread.java:764)
E AndroidRuntime: Caused by: 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.
E AndroidRuntime:   at androidx.room.RoomOpenHelper.checkIdentity(RoomOpenHelper.java:154)
E AndroidRuntime:   at androidx.room.RoomOpenHelper.onOpen(RoomOpenHelper.java:135)
E AndroidRuntime:   at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onOpen(FrameworkSQLiteOpenHelper.java:142)
E AndroidRuntime:   at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:409)
E AndroidRuntime:   at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:298)
E AndroidRuntime:   at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:92)
E AndroidRuntime:   at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:53)
E AndroidRuntime:   at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:476)
E AndroidRuntime:   at androidx.room.RoomDatabase.assertNotSuspendingTransaction(RoomDatabase.java:281)
E AndroidRuntime:   at androidx.room.RoomDatabase.query(RoomDatabase.java:324)
E AndroidRuntime:   at androidx.room.util.DBUtil.query(DBUtil.java:83)

我知道这是由于表已更改（当我手动删除数据库并使用新实体创建新数据库时，错误消失了）。

在访问数据库/表之前，如何检查其完整性（即它们的NameList数据库是否与所访问的数据库匹配）？ Room是否为此目的提供了一种我错过的特定方法？

编辑：我想我现在知道版本错误所在。但是仍然可以检查完整性，以便在新旧数据库不匹配的情况下，我可以做不同的事情，例如删除旧数据库或拥有两个不同的数据库等。

Answer 1

每次更改结构时，都必须更新数据库版本。如错误所说

您只需增加版本号即可解决此问题。

Room会照顾您，以防止在运行时崩溃。

如何检查会议室数据库的完整性？

1 个答案: