我正在使用带有 RxJava2 的 Room。我在我的表中添加了一列,所以我正在迁移到新版本。我已将我的数据库版本更改为 2。
以下是我的迁移代码
static final Migration MIGRATION_1_2 = new Migration(1, 2) {
@Override
public void migrate(SupportSQLiteDatabase database) {
database.execSQL("ALTER TABLE users "
+"ADD COLUMN address String");
}
};
AppDatabase db = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, DB_NAME)
.addMigrations(MIGRATION_1_2)
.build();
如果你想看完整代码, 我指的是Github上的这个例子,它没有迁移代码
https://github.com/alahammad/RoomSample
我按照文档中描述的步骤操作,但我的应用程序仍然崩溃。
错误日志
Process: demo.karaoke.sensibol.com.roomrajava2, PID: 13655
io.reactivex.exceptions.OnErrorNotImplementedException: A migration from 1 to 2 is necessary. Please provide a Migration in the builder or call fallbackToDestructiveMigration in the builder in which case Room will re-create all of the tables.
at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704)
at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701)
at io.reactivex.internal.operators.maybe.MaybeCallbackObserver.onError(MaybeCallbackObserver.java:83)
at io.reactivex.internal.operators.maybe.MaybeObserveOn$ObserveOnMaybeObserver.run(MaybeObserveOn.java:99)
at io.reactivex.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:109)
at android.os.Handler.handleCallback(Handler.java:815)
at android.os.Handler.dispatchMessage(Handler.java:104)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5643)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:960)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.IllegalStateException: A migration from 1 to 2 is necessary. Please provide a Migration in the builder or call fallbackToDestructiveMigration in the builder in which case Room will re-create all of the tables.
at android.arch.persistence.room.RoomOpenHelper.onUpgrade(RoomOpenHelper.java:82)
at android.arch.persistence.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onUpgrade(FrameworkSQLiteOpenHelper.java:118)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:256)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
at android.arch.persistence.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:93)
at android.arch.persistence.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:54)
at android.arch.persistence.room.RoomDatabase.query(RoomDatabase.java:193)
at demo.karaoke.sensibol.com.roomrajava2.UserDao_Impl$4.call(UserDao_Impl.java:137)
at demo.karaoke.sensibol.com.roomrajava2.UserDao_Impl$4.call(UserDao_Impl.java:135)
at io.reactivex.internal.operators.maybe.MaybeFromCallable.subscribeActual(MaybeFromCallable.java:46)
at io.reactivex.Maybe.subscribe(Maybe.java:3749)
at io.reactivex.internal.operators.maybe.MaybeSubscribeOn$SubscribeTask.run(MaybeSubscribeOn.java:54)
at io.reactivex.Scheduler$DisposeTask.run(Scheduler.java:452)
at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:66)
at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:57)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:152)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:265)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:818)
最佳答案
如果您不想提供迁移,并且特别希望在升级版本时清除数据库,请在数据库构建器中调用 fallbackToDestructiveMigration
database = Room.databaseBuilder(context.getApplicationContext(),
UsersDatabase.class, "Sample.db")
.fallbackToDestructiveMigration()
.build();
关于android - 请在构建器中提供迁移或在构建器中调用 fallbackToDestructiveMigration,在这种情况下 Room 将重新创建所有表,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49629656/