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DAO实现中的可完成删除函数产生IllegalStateException

android-room kotlin android

Nominalista · 技术社区 · 6 年前

假设我们有简单的DAO接口:

@Dao
interface MyDao {
    @Delete
    fun delete(entity: MyEntity): Completable
}

我们期望从Room中,它会生成返回的函数 Completable . 本协议的执行 完全的 应该从数据库中删除实体。

现在我们打电话 delete

// Called in the main thread
myDao.delete(myEntity)
    .subscribeOn(Schedulers.background())
    .subscribe()

问题是这个调用导致 IllegalStateException

Cannot access database on the main thread since it may potentially lock the UI for a long period of time.

有趣的是,其他函数如select(返回 Single<MyEntity> 非法状态例外 在删除实现中:

public SupportSQLiteStatement acquire() {
    assertNotMainThread();
    return getStmt(mLock.compareAndSet(false, true));
}

问题是,这是一个bug还是我应该用另一种方式调用delete,比如: Completale.defer { myDao.delete(myEntity)) } ?

编辑

更具体地说:我使用自定义查询进行删除( "DELETE FROM myentities WHERE id = :id )下面是生成的代码:

@Override
public Completable deleteByIdInternal(final long id) {
  final SupportSQLiteStatement _stmt = __preparedStmtOfDeleteByIdInternal.acquire();
  int _argIndex = 1;
  _stmt.bindLong(_argIndex, id);
  return Completable.fromCallable(new Callable<Void>() {
    @Override
    public Void call() throws Exception {
      __db.beginTransaction();
      try {
        _stmt.executeUpdateDelete();
        __db.setTransactionSuccessful();
        return null;
      } finally {
        __db.endTransaction();
        __preparedStmtOfDeleteByIdInternal.release(_stmt);
      }
    }
  });
}