如何实施收房查询

Question

I'm quite new to Room and RXJava and I want to use them to perform a quite simple query but I have problem implementing the RX part and handle results.

@Dao
interface DepartmentDao{
//....
@Query ("SELECT employeesIds FROM Department WHERE Department_name LIKE :name")
 fun getEmployeesIds(name:String):String //this is a jsonArray stored as string
}

Then I have Kotlin object where I write some other methods related to the database others than ones from @Dao

object DBManager {
  fun getEmployeesIdsJsonArray():Completable = Completable.fromCallable {
        mDataBase.DepartmentDao().getEmployeesIds(deptName)
    }
}

I want to query this in my Fragment and use the query result (a string in this case) when the query completes. This is where I get locked and need your help.

DBManager.getEmployeesIdsJsonArray()
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe( //here I get locked, how can I handle this?)

I expect to have something like

{
  onSuccess -> jsonString , //this is the string resulted, feel free to use it
  onError -> Log.e(TAG, "query failed")
}

but I'm not able to implement it successfully without all kind of errors regarding type expectations.

Answer 1

I think the syntax you're looking for is this:

  DBManager.getEmployeesIdsJsonArray()
        .subscribeOn(Schedulers.newThread())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe( { jsonString ->
           // onNext
           // Do something with jsonString
        }, { throwable ->
           // onError
           // Do somethign with throwable
        } )

Answer 2

Well. Completable returns nothing, just termination event onComplete/onError

Try :

• Return Single in your Dao
• Your subscribe method should looks like subscribe({function1},{function2})

And never use Schedulers.newThread() for IO operations. Instead this prefer Schedulers.io(), because it use reusable threads from thread pool, while Schedulers.newThread() create just a new thread, which is not reusable