无法解析定义的 Disposable

Question

有一个函数从数据库中查询数据并返回一个Flowable

       @Dao
        interface DataDao {
            @Query("SELECT * FROM DataTable ORDER BY `order`")
            fun listenToAll():Flowable<List<DataRoomEntity>>
        }

当订阅它时，disposable 没有被解析（见截图）。

        var dataDao: DataDao
        fun listenToDataDb(): Flowable<Data> = dataDao.listenToAll()
                .map { convertEntitiesToData(it) }

        fun getData(){
            //var disposable: Disposable? = null
            var disposable = listenToDataDb()
                    .subscribe({ data ->
                            // do something with data
                            disposable?.dispose() //<== disposable is unresolved
            }, { throwable ->
                    disposable?.dispose(). //<== disposable is unresolved
            })
        }
    }

但如果先定义 var disposable: Disposable = null 就可以了

fun test(){
            var disposable: Disposable? = null
            disposable = listenToDataDb()
                    .subscribe({ data ->
                            // do something with data
                            disposable?.dispose() //<=== it is fine
            }, { throwable ->
                    disposable?.dispose()
            })
        }

如果不先定义，为什么会出现unresolved 错误？

Answer 1

Disposable 是 Observable 和 Observer 之间的流或链接。您可以像下面这样全局声明

       lateinit var disposable: Disposable

然后

       if(!disposable.isDisposed){
         disposable.dispose()
        }