how to fix required Long found Long?-CodePudding

i am trying to add two number whose type is Long

@Entity
data class Monitor(
        @PrimaryKey
        @NonNls
        var parentUsageDuration: Long? = 0L,
        var childUsageDuration: Long ?= 0L
)

there is two number

var parentTime = homeViewModel.getMonitorAllDataItem()?.parentUsageDuration
var childTime =  homeViewModel.getMonitorAllDataItem()?.childUsageDuration

when i try to add this two number

 var totalTime =  parentTime  childTime

I am getting error

required Long found Long ?

unable to add this two number please help me to fix this issue.

CodePudding user response：

Problem is that parentTime and childTime numbers are not just numbers. They are numbers or nulls - notice ? char in Long?. It is not possible to perform math operations on nulls, so we need to decide what do to in the case of nulls. Most common solutions are:

Set totalTime to null if at least one of numbers is null:

var totalTime = if (parentTime == null || childTime == null) null else parentTime   childTime

Replace nulls with some defaults, e.g. 0:

var totalTime = (parentTime ?: 0)   (childTime ?: 0)

Or, if we are sure that in fact these values can't be null:

var totalTime = parentTime!!   childTime!!

If this is the case then you should also consider changing the type of parentUsageDuration and childUsageDuration to not-nullable Long, but it really depends on your specific case.

CodePudding user response：

parentTime and childTime have type Long? while totalTime has type Long. You can fix it via changing type. Like

var parentTime:Long = homeViewModel.getMonitorAllDataItem()?.parentUsageDuration!!