Android Question NullPointerException

jkhazraji · Apr 6, 2017

I have this type declaration in Process_Global:

B4X:

    Type tempbox(X(4) As Int,Y(4) As Int ,r As Int, g As Int, b As Int, rot As Int)
    Dim Box(8) As tempbox

When I try to fill some of the type members with values, in Start_Activity or in any other sub , as in the following:

B4X:

    Box(1).rot = 4
    Box(2).rot = 1
    For i = 3 To 6
        Box(i).rot = 4
    Next
    Box(7).rot = 2

or the following in a Timer after being initialized and enabled:

B4X:

        For i = 1 To 4
            Box(rnum).Y(i) =  Box(rnum).Y(i) + boxwidth
        Next

I will get the following error:
(NullPointerException) java.lang.NullPointerException

Any help to fix it?

udg · Apr 6, 2017

Did you initialize the tempobox items in the array?

DonManfred · Apr 6, 2017

As said by @udg
Initialize the Types first...

B4X:

For i = 0 To 7
        Box(i).initialize
Next

jkhazraji · Apr 6, 2017

Thanks a lot.. but what about this error?

B4X:

    Dim tempx(4) As Int 'in Process_Globals
.
.
.
sub init(i as int)
    For i = 1 To 4
        box(rnum).X(i) = tempx(i)
        box(rnum).Y(i) = tempy(i)
    Next 
end sub

will give an error of: java.lang.ArrayIndexOutOfBoundsException: length=4; index=4

udg · Apr 6, 2017

Arrays have index starting at 0
So Dim tempx(4) leads to indexes 0,1,2,3 while your For loop counts from 1 to 4. That causes the Index Out Of Bounds error.

jkhazraji · Apr 6, 2017

Many Thanks

Android Question NullPointerException

jkhazraji

Active Member

udg

Expert

DonManfred

Expert

jkhazraji

Active Member

udg

Expert

jkhazraji

Active Member

Similar Threads

Android Question NullPointerException

jkhazraji

Active Member

udg

Expert

DonManfred

Expert

jkhazraji

Active Member

udg

Expert

jkhazraji

Active Member

Similar Threads

Privacy & Transparency

Privacy & Transparency