B4J Question List from Array and then Add = Exception?

[tchart]

I have a list that is created like this;

Dim Header As List = Array("Name", "Status", "Public IP", "Control")

I've found that if I then do this;

Header.Add("New")

B4J 5.5 is throwing this exception;

Caused by: java.lang.UnsupportedOperationException
at java.util.AbstractList.add(Unknown Source)
at java.util.AbstractList.add(Unknown Source)
at anywheresoftware.b4a.objects.collections.List.Add(List.java:71)

Are lists created like this read only?

 

[Daestrum]

It looks like a list created this way has a fixed length and other limits, ie you can't remove an item from it.
Probably safer to do

Dim Header as List
...
Header.Initialize
Header.AddAll(Array("Name", "Status", "Public IP", "Control"))
...
Header.Add("New")
...

Then it works as expected.

Also you can force it to become a normal list with 4 lines of code

Dim tempList As List
tempList.Initialize
tempList.AddAll(originalList)
originalList = tempList ' now it will work as normal list
...

But this will create a second list mirroring the first one, so first solution is better.

 

[Erel]

A list that wraps an array will be read-only.

As @Daestrum wrote you should initialize a new list and add the items.

 

[tchart]

Thanks to both of you for your replies.