Java Development

[myraddin]

Hi all.

I am trying to replace a field of my screen and have done it already:

fOriginalField.getManager().replace(fOriginalField, fNewField);

But now I cannot do the opposite (I want to return it to its original state). I get a null pointer exception when I try that.

fOriginalField.getManager().replace(fNewField, fOriginalField); -> null pointer exception !

Should this work ? I know that the replacement field must not belong to any manager, and I believe that causes the mess. Am I right ?

Or some intermediate code messes up with this procedure ?

[simon_hain · Accepted solution]

that is a tricky one.

in the first call you delete fOriginalField from the manager. fOriginalField is now a homeless field without any manager to take care of it.

in the second call you ask fOriginalField for its manager. fOriginalField is very unhappy about having no manager and throws a NullPointerException at you.

getting the manager from fields you add and delete just cries for this error

[myraddin]

Yes,

Silly I was just writing a reply to this thread explaining what a stupid thing I did, when I got an email with your reply.

Thanks for your interest   and kind explanation

Message Edited by myraddin on 02-05-2009 03:37 PM

[rentepatrick]

Hi to all!

I have the exact same problem.

But I am not so good in english!

Can you tell me how to solve it please?

[simon_hain]

hello rentepatrick,

please create an own thread for your question as this topic is already solved. did you try the solution already?

[rentepatrick]

hi,

the problem is that I don't understant de solution.

Best regards

[simon_hain]

if you remove a field from a manager this field now is not added to a manager. because you removed it.

if you call getManager on the field you get null. because it is not added to a manager.

if you try to do some operation on this non-existing manager you get a nullpointerexception. you can avoid this if you check for getManager returning null or change the logic of the code.

[rentepatrick]

Thank you for your reply!

I have this:

public void fieldChanged(Field field, int context) {
        // TODO Auto-generated method stub
        if(field == lst_City.typeField){  
            String s_Type = (String)lst_City.typeField.getChoice(lst_City.typeField.getSelectedIndex());
            s_Type = s_Type.toLowerCase();
            lst_City.constructRestList(s_Type);
            if(lst_City.typeField.getSelectedIndex()==0){
                lst_City.filteredRestListField.getManager().replace(lst_City.filteredRestListField, lst_City.restListField);
        
              }
            UiApplication.getUiApplication().invokeLater (new Runnable() {
                public void run()
                {
                   //Perform screen changes here.
               // replace(lst_City.restListField, lst_City.filteredRestListField);
                lst_City.restListField.getManager().replace(lst_City.restListField, lst_City.filteredRestListField);
                   lst_City.restListField = lst_City.filteredRestListField;

[rentepatrick]

i also try this, I changed my code as you sugested and didn't work.

public void fieldChanged(Field field, int context) {
        // TODO Auto-generated method stub
        if(field == lst_City.typeField){  
            String s_Type = (String)lst_City.typeField.getChoice(lst_City.typeField.getSelectedIndex());
            s_Type = s_Type.toLowerCase();
            lst_City.constructRestList(s_Type);
            if(lst_City.typeField.getSelectedIndex()==0){
                l  st_City.filteredRestListField =  lst_City.restListField;
              }
            UiApplication.getUiApplication().invokeLater (new Runnable() {
                public void run()
                {
                   //Perform screen changes here.
                lst_City.restListField.getManager().replace(lst_City.restListField, lst_City.filteredRestListField);
                   lst_City.restListField = lst_City.filteredRestListField;
                //Calling invalidate() on your screen forces the paint
                //method to be called.
                //invalidate();
                }

Please help me.