Getting all entries from TGListBox

ROOT
1

Hi,

I’m have a TGListBox in which I can select multiple choices… How do I get what was selected?

I’m assuming it’s

TList* selected = new TList;
listBox->GetSelectedEntries(selected);

But when what do I do from there?

Thanks.

2

Hi,

Depends on what you want to do… Maybe something like this :

   listbox->GetSelectedEntries(selected);
   TGTextLBEntry *entry;
   TIter next(selected);
   while ((entry = (TGTextLBEntry *)next())) {
      TString name = obj->GetTitle();
      // Do whatever you want...
   }

Cheers,
Bertrand.

3

Hi,

Thanks for the reply.

I did that:

TGListBox *fListBox;
[…]
TGListBox fListBox = new TGListBox(hframe, 90);
fListBox->AddEntry(“hi”, 1);
fListBox->Resize(150,80);
hframe->AddFrame(fListBox, new TGLayoutHints(kLHintsCenterX, 5, 5, 3, 4));
[…]
TList selected = new TList;
fListBox->GetSelectedEntries(selected);
TIter next(selected);
while ((entry = (TGTextLBEntry *)next())){
TString name = obj->GetTitle();
}

When that last bit of code is executed, I get one of two things:
If I selected nothing in the list box, I get:
root [0] .L numberEntry.C
root [1] example()
root [2] Error: illegal pointer to class object fListBox 0x0 795 FILE:numberEntry.C LINE:170
*** Interpreter error recovered ***

If I selected something in the list box, I get:
root [0] .L numberEntry.C
root [1] example()
root [2]
*** Break *** segmentation violation
Generating stack trace…
[…]

Thanks again,
Mikhail

4

Hi Mikhail,

Please attach - or send me ( bertrand.bellenot@cern.ch ) your code or a short macro reproducing the problem.

Cheers,
Bertrand.

5

Hi,

After a second look, I realized that you define fListBox twice :

TGListBox *fListBox;
[…]
TGListBox *fListBox = new TGListBox(hframe, 90);

First of all, you should avoid this kind of double definition…
If you still have problems, please send the code.

Cheers,
Bertrand.

6

Here it is… run with:

root [0] .L numberEntry.C
root [1] example()

I commented out any other dependencies.

Thank you very much,
Mikhail
numberEntry.C (6.01 KB)

7

Hi Mikhail,

If you declare your listbox as a class member :

class MyMainFrame {
[…]
public:
TGListBox *fListBox;

You MUST NOT redeclare it later in the code:

TGListBox *fListBox = new TGListBox(hframe, 90);

but just initialize (create) it:

fListBox = new TGListBox(hframe, 90);

Because the second definition becomes invalid when going out of scope, and the class member is still not initialized.

Cheers,
Bertrand.

8

Hi Bertrand,

Good call.

One other question though… what does this line do? TString name = obj->GetTitle();
What is obj?

Definitely seems to crash my little application if you run it
Root[] example()
select something in dropdown
press go…

I don’t think obj was ever declared anywhere? What is that?

Thank you,
Mikhail

9

Never mind, I figured it out… Should be:

TList* selected = new TList;
fListBox->GetSelectedEntries(selected);
TIter next(selected);
TString name;
while ((entry = (TGTextLBEntry *)next())){
	name = entry->GetTitle();
}

Thanks again

10

Ooops! Sorry, it was a typo. The correct code is :

Cheers,
Bertrand.