WxListBox1->Append(const wxString &Item, void *client Topic is solved

[liangbowen]

How Can i Add an Int clientdata to listbox item?
this is how i do, but doesn't work at all.

void testwxdlgDlg::WxButton1Click(wxCommandEvent& event)
{
int a=10;

WxListBox1->Append("cccc", &a);
a = 13;
WxListBox1->Append("aaaa", &a);
a = 22;
WxListBox1->Append("bbbb", &a);
}

//select one listbox item
void testwxdlgDlg::WxListBox1Selected(wxCommandEvent& event)
{
char temp[20];
sprintf(temp,"%d",(int*)event.GetClientData());
MessageBox(NULL,event.GetString(),temp,MB_OKCANCEL);

}

[benedicte]

You cannot use pointers/references on local variables as client data. These are lost when you exit the function.

Either you save them in an array (or any other structure) in a class member object,
or you convert the [const] values into void* ...

Code: Select all

void testwxdlgDlg::WxButton1Click(wxCommandEvent& event) 
{ 
int a=10; 

WxListBox1->Append("cccc", (void*)a); 
a = 13; 
WxListBox1->Append("aaaa", (void*)a); 
a = 22; 
WxListBox1->Append("bbbb", (void*)a); 
} 

[liangbowen]

I know I can't use local variables. But I thought that the Append() will create another copy of data on heap(which I don't know if it's true) before the function exits.

And then I later evoke a select item event, say "WxListBox1Selected(wxCommandEvent& event) {}", it will retrun the pointer to the data on heap to me via event.GetClientData(). (which I don't know if it's true either)

I also tried:

Code: Select all

int a;
void testwxdlgDlg::WxButton1Click(wxCommandEvent& event) {
 WxListBox1->Append("cccc", (void*)&a); 
a = 13; 
WxListBox1->Append("aaaa", (void*)&a); 
a = 22; 
WxListBox1->Append("bbbb", (void*)&a); 
}
void testwxdlgDlg::WxListBox1Selected(wxCommandEvent& event) 
{ 
char temp[20]; 
sprintf(temp,"%d",(int*)event.GetClientData()); 
MessageBox(NULL,event.GetString(),temp,MB_OKCANCEL); 
}

yet still can't work, I just want a simple example tell me how to associate Int values with listbox items, and how to get the values back when I later select items.

do I have to create a global int array say int a[10] and write codes as follow? :

Code: Select all

int a[10];
void testwxdlgDlg::WxButton1Click(wxCommandEvent& event) {
 WxListBox1->Append("cccc", (void*)&a); 
a[0] = 13; 
WxListBox1->Append("aaaa", (void*)&a); 
a[1] = 22; 
WxListBox1->Append("bbbb", (void*)&a); 
a[2] = 32;
}
void testwxdlgDlg::WxListBox1Selected(wxCommandEvent& event) 
{ 
char temp[20]; 
sprintf(temp,"%d",a[event.GetInt()]);
MessageBox(NULL,event.GetString(),temp,MB_OKCANCEL); 
}

I am sure it will work, but that seems stupid.

[Cursor]

IMHO wxListBox (or others) dont copy any data.
If you want to save a data, you must allocate it on the heap and assign the address as data.
If your data is just an integer, you can assign it direclyt with casting.

[liangbowen]

I am sorry benedicte, you are right!
I just notice you've worte (void*)a, not (void*)&a.

or you convert the [const] values into void*

yeah, that's right.
thanks very much benedicte.