问题
I am trying to create a window in GTK+ that has tab looks like this:
Whenever the user clicks in the "New" button, there is a new tab appear.
However, when I was compiling my program I got an error: void value not ignored as it ought to be
phongcao@phongcao:~$ g++ /home/phongcao/C++/GTK+/newtab.cc -o /home/phongcao/C++/GTK+/newtab `pkg-config gtk+-2.0 --cflags --libs`
/home/phongcao/C++/GTK+/newtab.cc: In function ‘int main(int, char**)’:
/home/phongcao/C++/GTK+/newtab.cc:51:3: error: void value not ignored as it ought to be
And here is the code:
#include <gtk/gtk.h>
void destroy(GtkWidget *window, gpointer data) {
gtk_main_quit();
}
void new_tab(GtkNotebook *notebook, GtkWidget *content, GtkWidget *hbox) {
gtk_notebook_append_page(notebook, content, hbox);
}
int main(int argc, char *argv[])
{
GtkWidget *window, *label, *content;
GtkWidget *button, *hbox, *notebook;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_container_set_border_width(GTK_CONTAINER(window), 10);
gtk_window_set_title(GTK_WINDOW(window), "New Tab");
gtk_widget_set_size_request(window, 300, 200);
notebook = gtk_notebook_new();
button = gtk_button_new_with_label("New");
label = gtk_label_new("Tab");
hbox = gtk_hbox_new(FALSE, 5);
content = gtk_label_new("This is a tab");
gint a = 0;
gtk_box_pack_start_defaults(GTK_BOX(hbox), label);
gtk_box_pack_start_defaults(GTK_BOX(hbox), button);
gtk_notebook_append_page(GTK_NOTEBOOK(notebook), content, hbox);
gtk_notebook_set_tab_pos(GTK_NOTEBOOK(notebook), GTK_POS_TOP);
//This following line is where the error is from:
g_signal_connect(G_OBJECT(button), "new_tab", G_CALLBACK(new_tab(GTK_NOTEBOOK(notebook), content, hbox)), NULL);
g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(destroy), NULL);
gtk_container_add(GTK_CONTAINER(window), notebook);
gtk_widget_show_all(hbox);
gtk_widget_show_all(window);
gtk_main();
return 0;
}
Thanks for your help!! I really appreciate it!!
回答1:
The line number doesn't make much sense to me but I think your problem is right here (reformatted for illustrative purposes):
g_signal_connect(G_OBJECT(button), "new_tab",
G_CALLBACK(new_tab(GTK_NOTEBOOK(notebook), content, hbox)), /* <== Badness */
NULL
);
You're calling the new_tab
function inside the G_CALLBACK
macro. The new_tab
function returns void
(i.e. no return value) but it is being called in a context that needs a value and hence the "void value not ignored" error. I think you mean to say something more like this:
g_signal_connect(G_OBJECT(button), "new_tab", G_CALLBACK(new_tab), NULL);
回答2:
g_signal_connect(G_OBJECT(button), "new_tab", G_CALLBACK(new_tab(GTK_NOTEBOOK(notebook), content, hbox)), NULL);
Are you sure you want to pass parameters to new_tab()
? Simply put G_CALLBACK(new_tab)
. That will resolve error.
If you want to call "new_tab" then you have to call the function explicitly at proper place (say before passing to G_CALLBACK
).
For your query you can refer to this small tutorial.
来源:https://stackoverflow.com/questions/5752794/error-void-value-not-ignored-as-it-ought-to-be-c-gtk