Accès aux éléments graphiques
To access a widget, for instance to show() a dialog, use the get_widget() method, providing the widget's name. This name should be specified in the Glade Properties window. If the widget could not be found, or is of the wrong type, then the pointer will be set to nullptr.
auto pDialog = builder->get_widget<Gtk::Dialog>("DialogBasic");
Gtk::Builder vérifie qu'il ne s'agit pas d'un pointeur NULL et que l'élément graphique est du type attendu ; il affiche des avertissements sur la ligne de commande s'il y a de telles anomalies.
Souvenez-vous que get_widget() ne crée pas un nouvel exemplaire d'élément graphique ; avec cette fonction, vous obtenez simplement un pointeur sur un élément graphique qui existe déjà. Vous obtenez toujours un pointeur sur le même élément graphique quand vous appelez get_widget() sur le même Gtk::Builder, avec le même nom d'élément graphique. Les éléments graphiques sont créés pendant l'appel à Gtk::Builder::create_from_file().
get_widget() returns child widgets that are manage()ed (see the Memory Management chapter), so they will be deleted when their parent container is deleted. Windows (such as Dialogs) cannot be managed because they have no parent container, so you must delete them at some point. The documentation of Gtk::Builder has more to say about the memory management of different kinds of objects.
- XXIV.II.I. Exemple
XXIV.II.I. Exemple
Cet exemple simple montre comment charger un fichier Glade au cours de l'exécution et accéder aux éléments graphiques avec Gtk::Builder.
File: main.cc (For use with gtkmm 4)
#include <gtkmm.h>
#include <iostream>
namespace
{
Gtk::Dialog* pDialog = nullptr;
Glib::RefPtr<Gtk::Application> app;
void on_button_clicked()
{
if (pDialog)
pDialog->hide(); //hide() will cause Gtk::Application::run() to end.
}
void on_app_activate()
{
// Load the GtkBuilder file and instantiate its widgets:
auto refBuilder = Gtk::Builder::create();
try
{
refBuilder->add_from_file("basic.glade");
}
catch(const Glib::FileError& ex)
{
std::cerr << "FileError: " << ex.what() << std::endl;
return;
}
catch(const Glib::MarkupError& ex)
{
std::cerr << "MarkupError: " << ex.what() << std::endl;
return;
}
catch(const Gtk::BuilderError& ex)
{
std::cerr << "BuilderError: " << ex.what() << std::endl;
return;
}
// Get the GtkBuilder-instantiated dialog:
pDialog = refBuilder->get_widget<Gtk::Dialog>("DialogBasic");
if (!pDialog)
{
std::cerr << "Could not get the dialog" << std::endl;
return;
}
// Get the GtkBuilder-instantiated button, and connect a signal handler:
auto pButton = refBuilder->get_widget<Gtk::Button>("quit_button");
if (pButton)
pButton->signal_clicked().connect([] () { on_button_clicked(); });
// It's not possible to delete widgets after app->run() has returned.
// Delete the dialog with its child widgets before app->run() returns.
pDialog->signal_hide().connect([] () { delete pDialog; });
app->add_window(*pDialog);
pDialog->show();
}
} // anonymous namespace
int main(int argc, char** argv)
{
app = Gtk::Application::create("org.gtkmm.example");
// Instantiate a dialog when the application has been activated.
// This can only be done after the application has been registered.
// It's possible to call app->register_application() explicitly, but
// usually it's easier to let app->run() do it for you.
app->signal_activate().connect([] () { on_app_activate(); });
return app->run(argc, argv);
}