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访问部件

要访问部件，例如show()一个对话框，请使用get_widget()方法，并向其提供一个部件名。这个名称应该在Glade的窗口属性中指定。如果找不到该部件或是部件的类型不对，则指针将被设为nullptr。

auto pDialog = builder->get_widget<Gtk::Dialog>("DialogBasic");

Gtk::Builder会进行空指针和部件类型检查，并在命令行上显示相关的警告。

请注意，你并没有使用get_widget()实例化部件，你只是获得了指向已经存在的部件的指针。当你在同一个Gtk::Builder上用同一个名称调用get_widget()你总是会得到指向同一实例的指针。部件在函数Gtk::Builder::create_from_file()执行期间被实例化。

get_widget()返回一个经manage()处理的子部件（参阅内存管理章节），因此在删除其父部件时它们将被一并删除。无法管理Windows（例如Dialogs）因为它们没有父容器，所以你必须在某个时候删除它们。Gtk::Builder的文档中有更多关于对不同类型的对象如何进行内存管理的介绍。

参考

24.2.1. 示例

这个简单示例展示了如何在运行时加载Glade文件并使用Gtk::Builder访问部件。

源代码

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);
}
加载.glade文件 使用派生部件

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