问题描述
在下面的代码中,我在网格容器上设置 ScrolledWindows,然后在循环中设置它们的属性,因为我想将 TextViews 放在网格上。我不想使用 TreeView,因为在那里放置长文本或中等文本是不合适的,这就是我的意图。不幸的是,函数 get_child_at(int col,int row),为了获取附加的小部件返回 Gtk::Widget,对于我需要的属性,我必须为 Gtk::ScrolledWindow 做一个强制转换;这是我做不到的。
(some code)
descriptors->attach(* (new Gtk::ScrolledWindow ()),0);
descriptors->attach(* (new Gtk::ScrolledWindow ()),1,2,0);
(some other code)
for(int i = 0; i < 3; i++)
{
//Glib::RefPtr<Gtk::ScrolledWindow> * disposable_pointer = new Glib::RefPtr<Gtk::ScrolledWindow>();
//disposable_pointer = descriptors->get_child_at (i,0);
//Glib::RefPtr<Gtk::ScrolledWindow> disposable_pointer = Glib::RefPtr<Gtk::Widget>::cast_dynamic(*descriptors->get_child_at (i,0));
//Glib::RefPtr<Gtk::ScrolledWindow>Glib::RefPtr<Gtk::ScrolledWindow>::cast_dynamic
//current_grid_child_scrolledWin = Glib::RefPtr<Gtk::ScrolledWindow>cast_dynamic(descriptors->get_child_at (i,0));
//current_grid_child_scrolledWin = disposable_pointer->get();
Glib::RefPtr<Gtk::Widget> * something = new Glib::RefPtr<Gtk::Widget>(descriptors->get_child_at (i,0));
Glib::RefPtr<Gtk::ScrolledWindow> disposable_pointer = *something;
current_grid_child_scrolledWin->set_vadjustment (Glib::RefPtr<Gtk::Adjustment>());
current_grid_child_scrolledWin->set_hadjustment (Glib::RefPtr<Gtk::Adjustment>());
current_grid_child_scrolledWin->set_policy (Gtk::PolicyType::POLICY_AUTOMATIC,Gtk::PolicyType::POLICY_AUTOMATIC);
current_grid_child_scrolledWin->set_vexpand (true);
current_grid_child_scrolledWin->set_hexpand (true);
current_grid_child_scrolledWin->set_margin_end (10);
current_grid_child_scrolledWin->set_margin_bottom (10);
current_grid_child_scrolledWin->set_visible (true);
}
/usr/include/glibmm-2.4/glibmm/refptr.h:309:31: error: invalid conversion from 'Gtk::Widget*' to 'Gtk::ScrolledWindow*' [-fpermissive]
309 | pCppObject_(src.operator->())
| ^
| |
| Gtk::Widget*
我考虑过the gtkmm documentation on using casting with Glib::RefPtr
解决方法
正如我们从 Gtk::Grid
documentation 中看到的,get_child_at
的返回类型是一个指向小部件的原始指针:
Widget* Gtk::Grid::get_child_at(int column,int row
)
而不是智能指针(在您的情况下是 Glib::Refptr
)。这是因为 get_child_at
的调用者不负责管理返回指针指向的对象的生命周期。您只需掌握一个句柄,对其进行处理,然后就不管它了。其他人负责对其调用 delete
。在你的情况下,我会这样做:
#include <gtkmm.h>
#include <iostream>
int main(int argc,char *argv[])
{
// Initialize Gtkmm:
auto app = Gtk::Application::create(argc,argv,"so.question.q66162108");
// Create a grid and attach a scrolled window:
Gtk::Grid container;
Gtk::ScrolledWindow scrolledWindow;
// Add the scrolled window to the grid. Make sure the container is responsible
// of deleting it! Otherwise,remeber to call delete on it:
container.attach(*Gtk::manage(new Gtk::ScrolledWindow()),1,1);
// Here,you get a raw pointer to a widget:
Gtk::Widget* pWidget = container.get_child_at(0,0);
// We cast it to its most derived type:
Gtk::ScrolledWindow* pScrolledWindow = dynamic_cast<Gtk::ScrolledWindow*>(pWidget);
// If the cast fail (i.e. not a ScrolledWindow at (0,0),then the
// casted pointer will be set to nullptr:
if(pScrolledWindow)
{
std::cout << "Casting worked" << std::endl;
// Handle properties here...
pScrolledWindow->set_visible (true);
// Set other properties here...
}
return 0;
} // At this point the container is destroyed and since Gtk::manage
// was used,the scrolled window will be automatically deleted.
请注意,我在使用智能指针的这段代码没有任何地方。这是因为当我 new
我的 Gtk::ScrolledWindow
时,我使用 Gtk::manage
*。此函数将对象(此处为 Gtk::ScrolledWindow
)标记为其父容器小部件(此处为 Gtk::Grid
)所有,因此您无需手动删除它。当容器消失时,我成为容器的责任,在其子项上调用 delete
。
*如果您使用较新的 Gtkmm 版本,则必须改用 make_managed<T>
。见here。