c++ - 尝试将简单按钮绑定(bind)到SFGUI中的OnClick函数

因此，我刚刚开始在SFML项目中使用SFGUI，而我正努力了解所有工作原理。我一直在阅读Hello World教程以及该库本身在其文件夹中提供的一些示例。

我现在正在尝试创建一个简单的按钮，该按钮在检测到左键单击时会执行某些操作，但是我什至无法使其正常工作。错误窗口显示button变量未在OnClick方法中定义，如果我尝试使用button的参数发送std::bind，我将得到典型的“无匹配功能...”。

在该库的大多数示例中，此问题都通过使用this作为函数名称旁边的第二个参数来解决，但对我来说似乎不起作用。

应该怎么做？

我的代码:

void pressEnter(){
    button->SetLabel("Tocado"); // FIRST ERROR IN THIS LINE
}

int main(){

    sfg::SFGUI sfgui;

    sf::VideoMode video_mode( 800, 600 );
    sf::RenderWindow rwindow( video_mode, "In-joked - Menu Principal");
    sf::Event event;

    auto button = sfg::Button::Create("Status");
    button->GetSignal(sfg::Button::OnLeftClick).Connect(
            std::bind(&pressEnter, button)); //SECOND ERROR IN THIS LINE

    ...
}

NetBeans第一行显示错误:
“无法解析标识符“按钮”。未在此范围内声明”按钮””

第二行:

“包含在来自

错误:没有匹配的函数可以调用“sfg::Signal::Connect(std::_ Bind_helper＆>::type)”
std::bind(＆pressEnter，button));“

运行控制台输出中完全错误:

main.cpp: In function ‘void pressEnter()’:
main.cpp:7:5: error: ‘button’ was not declared in this scope
     button->SetLabel("Tocado");
     ^
In file included from /usr/include/c++/5/memory:79:0,
                 from /usr/local/include/SFGUI/Signal.hpp:6,
                 from /usr/local/include/SFGUI/Object.hpp:4,
                 from /usr/local/include/SFGUI/Adjustment.hpp:3,
                 from /usr/local/include/SFGUI/Widgets.hpp:6,
                 from main.cpp:2:
/usr/include/c++/5/functional: In instantiation of ‘struct std::_Bind_check_arity<void (*)(), std::shared_ptr<sfg::Button>&>’:
/usr/include/c++/5/functional:1439:12:   required from ‘struct std::_Bind_helper<false, void (*)(), std::shared_ptr<sfg::Button>&>’
/usr/include/c++/5/functional:1462:5:   required by substitution of ‘template<class _Func, class ... _BoundArgs> typename std::_Bind_helper<std::__is_socketlike<_Func>::value, _Func, _BoundArgs ...>::type std::bind(_Func&&, _BoundArgs&& ...) [with _Func = void (*)(); _BoundArgs = {std::shared_ptr<sfg::Button>&}]’
main.cpp:20:42:   required from here
/usr/include/c++/5/functional:1410:7: error: static assertion failed: Wrong number of arguments for function
       static_assert(sizeof...(_BoundArgs) == sizeof...(_Args),
       ^
main.cpp: In function ‘int main()’:
main.cpp:20:43: error: no matching function for call to ‘sfg::Signal::Connect(std::_Bind_helper<false, void (*)(), std::shared_ptr<sfg::Button>&>::type)’
             std::bind(&pressEnter, button));
                                           ^
In file included from /usr/local/include/SFGUI/Object.hpp:4:0,
                 from /usr/local/include/SFGUI/Adjustment.hpp:3,
                 from /usr/local/include/SFGUI/Widgets.hpp:6,
                 from main.cpp:2:
/usr/local/include/SFGUI/Signal.hpp:40:16: note: candidate: unsigned int sfg::Signal::Connect(std::function<void()>)
   unsigned int Connect( std::function<void()> delegate );
                ^
/usr/local/include/SFGUI/Signal.hpp:40:16: note:   no known conversion for argument 1 from ‘std::_Bind_helper<false, void (*)(), std::shared_ptr<sfg::Button>&>::type {aka std::_Bind<void (*(std::shared_ptr<sfg::Button>))()>}’ to ‘std::function<void()>’
nbproject/Makefile-Debug.mk:78: recipe for target 'build/Debug/GNU-Linux/main.o' failed
make[2]: *** [build/Debug/GNU-Linux/main.o] Error 1
make[2]: Leaving directory '/home/manu/NetBeansProjects/GameMenu'
nbproject/Makefile-Debug.mk:59: recipe for target '.build-conf' failed
make[1]: *** [.build-conf] Error 2
make[1]: Leaving directory '/home/manu/NetBeansProjects/GameMenu'
nbproject/Makefile-impl.mk:39: recipe for target '.build-impl' failed
make: *** [.build-impl] Error 2

BUILD FAILED (exit value 2, total time: 953ms)

最佳答案

一种选择是将变量放在一个都可以访问它的范围内。

sfg::Button::Ptr button;

void pressEnter(){
    button->SetLabel("Tocado");
}

int main(){

    sfg::SFGUI sfgui;

    sf::VideoMode video_mode( 800, 600 );
    sf::RenderWindow rwindow( video_mode, "In-joked - Menu Principal");
    sf::Event event;

    button = sfg::Button::Create("Status");
    button->GetSignal(sfg::Button::OnLeftClick).Connect(&pressEnter);

    ...
}

这是一个全局变量，可能不是执行此操作的最佳方法，但是它将起作用。对于这里的问答，如何构造程序以使其不具有全局变量太宽泛了。

关于c++ - 尝试将简单按钮绑定(bind)到SFGUI中的OnClick函数，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/42812997/