c++ - 当按下鼠标左键时，在 SFML 2.0 中也按下了

Question

我刚开始学习 SFML 2.0，但遇到了一些小问题。问题是当我按下按钮“A”然后在输出中它也显示“鼠标左键按下”。我正在使用代码:: block 16.04 和 SFML 2.0。 如果我按任何其他数字，则“MouseWheelMoved”事件也会发生同样的事情，然后它会显示消息“MouseWheelMoved”。这是代码。

#include <SFML/Graphics.hpp>
#include <iostream>
int main()
{
    sf::RenderWindow window(sf::VideoMode(400,400),"All Events ");
    sf::Event event;
    window.setKeyRepeatEnabled(false);
    while(window.isOpen())
    {
        while(window.pollEvent(event))
        {
            switch(event.type)
            {
            case sf::Event::Closed:
                window.close();
                break;
            case sf::Event::KeyPressed:
                switch(event.key.code)
                {
                case sf::Keyboard::A:
                    std::cout<<"A Button Pressed "<<std::endl;
                    break;
                case sf::Keyboard::S:
                    std::cout<<"S Button Pressed "<<std::endl;
                    break;
                case sf::Keyboard::D:
                    std::cout<<"D Button Pressed "<<std::endl;
                    break;
                case sf::Keyboard::W:
                    std::cout<<"W Button Pressed "<<std::endl;
                    break;
                case sf::Keyboard::Return:
                    std::cout<<"Enter Button Pressed"<<std::endl;
                    break;
                case sf::Keyboard::Up:
                    std::cout<<"Up Button Pressed "<<std::endl;
                    break;
                }
                case sf::Event::MouseButtonPressed:
                    if(event.mouseButton.button == sf::Mouse::Left)     {std::cout<<"Mouse Left Button Pressed "<<std::endl;
                    break;}
                    else if(event.mouseButton.button == sf::Mouse::Right){std::cout<<"Mouse Right Button Pressed"<<std::endl;
                    break;}
                case sf::Event::MouseWheelMoved:
                    std::cout<<"Mouse Wheel Moved "<<event.mouseWheel.delta<<std::endl;
                    break;
            }
        }
    }
}

Answer 1

您嵌套了两个 switch，其中一个缺少 break

switch(event.type) // switch 1
{
  // (...)
  case sf::Event::KeyPressed:
      switch(event.key.code) // switch 2
      {
      case sf::Keyboard::A:
          std::cout<<"A Button Pressed "<<std::endl;
          break; // <- this breaks switch 2 and...
      // (...)
      } 
      // ...you end up here. Here switch 1 doesn't have a break 
      // so it falls through to the next case.
      case sf::Event::MouseButtonPressed:
        // (...)
        // here also falls through.
      case sf::Event::MouseWheelMoved:
          std::cout<<"Mouse Wheel Moved ";
          break;
}