Sfml pollEvent，每个新的图像删除前一个

Question

我的问题是，该功能不做我想要的。 这个“CreateWindow”函数有主循环。在主循环中，我想要一个固定的背景，每次按H按钮，我都想在背景上绘制一张卡片（精灵）。 这里有什么问题？我的功能画卡，但是当我按下H时，先前的卡被删除并且下一张卡被绘制。 这是关于我认为的事件，因为每次发生事件（我移动鼠标，我按其他键等）以前的卡被删除... 我使用sfml 2.0

这是我的实现图形类

#include "Graphic.h" 
#include "SFML/Graphics.hpp" 
#include <iostream> 
#include <string> 
#include "Card.h" 
#include <string> 
#include <sstream> 

Graphic::Graphic(int offset) 
{ 
    this->offset = offset; 
} 

Graphic::~Graphic() 
{ 
    //dtor 
} 

int Graphic::CreateWindow(sf::RenderWindow& window, Deck &deck0) 
{ 
    sf::Vector2i screenDimensions(800, 600); 

    //Dimensioni della window 
    window.create(sf::VideoMode(screenDimensions.x, screenDimensions.y), "BlackJack", sf::Style::Titlebar | sf::Style::Close); 

    int index = 0; 
    window.setKeyRepeatEnabled(false); 

    //settare il background 
    sf::Texture bTexture; 
    sf::Sprite bImage; 
    if(!bTexture.loadFromFile("Background.png")) 
     std::cout << "Error" << std::endl; 
    bImage.setTexture(bTexture); 
    bImage.setScale(1.0, (float)screenDimensions.y/bTexture.getSize().y); 

    //MAIN LOOP---------------------- 
    while(window.isOpen()) 
    { 
     sf::Event Event; 

     while(window.pollEvent(Event)) 
     { 
      window.clear(); 
      window.draw(bImage); // this is the function which draw the background 

      if (Event.type == sf::Event::Closed) 
      { 
       window.close(); 
      } 

      if(Event.key.code == sf::Keyboard::H) 
      { 

       Card * y = deck0.dealFirst(); 
       drawCard(window,y->graphNumber,y->getSeed(),offset); 
       offset = offset + 50; 
      } 

      window.display(); 

     } 
    } 
} 

int Graphic::drawCard(sf::RenderWindow &window, int graphNumber, string seed, int offset) 
{ 
    std::ostringstream oss; 
    oss << graphNumber << seed << ".png"; 
    std::string var = oss.str(); 

    sf::Texture QHTexture; 
    sf::Sprite QHImage; 
    if(!QHTexture.loadFromFile(var)) 
     std::cout<< "Error" <<std::endl; 
    QHImage.setTexture(QHTexture); 
    QHImage.setScale(0.5, 0.5); 
    QHImage.setPosition(offset + 100, 400); 
    window.draw(QHImage); //this is the function which draw the card's sprite 
    return 0; 
} 

Answer 1

好吧，你不应该你while(window.pollEvent())循环内进行绘制的，你应该画这样的事：

while(window.isOpen()) 
    { 
    sf::Event Event; 
    while(window.pollEvent(Event)) 
    { 
     if (Event.type == sf::Event::Closed) 
     { 
      window.close(); 
     } 

     if(Event.key.code == sf::Keyboard::H) 
     { 

      Card * y = deck0.dealFirst(); 
      drawCard(window,y->graphNumber,y->getSeed(),offset); 
      offset = offset + 50; 
     } 
    } 

    window.clear(); 
    window.draw(bImage); // this is the function which draw the background 

    window.display(); 
} 

的方式你画你的画，来电会只有在发生SFML事件时才会发生，并且只有在发生sfml事件时才会清除（如果您不希望它持续呈现每一帧，并且不计划任何类型的动画，则可以这样做） 。

所以当你点击H时，一个sfml事件是触发器，它会调用你的绘图卡功能，但是因为你的卡是你写的函数的局部变量，所以在函数结束时它被清除。你需要将你的卡片存放在某个地方，比如一个向量或sf :: Sprite列表。所以一个例子是：

#include "Graphic.h" 
#include "SFML/Graphics.hpp" 
#include <iostream> 
#include <string> 
#include "Card.h" 
#include <string> 
#include <sstream> 

Graphic::Graphic(int offset) 
{ 
    this->offset = offset; 
} 

Graphic::~Graphic() 
{ 
    //dtor 
} 

int Graphic::CreateWindow(sf::RenderWindow& window, Deck &deck0) 
{ 
    sf::Vector2i screenDimensions(800, 600); 

    //Dimensioni della window 
    window.create(sf::VideoMode(screenDimensions.x, screenDimensions.y), "BlackJack", sf::Style::Titlebar | sf::Style::Close); 

    int index = 0; 
    window.setKeyRepeatEnabled(false); 

    //settare il background 
    sf::Texture bTexture; 
    sf::Sprite bImage; 
    if(!bTexture.loadFromFile("Background.png")) 
     std::cout << "Error" << std::endl; 
    bImage.setTexture(bTexture); 
    bImage.setScale(1.0, (float)screenDimensions.y/bTexture.getSize().y); 

    //MAIN LOOP---------------------- 
     while(window.isOpen()) 
    { 
    sf::Event Event; 
    while(window.pollEvent(Event)) 
    { 
     if (Event.type == sf::Event::Closed) 
     { 
      window.close(); 
     } 

     if(Event.key.code == sf::Keyboard::H) 
     { 

      Card * y = deck0.dealFirst(); 
      drawCard(window,y->graphNumber,y->getSeed(),offset); 
      offset = offset + 50; 
     } 
    } 

    window.clear(); 
    window.draw(bImage); // this is the function which draw the background 

    for(int i = 0; i < cardList.size(); ++i) 
    { 
     window.draw(cardList[i]); 
    } 

    window.display(); 
    } 

} 

int Graphic::drawCard(sf::RenderWindow &window, int graphNumber, string seed, int offset) 
{ 
    std::ostringstream oss; 
    oss << graphNumber << seed << ".png"; 
    std::string var = oss.str(); 

    sf::Texture QHTexture; 
    sf::Sprite QHImage; 
    if(!QHTexture.loadFromFile(var)) 
     std::cout<< "Error" <<std::endl; 
    QHImage.setTexture(QHTexture); 
    QHImage.setScale(0.5, 0.5); 
    QHImage.setPosition(offset + 100, 400); 
    cardList.push_back(QHImage); //this adds the sprite to our list 
    return 0; 
}