使用SFML中的精灵不显示图像

我在Linux Mint 18.1上使用C++ 17学习了使用GUI的SFML 2.3.2。作为Hello World之后的第二个项目，我试图重新制作Snake，这款游戏旧手机已经预装了。大部分的东西一直工作到现在，除了一些小例外，我将不得不在稍后处理，一些由游戏尚未完全完成。使用SFML中的精灵不显示图像

只是为了确保正确理解此事，因为我以前从未使用过较低级语言的GUI和图像。首先将图像加载到纹理中，然后将纹理添加到sprite，然后将该sprite绘制到窗口上？

该程序完美编译，正确初始化所有内容，并且运行时没有任何重大不明原因的问题。除了图像不显示。精灵在那里，并以默认的单色背景颜色显示，但不显示任何图像。

我该怎么做，我该如何解决？谢谢！

// HEADERS 
#include <iostream> 
#include <SFML/Graphics.hpp> 
#include <SFML/Graphics/Color.hpp> 
#include <SFML/Graphics/Font.hpp> 
#include <SFML/Graphics/Image.hpp> 
#include <SFML/Graphics/Rect.hpp> 
#include <SFML/Graphics/Sprite.hpp> 
#include <SFML/Graphics/Texture.hpp> 
#include <SFML/System/String.hpp> 
#include <SFML/Window/Keyboard.hpp> 

// CREATE NEW FONT 
sf::Font create_font() 
{ 
    sf::Font f; 
    bool id = f.loadFromFile("/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-B.ttf"); 

    if (id == false) 
    { 
     std::cerr << "Font:\tCould not be loaded." << std::endl; 
    } 
    else 
    { 
     std::cerr << "Font:\tLoaded successfully." << std::endl; 
    } 

    return f; 

} 

// CREATE NEW SPRITE USING TEXTURE, GIVEN ARE PATH WITH COORDINATES AND DIMENSIONS 
sf::Sprite load_img(std::string path, long x, long y, long w, long h) 
{ 
    sf::Texture t; 
    bool id = t.loadFromFile(path); 

    if (id == false) 
    { 
     std::cerr << "Texture:\t" << path << "\tFailed to load." << std::endl; 
    } 
    else 
    { 
     std::cerr << "Texture:\t" << path << "\tLoaded successfully." << std::endl; 
    } 

    sf::Sprite s(t); 
    s.setTextureRect(sf::IntRect((int)x, (int)y, (int)w, (int)h)); 
    s.setPosition(x, y); 
    return s; 
} 


// MAIN FUNCTION 
int main() 
{ 
    // DECLARING/DEFINING VARIABLES 
    unsigned long window_width = 512; 
    unsigned long window_height = 512; 
    unsigned long score = 0; 
    unsigned long head_old_position_x, head_old_position_y; 
    std::string title = "Snek"; 
    std::string wdir = "/home/kate/Documents/coding/snek/"; 

    // WINDOW 
    sf::RenderWindow window(sf::VideoMode(window_width, window_height), title); 
    window.setFramerateLimit(60); 

    // SPRITES 
    sf::Sprite background = load_img(wdir + "img/background.png", 0, 0, 512, 512); 
    sf::Sprite head = load_img(wdir + "img/head.png", 47, 39, 8, 8); 
    sf::Sprite body = load_img(wdir + "img/body.png", 39, 39, 8, 8); 
    sf::Sprite poison = load_img(wdir + "img/poison.png", 119, 119, 8, 8); 
    sf::Sprite trap = load_img(wdir + "img/trap.png", 159, 159, 8, 8); 
    sf::Sprite candy = load_img(wdir + "img/candy.png", 199, 199, 8, 8); 

    // FONT 
    sf::Font font = create_font(); 

    // TEXT 
    sf::Text score_display(title, font, 20); 
    sc// HEADERS 
#include <iostream> 
#include <SFML/Graphics.hpp> 
#include <SFML/Graphics/Color.hpp> 
#include <SFML/Graphics/Font.hpp> 
#include <SFML/Graphics/Image.hpp> 
#include <SFML/Graphics/Rect.hpp> 
#include <SFML/Graphics/Sprite.hpp> 
#include <SFML/Graphics/Texture.hpp> 
#include <SFML/System/String.hpp> 
#include <SFML/Window/Keyboard.hpp> 

// CREATE NEW FONT 
sf::Font create_font() 
{ 
    sf::Font f; 
    bool id = f.loadFromFile("/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-B.ttf"); 

    if (id == false) 
    { 
     std::cerr << "Font:\tCould not be loaded." << std::endl; 
    } 
    else 
    { 
     std::cerr << "Font:\tLoaded successfully." << std::endl; 
    } 

    return f; 

} 

// CREATE NEW SPRITE USING TEXTURE, GIVEN ARE PATH WITH COORDINATES AND DIMENSIONS 
sf::Sprite load_img(std::string path, long x, long y, long w, long h) 
{ 
    sf::Texture t; 
    bool id = t.loadFromFile(path); 

    if (id == false) 
    { 
     std::cerr << "Texture:\t" << path << "\tFailed to load." << std::endl; 
    } 
    else 
    { 
     std::cerr << "Texture:\t" << path << "\tLoaded successfully." << std::endl; 
    } 

    sf::Sprite s(t); 
    s.setTextureRect(sf::IntRect((int)x, (int)y, (int)w, (int)h)); 
    s.setPosition(x, y); 
    return s; 
} 


// MAIN FUNCTION 
int main() 
{ 
    // DECLARING/DEFINING VARIABLES 
    unsigned long window_width = 512; 
    unsigned long window_height = 512; 
    unsigned long score = 0; 
    unsigned long head_old_position_x, head_old_position_y; 
    std::string title = "Snek"; 
    std::string wdir = "/home/kate/Documents/coding/snek/"; 

    // WINDOW 
    sf::RenderWindow window(sf::VideoMode(window_width, window_height), title); 
    window.setFramerateLimit(60); 

    // SPRITES 
    sf::Sprite background = load_img(wdir + "/img/background.png", 0, 0, 512, 512); 
    sf::Sprite head = load_img(wdir + "/img/head.png", 47, 39, 8, 8); 
    sf::Sprite body = load_img(wdir + "/img/body.png", 39, 39, 8, 8); 
    sf::Sprite poison = load_img(wdir + "/img/poison.png", 119, 119, 8, 8); 
    sf::Sprite trap = load_img(wdir + "/img/trap.png", 159, 159, 8, 8); 
    sf::Sprite candy = load_img(wdir + "/img/candy.png", 199, 199, 8, 8); 

    // FONT 
    sf::Font font = create_font(); 

    // TEXT 
    sf::Text score_display(title, font, 20); 
    score_display.setString(std::to_string(score)); 
    score_display.setPosition(5, 5); 

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

      head_old_position_x = head.getPosition().x; 
      head_old_position_y = head.getPosition().y; 

      // MOVEMENT BASED ON KEYBOARD INPUT 
      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Left)) 
      { 
       head.setPosition(head.getPosition().x - 8, head.getPosition().y); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 

      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Up)) 
      { 
       head.setPosition(head.getPosition().x, head.getPosition().y - 8); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 

      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Right)) 
      { 
       head.setPosition(head.getPosition().x + 8, head.getPosition().y); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 

      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Down)) 
      { 
       head.setPosition(head.getPosition().x, head.getPosition().y + 8); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 


      if (body.getPosition().x == candy.getPosition().x && body.getPosition().y == candy.getPosition().y) 
      { 
       score ++; 
       score_display.setString(std::to_string(score)); 
      } 


      // REFRESH WINDOW 
      window.clear(); 
      window.draw(background); 
      window.draw(head); 
      window.draw(body); 
      window.draw(poison); 
      window.draw(trap); 
      window.draw(candy); 
      window.draw(score_display); 
      window.display(); 
     } 
    } 

    return 0; 
} 
ore_display.setString(std::to_string(score)); 
    score_display.setPosition(5, 5); 

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

      head_old_position_x = head.getPosition().x; 
      head_old_position_y = head.getPosition().y; 

      // MOVEMENT BASED ON KEYBOARD INPUT 
      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Left)) 
      { 
       head.setPosition(head.getPosition().x - 8, head.getPosition().y); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 

      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Up)) 
      { 
       head.setPosition(head.getPosition().x, head.getPosition().y - 8); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 

      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Right)) 
      { 
       head.setPosition(head.getPosition().x + 8, head.getPosition().y); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 

      if (sf::Keyboard::isKeyPressed(sf::Keyboard::Down)) 
      { 
       head.setPosition(head.getPosition().x, head.getPosition().y + 8); 
       body.setPosition(head_old_position_x, head_old_position_y); 
      } 


      if (body.getPosition().x == candy.getPosition().x && body.getPosition().y == candy.getPosition().y) 
      { 
       score ++; 
       score_display.setString(std::to_string(score)); 
      } 


      // REFRESH WINDOW 
      window.clear(); 
      window.draw(background); 
      window.draw(head); 
      window.draw(body); 
      window.draw(poison); 
      window.draw(trap); 
      window.draw(candy); 
      window.draw(score_display); 
      window.display(); 
     } 
    } 

    return 0; 
}

来源

2017-09-23 Katembers

控制台中是否有任何消息？ –

不显示图像的常见原因是因为纹理超出了范围，或者无法加载。 –

@ArnavBorborah不，没有任何SFML功能。我自己的错误检查确认一切*应该*按预期工作。 – Katembers

好吧，我想我已经得到它了。

可能什么也看不见了，因为你把所有绘制的东西事件循环内

试图把这些东西在while(window.isOpen())环范围。

来源

2017-09-28 12:26:29 alseether

是的。而已！谢谢！最后：D在上周疯狂地浏览了我的代码，但无法找到它。 – Katembers

您的纹理超出了范围，有关更多详细信息，请参阅When is an object "out of scope"?。你在load_img函数中声明了纹理，但是在退出load_img并返回精灵之后，sf::Texture t;被删除。

所以这里是一个更新函数，其中您将纹理存储在load_img函数之外并通过引用传递它。只显示相关部分。首先将纹理传递给load_img函数。删除sf::Texture t;。

sf::Sprite load_img(std::string path, long x, long y, long w, long h, sf::Texture& t) 
{ 
    bool id = t.loadFromFile(path); 
    [...] 
}

声明一个纹理并将其传递给load_img函数。

sf::Texture headtexture; 
sf::Sprite head = load_img(wdir + "img/head.png", 47, 39, 8, 8, headtexture);

如果你对所有的精灵都这样做，它的工作原理和正确显示图像/精灵。

编辑 25月 - 2017年

根据该意见，在这里是没有功能的最小工作示例：

// HEADERS 
#include <iostream> 
#include <SFML/Graphics.hpp> 
#include <SFML/Graphics/Color.hpp> 
#include <SFML/Graphics/Font.hpp> 
#include <SFML/Graphics/Image.hpp> 
#include <SFML/Graphics/Rect.hpp> 
#include <SFML/Graphics/Sprite.hpp> 
#include <SFML/Graphics/Texture.hpp> 
#include <SFML/System/String.hpp> 
#include <SFML/Window/Keyboard.hpp> 

// MAIN FUNCTION 
int main() 
{ 
    // DECLARING/DEFINING VARIABLES 
    unsigned long window_width = 512; 
    unsigned long window_height = 512; 
    std::string title = "Snek"; 
    std::string wdir = "/home/kate/Documents/coding/snek/"; 

    // WINDOW 
    sf::RenderWindow window(sf::VideoMode(window_width, window_height), title); 
    window.setFramerateLimit(60); 

    // SPRITES 
    sf::Texture headtexture; 
    sf::Sprite head; 

    headtexture.loadFromFile(wdir + "img/head.png"); 
    head.setTexture(headtexture); 
    head.setTextureRect(sf::IntRect(47, 39, 8, 8)); 
    head.setPosition(30, 30); 

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

      // REFRESH WINDOW 
      window.clear(); 
      window.draw(head); 
      window.display(); 
     } 
    } 

    return 0; 
}

来源

2017-09-24 07:15:18

我已经怀疑已经是昨天了，并且把所有东西都移到了'int main（）'中，以确保100％。精灵以默认的单色背景颜色显示，但图像不存在。基本上，我看到的只是窗口的黑色背景。 – Katembers

是的，但是目前您在函数中定义了纹理，并且在退出时会超出范围，导致未定义的行为。 –

我改变了它，以便纹理和精灵都在'int main（）'中独占使用。它永远不会去其他任何地方。仍然不起作用。 – Katembers

也许你已经失去了参考你的纹理。在你的情况下，纹理是load_img()函数中的局部变量。

你应该保持你的纹理加载和可用，而任何精灵正在使用它。

我建议您阅读SFML教程的this部分，其中解释了此问题。

来源

2017-09-27 15:28:21 alseether

我读过评论，你把所有东西都移到'main'。你能用那个代码更新吗？也许这样我们可以发现任何错误 – alseether

这是问题的一部分，但主要问题在其他地方。查看我标记为解决方案的答案。这是这里的主要问题。 – Katembers

使用SFML中的精灵不显示图像

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