Question

我知道这个主题在论坛中很丰富，但我需要帮助解决这个问题。我正在关注this tutorial为一个tic tac toe游戏制作一个基本的sfml ImageManager类。我在理解如何在我的游戏引擎中实现这个类时遇到了麻烦。我将发布大量代码，因为涉及多个类： Board.h：我的tic-tac-toe游戏板。

#pragma once
#include "stdafx.h"
#include <vector>
#include "Box.h"
#include "SFML/Graphics.hpp"
#include "ImageManager.h"

class Board{
public:
Board();
~Board();

std::vector<Box> &GetBoxes();

sf::Sprite GetGameBoard();
private:
sf::Sprite gameBoard;

std::vector<Box> boxes;
};

这是Board.cpp：

#include "stdafx.h"
#include "Board.h"
#include "SFML/Graphics.hpp"

Board::Board(){
ImageManager imgr;
imgr.AddResourceDirectory("images/");
gameBoard.setTexture(imgr.GetImage("images/t3board.png"));
}

Board::~Board(){

}

std::vector<Box> &Board::GetBoxes(){
return boxes;
}

sf::Sprite Board::GetGameBoard(){
return gameBoard;
}

以下是教程中ImageManager类的相关内容：

const sf::Texture &ImageManager::GetImage(const std::string &filename){
    for(std::map<std::string, sf::Texture>::const_iterator it = textures_.begin(); it != textures_.end(); ++it){
        if(filename == it->first){
            std::cout << "DEBUG_MESSAGE: " << filename << " using existing image.\n";
            return it->second;
        }
    }

    //if image doesn't exist (no need for else since it will return if filename is found
    sf::Texture texture;
    if(texture.loadFromFile(filename)){
        //create both a string and matching image in the map
        textures_[filename] = texture;
        std::cout << "DEBUG_MESSAGE: " << filename << " loading image.\n";
        return textures_[filename];
    }

    // If the image has still not been found, search all registered directories
    //of course, it will be empty until I specify extra directories by adding them into the vector
    for(std::vector< std::string >::iterator it = resourceDirectories_.begin(); it != resourceDirectories_.end(); ++it){
        if(texture.loadFromFile((*it) + filename )){
            textures_[filename] = texture;
            std::cout << "DEBUG_MESSAGE: " << filename << " loading image 2.\n";
            return textures_[filename];
        }
    }

    //again, notice there's no elses because returns serve as breaks
    std::cout << "GAME_ERROR: Image was not found. It is filled with an empty image.\n";
    textures_[filename] = texture;
    return textures_[filename];
}

最后，在我的引擎中，我得到gameBoard并将其绘制到我的窗口：

void Engine::Render(){
    window.clear();
    window.draw(board.GetGameBoard());
    window.display();
}

我的窗口只显示一个完整的白色背景，但它仍然有效。谁能看到我做错了什么？

Answer 1

我认为textures_是ImageManager类的私有成员？在这种情况下，您有undefined behavior，因为ImageManager::GetImage会将引用返回到存储在已销毁的容器中的数据（请记住imgr是构造函数中的局部变量）。

Answer 2

好的，我有。这是一个非常令人尴尬的解决方案，但在ImageManager imgr的构造函数中声明我的Board正在立即销毁我的ImageManager，所以我只剪切该实例并将其粘贴到头文件中。由于某些原因，返回引用而不是实际的纹理值是必要的，这也让我感到难过。

我的sfml ImageManager类只在c ++中显示一个白色方块

2 个答案: