javascript:未捕获引用错误
javascript:未捕获引用错误
提问于 2018-07-15 00:48:55
我正在做一个javascript游戏，使用画布。然而，我得到了错误(下图)，背景图像没有显示。我怀疑下面4个文件，因为其他文件没有任何麻烦。我猜这个问题和game_state...how有关，我能解决这个问题吗？我苦恼了两天：(请帮帮我)
index.html
<!DOCTYPE html>
<html lang="ko">
<head>
<meta charset="utf-8">
<title>Lion Travel</title>
<!--GameFramework-->
<script src="/.c9/gfw/GameFramework.js"></script>
<script src="/.c9/gfw/FrameCounter.js"></script>
<script src="/.c9/gfw/InputSystem.js"></script>
<script src="/.c9/gfw/SoundManager.js"></script>
<script src="/.c9/gfw/GraphicObject.js"></script>
<script src="/.c9/gfw/SpriteAnimation.js"></script>
<script src="/.c9/gfw/ResourcePreLoader.js"></script>
<script src="/.c9/gfw/DebugSystem.js"></script>
<script src="/.c9/gfw/Timer.js"></script>
<script src="/.c9/gfw/FrameSkipper.js"></script>
<script src="/.c9/gfw/TransitionState.js"></script>
<!--GameInit-->
<script src="/.c9/gfw/gfw.js"></script>
<!--Game Logic-->
<script src="/.c9/RS_Title.js"></script>
</head>
<body>
<canvas id="GameCanvas" width="800" height="600">html5 canvas is not supported.</canvas>
</body>
</html>gfw.js
function onGameInit() {
document.title = "Lion Travel";
GAME_FPS = 30;
debugSystem.debugMode = true;
resourcePreLoader.AddImage("/.c9/title_background.png");
soundSystem.AddSound("/.c9/background.mp3", 1);
after_loading_state = new TitleState();
setInterval(gameLoop, 1000 / GAME_FPS);
}
window.addEventListener("load", onGameInit, false);RS_Title.js
function TitleState()
{
this.imgBackground = resourcePreLoader.GetImage("/.c9/title_background.png");
soundSystem.PlayBackgroundMusic("/.c9/background.mp3");
return this;
}
TitleState.prototype.Init = function()
{
soundSystem.PlayBackgroundMusic("/.c9/background.mp3");
};
TitleState.prototype.Render = function()
{
var theCanvas = document.getElementById("GameCanvas");
var Context = theCanvas.getContext("2d");
//drawing backgroundimage
Context.drawImage(this.imgBackground, 0, 0);
};
TitleState.prototype.Update = function()
{
};GameFramework.js
var GAME_FPS;
var game_state = after_loading_state;
function ChangeGameState(nextGameState)
{
//checking essential function
if(nextGameState.Init == undefined)
return;
if(nextGameState.Update == undefined)
return;
if(nextGameState.Render == undefined)
return;
game_state = nextGameState;
game_state.Init();
}
function Update()
{
timerSystem.Update();
game_state.Update();
debugSystem.UseDebugMode();
}
function Render()
{
//drawing
var theCanvas = document.getElementById("GameCanvas");
var Context = theCanvas.getContext("2d");
Context.fillStyle = "#000000";
Context.fillRect(0, 0, 800, 600);
//game state
game_state.Render();
if(debugSystem.debugMode)
{
//showing fps
Context.fillStyle = "#ffffff";
Context.font = '15px Arial';
Context.textBaseline = "top";
Context.fillText("fps: "+ frameCounter.Lastfps, 10, 10);
}
}
function gameLoop()
{
Update();
Render();
frameCounter.countFrame();
}回答 1
Stack Overflow用户
回答已采纳
发布于 2018-07-15 04:53:49
这里的问题是，您甚至在初始化after_loading_state (只有在加载文档之后才初始化)之前就使用对象after_loading_state来初始化game_state。因此，game_state仍然是undefined。
要解决此问题，请将GameFramework.js中的var game_state = after_loading_state;更改为var game_state;。并在gameLoop函数中添加game_state = after_loading_state;作为第一行。这样，变量的初始化就会以正确的顺序发生。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/51341458
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