Question

我只是用它来学习HTML，PHP，MySQL和Javascript作为一种爱好。游戏代码直接来自w3schools，我只添加了一个按钮来启动游戏。出于某种原因，canvas继续显示在标题上方，如下所示：https://gyazo.com/9fa59ccfe238b2147583e036a69e88c7

如何在页眉和页脚之间显示画布？

以下是游戏的代码：

        <body>
    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    <style>
    canvas {
        border:1px solid #d3d3d3;
        background-color: #f1f1f1;
    }
    </style>
    </body>
    <button type="button"
    onclick="startGame()">Click here to play!</button>
    <script>

    var myGamePiece;
    var myObstacles = [];
    var myScore;

    function startGame() {
        myGamePiece = new component(30, 30, "red", 10, 120);
        myGamePiece.gravity = 0.05;
        myScore = new component("30px", "Consolas", "black", 280, 40, "text");
        myGameArea.start();
    }

    var myGameArea = {
        canvas : document.createElement("canvas"),
        start : function() {
            this.canvas.width = 480;
            this.canvas.height = 270;
            this.context = this.canvas.getContext("2d");
            document.body.insertBefore(this.canvas, document.body.childNodes[0]);
            this.frameNo = 0;
            this.interval = setInterval(updateGameArea, 20);
            },
        clear : function() {
            this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
        }
    }

    function component(width, height, color, x, y, type) {
        this.type = type;
        this.score = 0;
        this.width = width;
        this.height = height;
        this.speedX = 0;
        this.speedY = 0;    
        this.x = x;
        this.y = y;
        this.gravity = 0;
        this.gravitySpeed = 0;
        this.update = function() {
            ctx = myGameArea.context;
            if (this.type == "text") {
                ctx.font = this.width + " " + this.height;
                ctx.fillStyle = color;
                ctx.fillText(this.text, this.x, this.y);
            } else {
                ctx.fillStyle = color;
                ctx.fillRect(this.x, this.y, this.width, this.height);
            }
        }
        this.newPos = function() {
            this.gravitySpeed += this.gravity;
            this.x += this.speedX;
            this.y += this.speedY + this.gravitySpeed;
            this.hitBottom();
        }
        this.hitBottom = function() {
            var rockbottom = myGameArea.canvas.height - this.height;
            if (this.y > rockbottom) {
                this.y = rockbottom;
                this.gravitySpeed = 0;
            }
        }
        this.crashWith = function(otherobj) {
            var myleft = this.x;
            var myright = this.x + (this.width);
            var mytop = this.y;
            var mybottom = this.y + (this.height);
            var otherleft = otherobj.x;
            var otherright = otherobj.x + (otherobj.width);
            var othertop = otherobj.y;
            var otherbottom = otherobj.y + (otherobj.height);
            var crash = true;
            if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
                crash = false;
            }
            return crash;
        }
    }

    function updateGameArea() {
        var x, height, gap, minHeight, maxHeight, minGap, maxGap;
        for (i = 0; i < myObstacles.length; i += 1) {
            if (myGamePiece.crashWith(myObstacles[i])) {
                return;
            } 
        }
        myGameArea.clear();
        myGameArea.frameNo += 1;
        if (myGameArea.frameNo == 1 || everyinterval(150)) {
            x = myGameArea.canvas.width;
            minHeight = 20;
            maxHeight = 200;
            height = Math.floor(Math.random()*(maxHeight-minHeight+1)+minHeight);
            minGap = 50;
            maxGap = 200;
            gap = Math.floor(Math.random()*(maxGap-minGap+1)+minGap);
            myObstacles.push(new component(10, height, "green", x, 0));
            myObstacles.push(new component(10, x - height - gap, "green", x, height + gap));
        }
        for (i = 0; i < myObstacles.length; i += 1) {
            myObstacles[i].x += -1;
            myObstacles[i].update();
        }
        myScore.text="SCORE: " + myGameArea.frameNo;
        myScore.update();
        myGamePiece.newPos();
        myGamePiece.update();
    }

    function everyinterval(n) {
        if ((myGameArea.frameNo / n) % 1 == 0) {return true;}
        return false;
    }

function accelerate(n) {
    myGamePiece.gravity = n;
}
</script>
<br>
<button onmousedown="accelerate(-0.2)" onmouseup="accelerate(0.05)">ACCELERATE</button>
<p>Use the ACCELERATE button to stay in the air</p>
<p>How long can you stay alive?</p>

此外，以下是标题的代码，以防出现问题：

<!DOCTYPE html>
<html>
<head>
    <title>This is my PHP site</title>
    <?php include ('log-ip.php') ?>
</head>
<body>
    <header>
        <link type="text/css" rel="stylesheet" href="style/core.css" />
        <p id="time1"></p>
        <script>
            document.getElementById('time1').innerHTML = Date();
        </script

        <h2>Test Site</h2> 

        <nav>
            <ul>
                <li><a href="index.php">Home</a></li>
                <li><a href="index.php?products">Products</a></li>
                <li><a href="index.php?contact">Contact</a></li>
                <li><a href="index.php?TN">Ayy</a></li>
                <li><a href="http://aviii400.chem.arizona.edu/">NMR Data</a></li>
                <li><a href="index.php?about">About</a></li>
                <li><a href="index.php?Location">Location</a></li>
                <li><a href="index.php?Game">Game</a></li>
                <li><a href="index.php">Chat</a></li>
            </ul>
        </nav>
    </header>
</body>
</html>

是否可能有一些代码会告诉标题始终保持最佳状态？

Answer 1

此行说明在canvas中的所有其他元素之前插入body元素：

document.body.insertBefore(this.canvas, document.body.childNodes[0])

如果标题和游戏都是body的子项，您可以尝试

document.body.insertAfter(this.canvas, document.getElementsByTagName('header')[0])

试图在我的网站上实现一个游戏，但是标题上方是否显示了画布？

1 个答案: