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css - Canvas 位于导航栏上方

转载 作者：太空宇宙 更新时间：2023-11-04 06:15:25 25 4
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出于某种原因，我的 Canvas 位于导航栏上方。我早些时候纠正了它并改变了一些东西，但我现在无法弄清楚我的生活。我希望页面在顶部加载导航栏，并在导航栏下方的页面中心加载 Canvas 。它与 CSS 或某处放错位置的标签有关吗？感谢您的帮助。

<!DOCTYPE html>
<html lang="en">
   <head>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
      <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
      <title>Square Up</title>
   </head>
<body>
    <style>
        .navbar-brand {
            font-family: arial;
            font-size: 35px;
            font-color: #00FA9A;
        }
        body {
            background-color: whitesmoke;  
        }

        canvas {
             border:1px solid #d3d3d3;
             background-color: #f1f1f1;
             padding-left: 0;
             padding-right: 0;
             margin-left: auto;
             margin-right: auto;
             display: block;
             width: 600px;
             top: 0;
            bottom: 0;
            left: 0;
            right: 0;
        }
    </style>
         <nav class="navbar navbar-expand-sm navbar-dark bg-secondary">
            <a class="navbar-brand" href="index.html">Square Up</a>
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
            </button>
            <div class="collapse navbar-collapse" id="navbarSupportedContent">
               <ul class="navbar-nav mr-auto">
                  <li class="nav-item">
                     <a class="nav-link" href="index.html">Home <span class="sr-only">(current)</span></a>
                  </li>
                  <li class="nav-item active">
                     <a class="nav-link" href="game.html">Play<span class="sr-only">(current)</span></a>
                  </li>
                  <li class="nav-item">
                     <a class="nav-link" href="instructions.html">Instructions</a>
                  </li>
               </ul>
            </div>
         </nav>

<body onload="startGame()">

<script>
var Square;
var Course = [];
var myScore;
function startGame() {
    Square = new component(30, 30, "red", 10, 120);
    Square.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 < Course.length; i += 1) {
        if (Square.crashWith(Course[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);
        Course.push(new component(10, height, "green", x, 0));
        Course.push(new component(10, x - height - gap, "green", x, height + gap));
    }
    for (i = 0; i < Course.length; i += 1) {
        Course[i].x += -1;
        Course[i].update();
    }
    myScore.text="SCORE: " + myGameArea.frameNo;
    myScore.update();
    Square.newPos();
    Square.update();
}
function everyinterval(n) {
    if ((myGameArea.frameNo / n) % 1 == 0) {return true;}
    return false;
}
function accelerate(n) {
    Square.gravity = n;
}
</script>
<br>
<button onmousedown="accelerate(-0.2)" onmouseup="accelerate(0.05)">Click me to move!</button>

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>

最佳答案

请看下面的演示，它应该适合您，您还可以向 Canvas 添加一些类并为其留出边距

.navbar.navbar-fixed{
  position: fixed;
  top: 0;
  left: 0;
  width: 100%; 
} 
canvas{
  margin-top: 100px;
}
<!DOCTYPE html>
<html lang="en">
   <head>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
      <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
      <title>Square Up</title>
   </head>
<body onload="startGame()"> 
    <style>
        .navbar-brand {
            font-family: arial;
            font-size: 35px;
            font-color: #00FA9A;
        }
        body {
            background-color: whitesmoke;  
        }

        canvas {
             border:1px solid #d3d3d3;
             background-color: #f1f1f1;
             padding-left: 0;
             padding-right: 0;
             margin-left: auto;
             margin-right: auto;
             display: block;
             width: 600px;
             top: 0;
            bottom: 0;
            left: 0;
            right: 0;
        }
    </style>
         <nav class="navbar navbar-expand-sm navbar-dark navbar-fixed bg-secondary">
            <a class="navbar-brand" href="index.html">Square Up</a>
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
            </button>
            <div class="collapse navbar-collapse" id="navbarSupportedContent">
               <ul class="navbar-nav mr-auto">
                  <li class="nav-item">
                     <a class="nav-link" href="index.html">Home <span class="sr-only">(current)</span></a>
                  </li>
                  <li class="nav-item active">
                     <a class="nav-link" href="game.html">Play<span class="sr-only">(current)</span></a>
                  </li>
                  <li class="nav-item">
                     <a class="nav-link" href="instructions.html">Instructions</a>
                  </li>
               </ul>
            </div>
         </nav>



<script>
var Square;
var Course = [];
var myScore;
function startGame() {
    Square = new component(30, 30, "red", 10, 120);
    Square.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 < Course.length; i += 1) {
        if (Square.crashWith(Course[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);
        Course.push(new component(10, height, "green", x, 0));
        Course.push(new component(10, x - height - gap, "green", x, height + gap));
    }
    for (i = 0; i < Course.length; i += 1) {
        Course[i].x += -1;
        Course[i].update();
    }
    myScore.text="SCORE: " + myGameArea.frameNo;
    myScore.update();
    Square.newPos();
    Square.update();
}
function everyinterval(n) {
    if ((myGameArea.frameNo / n) % 1 == 0) {return true;}
    return false;
}
function accelerate(n) {
    Square.gravity = n;
}
</script>
<br>
<button onmousedown="accelerate(-0.2)" onmouseup="accelerate(0.05)">Click me to move!</button>

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>

关于css - Canvas 位于导航栏上方，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56015666/

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