我正在为我的JavaScript Breakout游戏制作一个开始屏幕。我(糟糕地(制作了背景和播放按钮。
背景在画布内，我想要。但是当我想将可点击的播放按钮放在画布中背景的顶部时，它会消失。我试过制作另一张照片，我可以把它放在上面，我只是不能让它可点击。
我不知道最好的解决方案是什么，我对JavaScript很陌生。
//Script
var background = new Image();
background.src="breakoutbg.png";
var play = new Image();
play.src="breaoutplay.png";
var startBtn = document.getElementById('startBtn');
//game
function drawCanvas() {
ctx.beginPath();
ctx.drawImage(background,0,0);
ctx.fill();
ctx.closePath();
}
function drawPlay() {
ctx.beginPath();
ctx.drawImage(play,250,250);
ctx.fill();clickable;
ctx.closePath();
}
<div id="container">
<button type="button" id="startBtn" onclick="draw()" >
<img src="breaoutplay.png">
</button>
<canvas id="myCanvas" width="600" height="550"></canvas>
</div>
我不知道我是否提供了足够的代码，让某人对此有一个想法。整个代码都在github上：https://github.com/katrinemira/katrinemira.github.io/blob/master/breakout.html
将其添加到您的 CSS 中
#container {
display: inline-block;
position: relative;
}
#startBtn {
border: none;
background: none;
position: absolute;
top: 50%;
left: 50%;
z-index: 1;
transform: translate(-50%,-50%);
-webkit-transform: translate(-50%,-50%);
-moz-transform: translate(-50%,-50%);
-ms-transform: translate(-50%,-50%);
}
上面的代码会将按钮放在画布上的中心位置。 还可以向按钮添加z-index: 1;以将其放置在画布顶部
<html>
<head>
<center>
<style>
body {
background-color: black;
}
* {
padding: 0;
margin: 0;
}
canvas {
background: #353d49;
display: block;
margin: 100px;
}
#startBtn {
border: none;
background: none;
position: absolute;
top: 50%;
left: 50%;
z-index: 1;
transform: translate(-50%,-50%);
-webkit-transform: translate(-50%,-50%);
-moz-transform: translate(-50%,-50%);
-ms-transform: translate(-50%,-50%);
}
#container {
display: inline-block;
position: relative;
}
#myCanvas {
position: relative;
}
</style>
</head>
<body>
<div id="container">
<button type="button" id="startBtn" onclick="draw()"><img src="https://1.bp.blogspot.com/-fVAKH-3TLuo/W5onDDHje0I/AAAAAAAAB4I/q2ooE6GuzQkS80dtw1JILXjFWdfQ3IKkwCLcBGAs/s1600/breaoutplay.png">
</button>
<canvas id="myCanvas" width="600" height="550"></canvas>
</div>
<script>
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
var ballRadius = 9;
var x = canvas.width - Math.floor(Math.random() * 600)
var y = canvas.height - 30;
var dx = 5;
var dy = -4;
var paddleHeight = 10;
var paddleWidth = 75;
var paddleX = (canvas.width - paddleWidth) / 2;
var rightPressed = false;
var leftPressed = false;
var brickRowCount = 7;
var brickColumnCount = 5;
var brickWidth = 75;
var brickHeight = 20;
var brickPadding = 4;
var brickOffsetTop = 30;
var brickOffsetLeft = 30;
var score = 0;
var lives = 3;
var background = new Image();
background.src = "https://1.bp.blogspot.com/-hs2fckXJBkE/W5obuBm9kII/AAAAAAAAB38/C89KFBJCIlEwfl-g8d-T1Cu4cHFWjYI2QCLcBGAs/s1600/breakoutbg.png";
var play = new Image();
play.src = "https://1.bp.blogspot.com/-fVAKH-3TLuo/W5onDDHje0I/AAAAAAAAB4I/q2ooE6GuzQkS80dtw1JILXjFWdfQ3IKkwCLcBGAs/s1600/breaoutplay.png";
var startBtn = document.getElementById('startBtn');
//game
function drawCanvas() {
ctx.beginPath();
ctx.drawImage(background, 0, 0);
ctx.fill();
ctx.closePath();
}
function drawPlay() {
ctx.beginPath();
ctx.drawImage(play, 250, 250);
ctx.fill();
clickable;
ctx.closePath();
}
function newBrick() {
return {
x: 0,
y: 0,
status: 1
};
}
var bricks = [];
for (var c = 0; c < brickColumnCount; c++) {
bricks[c] = [];
for (var r = 0; r < brickRowCount; r++) {
bricks[c].unshift(newBrick());
}
}
document.addEventListener("keydown", keyDownHandler, false);
document.addEventListener("keyup", keyUpHandler, false);
document.addEventListener("mousemove", mouseMoveHandler, false);
function keyDownHandler(e) {
if (e.keyCode == 39) {
rightPressed = true;
} else if (e.keyCode == 37) {
leftPressed = true;
}
}
function keyUpHandler(e) {
if (e.keyCode == 39) {
rightPressed = false;
} else if (e.keyCode == 37) {
leftPressed = false;
}
}
function mouseMoveHandler(e) {
var relativeX = e.clientX - canvas.offsetLeft;
if (relativeX > 0 && relativeX < canvas.width) {
paddleX = relativeX - paddleWidth / 2;
}
}
function collisionDetection() {
for (var c = 0; c < brickColumnCount; c++) {
for (var r = 0; r < brickRowCount; r++) {
var b = bricks[c][r];
if (b.status == 1) {
if (x > b.x && x < b.x + brickWidth + ballRadius && y > b.y && y < b.y + brickHeight + ballRadius) {
dy = -dy;
b.status = 0;
score++;
if (score == 9999) {
alert("YOU WIN, CONGRATS!");
document.location.reload();
}
}
}
}
}
}
function drawBall() {
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI * 2);
ctx.fillStyle = "#0095DD";
ctx.fill();
ctx.closePath();
}
function drawPaddle() {
ctx.beginPath();
ctx.rect(paddleX, canvas.height - paddleHeight, paddleWidth, paddleHeight);
ctx.fillStyle = "#0095DD";
ctx.fill();
ctx.closePath();
}
function moreBricks() {
bricks.unshift([]);
newBrick();
brickColumnCount++;
for (r = 0; r < brickRowCount; r++) {
bricks[0].unshift(newBrick());
}
}
function drawBricks() {
for (var c = 0; c < brickColumnCount; c++) {
for (var r = 0; r < brickRowCount; r++) {
if (bricks[c][r].status == 1) {
var brickX = (r * (brickWidth + brickPadding)) + brickOffsetLeft;
var brickY = (c * (brickHeight + brickPadding)) + brickOffsetTop;
bricks[c][r].x = brickX;
bricks[c][r].y = brickY;
ctx.beginPath();
ctx.rect(brickX, brickY, brickWidth, brickHeight);
ctx.fillStyle = "#0095DD";
ctx.fill();
ctx.closePath();
}
}
}
}
function drawScore() {
ctx.font = "16px Arial";
ctx.fillStyle = "#0095DD";
ctx.fillText("Score: " + score, 8, 20);
}
function drawLives() {
ctx.font = "16px Arial";
ctx.fillStyle = "#0095DD";
ctx.fillText("Lives: " + lives, canvas.width - 65, 20);
}
var frameCount = 0;
const FRAME_COUNT_NEW_LINE = 500;
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
startBtn.style.display = 'none';
frameCount += 1;
if (frameCount === FRAME_COUNT_NEW_LINE) {
frameCount = 0;
moreBricks();
}
drawBricks();
drawBall();
drawPaddle();
drawScore();
drawLives();
collisionDetection();
if (x + dx > canvas.width - ballRadius || x + dx < ballRadius) {
dx = -dx;
}
if (y + dy < ballRadius) {
dy = -dy;
} else if (y + dy > canvas.height - ballRadius) {
if (x > paddleX && x < paddleX + paddleWidth) {
dy = -dy;
} else {
lives--;
if (!lives) {
document.location.reload();
} else {
x = canvas.width - Math.floor(Math.random() * 600);
y = canvas.height - 30;
dx = 5;
dy = -4;
paddleX = (canvas.width - paddleWidth) / 2;
}
}
}
if (rightPressed && paddleX < canvas.width - paddleWidth) {
paddleX += 7;
} else if (leftPressed && paddleX > 0) {
paddleX -= 7;
}
x += dx;
y += dy;
requestAnimationFrame(draw);
}
drawCanvas();
drawPlay();
</script>
</body>
</html>