用html5中canvas实现的弹跳小球
<!DOCTYPE> <html> <head> <title>canvas 测试案例二：弹球游戏</title> <style> </style> </head> <body> <canvas id="canvas" class="canvas" width='400px' height='300px'>Your browser does not support the HTML5 element canvas</canvas> <script> var boxX = 20, boxY = 30, //盒子的左上角 x y 的初始位置 boxWidth = 350, boxHeight = 250, //盒子的宽高 ballRad = 10, // 球的半径 boxRoundX = boxWidth boxX - ballRad, //右边界 boxRoundY= boxHeight boxY - ballRad, //下边界 inboxRoundX = boxX ballRad, //左边界 inboxRoundY= boxY ballRad, // 上边界 ballX = 50, ballY = 60, //球的初始位置 ballVX = 4, //初始水平位移 ballVY= 8; //初始垂直位移 function init () { var ctx = document.getElementById('canvas').getContext('2d'); ctx.linewidth = ballRad; ctx.fillStyle = 'rgb(200, 0, 50)'; moveBall(); setInterval(moveBall, 25); // 移动球的函数 function moveBall () { ctx.clearRect(boxX, boxY, boxWidth, boxHeight); changDirect(); ctx.beginPath(); ctx.arc(ballX, ballY, ballRad, 0, Math.PI * 2, false); ctx.fill(); ctx.strokeRect(boxX, boxY, boxWidth, boxHeight); } // 判断距离方向函数 function changDirect () { var nextX = ballX ballVX, nextY = ballY ballVY; if (nextX > boxRoundX) { ballVX = -ballVX; nextX = boxRoundX; } if (nextX < inboxRoundX) { ballVX = -ballVX; nextX = inboxRoundX; } if (nextY > boxRoundY) { ballVY = -ballVY; nextY = boxRoundY; } if (nextY < inboxRoundY) { ballVY = -ballVY; nextY = inboxRoundY; } ballX = nextX; ballY = nextY; } } init(); </script> </body> </html>来自：https://github.com/chenkehxx/practice/commit/65067f7bb7948abe94b052f3e69fc2b1892ab167 本文由用户 jopen 自行上传分享，仅供网友学习交流。所有权归原作者，若您的权利被侵害，请联系管理员。
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