以小鱼摇尾巴和眨眼睛为例
动画思路：
1.将图片资源放在数组里面
2.通过计时器来设定间隔时间
3.通过计数器来取相应的图片
第一步：基本框架，鱼身体
<body>
<canvas id="canvas1" width="800" height="600"></canvas>
</body>
document.body.onload = game; var can1,
ctx1,
canWidth,
canHeight,
lastTime = Date.now(),
deltaTime = 0,
body = new Image(); function game() {
init();
gameloop();
} function init() {
can1 = document.getElementById("canvas1"); //fonr--fishes, UI, circles, dust
ctx1 = can1.getContext("2d");
canWidth = can1.width;
canHeight = can1.height; body.src = './src/baby.png';
} function bodyDraw(){
ctx1.drawImage( body, -body.width * 0.5, -body.height * 0.5);
} function gameloop() {
requestAnimFrame(gameloop); //时间帧间隔
var now = Date.now();
deltaTime = now - lastTime;
lastTime = now; ctx1.clearRect(0, 0, canWidth, canHeight); bodyDraw();
} window.requestAnimFrame = (function() {
return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame ||
function( /* function FrameRequestCallback */ callback, /* DOMElement Element */ element) {
return window.setTimeout(callback, 1000 / 60);
};
})();
第二步：摇动尾巴
1.图片资源有8张，从tail0.png ~ tail7.png
2.尾巴是匀速的运动，间隔时间为固定值
var bTailTimer, //计时器
bTailCount, //计数器
babyTail = []; //图片数组 function init() {
//尾巴初始化
bTailTimer = 0; bTailCount = 0; for (var i = 0; i < 8; i++) {
babyTail[i] = new Image();
babyTail[i].src = './src/tail' + i +'.png';
}
} function tailDraw(){
bTailTimer += deltaTime;
if(bTailTimer > 50){
bTailCount = (bTailCount + 1)% 8;
bTailTimer %= 50; //初始化计数器
}
ctx1.drawImage( babyTail[bTailCount], -babyTail[bTailCount].width * 0.5, -babyTail[bTailCount].height * 0.5);
} function gameloop() {
ctx1.clearRect(0, 0, canWidth, canHeight); bodyDraw();
tailDraw();
}
第二步：眨眼睛
1.图片资源有2张，从eye0.png ~ eye7.png
2.眼睛睁开时间不定时，闭上时间固定值
var bEyeTimer,
bEyeCount,
bEyeInterval, //时间间隔变量
babyEye = []; function init() {
//眼睛初始化
bEyeTimer = 0;
bEyeCount = 0;
bEyeInterval = 1000; //间隔时间
for (var i = 0; i < 2; i++) {
babyEye[i] = new Image();
babyEye[i].src = './src/Eye' + i + '.png';
}
} function eyeDraw() {
bEyeTimer += deltaTime;
if (bEyeTimer > bEyeInterval)
{
bEyeCount = (bEyeCount + 1)% 2;
bEyeTimer %= bEyeInterval; if (bEyeCount == 0)
{
//眼睛睁开保持的时间随机
bEyeInterval = Math.random() * 1500 + 2000; //[2000,3500)
} else
{
//眼睛闭上保持时间固定为100ms
bEyeInterval = 100;
}
}
} function gameloop() {
eyeDraw();
}