javascript原生框架(七)--动画模块

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匀速直线动画

  1. 固定时间
  2. 固定距离
  3. 如何判定动画结束的时机？
    • 使用时间来判断是否结束动画。
    • 如果动画时间到达了 指定的时间，那么就结束动画，并且让动画元素到达终点
  4. 实现思路
    • 定义动画函数，animate函数。当调用animate函数时，即动画开始的时间
    • 定义render函数，用来给动画元素设置 属性值
      • 计算当前动画元素所在的位置，然后累计到其对应属性值上。
      • 首先计算动画的时间间隔
      • 如果时间间隔大于或等于指定的总时间，那么就停止动画并设置动画元素到达终点
      • 否则，根据速度，动画时间间隔计算出位移。在将其与起始位置累加后赋值给elem
    • 定义定时器，开始动画

匀减速直线动画

  1. 物理公式
    • a: 加速度
    • t： 时间间隔
    • v0：初始速度
    • vt：末速度
    • S： 位移
    • 正方向：S = v0 t + a t * t / 2;
    • 末速度：vt = v0 + at
  2. S ==> target - location
    t ==> duration
    v0 = 0

  3. 正方向 a = 2 ( S - v0 t) / ( t * t)

    ==>   = 2 * S / ( t * t )
==>   = 2 * (target - location) /( duration * duration)

    vt = 2 * (target - location) / duration

  4. time时间间隔内的 匀减速位移tween = v0 time - a time time / 2
    ==> tween = 2     distance * time / duration

    - distance * time * time /( duration * duration)

动画的基本结构

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function animate() {
	function render() {
		
	}
	window.setInterval(render, time);
}

animate动画的封装代码(曲线代码不是自己写的,哈哈)

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// 动画模块
	var easing = {
		linear: function(x, t, b, c, d) {
			return (c - b) * t / d;
		},
		minusspeed: function(x, t, b, c, d) {
			return 2 * (c - b) * t / d - (c - b) * t * t / (d * d);
		},
		easeInQuad: function(x, t, b, c, d) {
			return c * (t /= d) * t + b;
		},
		easeOutQuad: function(x, t, b, c, d) {
			return -c * (t /= d) * (t - 2) + b;
		},
		easeInOutQuad: function(x, t, b, c, d) {
			if ((t /= d / 2) < 1) return c / 2 * t * t + b;
			return -c / 2 * ((--t) * (t - 2) - 1) + b;
		},
		easeInCubic: function(x, t, b, c, d) {
			return c * (t /= d) * t * t + b;
		},
		easeOutCubic: function(x, t, b, c, d) {
			return c * ((t = t / d - 1) * t * t + 1) + b;
		},
		easeInOutCubic: function(x, t, b, c, d) {
			if ((t /= d / 2) < 1) return c / 2 * t * t * t + b;
			return c / 2 * ((t -= 2) * t * t + 2) + b;
		},
		easeInQuart: function(x, t, b, c, d) {
			return c * (t /= d) * t * t * t + b;
		},
		easeOutQuart: function(x, t, b, c, d) {
			return -c * ((t = t / d - 1) * t * t * t - 1) + b;
		},
		easeInOutQuart: function(x, t, b, c, d) {
			if ((t /= d / 2) < 1) return c / 2 * t * t * t * t + b;
			return -c / 2 * ((t -= 2) * t * t * t - 2) + b;
		},
		easeInQuint: function(x, t, b, c, d) {
			return c * (t /= d) * t * t * t * t + b;
		},
		easeOutQuint: function(x, t, b, c, d) {
			return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
		},
		easeInOutQuint: function(x, t, b, c, d) {
			if ((t /= d / 2) < 1) return c / 2 * t * t * t * t * t + b;
			return c / 2 * ((t -= 2) * t * t * t * t + 2) + b;
		},
		easeInSine: function(x, t, b, c, d) {
			return -c * Math.cos(t / d * (Math.PI / 2)) + c + b;
		},
		easeOutSine: function(x, t, b, c, d) {
			return c * Math.sin(t / d * (Math.PI / 2)) + b;
		},
		easeInOutSine: function(x, t, b, c, d) {
			return -c / 2 * (Math.cos(Math.PI * t / d) - 1) + b;
		},
		easeInExpo: function(x, t, b, c, d) {
			return (t == 0) ? b : c * Math.pow(2, 10 * (t / d - 1)) + b;
		},
		easeOutExpo: function(x, t, b, c, d) {
			return (t == d) ? b + c : c * (-Math.pow(2, -10 * t / d) + 1) + b;
		},
		easeInOutExpo: function(x, t, b, c, d) {
			if (t == 0) return b;
			if (t == d) return b + c;
			if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b;
			return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b;
		},
		easeInCirc: function(x, t, b, c, d) {
			return -c * (Math.sqrt(1 - (t /= d) * t) - 1) + b;
		},
		easeOutCirc: function(x, t, b, c, d) {
			return c * Math.sqrt(1 - (t = t / d - 1) * t) + b;
		},
		easeInOutCirc: function(x, t, b, c, d) {
			if ((t /= d / 2) < 1) return -c / 2 * (Math.sqrt(1 - t * t) - 1) + b;
			return c / 2 * (Math.sqrt(1 - (t -= 2) * t) + 1) + b;
		},
		easeInElastic: function(x, t, b, c, d) {
			var s = 1.70158;
			var p = 0;
			var a = c;
			if (t == 0) return b;
			if ((t /= d) == 1) return b + c;
			if (!p) p = d * .3;
			if (a < Math.abs(c)) {
				a = c;
				var s = p / 4;
			} else var s = p / (2 * Math.PI) * Math.asin(c / a);
			return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
		},
		easeOutElastic: function(x, t, b, c, d) {
			var s = 1.70158;
			var p = 0;
			var a = c;
			if (t == 0) return b;
			if ((t /= d) == 1) return b + c;
			if (!p) p = d * .3;
			if (a < Math.abs(c)) {
				a = c;
				var s = p / 4;
			} else var s = p / (2 * Math.PI) * Math.asin(c / a);
			return a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b;
		},
		easeInOutElastic: function(x, t, b, c, d) {
			var s = 1.70158;
			var p = 0;
			var a = c;
			if (t == 0) return b;
			if ((t /= d / 2) == 2) return b + c;
			if (!p) p = d * (.3 * 1.5);
			if (a < Math.abs(c)) {
				a = c;
				var s = p / 4;
			} else var s = p / (2 * Math.PI) * Math.asin(c / a);
			if (t < 1) return -.5 * (a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
			return a * Math.pow(2, -10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p) * .5 + c + b;
		},
		easeInBack: function(x, t, b, c, d, s) {
			if (s == undefined) s = 1.70158;
			return c * (t /= d) * t * ((s + 1) * t - s) + b;
		},
		easeOutBack: function(x, t, b, c, d, s) {
			if (s == undefined) s = 1.70158;
			return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
		},
		easeInOutBack: function(x, t, b, c, d, s) {
			if (s == undefined) s = 1.70158;
			if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;
			return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;
		},
		easeOutBounce: function(x, t, b, c, d) {
			if ((t /= d) < (1 / 2.75)) {
				return c * (7.5625 * t * t) + b;
			} else if (t < (2 / 2.75)) {
				return c * (7.5625 * (t -= (1.5 / 2.75)) * t + .75) + b;
			} else if (t < (2.5 / 2.75)) {
				return c * (7.5625 * (t -= (2.25 / 2.75)) * t + .9375) + b;
			} else {
				return c * (7.5625 * (t -= (2.625 / 2.75)) * t + .984375) + b;
			}
		}
	};
	// 获取所有动画属性的起始值
	var kv = {
		'left': 'offsetLeft',
		'top': 'offsetTop',
		'width': 'offsetWidth',
		'height': 'offsetHeight'
	};
	function getLocation(elem, target) {
		var obj = {};
		for (var k in target) {
			obj[k] = elem[kv[k]];
		}
		return obj;
	}
	function getDistance(location, target) {
		var obj = {};
		for (var k in target) {
			obj[k] = parseFloat(target[k]) - location[k];
		}
		return obj;
	}
	function getTween(time, location, target, duration, easingName) {
		var obj = {};
		for (var k in target) {
			obj[k] = easing[easingName](null, time, location[k], target[k], duration);
		}
		return obj;
	}
	function setStyles(elem, location, tween) {
		var k;
		for (k in location) {
			elem.style[k] = location[k] + tween[k] + 'px';
		}
	}
	var animate = function(elem, target, duration, easingName) {
		var timer, // 定时器id
			tween, // 单位时间间隔的位移{left: 800, top:400}
			location, // 起始位置{left: 8,top: 8}
			distance, // 动画总距离{left: 992, top: 792}
			startTime, // 动画开始时间
			currentTime, // 动画当前时间
			time; // 当前动画经过总时间间隔
		location = getLocation(elem, target);
		distance = getDistance(location, target);
		startTime = +new Date; // 转换毫秒值
		// 用来计算动画当前位移，并制定动画元素的位置
		var render = function() {
			currentTime = +new Date;
			time = currentTime - startTime;
			// 如果当前动画经过总时间间隔大于或等于 指定总时间
			// 停止动画,并设置动画元素到达终点
			if (time >= duration) {
				// console.log(time);
				// 1 设置动画元素到达终点
				tween = distance;
				// 2 停止动画，即清楚定时器
				global.clearInterval(timer);
				// 3 删除动画元素的timerId属性
				delete elem.timerId;
			} else { // 否则, 根据匀减速运动公式来求time时间间隔内的位移
				// 指定动画元素的位置
				// 注意： 要加上 起始位置
				tween = getTween(time, location, target, duration, easingName);
			}
			// 设置动画属性值
			setStyles(elem, location, tween);
		};
		// 启动定时器 开始动画
		timer = global.setInterval(render, 1000 / 60);
		// 把定时器id存储在动画元素上（以自定义属性）
		elem.timerId = timer;
	};
	moyas.fn.extend({
		animate: function(target, duration, easingName) {
			easingName = easingName || 'linear';
			return this.each(function() {
				if(!('timerId' in this)){
					animate(this, target, duration, easingName);
				}
			});
		},
		stop: function() {
			return this.each(function() {
				if('timerId' in this){
					global.clearInterval(this.timerId);
					delete this.timerId;
				}
			});
		}
	});