AlloyTouch源码分析
;(function () {
'use strict';
if (!Date.now)
Date.now = function () { return new Date().getTime(); };
var vendors = ['webkit', 'moz'];
for (var i = 0; i < vendors.length && !window.requestAnimationFrame; ++i) {
var vp = vendors[i];
window.requestAnimationFrame = window[vp + 'RequestAnimationFrame'];
window.cancelAnimationFrame = (window[vp + 'CancelAnimationFrame']
|| window[vp + 'CancelRequestAnimationFrame']);
}
if (/iP(ad|hone|od).*OS 6/.test(window.navigator.userAgent) // iOS6 is buggy
|| !window.requestAnimationFrame || !window.cancelAnimationFrame) {
var lastTime = 0;
window.requestAnimationFrame = function (callback) {
var now = Date.now();
var nextTime = Math.max(lastTime + 16, now);
return setTimeout(function () { callback(lastTime = nextTime); },
nextTime - now);
};
window.cancelAnimationFrame = clearTimeout;
}
}());上面是为了兼容各个浏览器的requestAnimationFrame和cancelAnimationFrame，AlloyTouch后面对目标属性的运动都是通过requestAnimationFrame进行的。这里不进行详细说明，主要是利用setTimeout来兼容不支持requestAnimationFrame的浏览器。
(function () {
function bind(element, type, callback) {
element.addEventListener(type, callback, false);
}绑定事件封装成bind
function ease(x) {
return Math.sqrt(1 - Math.pow(x - 1, 2));
}运动使用的缓动函数，根据x求y。即如下图所示，一个先加速再减速的过程，用来模拟摩擦力非常合适，当然回弹也是用的这段缓动。
function reverseEase(y) {
return 1 - Math.sqrt(1 - y * y);
}逆向缓动，根据y的值求x。和上面的缓动函数相反。注意这里求解出来y有两个值。即1 - Math.sqrt(1 - y * y)和1 + Math.sqrt(1 - y * y)。 1 + Math.sqrt(1 - y * y)大于1，所以不采用。使用1 - Math.sqrt(1 - y * y)。 这个函数主要用于当运动超出min和max边界不能完整完成一次运动过程的时候求出其中不完整的路程的消耗的时间。
function preventDefaultTest(el, exceptions) {
for (var i in exceptions) {
if (exceptions[i].test(el[i])) {
return true;
}
}
return false;
}用来检测INPUT|TEXTAREA|BUTTON|SELECT标签的，如果是这些标签将不会去阻止默认事件。负责会导致这些控件不可点
var AlloyTouch = function (option) {
//this.element是用户触摸的对象
this.element = typeof option.touch === "string" ? document.querySelector(option.touch) : option.touch;
//this.target是反馈触摸进行运动的对象
this.target = this._getValue(option.target, this.element);
//监听用户垂直方向上的触摸还是水平方向上的触摸，默认值是监听垂直方向上的
this.vertical = this._getValue(option.vertical, true);
//进行运动的属性
this.property = option.property;
this.tickID = 0;
//this.target的初始值
this.initialVaule = this._getValue(option.initialVaule, this.target[this.property]);
this.target[this.property] = this.initialVaule;
this.fixed = this._getValue(option.fixed, false);
//灵敏度，类似鼠标灵敏度的概念。就是你移动10CM，光标也移动10CM?或者20CM?都可以通过灵敏度配出来~~
this.sensitivity = this._getValue(option.sensitivity, 1);
//touch move时候的摩擦系数
this.moveFactor = this._getValue(option.moveFactor, 1);
this.factor = this._getValue(option.factor, 1);
this.outFactor = this._getValue(option.outFactor, 0.3);
//最小值，超出会回弹
this.min = option.min;
//最大值，超出会回弹
this.max = option.max;
//加速度系数
this.deceleration = 0.0006;
//惯性运动超出边界的最大值，默认是60
this.maxRegion = this._getValue(option.maxRegion, 60);
var noop = function () { };
this.change = option.change || noop;
this.touchEnd = option.touchEnd || noop;
this.touchStart = option.touchStart || noop;
this.touchMove = option.touchMove || noop;
this.touchCancel = option.touchCancel || noop;
this.reboundEnd = option.reboundEnd || noop;
this.animationEnd = option.animationEnd || noop;
this.correctionEnd = option.correctionEnd || noop;
this.tap = option.tap || noop;
this.pressMove = option.pressMove || noop;
this.preventDefault = this._getValue(option.preventDefault, true);
this.preventDefaultException = { tagName: /^(INPUT|TEXTAREA|BUTTON|SELECT)$/ };
this.hasMin = !(this.min === undefined);
this.hasMax = !(this.max === undefined);
//最大值不能小于最小值
if (this.hasMin && this.hasMax && this.min > this.max) {
throw "the min value can't be greater than the max value."
}
this.isTouchStart = false;
this.step = option.step;
this.inertia = this._getValue(option.inertia, true);
this._calculateIndex();
this.eventTarget = window;
if(option.bindSelf){
this.eventTarget = this.element;
}
this._moveHandler = this._move.bind(this);
bind(this.element, "touchstart", this._start.bind(this));
bind(this.eventTarget, "touchend", this._end.bind(this));
bind(this.eventTarget, "touchcancel", this._cancel.bind(this));
this.eventTarget.addEventListener("touchmove", this._moveHandler, { passive: false, capture: false });
this.x1 = this.x2 = this.y1 = this.y2 = null;
};
AlloyTouch.prototype = {
_getValue: function (obj, defaultValue) {
return obj === undefined ? defaultValue : obj;
},
_start: function (evt) {
this.isTouchStart = true;
this.touchStart.call(this, evt, this.target[this.property]);
cancelAnimationFrame(this.tickID);
this._calculateIndex();
this.startTime = new Date().getTime();
this.x1 = this.preX = evt.touches[0].pageX;
this.y1 = this.preY = evt.touches[0].pageY;
this.start = this.vertical ? this.preY : this.preX;
this._firstTouchMove = true;
this._preventMove = false;
},
_move: function (evt) {
if (this.isTouchStart) {
var len = evt.touches.length,
currentX = evt.touches[0].pageX,
currentY = evt.touches[0].pageY;
if (this._firstTouchMove) {
var dDis = Math.abs(currentX - this.x1) - Math.abs(currentY - this.y1);
if (dDis > 0 && this.vertical) {
this._preventMove = true;
} else if (dDis < 0 && !this.vertical) {
this._preventMove = true;
}
this._firstTouchMove = false;
}
if(!this._preventMove) {
var d = (this.vertical ? currentY - this.preY : currentX - this.preX) * this.sensitivity;
var f = this.moveFactor;
if (this.hasMax && this.target[this.property] > this.max && d > 0) {
f = this.outFactor;
} else if (this.hasMin && this.target[this.property] < this.min && d < 0) {
f = this.outFactor;
}
d *= f;
this.preX = currentX;
this.preY = currentY;
if (!this.fixed) {
this.target[this.property] += d;
}
this.change.call(this, this.target[this.property]);
var timestamp = new Date().getTime();
if (timestamp - this.startTime > 300) {
this.startTime = timestamp;
this.start = this.vertical ? this.preY : this.preX;
}
this.touchMove.call(this, evt, this.target[this.property]);
}
if (this.preventDefault && !preventDefaultTest(evt.target, this.preventDefaultException)) {
evt.preventDefault();
}
if (len === 1) {
if (this.x2 !== null) {
evt.deltaX = currentX - this.x2;
evt.deltaY = currentY - this.y2;
} else {
evt.deltaX = 0;
evt.deltaY = 0;
}
this.pressMove.call(this, evt, this.target[this.property]);
}
this.x2 = currentX;
this.y2 = currentY;
}
},
_cancel: function (evt) {
var current = this.target[this.property];
this.touchCancel.call(this, evt, current);
if (this.hasMax && current > this.max) {
this._to(this.max, 200, ease, this.change, function (value) {
this.reboundEnd.call(this, value);
this.animationEnd.call(this, value);
}.bind(this));
} else if (this.hasMin && current < this.min) {
this._to(this.min, 200, ease, this.change, function (value) {
this.reboundEnd.call(this, value);
this.animationEnd.call(this, value);
}.bind(this));
} else {
this._correction();
}
this.x1 = this.x2 = this.y1 = this.y2 = null;
},
to: function (v, time, user_ease) {
this._to(v, this._getValue(time, 600), user_ease || ease, this.change, function (value) {
this._calculateIndex();
this.reboundEnd.call(this, value);
this.animationEnd.call(this, value);
}.bind(this));
},
_calculateIndex: function () {
if (this.hasMax && this.hasMin) {
this.currentPage = Math.round((this.max - this.target[this.property]) / this.step);
}
},
_end: function (evt) {
if (this.isTouchStart) {
this.isTouchStart = false;
var self = this,
current = this.target[this.property];
if (Math.abs(evt.changedTouches[0].pageX - this.x1) < 30 && Math.abs(evt.changedTouches[0].pageY - this.y1) < 30) {
this.tap.call(this, evt, current);
}
if (this.touchEnd.call(this, evt, current, this.currentPage) === false) return;
if (this.hasMax && current > this.max) {
this._to(this.max, 200, ease, this.change, function (value) {
this.reboundEnd.call(this, value);
this.animationEnd.call(this, value);
}.bind(this));
} else if (this.hasMin && current < this.min) {
this._to(this.min, 200, ease, this.change, function (value) {
this.reboundEnd.call(this, value);
this.animationEnd.call(this, value);
}.bind(this));
} else if (this.inertia) {
var dt = new Date().getTime() - this.startTime;
if (dt < 300) {
var distance = ((this.vertical ? evt.changedTouches[0].pageY : evt.changedTouches[0].pageX) - this.start) * this.sensitivity,
speed = Math.abs(distance) / dt,
speed2 = this.factor * speed,
destination = current + (speed2 * speed2) / (2 * this.deceleration) * (distance < 0 ? -1 : 1);
var tRatio = 1;
if (destination < this.min - this.maxRegion) {
tRatio = reverseEase((current - this.min + this.maxRegion) / (current - destination));
destination = this.min - this.maxRegion;
} else if (destination > this.max + this.maxRegion) {
tRatio = reverseEase((this.max + this.maxRegion - current) / (destination - current));
destination = this.max + this.maxRegion;
}
var duration = Math.round(speed / self.deceleration) * tRatio;
self._to(Math.round(destination), duration, ease, self.change, function (value) {
if (self.hasMax && self.target[self.property] > self.max) {
cancelAnimationFrame(self.tickID);
self._to(self.max, 600, ease, self.change, self.animationEnd);
} else if (self.hasMin && self.target[self.property] < self.min) {
cancelAnimationFrame(self.tickID);
self._to(self.min, 600, ease, self.change, self.animationEnd);
} else {
self._correction();
}
self.change.call(this, value);
});
} else {
self._correction();
}
} else {
self._correction();
}
if (this.preventDefault && !preventDefaultTest(evt.target, this.preventDefaultException)) {
evt.preventDefault();
}
}
this.x1 = this.x2 = this.y1 = this.y2 = null;
},
_to: function (value, time, ease, onChange, onEnd) {
if (this.fixed) return;
var el = this.target,
property = this.property;
var current = el[property];
var dv = value - current;
var beginTime = new Date();
var self = this;
var toTick = function () {
var dt = new Date() - beginTime;
if (dt >= time) {
el[property] = value;
onChange && onChange.call(self, value);
onEnd && onEnd.call(self, value);
return;
}
el[property] = dv * ease(dt / time) + current;
self.tickID = requestAnimationFrame(toTick);
//cancelAnimationFrame必须在 tickID = requestAnimationFrame(toTick);的后面
onChange && onChange.call(self, el[property]);
};
toTick();
},
_correction: function () {
if (this.step === undefined) return;
var el = this.target,
property = this.property;
var value = el[property];
var rpt = Math.floor(Math.abs(value / this.step));
var dy = value % this.step;
if (Math.abs(dy) > this.step / 2) {
this._to((value < 0 ? -1 : 1) * (rpt + 1) * this.step, 400, ease, this.change, function (value) {
this._calculateIndex();
this.correctionEnd.call(this, value);
this.animationEnd.call(this, value);
}.bind(this));
} else {
this._to((value < 0 ? -1 : 1) * rpt * this.step, 400, ease, this.change, function (value) {
this._calculateIndex();
this.correctionEnd.call(this, value);
this.animationEnd.call(this, value);
}.bind(this));
}
}
};
if (typeof module !== 'undefined' && typeof exports === 'object') {
module.exports = AlloyTouch;
} else {
window.AlloyTouch = AlloyTouch;
}
})();