hammerjs的初始化发生了什么

hammerjs ———— 一个移动端的手势库。

New Hammer 的过程

最简单的使用一个手势的demo

// 定义 Manager
 var hammertime = new Hammer(element, {});
 // 绑定事件
 hammertime.on('pan', function(e) {
 TODO Logic...
})

• 调用 Hammer function 初始化

在hammer.js中可以看到下面一段代码用于定义一个Manager(element, options)
element: 手势操作的元素
options: 定义配置参数

function Hammer(element, options) {   
 options = options || {};
    // 定义recongnizers, 如果 options.recongnizers 为 undefined, 默认 'Hammer.defaults.preset'
    options.recognizers = ifUndefined(options.recognizers, Hammer.defaults.preset);
    return new Manager(element, options);
}

• 默认 recongnizers, TapRecognizer 同步注册了 TapRecognizer, 同理 PinchRecognizer 同步注册 RotateRecognizer (也可以外部采用 recognizer.recognizeWith() 注册同步Recognizer.)

  preset: [

  // RecognizerClass, options, [recognizeWith, ...], [requireFailure, ...]
    [RotateRecognizer, {enable: false}],
    [PinchRecognizer, {enable: false}, ['rotate']],
    [SwipeRecognizer, {direction: DIRECTION_HORIZONTAL}],
    [PanRecognizer, {direction: DIRECTION_HORIZONTAL}, ['swipe']],
    [TapRecognizer],
    [TapRecognizer, {event: 'doubletap', taps: 2}, ['tap']],
    [PressRecognizer]

  ],

• 绑定事件handler (hammertime.on)

demo中的 hammertime.on('pan', function(e) { }) 实际上为调用 manager.js 中的 on function

on: function(events, handler) {
    if (events === undefined) {
        return;
    }
    if (handler === undefined) {
        return;
    }
    var handlers = this.handlers; // bind handlers to Manager.handler
    each(splitStr(events), function(event) {
        handlers[event] = handlers[event] || [];
        handlers[event].push(handler);
    });
    return this; // this = Manager
},