事件监听

1、实现的逻辑

1. 使用单例
2. key，value的形式，储存事件

    private _eventListeners: { [key: string]: CallBackTarget[] } = {};

    

3. 事件监听，使用开放方法on

    /**添加监听（会做所有不重复的事件监听）
        * @param eventName 事件名字
        * @param callBack 事件回调函数
        * @param target 目标类
        * */
       on(eventName: string, callBack: EventMaCallFunc, target?: any): boolean {
           if (!eventName) {
               DEBUG && console.error("eventName is empty" + eventName);
               return false;
           }
   
           if (null == callBack) {
               DEBUG && console.error('addEventListener callBack is nil');
               return false;
           }
           let callTarget: CallBackTarget = { callBack: callBack, target: target };
           if (null == this._eventListeners[eventName]) {
               this._eventListeners[eventName] = [callTarget];
   
           } else {
               let index = this.getEventListenersIndex(eventName, callBack, target);
               if (-1 == index) {
                   this._eventListeners[eventName].push(callTarget);
               }
           }
   
           return true;
       }

    

4. 移除事件监听

   /**移除监听
        * @param eventName 事件名字
        * @param callBack 事件回调函数
        * @param target 目标类
        * */
       of(eventName: string, callBack: EventMaCallFunc, target?: any) {
           if (null != this._eventListeners[eventName]) {
               let index = this.getEventListenersIndex(eventName, callBack, target);
               if (-1 != index) {
                   this._eventListeners[eventName].splice(index, 1);
               }
           }
       }
     private getEventListenersIndex(eventName: string, callBack: EventMaCallFunc, target?: any): number {
           let index = -1;
           for (let i = 0; i < this._eventListeners[eventName].length; i++) {
               let iterator = this._eventListeners[eventName][i];
               if (iterator.callBack == callBack && (!target || iterator.target == target)) {
                   index = i;
                   break;
               }
           }
           return index;
       }

    

5. 调用事件

       /**提高监听条件
        * @param eventName 事件名字
        * @param eventData 事件回调参数
        * */
       raiseEvent(eventName: string, eventData?: any) {
           DEBUG && console.log(`==================== raiseEvent ${eventName} begin | ${JSON.stringify(eventData)}`);
           if (null != this._eventListeners[eventName]) {
               // 将所有回调提取出来，再调用，避免调用回调的时候操作了事件的删除
               let callbackList: CallBackTarget[] = [];
               for (const iterator of this._eventListeners[eventName]) {
                   callbackList.push({ callBack: iterator.callBack, target: iterator.target });
               }
               for (const iterator of callbackList) {
                   iterator.callBack.call(iterator.target, eventName, eventData);
               }
           }
           DEBUG && console.log(`==================== raiseEvent ${eventName} end`);
       }