<!-- 当自定义组件触发“myevent”事件时，调用“onMyEvent”方法 -->
<component-tag-name bindmyevent="onMyEvent" />

<!-- 在自定义组件中 -->
<button bindtap="onTap">点击这个按钮将触发“myevent”事件</button>
Component({
 methods: {
  onTap() {
   const myEventDetail = {} // detail对象，提供给事件监听函数
   const myEventOption = {} // 触发事件的选项
   this.triggerEvent('myevent', myEventDetail, myEventOption)
  }
 }
})

<!--app.js-->
App({
  globalData: { count: 0 },
});

<!--页面A-->
onShow(){
  let countValue = wx.getStorageSync('count');
  
  <!--globalData的方式-->
  let countValue = getApp().globalData.count;
  <!---->
  
  if(countValue){
    this.setData({
      count:countValue
    })
  }
  
  <!--globalData的方式 清除数据-->
  getApp().globalData.count = null
  <!---->
}
onHide(){
  wx.removeStorageSync('count') 
}

<!--页面B-->
onShow(){
  <!--globalData的方式-->
  getApp().globalData.count = 1
  <!---->
  
  wx.setStorageSync('count',1);
}

<!--第一步：实现一个事件总栈类-->
class EventBus {
  constructor() {
    this.bus = {};
  }
  // on 订阅
  on(type, fun) {
    if (typeof fun !== 'function') {
      console.error('fun is not a function');
      return;
    }
    (this.bus[type] = this.bus[type] || []).push(fun);
  }
  // emit 触发
  emit(type, ...param) {
    let cache = this.bus[type];
    if (!cache) return;
    for (let event of cache) {
      event.call(this, ...param);
    }
  }
  // off 释放
  off(type, fun) {
    let events = this.bus[type];
    if (!events) return;
    let i = 0,
      n = events.length;
    for (i; i < n; i++) {
      let event = events[i];
      if (fun === event) {
        events.splice(i, 1);
        break;
      }
    }
  }
}
module.exports = EventBus;

<!--第二步：在app.js文件中引入-->
import EventBus from './common/event-bus/index.js';
App({
  eventBus: new EventBus(),
});

<!--第三步：在父页面或者父组件中监听某个事件-->
onLoad: function(options) {
  app.eventBus.on('add-count', this.addCount);
}
onUnload: function(options) {
  app.eventBus.off('add-count', this.addCount);
}


<!--第四步：在子组件里面触发事件-->
methods: {
  addCount() {
    app.eventBus.emit('add-count');
  }
}

<!--第一步：实现一个pageModel，用来缓存页面对象-->
class PageModel {
  constructor() {
    this.pageCache = {};
  }

  add(page) {
    let pagePath = this._getPageModelPath(page);
    this.pageCache[pagePath] = page;
  }

  get(path) {
    return this.pageCache[path];
  }

  delete(page) {
    delete this.pageCache[this._getPageModelPath(page)];
  }
  <!--这一段代码是关键，存储的是__route__属性-->
  _getPageModelPath(page) {
    return page.__route__;
  }
}

export default PageModel ;

<!--第二步：app.js中引入-->
import PageModel from './common/page-model/index.js';

App({
  pageModel: new PageModel(),
});

<!--第三步：页面onLoad周期里缓存页面-->
onLoad: function(options) {
  app.pageModel.add(this);
}

<!--第四步：子孙获取祖辈方法-->
methods: {
  addCount() {
    app.pageModel.get('pages/communicate/index').addCount();
  }
}