使用wxs自定义微信小程序下拉刷新

使用场景：（1）自定义导航栏（2）scroll-view存在时

wxs代码：

var touchStartVal = 0,
  timeStamp = 0,
  height = 0,
  pullDownObj = {
    isCanPullDown: true,
    threshold: 50,
    maxHeight: 100,
    callMethodName: 'onPullDownRefresh',
    pullDownAreaSelector: '.pulldown'
  }

function touchStart(e, ownerInstance) {
  if (pullDownObj.isCanPullDown) {
    touchStartVal = e.changedTouches[0].pageY
  }
}

function touchMove(e, ownerInstance) {
  timeStamp = e.timeStamp
  if (!pullDownObj.isCanPullDown) {
    return
  }
  var oldHeight = height

  if (oldHeight > pullDownObj.maxHeight) {
    return;
  }
  var end = e.changedTouches[0].pageY
  height = end - touchStartVal;

  var deltaHeight = height - oldHeight;
  deltaHeight = deltaHeight

  height = pullDownObj.maxHeight >= height ? height : pullDownObj.maxHeight

  var instance = ownerInstance.selectComponent(pullDownObj. pullDownAreaSelector) // 返回组件的实例
  instance.setStyle({
    'height': height + 'px' // 支持rpx
  })

}

function touchEnd(e, ownerInstance) {
  if (!pullDownObj.isCanPullDown) {
    return
  }

  var instance = ownerInstance.selectComponent(pullDownObj.pullDownAreaSelector) // 返回组件的实例
  if (height > pullDownObj.threshold) {
    instance.callMethod(pullDownObj.callMethodName)

  }
  instance.setStyle({
    'height': 0 + 'px' // 支持rpx
  })

}

function propObserver(newValue, oldValue, ownerInstance, instance) {

  pullDownObj = newValue
  console.log(JSON.stringify(pullDownObj))
}
module.exports = {
  touchMove: touchMove,
  touchStart: touchStart,
  touchEnd: touchEnd,
  propObserver: propObserver
}
           

wxml:

<view  change:prop="{{pulldown.propObserver}}"
  prop="{{propValue}}" bindtouchstart='{{pulldown.touchStart}}' bindtouchmove='{{pulldown.touchMove}}' bindtouchend="{{pulldown.touchEnd}}"  class='container'>
</view>
           

页面js:propValue的值不可以缺失

Page({
	data:{
		propValue: {
		      isCanPullDown: true,
		      threshold: 50,
		      maxHeight: 80,
		      callMethodName: 'onPullDownRefresh',//触发下拉刷新时，会调用此方法，需在js里面声明
		      pullDownAreaSelector: ".pulldown"//展示下拉刷新文字的dom选择器
		 }
	},
	onPullDownRefresh(){},
	 onPageScroll(e) {
	    let scrollTop = e.scrollTop
	    let propValue = this.data.propValue;
	    let isCanPullDown = !scrollTop
	    if (propValue.isCanPullDown != isCanPullDown) {
	      propValue.isCanPullDown = isCanPullDown
	      this.setData({
	        propValue
	      })
  	  }
  	 }
})