mp-sticky.js
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const selectQuery = require('./selectQuery')
const target = '.weui-sticky'
Component({
options: {
addGlobalClass: true,
// 指定所有 _ 开头的数据字段为纯数据字段
pureDataPattern: /^_/,
multipleSlots: true // 在组件定义时的选项中启用多slot支持
},
behaviors: [selectQuery],
properties: {
offsetTop: {
type: Number,
value: 0
},
zIndex: {
type: Number,
value: 99
},
disabled: {
type: Boolean,
value: false,
},
container: {
type: null
}
},
data: {
fixed: false,
height: 0,
_attached: false,
_containerHeight: 0,
},
observers: {
disabled: function(newVal) {
if (!this.data._attached) return
newVal ? this.disconnectObserver() : this.initObserver()
},
container: function(newVal) {
if (typeof newVal !== 'function' || !this.data.height) return
this.observerContainer()
},
offsetTop: function(newVal){
if(typeof newVal !== 'number' || !this.data._attached) return
this.initObserver()
}
},
lifetimes: {
attached() {
this.data._attached = true
if (!this.data.disabled) this.initObserver()
},
detached() {
this.data._attached = false
this.disconnectObserver()
}
},
methods: {
getContainerRect () {
const nodesRef = this.data.container()
return new Promise(resolve => nodesRef.boundingClientRect(resolve).exec())
},
initObserver() {
this.disconnectObserver()
this.getRect(target).then(rect => {
this.setData({
height: rect.height
})
this.observerContent()
this.observerContainer()
})
},
disconnectObserver(observerName) {
if (observerName) {
const observer = this[observerName]
observer && observer.disconnect()
} else {
this.contentObserver && this.contentObserver.disconnect()
this.containerObserver && this.containerObserver.disconnect()
}
},
observerContent() {
const {offsetTop} = this.data
this.disconnectObserver('contentObserver')
const contentObserver = this.createIntersectionObserver({
thresholds: [1],
initialRatio: 1
})
contentObserver.relativeToViewport({
top: -offsetTop
})
contentObserver.observe(target, res => {
if (this.data.disabled) return
this.setFixed(res.boundingClientRect.top)
})
this.contentObserver = contentObserver
},
observerContainer() {
const {container, height, offsetTop} = this.data
if (typeof container !== 'function') return
this.disconnectObserver('containerObserver')
this.getContainerRect().then(rect => {
this.getRect(target).then(contentRect => {
const _contentTop = contentRect.top
const _containerTop = rect.top
const _containerHeight = rect.height
const _relativeTop = _contentTop - _containerTop
const containerObserver = this.createIntersectionObserver({
thresholds: [1],
initialRatio: 1
})
containerObserver.relativeToViewport({
top: _containerHeight - height - offsetTop - _relativeTop
})
containerObserver.observe(target, (res) => {
if (this.data.disabled) return
this.setFixed(res.boundingClientRect.top);
})
this.data._relativeTop = _relativeTop
this.data._containerHeight = _containerHeight
this.containerObserver = containerObserver
})
})
},
setFixed(top) {
const {height, _containerHeight, _relativeTop, offsetTop} = this.data
const fixed = _containerHeight && height
? (top >= height + offsetTop + _relativeTop - _containerHeight) && (top < offsetTop)
: top < offsetTop
this.triggerEvent('scroll', {
scrollTop: top,
isFixed: fixed
})
this.setData({fixed})
}
}
})