tqpulldownrefresh/core.js

import { nextFrame, cancelFrame, slideTo } from './animate.js'

const masDragDistance = 300 // 最大拖动距离

let timer = null

export default class TQPullDownRefresh {

  constructor(onPullStart, onReleaseToRefresh, onPulling) {

    this.state = {
      x: 0,
      y: 0,
      endY: 0,
      ladderDistance: 0, // 阶梯下降时阶梯的数值
      lastY: 0,
      rate: 1,
      isRunning: false
    }

    this.containerRef = null
    this.areaRect = null
    this.refresherRef = null
    this.refresherRect = null

    this.onPullStart = onPullStart
    this.onReleaseToRefresh = onReleaseToRefresh
    this.onPulling = onPulling

    // 手动创建 dom
    const link = document.createElement('link')
    link.rel = 'stylesheet'
    link.href = './refresh.css'
    document.head.appendChild(link)

    this.containerRef = document.createElement('div')
    this.containerRef.className = 'container'
    document.body.appendChild(this.containerRef)

    this.refresherRef = document.createElement('div')
    this.refresherRef.className = 'refresher'
    this.containerRef.appendChild(this.refresherRef)

    const img = document.createElement('img')
    img.src = './refresh.png'
    img.style.width = '100%'
    img.style.height = '100%'
    this.refresherRef.appendChild(img)

    this.containerRef.addEventListener('touchstart', this.touchStart.bind(this))
    this.containerRef.addEventListener('touchmove', this.touchMove.bind(this))
    this.containerRef.addEventListener('touchend', this.touchEnd.bind(this))
  }

  prepare(touch) {
    this.refresherRect = this.refresherRef.getBoundingClientRect()

    this.state.x = this.refresherRect.left
    this.state.y = this.refresherRect.top

    this.state.lastY = touch.clientY

    this.state.isRunning = true
  }

  destroy() {
    this.containerRef.removeEventListener('touchstart', this.touchStart.bind(this))
    this.containerRef.removeEventListener('touchmove', this.touchMove.bind(this))
    this.containerRef.removeEventListener('touchend', this.touchEnd.bind(this))
  }

  // 记录日志：动画结束的时机
  rotate(angle) {
    console.log('旋转动画开始')

    cancelFrame(timer)
    this.animate(angle)
  }

  animate(angle) {
    this.refresherRef.style.transform = `translate(0px, ${this.state.y}px)  rotate(${angle}deg`

    angle = angle === -360 ? 0 : angle - 5

    timer = nextFrame(() => {
      this.animate(angle - 5)
    })
  }

  // 回弹
  springBack() {
    console.log('旋转动画结束')
    console.log(`打印要结束的旋转动画 id: ${timer}`)
    cancelFrame(timer)
    this.state.y = 0

    const rect = this.refresherRef.getBoundingClientRect()
    console.log('回弹动画开始')
    slideTo(this.refresherRef, rect.top, () => {
      this.isSpringBack = true
      this.state.isRunning = false
    })

    this.state.rate = 1
    this.state.lastY = 0
  }

  move(touch) {
    const dy = touch.clientY - this.state.lastY

    this.state.lastY = touch.clientY
    this.state.rate = this.getRate(dy, this.state.rate)
    this.state.y += dy * this.state.rate

    if (this.state.y >= masDragDistance) {
      this.state.y = masDragDistance
    }

    if (this.state.y < 0) {
      this.state.y = 0
    }

    this.dragMove(this.state.y)
  }

  // 手势
  getRate(distance, rate) {
    this.state.ladderDistance += distance

    if (distance > 0) {
      if (this.state.ladderDistance >= 100) {
        rate = Math.max(0, rate - 0.1)
        this.state.ladderDistance = 0
      }

    } else {
      if (this.state.ladderDistance < -100) {
        rate = Math.min(1, rate + 0.1)
        this.state.ladderDistance = 0
      }
    }

    return rate
  }

  dragMove(translateY) {
    if (!this.refresherRef) 
      return

    const angle = ~~(translateY / masDragDistance * 360) * -1
    this.refresherRef.style.transform = `translate(0px, ${translateY}px) rotate(${angle}deg)`

    this.onPulling && this.onPulling(translateY)
  }

  touchStart(e) {   
    const touch = e.touches[0]
    this.prepare(touch)
    this.isSpringBack = false
    this.onPullStart && this.onPullStart()
  }

  touchEnd(e) {
    if (this.state.y >= masDragDistance) {
      console.log('触发旋转动画')
      this.rotate(0)
      this.onReleaseToRefresh && this.onReleaseToRefresh()
    } else {
      console.log('触发回弹动画')
      this.springBack()
    }
    this.destroy()
  }

  touchMove(e) {
    const touch = e.touches[0]
    this.move(touch)
  }
}