這兩週做一個新的項目,人員比較緊張,除了需求和UI,前端後端一個人來幹。
在項目需求確定後,UI隔了幾天設計出了UI界面,拿到UI效果圖後見有一個界面有波浪效果的我當時就蒙圈了,這都啥玩意啊?轉念想到了最近在IT圈挺火的那個事件:產品要求安卓程序員實現根據用戶手機殼顏色自動更換APP主題的需求後,頓時覺得畫個波浪這個壓根就不是事啊。
二次貝塞爾曲線
在微信官方的二次貝塞爾曲線畫法連接如下:
https://developers.weixin.qq.com/miniprogram/dev/api/canvas/quadratic-curve-to.html
畫波浪
思路:
在屏幕左邊畫一個波,然後讓它一直向屏幕右邊平移過去。其X的值由負數變爲正數依次增大;然後一直重複此操作。
我畫出來的波浪如下(感覺還是有那麼一點波浪的感覺):
界面代碼爲(index.wxml):
<view class="page-body">
<view class="page-body-wrapper">
<canvas canvas-id="myCanvas3" class="canvas3"></canvas>
</view>
</view>
JS代碼爲(index.js):
Page({
onReady: function() {
this.position = {
x: 150,
y: 150,
vx: 2,
vy: 2
},
this.obj = {
offset: 0,
baseLine: 40,
direction: 1,
waveDirection: 1
},
// var offset = 5
this.drawQuadraticCurve3()
this.interval = setInterval(this.drawQuadraticCurve3, 1)
console.log(">>>>>>>>>" + this.obj.offset)
},
/**
* 畫大波浪
*/
drawQuadraticCurve3: function() {
var obj = this.obj
var startX = 20,
itemWidth = 100,
offset = obj.offset,
baseLine = obj.baseLine,
waveHeight = 10,
direction = obj.direction,
waveDirection = obj.waveDirection
const ctx = wx.createCanvasContext('myCanvas3')
function getWaveHeigh(i) {
if (i % 2 == 0) {
// return baseLine + waveHeight
}
return baseLine - waveHeight
}
ctx.beginPath()
ctx.moveTo(-itemWidth * 6, baseLine)
ctx.setFillStyle('#4BF6EE')
for (var i = -6; i < 5; i++) {
startX = i * itemWidth;
var currentX = startX + (itemWidth / 2) + offset
var currentY = getWaveHeigh(i)
var currentEndX = startX + itemWidth + offset
ctx.quadraticCurveTo(currentEndX - 10,
currentY, currentEndX, baseLine)
ctx.stroke()
}
//填充海水
ctx.lineTo(0, 2000)
ctx.setFillStyle('#4BF6EE')
ctx.fill()
ctx.draw()
if (obj.waveDirection == 1) {
obj.offset = obj.offset + 1
} else if (obj.waveDirection == -1) {
obj.offset = obj.offset - 1
}
if (obj.offset == 400) {
obj.offset = 0
}
if (obj.offset == 50 || obj.offset == 1) {
// obj.waveDirection = obj.waveDirection * -1
}
// if (direction == 1) {
// obj.baseLine = obj.baseLine + 1
// } else if (direction == -1) {
// obj.baseLine = obj.baseLine - 1
// }
if (obj.baseLine >= 50 || obj.baseLine <= 40) {
console.log("<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<")
//obj.direction = (obj.direction * -1)
}
},
onUnload: function() {
clearInterval(this.interval)
}
})