微信小程序笔记

1、切换tab，链接后面的参数携带不过去。解决方案有两种：

　　 (1)用数据缓存

 　　(2)用全局变量存储globalData

tab页面分享给别人时，参数是可以携带过去的。

2、判断是否连上wifi

wx.startWifi({
      complete: res => {
        wx.getConnectedWifi({
          success: res => {         
            // 连上wifi要做的操作
          }
        })
      }
    })

 3、使用mpvue写价格区域组件

html：

<div class="recd-post__slide__wraper">
      <div class="recd-post__slidegray" :style="{price1*580/1000-28+'rpx'}"></div>
      <slider :value='price1' @changing="slider1changing" @change="slider1change" activeColor="#E4E4E4" class="recd-post__slide" :min="0" :max="1000" />
      <slider :value='price2' @changing="slider2changing" @change="slider2change" activeColor="#4B9AFF" class="recd-post__slide" :min="0" :max="1000" />
      <div class="recd-post__lable" :style="{left:price1*580/1000-28+'rpx'}">{{price1+'w'}}</div>
      <div class="recd-post__lable" :style="{left:price2*580/1000-28+'rpx'}">{{price2+'w'}}</div>
    </div>

sass：

.recd-post{
    &__slide{
    width:580px;
    position: absolute;
    top:80px;
    left:0;
    margin:0;
    &__wraper{
      width:580px;
      margin:0px auto;
      padding:25px 0;
      height: 100px;
      position: relative;
    }
  }
   &__slidegray{
    height: 6px;
    background: #e9e9e9;
    position:absolute;
    top:97px;
    left:0;
    z-index:4;
    // width:200px;
  }
}

js:

data() {
    return {
      price1Right: 200,
      price2Right: 500,
      price1: 200,
      price2: 500,
      percent1: 200
    }
  },
methods: {
    slider1change(x) {
      if (x.target.value >= this.price2) {
        this.price1 = this.price1Right
      } else {
        this.price1Right = x.target.value
      }
    },
    slider2change(x) {
      if (x.target.value <= this.price1) {
        this.price2 = this.price2Right
      } else {
        this.price2Right = x.target.value
      }
    },
    slider1changing(x) {
      this.percent1 = x.target.value
      this.price1 = x.target.value
      // console.log(x)
    },
    slider2changing(x) {
      this.price2 = x.target.value
    }
}

效果如下图

 4、去处button按钮默认边框

button::after{border:none;}

5、小程序图片压缩（原博https://blog.csdn.net/qq_41473887/article/details/80678276）

wxml：

<view bindtap='aa'>选择图片</view>
  <canvas canvas-id="photo_canvas" style="{{canvasWidth}}px;height:{{canvasHeight}}px;position: absolute;left:-300px;top:-300px;"></canvas>

js：

aa() {
    var _this = this;
    wx.chooseImage({
      count: 1,
      sizeType: ['compressed'],
      success: function (photo) {
        wx.getImageInfo({
          src: photo.tempFilePaths[0],
          success: function (res) {
            var ctx = wx.createCanvasContext('photo_canvas');
            var ratio = 10;
            var canvasWidth = res.width
            var canvasHeight = res.height;
            _this.setData({
              aaa: photo.tempFilePaths[0],
              canvasWidth2: res.width,
              canvasHeight2: res.height
            })
            // 保证宽高均在200以内
            while (canvasWidth > 200 || canvasHeight > 200) {
              //比例取整
              canvasWidth = Math.trunc(res.width / ratio)
              canvasHeight = Math.trunc(res.height / ratio)
              ratio++;
            }
            _this.setData({
              canvasWidth: canvasWidth,
              canvasHeight: canvasHeight
            })//设置canvas尺寸
            ctx.drawImage(photo.tempFilePaths[0], 0, 0, canvasWidth, canvasHeight)  //将图片填充在canvas上
            ctx.draw()
            //下载canvas图片
            setTimeout(function () {
              wx.canvasToTempFilePath({
                canvasId: 'photo_canvas',
                success: function (res) {
                  console.log(res.tempFilePath)
                  _this.setData({
                    bbb: res.tempFilePath
                  })
                },
                fail: function (error) {
                  console.log(error)
                }
              })
            }, 100)
          },
          fail: function (error) {
            console.log(error)
          }
        })

      },
      error: function (res) {
        console.log(res);
      }
    })
  }