微信小程序跑马灯完美实现源码

版权声明：本文为楠之枫雪的原创文章，未经博主允许不得转载。 https://blog.csdn.net/u014614038/article/details/82117764

网上很多实现跑马灯的文章，但是很多发现都是不行的，之一就是文字宽度居然是通过字符数*文字size计算，明显是不准确的计算方式。我看了下，发现可以通过计算控件宽度来精确计算文字宽度，这样实现的跑马灯是比较完善的。

效果如下：

实现代码如下：

wxml:

<view class="rollCon">
 <view class='box'> 
 <view class='text'style='left:{{offsetLeft}}px' >{{text}}</view>
</view>
</view>

wxss:

.rollCon {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 60rpx;
  z-index: 100;
  background: #fde8c7;
  font-size: 20rpx;
  line-height: 60rpx;
}

.box {
  width: 100%;
  position: relative;
}

.text {
  white-space: nowrap;
  position: absolute;
  top: 0;
  font-size: 24px;
}

js:

Page({

  /**
   * 页面的初始数据
   */
  data: {
    interval: null,
    text: '995年JavaScript诞生时如早一年',
    pace: 1.2, //滚动速度
    interval: 20, //时间间隔
    size: 24, //字体大小in px
    length: 0, //字体宽度
    offsetLeft: 0, //
    windowWidth: 0,
  },
  //根据viewId查询view的宽度
  queryViewWidth: function(viewId) {
    //创建节点选择器
    return new Promise(function(resolve) {
      var query = wx.createSelectorQuery();
      var that = this;
      query.select('.' + viewId).boundingClientRect(function(rect) {
        resolve(rect.width);
      }).exec();
    });

  },
  //停止跑马灯
  stopMarquee: function() {
    var that = this;
    //清除旧的定时器
    if (that.data != null) {
      clearInterval(that.interval);
    }
  },
  //执行跑马灯动画
  excuseAnimation: function() {
    var that = this;
    if (that.data.length > that.data.windowWidth) {
      //设置循环
      let interval = setInterval(function() {
        if (that.data.offsetLeft <= 0) {
          if (that.data.offsetLeft >= -that.data.length) {
            that.setData({
              offsetLeft: that.data.offsetLeft - that.data.pace,
            })
          } else {
            that.setData({
              offsetLeft: that.data.windowWidth,
            })
          }
        } else {
          that.setData({
            offsetLeft: that.data.offsetLeft - that.data.pace,
          })
        }
      }, that.data.interval);
    }
  },
  //开始跑马灯
  startMarquee: function() {
    var that = this;
    that.stopMarquee();
    //初始化数据
    that.data.windowWidth = wx.getSystemInfoSync().windowWidth;
    that.queryViewWidth('text').then(function(resolve) {
      that.data.length = resolve;
      console.log(that.data.length + "/" + that.data.windowWidth);
      that.excuseAnimation();
    });
  }
  })

源码下载：

https://github.com/bifan-wei/WXMarquee

转载注明:https://blog.csdn.net/u014614038/article/details/82117764