<scroll-view class="container">
 <view class="scrolltxt">
  <view class="marquee_box">
   <view class="marquee_text" >
    <text>{{text}}</text>
    <text ></text>
    <text >{{text}}</text>    
   </view>
  </view>
 </view>
</scroll-view>

.container {height: 100%;display: flex;flex-direction: column;justify-content: space-between;box-sizing: border-box;}
.scrolltxt{padding:0 20rpx;background:#f8f8f8;}
.marquee_box {position:relative;color:#333;height:90rpx;display:block;overflow:hidden;} 
.marquee_text {white-space: nowrap;position:absolute;top:0;font-size:14px;height:90rpx;line-height:90rpx;}

Page({
 /**
  * 页面的初始数据
  * Linyufan.com
  */
 data: {
  text: "这是一条测试公告，看看效果怎么样，2019年3月23日",
  marqueePace: 1,//滚动速度
  marqueeDistance: 0,//初始滚动距离
  marquee_margin: 30,
  size:14,
  interval: 20 // 时间间隔
 },
 
 /**
  * 生命周期函数--监听页面加载
  */
 onLoad: function (options) { 
 },
 onShow: function () {
  var that = this;
  var length = that.data.text.length * that.data.size;//文字长度
  var windowWidth = wx.getSystemInfoSync().windowWidth;// 屏幕宽度
  //console.log(length,windowWidth);
  that.setData({
   length: length,
   windowWidth: windowWidth
  });
  that.scrolltxt();// 第一个字消失后立即从右边出现
 },
 
 scrolltxt: function () {
  var that = this;
  var length = that.data.length;//滚动文字的宽度
  var windowWidth = that.data.windowWidth;//屏幕宽度
  if (length > windowWidth){
   var interval = setInterval(function () {
    var maxscrollwidth = length + that.data.marquee_margin;//滚动的最大宽度，文字宽度+间距，如果需要一行文字滚完后再显示第二行可以修改marquee_margin值等于windowWidth即可
    var crentleft = that.data.marqueeDistance;
    if (crentleft < maxscrollwidth) {//判断是否滚动到最大宽度
     that.setData({
      marqueeDistance: crentleft + that.data.marqueePace
     })
    }
    else {
     //console.log("替换");
     that.setData({
      marqueeDistance: 0 // 直接重新滚动
     });
     clearInterval(interval);
     that.scrolltxt();
    }
   }, that.data.interval);
  }
  else{
   that.setData({ marquee_margin:"1000"});//只显示一条不滚动右边间距加大，防止重复显示
  } 
 }
})