详细说明微信小程序开发弹幕的完成（无后台）

<!-- pages/index/index.wxml -->
<swiper indicator-dots="{{indicatorDots}}"
  autoplay="{{autoplay}}" interval="{{interval}}" duration="{{duration}}">
  <block wx:for="{{imgUrls}}" wx:key="unique">
    <swiper-item>
      <image src="{{item}}" class="slide-image"/>
    </swiper-item>
  </block>
</swiper>
<!--弹幕开关-->
<view class="barrage-Switch" style="color:{{barrageTextColor}};">
    <switch id="switch_" bindchange="barrageSwitch"/>
    <text>弹幕</text>
</view>
<!--弹幕输入框-->
  <view class="barrage-inputText" style="display:{{barrage_inputText}}">
      <view class="barrage-input">
        <input bindblur="bind_shoot" value="{{bind_shootValue}}"/>
      </view>
      <view class="barrage-shoot">
          <button class="shoot" size="mini" bindtap="shoot">发射</button>
      </view>
  </view>
<!--弹幕上单文字-->
<view class="barrage-fly" style="display:{{barragefly_display}}">
  <block wx:for="{{barrage_style}}" wx:key="unique">
   <text class="barrage-textFly" style="color:{{item.barrage_shoottextColor}};left:{{item.barrage_phoneWidth}}px;top:{{item.barrageText_height}}px;">{{item.barrage_shootText}}</text>
  </block>
</view>
wxss代码如下：
/* pages/index/index.wxss */
.slide-image{
    width: 100%;
}
/* 弹幕选择按钮的操作*/
.barrage-Switch{
    position: absolute;
    bottom: 10px;
    right: 10px;
    z-index: 2;
}
/* 弹幕输入框的操作*/
.barrage-inputText{
    position: absolute;
    display: flex;
    background-color: #BFBFBF;
    width: 100%;
    height: 40px;
    flex-direction: row;
    nav-index: 2;
    justify-content: center;
    align-items: center;
    bottom: 10%;
}
.barrage-input{
    background-color: greenyellow;
    width: 60%;
    height: 30px;
}
.barrage-shoot{
    margin-left: 10px;
    width: 25%;
    height: 30px;
}
.shoot{
    width: 100%;
    color: black;
}
/*弹幕飞飞飞*/
.barrage-fly{
    z-index: 3;
    height: 80%;
    width: 100%;
    position: absolute;
    top: 0;
}
.barrage-textFly{
    position: absolute;
}
这样基本的样式就都实现了。接下来要对弹幕上的字进行处理。
文字是从右往左移动，文字出现的位置top是随机，left则是取屏幕的宽度。移动的时候是用定时器进行处理。
还有就是字体的颜色是随机出现的。这些功能都是利用js处理的。
js的代码如下：
var barrage_style_arr = [];
var barrage_style_obj ={};
var phoneWidth = 0;
var timers = [];
var timer ;
Page({
  data: {
    imgUrls: [
      'http://img02.tooopen.com/images/20150928/tooopen_sy_143912755726.jpg',
      'http://img06.tooopen.com/images/20160818/tooopen_sy_175866434296.jpg',
      'http://img06.tooopen.com/images/20160818/tooopen_sy_175833047715.jpg'
    ],
    indicatorDots: true,
    autoplay: true,
    interval: 3000,
    duration: 500,
    barrageTextColor:"#D3D3D3",
    barrage_inputText:"none",
    barrage_shoottextColor:"black",
    bind_shootValue:"",
    barrage_style:[],
    barragefly_display:"none",
  },
    // 生命周期函数--监听页面加载
  onLoad:function(options){
    var that = this;
    //获取屏幕的宽度
      wx.getSystemInfo({
        success: function(res) {
           that.setData({
                barrage_phoneWidth:res.windowWidth-100,
           })
        }
      })
      phoneWidth = that.data.barrage_phoneWidth;
      console.log(phoneWidth);
  },
  //是否打开弹幕... 
  barrageSwitch: function(e){
    console.log(e);
    //先判断没有打开
    if(!e.detail.value){
    //清空弹幕
      barrage_style_arr = [];
      //设置data的值
      this.setData({
        barrageTextColor:"#D3D3D3",
        barrage_inputText:"none",
        barragefly_display:"none",
        barrage_style:barrage_style_arr,
      });
      //清除定时器
      clearInterval(timer);
    }else{
      this.setData({
        barrageTextColor:"#04BE02",
        barrage_inputText:"flex",
        barragefly_display:"block",
      });
      //打开定时器
        timer= setInterval(this.barrageText_move,800)
    }
  },
  //发射按钮
  shoot: function(e){
    //字体颜色随机
    var textColor = "rgb("+parseInt(Math.random()*256)+","+parseInt(Math.random()*256)+","+parseInt(Math.random()*256)+")";
    // //设置弹幕字体的水平位置样式
    // var textWidth = -(this.data.bind_shootValue.length*0);
    //设置弹幕字体的垂直位置样式
    var barrageText_height = (Math.random())*266;
     barrage_style_obj = {
      // textWidth:textWidth,
      barrageText_height:barrageText_height,
      barrage_shootText:this.data.bind_shootValue,
      barrage_shoottextColor : textColor,
      barrage_phoneWidth:phoneWidth
    };
    barrage_style_arr.push(barrage_style_obj);
    this.setData({ 
      barrage_style:barrage_style_arr,        //发送弹幕
      bind_shootValue:""                    //清空输入框
    })
      //定时器  让弹幕动起来
      //  this.timer= setInterval(this.barrageText_move,800);
  },
//定时器  让弹幕动起来
  barrageText_move: function(){
    var timerNum = barrage_style_arr.length;
    var textMove ;
    for(var i=0;i<timerNum;i++){
       textMove = barrage_style_arr[i].barrage_phoneWidth;
       console.log("barrage_style_arr["+i+"].barrage_phoneWidth----------:"+barrage_style_arr[i].barrage_phoneWidth);
       textMove = textMove -20;
      barrage_style_arr[i].barrage_phoneWidth = textMove;
      //走完的移除掉
      if(textMove<=-100){
 //         clearTimeout(this.timer);
          barrage_style_arr.splice(0,1);
          i--;
          //全部弹幕运行完
          if(barrage_style_arr.length==0){
            this.setData({
              barrage_style:barrage_style_arr, 
            })
            // clearInterval(this.timer);
            return;
          }
      }
      console.log("第"+i+"个定时器:",textMove);
      this.setData({
        barrage_style:barrage_style_arr, 
      })
    }
  },
  //绑定发射输入框，将值传递给data里的bind_shootValue，发射的时候调用
  bind_shoot:function(e){
    this.setData({
      bind_shootValue:e.detail.value