WeChat applet development picture drag and drop

<view class="container"> 
  <view class="cnt"> 
    <image class="image-style" src="../uploads/foods.jpg" style="left:{{ballleft}}px;width:{{screenWidth}}px" bindtouchmove="ballMoveEvent"> 
    </image> 
  </view> 
</view>

.container { 
  box-sizing:border-box; 
  padding:1rem; 
} 
.cnt{ 
  width:100%; 
  height:15rem; 
  border: 1px solid #ccc; 
  position:relative; 
  overflow: hidden; 
} 
.image-style{  
  position: absolute;  
  top: 0px;  
  left:0px;  
  height:100%;  
}

var app = getApp() 
Page({ 
  data: { 
    ballleft:-20, 
    screenWidth: 0, 
  }, 
  onLoad: function() { 
    var _this = this; 
    wx.getSystemInfo({ 
      success: function(res) { 
        _this.setData({ 
          screenHeight: res.windowHeight, 
          screenWidth: res.windowWidth, 
        }); 
      } 
    }); 
 
  }, 
  ballMoveEvent: function(e) { 
    var touchs = e.touches[0]; 
    var pageX = touchs.pageX; 
    console.log('宽度 '+this.data.screenWidth) 
    console.log('pageX: ' + pageX); 
    //这里用right和bottom.所以需要将pageX pageY转换  
    var x = this.data.screenWidth/2 - pageX-20; 
    if(this.data.screenWidth>385){ 
      if(x>42){x=42;} 
    }else{ 
      if(x>32){x=32;} 
    } 
    if(x<0){x=0;} 
    console.log(&#39;x:&#39; + x) 
    this.setData({ 
      ballleft: -x 
    }); 
  } 
})