微信小程式中實作瀑布流佈局和無限加載

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 3b7f08c33b880b29f189568e9347b46ff8e950ebc6c1ea27f76cf997b9216fe6de5f4c1163741e920c998275338d29b2

####我們可以在Page中透過資料綁定，來傳遞要載入的圖片資訊到wxml中，讓dc0870658837139040642baa5555a380元件去載入圖片資源，然後當圖片載入完成的時候，透過bindload指定的事件處理函數來做進一步處理。 ######

我們來看Page檔案中定義的onImageLoad函數。在其中，我們可以從傳入的事件物件e上，獲取到dc0870658837139040642baa5555a380組件的豐富信息，包括通過它加載進來的圖片的實際大小。然後我們將圖片依照頁面上實際需要顯示的尺寸，計算出同比例縮放後的尺寸。接著，我們可以根據左右兩列目前累積的內容高度，來決定把目前載入的圖片放到哪一邊。

#

let col1H = 0;let col2H = 0;

Page({    data: {        scrollH: 0,        imgWidth: 0,        loadingCount: 0,        images: [],        col1: [],        col2: []
   },    onLoad: function () {
       wx.getSystemInfo({            success: (res) => {                
       let ww = res.windowWidth;                
       let wh = res.windowHeight;                
       let imgWidth = ww * 0.48;                
       let scrollH = wh;                
       this.setData({                    
       scrollH: scrollH, 
       imgWidth: imgWidth
               });                //加载首组图片
               this.loadImages();
           }
       })
   },    onImageLoad: function (e) {        
   let imageId = e.currentTarget.id;        
   let oImgW = e.detail.width;         //图片原始宽度
       let oImgH = e.detail.height;        //图片原始高度
       let imgWidth = this.data.imgWidth;  //图片设置的宽度
       let scale = imgWidth / oImgW;        //比例计算
       let imgHeight = oImgH * scale;      //自适应高度

       let images = this.data.images;        let imageObj = null;        
       for (let i = 0; i < images.length; i++) {            let img = images[i];            
       if (img.id === imageId) {
               imageObj = img;                break;
           }
       }

       imageObj.height = imgHeight;        
       let loadingCount = this.data.loadingCount - 1;        
       let col1 = this.data.col1;        
       let col2 = this.data.col2;        //判断当前图片添加到左列还是右列
       if (col1H <= col2H) {
           col1H += imgHeight;
           col1.push(imageObj);
       } else {
           col2H += imgHeight;
           col2.push(imageObj);
       }        let data = {            
       loadingCount: loadingCount,            col1: col1,            col2: col2
       };        //当前这组图片已加载完毕，则清空图片临时加载区域的内容
       if (!loadingCount) {
           data.images = [];
       }        this.setData(data);
   },    loadImages: function () {        let images = [
           { pic: "../../images/1.png", height: 0 },
           { pic: "../../images/2.png", height: 0 },
           { pic: "../../images/3.png", height: 0 },
           { pic: "../../images/4.png", height: 0 },
           { pic: "../../images/5.png", height: 0 },
           { pic: "../../images/6.png", height: 0 },
           { pic: "../../images/7.png", height: 0 },
           { pic: "../../images/8.png", height: 0 },
           { pic: "../../images/9.png", height: 0 },
           { pic: "../../images/10.png", height: 0 },
           { pic: "../../images/11.png", height: 0 },
           { pic: "../../images/12.png", height: 0 },
           { pic: "../../images/13.png", height: 0 },
           { pic: "../../images/14.png", height: 0 }
       ];        let baseId = "img-" + (+new Date());       
        for (let i = 0; i < images.length; i++) {
           images[i].id = baseId + "-" + i;
       }        this.setData({            
       loadingCount: images.length,            images: images
       });
   }

})

  if (col1H <= col2H) {
            col1H += imgHeight;
            col1.push(imageObj);
        } else {
            col2H += imgHeight;
            col2.push(imageObj);
        }        let data = {            loadingCount: loadingCount,            col1: col1,            col2: col2
        };        //当前这组图片已加载完毕，则清空图片临时加载区域的内容
        if (!loadingCount) {
            data.images = [];
        }        this.setData(data);
    },    loadImages: function () {        let images = [
            { pic: "../../images/1.png", height: 0 },
            { pic: "../../images/2.png", height: 0 },
            { pic: "../../images/3.png", height: 0 },
            { pic: "../../images/4.png", height: 0 },
            { pic: "../../images/5.png", height: 0 },
            { pic: "../../images/6.png", height: 0 },
            { pic: "../../images/7.png", height: 0 },
            { pic: "../../images/8.png", height: 0 },
            { pic: "../../images/9.png", height: 0 },
            { pic: "../../images/10.png", height: 0 },
            { pic: "../../images/11.png", height: 0 },
            { pic: "../../images/12.png", height: 0 },
            { pic: "../../images/13.png", height: 0 },
            { pic: "../../images/14.png", height: 0 }
        ];        let baseId = "img-" + (+new Date());        
        for (let i = 0; i < images.length; i++) {
            images[i].id = baseId + "-" + i;
        }        this.setData({            loadingCount: images.length,            images: images
        });
    }
})

這裡是顯示在兩列圖片的wxml程式碼，我們可以看到在050e2adc6de973d5d8d682f9c1b9f656元件上，我們透過使用bindscrolltolower設定了事件監聽函數，當滾動到底部的時候，會觸發loadImages去再加載下一組的圖片數據，這樣就形成了無限的加載：

#

<scroll-view scroll-y="true" style="height:{{scrollH}}px" bindscrolltolower="loadImages">
  <view style="width:100%">
    <view class="img_item">
      <view wx:for="{{col1}}" wx:key="id">
        <image src="{{item.pic}}" style="width:100%;height:{{item.height}}px"></image>
      </view>
    </view>
    <view class="img_item">
      <view wx:for="{{col2}}" wx:key="id">
        <image src="{{item.pic}}" style="width:100%;height:{{item.height}}px"></image>
      </view>
    </view>
  </view>
</scroll-view>

#

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