uniapp-小程序-瀑布流布局-支持下拉刷新上拉加载更多

主要思路：

• 将父组件传递进来的list分为两组，leftList和rightList，初始化为空数组
• 页面布局分为左右两侧，左侧渲染leftList的数据，右侧渲染rightList的数据，并初始化左右两栏的高度为0
• 利用image标签中的load事件，在图片加载的时候，获取到图片的实际尺寸，计算出要显示的高度。比较两栏的高度，将对应的数据加到leftList或者rightList

我们在组件中写一个两列的布局，图片的宽度设定为345rpx，文字的高度定为100rpx，下边距定为20rpx，给image绑定一个load方法，onImageLoad，这个组件的核心就是这个方法。

//wterfall
<template>
    <view class="waterfall">
        <view class="left">
            <block v-for="(item, index) in leftList" :key="index">
                <view class="waterfall-item">
                    <image :src="item.src" mode="widthFix" lazy-load @load="onImageLoad"></image>
                    <view class="title">{{ item.title }}</view>
                </view>
            </block>
        </view>
        <view class="right">
            <block v-for="(item, index) in rightList" :key="index">
                <view class="waterfall-item">
                    <image :src="item.src" mode="widthFix" lazy-load @load="onImageLoad"></image>
                    <view class="title">{{ item.title }}</view>
                </view>
            </block>
        </view>
    </view>
</template>

<style lang="scss">
.waterfall {
    width: 100%;
    display: flex;
    justify-content: space-between;
    padding: 0 20rpx;
    box-sizing: border-box;
    .left,
    .right {
        .waterfall-item {
            width: 345rpx;
            margin-bottom: 20rpx;
            background-color: pink;
            box-sizing: border-box;
            image {
                width: 345rpx;
                display: block;
            }
            .title {
                width: 345rpx;
                height: 100rpx;
                overflow: hidden;
            }
        }
    }
}
</style>

可以看到，上面有两个view，分别是left和right，分别渲染的是leftList和rightList里面的数据，那么这两个数据是怎么来的呢？我们在组件中定义一个prop:

props: {
        list: {
            type: Array,
            default: []
        }
}

这个list是通过父组件传递过来的，也就是你原始的数据，我们在组件中再声明几个变量，并在created的时候，将list中的第一个数据存入到leftList中

data() {
        return {
            leftList: [],
            rightList: [],
            itemIndex: 0,
            leftHeight: 0,
            rightHeight: 0
        };
},
created() {
        this.leftList = [this.list[0]]; //第一张图片入栈
},

然后就是最重要的onImageLoad方法了

onImageLoad(e) {
            if (!e) {
                console.log('无图片！！！！');
                return;
            }
            let imgH = (e.detail.height / e.detail.width) * 345 + 100 + 20; //图片显示高度加上下面的文字的高度100rpx,加上margin-bottom20rpx
            let that = this;
            if (that.itemIndex === 0) {
                that.leftHeight += imgH; //第一张图片高度加到左边
                that.itemIndex++;
                that.rightList.push(that.list[that.itemIndex]); //第二张图片先入栈
            } else {
                that.itemIndex++;
                //再加高度
                if (that.leftHeight > that.rightHeight) {
                    that.rightHeight += imgH;
                } else {
                    that.leftHeight += imgH;
                }
                if (that.itemIndex < that.list.length) {
                    //下一张图片入栈
                    if (that.leftHeight > that.rightHeight) {
                        that.rightList.push(that.list[that.itemIndex]);
                    } else {
                        that.leftList.push(that.list[that.itemIndex]);
                    }
                }
            }
    }

上面注释的也比较清楚了，首先要将第一张图入栈，这个时候onImageLoad才会返回图片信息，不然的话是没有图片的，在onImageLoad方法执行的时候，先计算出图片的显示高度，然后计算leftHeight和rightHeight的高度，再将下一张图入栈。

上拉加载更多、下拉刷新

上拉加载更多的时候，监听list的变化，list的新的值会比旧的值length更大，这个时候将新添加进来的值的第一个数据先入栈，相当于是首次加载的时候第一个数据先放到leftList。

    watch: {
        list(n, o) {
            let that = this;
            // console.log('=====watch  list=====', n, o);
            let ol = o.length;
            let nl = n.length;
            if (nl > ol) {
                if (this.leftHeight > this.rightHeight) {
                    that.rightList.push(that.list[ol]);
                } else {
                    that.leftList.push(that.list[ol]);
                }
                this.onImageLoad();
            }
        }
    },

下拉刷新的时候有一点不一样，需要先将组件销毁掉，再重新渲染，可以在父组件中用v-if判断是否要销毁，父组件中的代码:

<waterFall v-if="goodsList.length > 0" :list="goodsList"></waterFall>

onPullDownRefresh() {
        this.goodsList = [];
        setTimeout(() => {
            this.goodsList = [...list];
        }, 500);

        uni.stopPullDownRefresh();
}

大致就是这样，我觉得还不够好，但在我的项目中也是够用了，贴上完整的代码：

//waterfall.vue
<template>
    <view class="waterfall">
        <view class="left">
            <block v-for="(item, index) in leftList" :key="index">
                <view class="waterfall-item">
                    <image :src="item.src" mode="widthFix" lazy-load @load="onImageLoad"></image>
                    <view class="title">{{ item.title }}</view>
                </view>
            </block>
        </view>
        <view class="right">
            <block v-for="(item, index) in rightList" :key="index">
                <view class="waterfall-item">
                    <image :src="item.src" mode="widthFix" lazy-load @load="onImageLoad"></image>
                    <view class="title">{{ item.title }}</view>
                </view>
            </block>
        </view>
    </view>
</template>

<script>
export default {
    name: 'water-fall',
    props: {
        list: {
            type: Array,
            default: []
        }
    },
    watch: {
        list(n, o) {
            let that = this;
            // console.log('=====watch  list=====', n, o);
            let ol = o.length;
            let nl = n.length;
            if (nl > ol) {
                if (this.leftHeight > this.rightHeight) {
                    that.rightList.push(that.list[ol]);
                } else {
                    that.leftList.push(that.list[ol]);
                }
                this.onImageLoad();
            }
        }
    },
    data() {
        return {
            leftList: [],
            rightList: [],
            itemIndex: 0,
            leftHeight: 0,
            rightHeight: 0
        };
    },
    created() {
        this.leftList = [this.list[0]]; //第一张图片入栈
    },
    destroyed() {
        console.log('destroy');
    },
    methods: {
        onImageLoad(e) {
            if (!e) {
                console.log('无图片！！！！');
                return;
            }
            let imgH = (e.detail.height / e.detail.width) * 345 + 100 + 20; //图片显示高度加上下面的文字的高度100rpx,加上margin-bottom20rpx
            let that = this;
            if (that.itemIndex === 0) {
                that.leftHeight += imgH; //第一张图片高度加到左边
                that.itemIndex++;
                that.rightList.push(that.list[that.itemIndex]); //第二张图片先入栈
            } else {
                that.itemIndex++;
                //再加高度
                if (that.leftHeight > that.rightHeight) {
                    that.rightHeight += imgH;
                } else {
                    that.leftHeight += imgH;
                }
                if (that.itemIndex < that.list.length) {
                    //下一张图片入栈
                    if (that.leftHeight > that.rightHeight) {
                        that.rightList.push(that.list[that.itemIndex]);
                    } else {
                        that.leftList.push(that.list[that.itemIndex]);
                    }
                }
            }
        }
    }
};
</script>

<style lang="scss">
.waterfall {
    width: 100%;
    display: flex;
    justify-content: space-between;
    padding: 0 20rpx;
    box-sizing: border-box;
    .left,
    .right {
        .waterfall-item {
            width: 345rpx;
            margin-bottom: 20rpx;
            background-color: pink;
            box-sizing: border-box;
            image {
                width: 345rpx;
                display: block;
            }
            .title {
                width: 345rpx;
                height: 100rpx;
                overflow: hidden;
            }
        }
    }
}
</style>

<template>
    <view>
        <waterFall v-if="goodsList.length > 0" :list="goodsList"></waterFall>
    </view>
</template>

<script>
const list = [
    { src: 'cardBg7.png', title: '1、非常好看的额图片，快起来这里买东西' },
    { src: 'ios.png', title: '2、这段文字要少' },
    { src: 'home_banner1.jpg', title: '3、大段文字展示' },
    { src: 'IMG17.jpeg', title: '4、特朗普的眼镜' },
    { src: 'cardBg5.png', title: '5、非常好看的额图片，快起来这里买东西' },
    { src: 'operation_pt_img.png', title: '6、非常好看的额图片，快起来这里买东西' }
];
import waterFall from '@/components/waterfall.vue';
export default {
    components: {
        waterFall
    },
    data() {
        return {
            goodsList: [...list] //商品列表
        };
    },
    onReachBottom() {
        if (this.goodsList.length > 29) {
            uni.showToast({
                title: '30条全部加载完毕！',
                icon: 'none'
            });
        } else {
            this.goodsList = this.goodsList.concat(list);
        }
    },
    onPullDownRefresh() {
        this.goodsList = [];
        setTimeout(() => {
            this.goodsList = [...list];
        }, 500);

        uni.stopPullDownRefresh();
    }
};
</script>