APICloud AVM框架列表组件list-view的使用、flex布局教程

avm.js 是APICloud 推出的多端开发框架。使用 avm.js 一个技术栈可同时开发 Android & iOS 原生 App、小程序和 iOS 轻 App，且多端渲染效果统一；全新的 App 引擎 3.0 不依赖 webView，提供百分百的原生渲染，保障 App 性能和体验与原生 App 一致。

list-view定义可复用内容的竖向滚动视图，可以优化内存占用和渲染性能，支持下拉刷新和上拉加载。可使用 scroll-view 的基本属性。

list-view 里面可放置 cell、list-header、list-footer、refresh 等组件，使用 cell 组件作为每项显示内容。

下面看一个list-view的示例：

<template>
	<list-view id="listView" class="main" enable-back-to-top onscrolltolower={this.onscrolltolower}>
		<cell class="cell c-lc-rl_ac c-sy-border_bottom c-lc-ptb" onclick={this.itemClick}>
			<img class="img" src={item.url} alt="">
			<text class="title c-filling-w c-pl">{item.title}</text>
		</cell>
		<list-footer class="footer">
			<text>加载中...</text>
		</list-footer>
	</list-view>
</template>
<style src='../../css/c-layout-mini.css' scoped>
</style>
<style>
.main {
	width: 100%;
	height: 100%;
}

.cell {
	width: 100%;
	height: 70px;
}

.img {
	height: 50px;
	width: 50px;
	margin-left: 10px;
}
.title {
	height: 50px;
	font-size: 20px;
	line-height: 50px;
}

.footer {
	justify-content: center;
	align-items: center;
}
</style>

<script>
export default {
	name: 'test',
	methods: {
		apiready() {
			this.initData(false);
		},
		initData(loadMore) {
			var that = this;
			var skip = that.dataList ? that.dataList.length : 0;
			var dataList = [];
			for (var i = 0; i < 20; i++) {
				dataList[i] = {
					title: '项目' + (i + skip),
					url: '../../image/nav_tab_2.png'
				}
			}
			var listView = document.getElementById('listView');
			if (loadMore) {
				that.dataList = that.dataList.concat(dataList);
				listView.insert({
					data: dataList
				});
			} else {
				that.dataList = dataList;
				listView.load({
					data: dataList
				});
			}
		},
		onscrolltolower() {
			this.initData(true);
		},
		itemClick(e) {
			api.alert({
				msg: '当前项索引：' + e.currentTarget.index
			});
		}
	}
}
</script>

效果如下图：

list-view 只支持APP，需要用自定义loader或APPloader 调试。调试教程可查看文档APICloud Studio3 WiFi真机同步和WiFi真机预览使用说明

list-view 自带内存回收功能，可以滚动加载更多。

给list-view 添加下拉刷新组件 refresh

根据refresh 组件文档，把 refresh 标签添加到 list-view 标签中，如下:

<template>
    <list-view id="listView" class="main" enable-back-to-top onscrolltolower={this.onscrolltolower}>
        <refresh class="refresh" state={refreshState} onstatechange={this.onstatechange}>
            <image class={refreshIconClass} src="../../image/refresh.png"></image>
            <image class={refreshLoadingClass} src="../../image/loading_more.gif"></image>
            <text class="refreshStateDesc">{refreshStateDesc}</text>
        </refresh>

		<cell class="cell c-lc-rl_ac c-sy-border_bottom c-lc-ptb" onclick={this.itemClick}>
            <img class="img" src={item.url} alt="">
            <text class="title c-filling-w c-pl">{item.title}</text>
        </cell>
        <list-footer class="footer">
            <text>加载中...</text>
        </list-footer>
    </list-view>
</template>

　　

把refresh 组件的css ，js 代码也复制到相应的style 和 script 标签中，并在项目目录image 标签下添加用到的两张下拉刷新图片。完整代码如下：

<template>
    <list-view id="listView" class="main" enable-back-to-top onscrolltolower={this.onscrolltolower}>
        <refresh class="refresh" state={refreshState} onstatechange={this.onstatechange}>
            <image class={refreshIconClass} src="../../image/refresh.png"></image>
            <image class={refreshLoadingClass} src="../../image/loading_more.gif"></image>
            <text class="refreshStateDesc">{refreshStateDesc}</text>
        </refresh>

		<cell class="cell c-lc-rl_ac c-sy-border_bottom c-lc-ptb" onclick={this.itemClick}>
            <img class="img" src={item.url} alt="">
            <text class="title c-filling-w c-pl">{item.title}</text>
        </cell>
        <list-footer class="footer">
            <text>加载中...</text>
        </list-footer>
    </list-view>
</template>
<style  src='../../css/c-layout-mini.css' scoped>
</style>
<style>
.main {
	width: 100%;
	height: 100%;
}

.cell{
	width: 100%;
	height: 70px;
}

.img{
	height: 50px;
	width: 50px;
	margin-left: 10px;
}
.title {
	height: 50px;
	font-size: 20px;
	line-height: 50px;
}

  .footer {
        justify-content: center;
        align-items: center;
    }

	.refresh {
        align-items: center;
        justify-content: center;
        background-color: #eee;
    }
    .refreshStateDesc {
        color: #e3007f;
        font-size: 13px;
    }
    .refreshIcon {
        position: absolute;
        width: 25px;
        height: 22px;
        bottom: 21px;
        left: 70px;
        transition-property: transform;
        transition-duration: 100ms;
    }
    .refreshIcon-normal {
        transform: rotate(0);
        visibility: visible;
    }
    .refreshIcon-dragging {
        transform: rotate(180deg);
        visibility: visible;
    }
    .refreshIcon-refreshing {
        visibility: hidden;
    }
    .refreshLoading {
        position: absolute;
        width: 22px;
        height: 22px;
        bottom: 21px;
        left: 70px;
        visibility: hidden;
    }
    .refreshLoading-refreshing {
        visibility: visible;
    }

</style>

<script>
    export default {
        name: 'test',
		 data(){
            return {
                refreshState: 'normal'
            }
        },
		computed: {
            refreshIconClass(){
                if (this.data.refreshState == 'normal') {
                    return 'refreshIcon refreshIcon-normal';
                } else if (this.data.refreshState == 'dragging') {
                    return 'refreshIcon refreshIcon-dragging';
                } else if (this.data.refreshState == 'refreshing') {
                    return 'refreshIcon refreshIcon-refreshing';
                }
            },
            refreshLoadingClass() {
                if (this.data.refreshState == 'refreshing') {
                    return 'refreshLoading refreshLoading-refreshing';
                } else {
                    return 'refreshLoading';
                }
            },
            refreshStateDesc() {
                if (this.data.refreshState == 'normal') {
                    return '下拉可以刷新';
                } else if (this.data.refreshState == 'dragging') {
                    return '松开可以刷新';
                } else if (this.data.refreshState == 'refreshing') {
                    return '刷新中...';
                }
            }
        },
        methods:{
            apiready() {
                this.initData(false);
            },
            initData(loadMore) {
                var that = this;
                var skip = that.dataList?that.dataList.length:0;
                var dataList = [];
                for (var i=0;i<20;i++) {
                    dataList[i] = {
                        title: '项目' + (i + skip),
                        url: '../../image/nav_tab_2.png'
                    }
                }
                var listView = document.getElementById('listView');
                if (loadMore) {
                    that.dataList = that.dataList.concat(dataList);
                    listView.insert({
                        data: dataList
                    });
                } else {
                    that.dataList = dataList;
                    listView.load({
                        data: dataList
                    });
                }
            },
            onscrolltolower() {
                this.initData(true);
            },
            itemClick(e) {
                api.alert({
                    msg: '当前项索引：' + e.currentTarget.index
                });
            },
			onstatechange(e) {
                var state = e.detail.state;
                if (state == 'normal') {
                    this.data.refreshState = 'normal';
                } else if (state == 'dragging') {
                    this.data.refreshState = 'dragging';
                } else if (state == 'refreshing') {
                    this.data.refreshState = 'refreshing';
                    var that = this;
                    setTimeout(function(){
                        that.data.refreshState = 'normal';
                    }, 2000);
                }
            }
        }
    }
</script>

　　

wi-fi 同步到手机 loader，下拉页面，运行效果如下：

Flex 布局介绍：

Flex 布局意思是弹性盒子布局，比较适合移动端场景，适配不同屏幕大小。

<div>

   <div>item</div>

   <div>item</div>

   <div>item</div>

</div>

　　

通常可以把父元素定义为弹性盒子或称为容器，其子元素为弹性盒子的项目。flex布局的主要功能是在主轴或交叉轴按预期排列分布项目，定义每个项目占用空间比例，并可跟随容器大小伸缩。

上图引自下面这篇博客，推荐阅读：

http://www.ruanyifeng.com/blog/2015/07/flex-grammar.html

推荐一个flex git:

https://gitee.com/jiang_xincheng/c-layout