关于android:列表组件listview的使用flex布局教程以APICloud-AVM框架为例

avm.js 是 APICloud 推出的多端开发框架。应用 avm.js 一个技术栈可同时开发 Android & iOS 原生 App、小程序和 iOS 轻 App，且多端渲染成果对立；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 统一。

list-view 定义可复用内容的竖向滚动视图，能够优化内存占用和渲染性能，反对下拉刷新和上拉加载。可应用 scroll-view 的根本属性。

list-view 外面可搁置 cell、list-header、list-footer、refresh 等组件，应用 cell 组件作为每项显示内容。

上面看一个 list-view 的示例：

<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: '我的项目' + (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: '以后项索引：' + e.currentTarget.index});
    }
}

}</script>
list-view 只反对 APP，须要用自定义 loader 或 APPloader 调试。调试教程可查看文档 APICloud Studio3 WiFi 真机同步和 WiFi 真机预览应用阐明

list-view 自带内存回收性能，能够滚动加载更多。

给 list-view 增加下拉刷新组件 refresh

依据 refresh 组件文档，把 refresh 标签增加到 list-view 标签中，如下:

<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，并在我的项目目录 image 标签下增加用到的两张下拉刷新图片。残缺代码如下：

<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 '下拉能够刷新';} else if (this.data.refreshState == 'dragging') {return '松开能够刷新';} 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: '我的项目' + (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: '以后项索引：' + 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>

Flex 布局介绍：

Flex 布局意思是弹性盒子布局，比拟适宜挪动端场景，能够主动伸缩适配不同屏幕大小。

<div>

</div>

通常能够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我的项目。flex 布局的次要性能是在主轴或穿插轴按预期排列散布我的项目，定义每个我的项目占用空间比例，并可追随容器大小伸缩。

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