<template> 
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    <view 
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        class="u-switch" 
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        :class="[disabled && 'u-switch--disabled']" 
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        :style="[switchStyle, $u.addStyle(customStyle)]" 
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        @tap="clickHandler" 
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    > 
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        <view 
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            class="u-switch__bg" 
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            :style="[bgStyle]" 
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        > 
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        </view> 
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        <view 
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            class="u-switch__node" 
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            :class="[value && 'u-switch__node--on']" 
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            :style="[nodeStyle]" 
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            ref="u-switch__node" 
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        > 
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            <u-loading-icon 
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                :show="loading" 
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                mode="circle" 
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                timingFunction='linear' 
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                :color="value ? activeColor : '#AAABAD'" 
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                :size="size * 0.6" 
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            /> 
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        </view> 
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    </view> 
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</template> 
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<script> 
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    import props from './props.js'; 
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    /** 
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     * switch 开关选择器 
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     * @description 选择开关一般用于只有两个选择,且只能选其一的场景。 
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     * @tutorial https://www.uviewui.com/components/switch.html 
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     * @property {Boolean}                        loading            是否处于加载中(默认 false ) 
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     * @property {Boolean}                        disabled        是否禁用(默认 false ) 
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     * @property {String | Number}                size            开关尺寸,单位px (默认 25 ) 
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     * @property {String}                        activeColor        打开时的背景色 (默认 '#2979ff' ) 
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     * @property {String}                         inactiveColor    关闭时的背景色 (默认 '#ffffff' ) 
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     * @property {Boolean | String | Number}    value            通过v-model双向绑定的值 (默认 false ) 
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     * @property {Boolean | String | Number}    activeValue        打开选择器时通过change事件发出的值 (默认 true ) 
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     * @property {Boolean | String | Number}    inactiveValue    关闭选择器时通过change事件发出的值 (默认 false ) 
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     * @property {Boolean}                        asyncChange        是否开启异步变更,开启后需要手动控制输入值 (默认 false ) 
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     * @property {String | Number}                space            圆点与外边框的距离 (默认 0 ) 
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     * @property {Object}                        customStyle        定义需要用到的外部样式 
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     * 
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     * @event {Function} change 在switch打开或关闭时触发 
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     * @example <u-switch v-model="checked" active-color="red" inactive-color="#eee"></u-switch> 
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     */ 
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    export default { 
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        name: "u-switch", 
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        mixins: [uni.$u.mpMixin, uni.$u.mixin,props], 
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        watch: { 
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            value: { 
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                immediate: true, 
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                handler(n) { 
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                    if(n !== this.inactiveValue && n !== this.activeValue) { 
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                        uni.$u.error('v-model绑定的值必须为inactiveValue、activeValue二者之一') 
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                    } 
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                } 
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            } 
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        }, 
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        data() { 
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            return { 
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                bgColor: '#ffffff' 
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            } 
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        }, 
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        computed: { 
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            isActive(){ 
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                return this.value === this.activeValue; 
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            }, 
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            switchStyle() { 
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                let style = {} 
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                // 这里需要加2,是为了腾出边框的距离,否则圆点node会和外边框紧贴在一起 
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                style.width = uni.$u.addUnit(this.size * 2 + 2) 
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                style.height = uni.$u.addUnit(Number(this.size) + 2) 
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                // style.borderColor = this.value ? 'rgba(0, 0, 0, 0)' : 'rgba(0, 0, 0, 0.12)' 
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                // 如果自定义了“非激活”演示,name边框颜色设置为透明(跟非激活颜色一致) 
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                // 这里不能简单的设置为非激活的颜色,否则打开状态时,会有边框,所以需要透明 
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                if(this.customInactiveColor) { 
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                    style.borderColor = 'rgba(0, 0, 0, 0)' 
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                } 
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                style.backgroundColor = this.isActive ? this.activeColor : this.inactiveColor 
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                return style; 
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            }, 
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            nodeStyle() { 
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                let style = {} 
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                // 如果自定义非激活颜色,将node圆点的尺寸减少两个像素,让其与外边框距离更大一点 
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                style.width = uni.$u.addUnit(this.size - this.space) 
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                style.height = uni.$u.addUnit(this.size - this.space) 
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                const translateX = this.isActive ? uni.$u.addUnit(this.space) : uni.$u.addUnit(this.size); 
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                style.transform = `translateX(-${translateX})` 
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                return style 
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            }, 
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            bgStyle() { 
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                let style = {} 
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                // 这里配置一个多余的元素在HTML中,是为了让switch切换时,有更良好的背景色扩充体验(见实际效果) 
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                style.width = uni.$u.addUnit(Number(this.size) * 2 - this.size / 2) 
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                style.height = uni.$u.addUnit(this.size) 
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                style.backgroundColor = this.inactiveColor 
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                // 打开时,让此元素收缩,否则反之 
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                style.transform = `scale(${this.isActive ? 0 : 1})` 
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                return style 
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            }, 
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            customInactiveColor() { 
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                // 之所以需要判断是否自定义了“非激活”颜色,是为了让node圆点离外边框更宽一点的距离 
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                return this.inactiveColor !== '#fff' && this.inactiveColor !== '#ffffff' 
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            } 
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        }, 
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        methods: { 
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            clickHandler() { 
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                if (!this.disabled && !this.loading) { 
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                    const oldValue = this.isActive ? this.inactiveValue : this.activeValue 
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                    if(!this.asyncChange) { 
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                        this.$emit('input', oldValue) 
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                    } 
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                    // 放到下一个生命周期,因为双向绑定的value修改父组件状态需要时间,且是异步的 
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                    this.$nextTick(() => { 
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                        this.$emit('change', oldValue) 
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                    }) 
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                } 
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            } 
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        } 
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    }; 
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</script> 
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<style lang="scss" scoped> 
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    @import "../../libs/css/components.scss"; 
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    .u-switch { 
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        @include flex(row); 
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        /* #ifndef APP-NVUE */ 
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        box-sizing: border-box; 
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        /* #endif */ 
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        position: relative; 
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        background-color: #fff; 
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        border-width: 1px; 
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        border-radius: 100px; 
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        transition: background-color 0.4s; 
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        border-color: rgba(0, 0, 0, 0.12); 
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        border-style: solid; 
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        justify-content: flex-end; 
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        align-items: center; 
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        // 由于weex为阿里逗着玩的KPI项目,导致bug奇多,这必须要写这一行, 
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        // 否则在iOS上,点击页面任意地方,都会触发switch的点击事件 
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        overflow: hidden; 
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        &__node { 
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            @include flex(row); 
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            align-items: center; 
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            justify-content: center; 
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            border-radius: 100px; 
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            background-color: #fff; 
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            border-radius: 100px; 
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            box-shadow: 1px 1px 1px 0 rgba(0, 0, 0, 0.25); 
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            transition-property: transform; 
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            transition-duration: 0.4s; 
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            transition-timing-function: cubic-bezier(0.3, 1.05, 0.4, 1.05); 
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        } 
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        &__bg { 
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            position: absolute; 
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            border-radius: 100px; 
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            background-color: #FFFFFF; 
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            transition-property: transform; 
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            transition-duration: 0.4s; 
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            border-top-left-radius: 0; 
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            border-bottom-left-radius: 0; 
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            transition-timing-function: ease; 
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        } 
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        &--disabled { 
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            opacity: 0.6; 
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        } 
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    } 
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</style> 
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