【报Bug】uni-swiper-list 中 header高度过高（满足swiper初始状态在屏外的高度） 引发的问题

示例代码：

<template>  
    <list :id="pageId" class="page" :bounce="false" fixFreezing="true">  
        <cell>  
            <view id="head" class="header"><text class="header-title">header</text></view>  
        </cell>  
        <cell>  
            <view class="tabs" :style="'height:' + pageHeight + 'px'">  
                <scroll-view  
                    ref="tabbar1"  
                    id="tab-bar"  
                    class="tab-bar"  
                    :scroll="false"  
                    :scroll-x="true"  
                    :show-scrollbar="false"  
                    :scroll-into-view="scrollInto"  
                >  
                    <view style="flex-direction: column;">  
                        <view style="flex-direction: row;">  
                            <view  
                                class="uni-tab-item"  
                                v-for="(tab, index) in tabList"  
                                :key="tab.id"  
                                :id="tab.id"  
                                :ref="'tabitem' + index"  
                                :data-id="index"  
                                :data-current="index"  
                                @click="ontabtap"  
                            >  
                                <text class="uni-tab-item-title" :class="tabIndex == index ? 'uni-tab-item-title-active' : ''">{{ tab.name }}</text>  
                            </view>  
                        </view>  
                        <view class="scroll-view-indicator">  
                            <view  
                                ref="underline"  
                                class="scroll-view-underline"  
                                :class="isTap ? 'scroll-view-animation' : ''"  
                                :style="{ left: indicatorLineLeft + 'px', width: indicatorLineWidth + 'px' }"  
                            ></view>  
                        </view>  
                    </view>  
                </scroll-view>  
                <view class="tab-bar-line"></view>  
                <swiper  
                    class="tab-view"  
                    id="tab-bar-view"  
                    :current="tabIndex"  
                    :duration="300"  
                    @change="onswiperchange"  
                    @transition="onswiperscroll"  
                    @animationfinish="animationfinish"  
                    @onAnimationEnd="animationfinish"  
                >  
                    <swiper-item class="swiper-item" v-for="(page, index) in tabList" :key="index">  
                        <swiper-page class="swiper-page" :pid="page.pageid" :parentId="pageId" ref="page"></swiper-page>  
                    </swiper-item>  
                </swiper>  
            </view>  
        </cell>  
    </list>  
</template>  

<script>  
// #ifdef APP-PLUS  
const dom = weex.requireModule('dom');  
// #endif  

// 缓存每页最多  
const MAX_CACHE_DATA = 100;  

// 缓存页签数量  
const MAX_CACHE_PAGE = 3;  
const TAB_PRELOAD_OFFSET = 1;  

import swiperPage from './swiper-page.nvue';  

export default {  
    components: {  
        swiperPage  
    },  
    data() {  
        return {  
            tabList: [],  
            tabIndex: 0,  
            cacheTab: [],  
            scrollInto: '',  
            indicatorLineLeft: 0,  
            indicatorLineWidth: 0,  
            isTap: false,  
            showTitleView: true,  
            pageHeight: 300,  
            pageId: 'page'  
        };  
    },  
    onLoad() {  
        for (var i = 0; i < 6; i++) {  
            this.tabList.push({  
                id: 'tab' + i,  
                name: 'Tab ' + (i + 1),  
                pageid: i + 1  
            });  
        }  
    },  
    onReady() {  
        this.pageHeight = uni.getSystemInfoSync().windowHeight;  
        this._lastTabIndex = 0;  
        this._touchTabIndex = 0;  
        this._headHeight = 100;  
        this.swiperWidth = 0;  
        this.tabbarWidth = 0;  
        this.tabListSize = {};  

        this.pageList = this.$refs.page;  
        this.selectorQuery();  
    },  
    methods: {  
        ontabtap(e) {  
            let index = e.target.dataset.current || e.currentTarget.dataset.current;  
            //let offsetIndex = this._touchTabIndex = Math.abs(index - this._lastTabIndex) > 1;  

            // #ifdef APP-PLUS || H5 || MP-WEIXIN || MP-QQ  
            this.isTap = true;  
            var currentSize = this.tabListSize[index];  
            this.updateIndicator(currentSize.left, currentSize.width);  
            this._touchTabIndex = index;  
            // #endif  

            this.switchTab(index);  
        },  
        onswiperchange(e) {  
            // 注意：百度小程序会触发2次  
            console.log(e);  
            // #ifndef APP-PLUS || H5 || MP-WEIXIN || MP-QQ  
            let index = e.target.current || e.detail.current;  
            this.switchTab(index);  
            // #endif  
        },  
        onswiperscroll(e) {  
            if (this.isTap) {  
                return;  
            }  

            var offsetX = e.detail.dx;  
            var preloadIndex = this._lastTabIndex;  
            if (offsetX > TAB_PRELOAD_OFFSET) {  
                preloadIndex++;  
            } else if (offsetX < -TAB_PRELOAD_OFFSET) {  
                preloadIndex--;  
            }  
            if (preloadIndex === this._lastTabIndex || preloadIndex < 0 || preloadIndex > this.pageList.length - 1) {  
                return;  
            }  
            if (this.pageList[preloadIndex].dataList.length === 0) {  
                this.loadTabData(preloadIndex);  
            }  

            // #ifdef APP-PLUS || H5 || MP-WEIXIN || MP-QQ  
            var percentage = Math.abs(this.swiperWidth / offsetX);  
            var currentSize = this.tabListSize[this._lastTabIndex];  
            var preloadSize = this.tabListSize[preloadIndex];  
            var lineL = currentSize.left + (preloadSize.left - currentSize.left) / percentage;  
            var lineW = currentSize.width + (preloadSize.width - currentSize.width) / percentage;  
            this.updateIndicator(lineL, lineW);  
            // #endif  
        },  
        animationfinish(e) {  
            // #ifdef APP-PLUS || H5 || MP-WEIXIN || MP-QQ  
            let index = e.detail.current;  
            if (this._touchTabIndex === index) {  
                this.isTap = false;  
            }  
            this._lastTabIndex = index;  
            this.switchTab(index);  
            this.updateIndicator(this.tabListSize[index].left, this.tabListSize[index].width);  
            // #endif  
        },  
        selectorQuery() {  
            // #ifdef APP-NVUE  
            uni.createSelectorQuery()  
                .in(this)  
                .select('#head')  
                .boundingClientRect()  
                .exec(rect => {  
                    this._headHeight = rect[0].height;  
                });  

            // 查询 tabbar 宽度  
            uni.createSelectorQuery()  
                .in(this)  
                .select('#tab-bar')  
                .boundingClientRect()  
                .exec(rect => {  
                    this.tabbarWidth = rect[0].width;  
                });  
            // 查询 tabview 宽度  
            uni.createSelectorQuery()  
                .in(this)  
                .select('#tab-bar-view')  
                .boundingClientRect()  
                .exec(rect => {  
                    this.swiperWidth = rect[0].width;  
                });  

            // 因 nvue 暂不支持 class 查询  
            var queryTabSize = uni.createSelectorQuery().in(this);  
            for (var i = 0; i < this.tabList.length; i++) {  
                queryTabSize.select('#' + this.tabList[i].id).boundingClientRect();  
            }  
            queryTabSize.exec(rects => {  
                rects.forEach(rect => {  
                    this.tabListSize[rect.dataset.id] = rect;  
                });  
                this.updateIndicator(this.tabListSize[this.tabIndex].left, this.tabListSize[this.tabIndex].width);  
                this.switchTab(this.tabIndex);  
            });  
            // #endif  

            // #ifdef MP-WEIXIN || H5 || MP-QQ  
            uni.createSelectorQuery()  
                .in(this)  
                .select('.tab-view')  
                .fields(  
                    {  
                        dataset: true,  
                        size: true  
                    },  
                    res => {  
                        this.swiperWidth = res.width;  
                    }  
                )  
                .exec();  
            uni.createSelectorQuery()  
                .in(this)  
                .selectAll('.uni-tab-item')  
                .boundingClientRect(rects => {  
                    rects.forEach(rect => {  
                        this.tabListSize[rect.dataset.id] = rect;  
                    });  
                    this.updateIndicator(this.tabListSize[this.tabIndex].left, this.tabListSize[this.tabIndex].width);  
                })  
                .exec();  
            // #endif  
        },  
        updateIndicator(left, width) {  
            this.indicatorLineLeft = left;  
            this.indicatorLineWidth = width;  
        },  
        switchTab(index) {  
            if (this.pageList[index].dataList.length === 0) {  
                this.loadTabData(index);  
            }  

            this.pageList[index].setScrollRef(this._headHeight);  

            if (this.tabIndex === index) {  
                return;  
            }  

            // 缓存 tabId  
            if (this.pageList[this.tabIndex].dataList.length > MAX_CACHE_DATA) {  
                let isExist = this.cacheTab.indexOf(this.tabIndex);  
                if (isExist < 0) {  
                    this.cacheTab.push(this.tabIndex);  
                }  
            }  

            this.tabIndex = index;  

            // #ifdef APP-NVUE  
            this.scrollTabTo(index);  
            // #endif  
            // #ifndef APP-NVUE  
            this.scrollInto = this.tabList[index].id;  
            // #endif  

            // 释放 tabId  
            if (this.cacheTab.length > MAX_CACHE_PAGE) {  
                let cacheIndex = this.cacheTab[0];  
                this.clearTabData(cacheIndex);  
                this.cacheTab.splice(0, 1);  
            }  
        },  
        scrollTabTo(index) {  
            const el = this.$refs['tabitem' + index][0];  
            let offset = 0;  
            // TODO fix ios offset  
            if (index > 0) {  
                offset = this.tabbarWidth / 2 - this.tabListSize[index].width / 2;  
                if (this.tabListSize[index].right < this.tabbarWidth / 2) {  
                    offset = this.tabListSize[0].width;  
                }  
            }  
            dom.scrollToElement(el, {  
                offset: -offset  
            });  
        },  
        loadTabData(index) {  
            this.pageList[index].loadData();  
        },  
        clearTabData(index) {  
            this.pageList[index].clear();  
        }  
    }  
};  
</script>  

<style>  
/* #ifndef APP-PLUS */  
page {  
    width: 100%;  
    min-height: 100%;  
    display: flex;  
}  

/* #endif */  

.page {  
    flex: 1;  
}  

.header {  
    height: 828px;  
    flex-direction: row;  
    align-items: center;  
    justify-content: center;  
    background-color: #f4f4f4;  
}  

.header-title {  
    font-size: 30px;  
    font-weight: bold;  
    color: #444;  
}  

.flexible-view {  
    background-color: #f823ff;  
}  

.page-head {  
    height: 200px;  
    flex-direction: column;  
    align-items: center;  
    justify-content: center;  
    background-color: red;  
}  

.tabs {  
    flex-direction: column;  
    overflow: hidden;  
    background-color: #ffffff;  
    /* #ifdef MP-ALIPAY || MP-BAIDU */  
    height: 100vh;  
    /* #endif */  
}  

.tab-bar {  
    width: 750upx;  
    height: 84upx;  
    flex-direction: row;  
    /* #ifndef APP-PLUS */  
    white-space: nowrap;  
    /* #endif */  
}  

/* #ifndef APP-NVUE */  
.tab-bar ::-webkit-scrollbar {  
    display: none;  
    width: 0 !important;  
    height: 0 !important;  
    -webkit-appearance: none;  
    background: transparent;  
}  

/* #endif */  

.scroll-view-indicator {  
    position: relative;  
    height: 2px;  
    background-color: transparent;  
}  

.scroll-view-underline {  
    position: absolute;  
    top: 0;  
    bottom: 0;  
    width: 0;  
    background-color: #007aff;  
}  

.scroll-view-animation {  
    transition-duration: 0.2s;  
    transition-property: left;  
}  

.tab-bar-line {  
    height: 1upx;  
    background-color: #cccccc;  
}  

.tab-view {  
    flex: 1;  
}  

.uni-tab-item {  
    /* #ifndef APP-PLUS */  
    display: inline-block;  
    /* #endif */  
    flex-wrap: nowrap;  
    padding-left: 25px;  
    padding-right: 25px;  
}  

.uni-tab-item-title {  
    color: #555;  
    font-size: 30upx;  
    height: 80upx;  
    line-height: 80upx;  
    flex-wrap: nowrap;  
    /* #ifndef APP-PLUS */  
    white-space: nowrap;  
    /* #endif */  
}  

.uni-tab-item-title-active {  
    color: #007aff;  
}  

.swiper-item {  
    flex: 1;  
    flex-direction: column;  
}  

.swiper-page {  
    flex: 1;  
    flex-direction: row;  
    position: absolute;  
    left: 0;  
    top: 0;  
    right: 0;  
    bottom: 0;  
}  
</style>  

操作步骤：

1、修改.header样式的高度：height: 828px （满足swiper初始状态在屏外的高度即可）
2、滚动到swiper且开始header置顶
3、用手滑动swiper到第二页，然后回到滑动到list顶部（swiper已在屏外）
4、重新滑到swiper且开始header置顶，这时滑动swiper，却发现swiper处于第一页（应该是之前滑动到的第二页才对）

预期结果：

swiper应该还是处于第二页

实际结果：

swiper处于第一页