IntersectionObserver.observe

解釋：指定目標(biāo)節(jié)點(diǎn)并開始監(jiān)聽相交狀態(tài)變化情況。

方法參數(shù)

String targetSelector, Function callback

targetSelector  參數(shù)說(shuō)明：選擇器。
callback  參數(shù)說(shuō)明：監(jiān)聽相交狀態(tài)變化的回調(diào)函數(shù)。
callback  返回參數(shù)說(shuō)明

intersectionRect 參數(shù)說(shuō)明

boundingClientRect 參數(shù)說(shuō)明

relativeRect 參數(shù)說(shuō)明

示例 

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圖片示例

代碼示例

<view class="wrap">
    <scroll-view class="scroll-view" scroll-y>
        <view class="scroll-area" style="{{appear ? 'background: #ccc' : ''}}">
            <text class="notice">向下滾動(dòng)讓小球出現(xiàn)</text>
            <!-- 占位元素 -->
            <view class="filling"></view> 
            <!-- 小球 -->
            <view class="ball"></view>
        </view>
    </scroll-view>
    <view class="list-area border-bottom">
        <view class="list-item-key-4">top:</view>
        <view class="list-item-value">{{intersectionRect.top}}</view>
    </view>
    <view class="list-area border-bottom">
        <view class="list-item-key-4">right:</view>
        <view class="list-item-value">{{intersectionRect.right}}</view>
    </view>
    <view class="list-area border-bottom">
        <view class="list-item-key-4">bottom:</view>
        <view class="list-item-value">{{intersectionRect.bottom}}</view>
    </view>
    <view class="list-area border-bottom">
        <view class="list-item-key-4">left:</view>
        <view class="list-item-value">{{intersectionRect.left}}</view>
    </view>
    <view class="list-area border-bottom">
        <view class="list-item-key-4">width</view>
        <view class="list-item-value">{{intersectionRect.width}}</view>
    </view>
    <view class="list-area border-bottom">
        <view class="list-item-key-4">height</view>
        <view class="list-item-value">{{intersectionRect.height}}</view>
    </view>
</view>

Page({
    data: {
        intersectionRect: ''
    },
    onReady() {
        swan.createIntersectionObserver(this)
            .relativeTo('.scroll-view')
            .observe('.ball', res => {
                this.setData('intersectionRect', res.intersectionRect);
                console.log(res.intersectionRect.left); // 相交區(qū)域的左邊界坐標(biāo)
                console.log(res.intersectionRect.right); // 相交區(qū)域的右邊界坐標(biāo)
                console.log(res.intersectionRect.top); // 相交區(qū)域的上邊界坐標(biāo)
                console.log(res.intersectionRect.bottom); // 相交區(qū)域的下邊界坐標(biāo)
                console.log(res.intersectionRect.width); // 相交區(qū)域的寬度
                console.log(res.intersectionRect.height); // 相交區(qū)域的高度
            });
    }
});