qzw_xcx/wxcomponents/dist/sticky/index.js

import { VantComponent } from '../common/component';
import { pageScrollMixin } from '../mixins/page-scroll';
const ROOT_ELEMENT = '.van-sticky';
VantComponent({
    props: {
        zIndex: {
            type: Number,
            value: 99
        },
        offsetTop: {
            type: Number,
            value: 0,
            observer: 'onScroll'
        },
        disabled: {
            type: Boolean,
            observer: 'onScroll'
        },
        container: {
            type: null,
            observer: 'onScroll'
        }
    },
    mixins: [
        pageScrollMixin(function (event) {
            this.onScroll(event);
        })
    ],
    data: {
        height: 0,
        fixed: false,
        transform: 0
    },
    mounted() {
        this.onScroll();
    },
    methods: {
        onScroll({ scrollTop } = {}) {
            const { container, offsetTop, disabled } = this.data;
            if (disabled) {
                this.setDataAfterDiff({
                    fixed: false,
                    transform: 0
                });
                return;
            }
            this.scrollTop = scrollTop || this.scrollTop;
            if (typeof container === 'function') {
                Promise.all([this.getRect(ROOT_ELEMENT), this.getContainerRect()]).then(([root, container]) => {
                    if (offsetTop + root.height > container.height + container.top) {
                        this.setDataAfterDiff({
                            fixed: false,
                            transform: container.height - root.height
                        });
                    }
                    else if (offsetTop >= root.top) {
                        this.setDataAfterDiff({
                            fixed: true,
                            height: root.height,
                            transform: 0
                        });
                    }
                    else {
                        this.setDataAfterDiff({ fixed: false, transform: 0 });
                    }
                });
                return;
            }
            this.getRect(ROOT_ELEMENT).then((root) => {
                if (offsetTop >= root.top) {
                    this.setDataAfterDiff({ fixed: true, height: root.height });
                    this.transform = 0;
                }
                else {
                    this.setDataAfterDiff({ fixed: false });
                }
            });
        },
        setDataAfterDiff(data) {
            wx.nextTick(() => {
                const diff = Object.keys(data).reduce((prev, key) => {
                    if (data[key] !== this.data[key]) {
                        prev[key] = data[key];
                    }
                    return prev;
                }, {});
                this.setData(diff);
                this.$emit('scroll', {
                    scrollTop: this.scrollTop,
                    isFixed: data.fixed || this.data.fixed
                });
            });
        },
        getContainerRect() {
            const nodesRef = this.data.container();
            return new Promise(resolve => nodesRef.boundingClientRect(resolve).exec());
        }
    }
});