fangliaoxiaochengxv/wxcomponents/vant/dist/sticky/index.js

import {getRect} from '../common/utils';
import {VantComponent} from '../common/component';
import {isDef} from '../common/validator';
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',
        },
        scrollTop: {
            type: null,
            observer(val) {
                this.onScroll({scrollTop: val});
            },
        },
    },
    mixins: [
        pageScrollMixin(function (event) {
            if (this.data.scrollTop != null) {
                return;
            }
            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([getRect(this, 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});
                        }
                    })
                    .catch(() => {
                    });
                return;
            }
            getRect(this, ROOT_ELEMENT).then((root) => {
                if (!isDef(root) || (!root.width && !root.height)) {
                    return;
                }
                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;
                }, {});
                if (Object.keys(diff).length > 0) {
                    this.setData(diff);
                }
                this.$emit('scroll', {
                    scrollTop: this.scrollTop,
                    isFixed: data.fixed || this.data.fixed,
                });
            });
        },
        getContainerRect() {
            const nodesRef = this.data.container();
            if (!nodesRef) {
                return Promise.reject(new Error('not found container'));
            }
            return new Promise((resolve) => nodesRef.boundingClientRect(resolve).exec());
        },
    },
});