index.js
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import { getRect } from '../common/utils';
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',
},
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 });
}
});
return;
}
getRect(this, 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()
);
},
},
});