]>
Commit | Line | Data |
---|---|---|
1 | import { distinct, distinctUntilChanged, filter, map, share, startWith, throttleTime } from 'rxjs/operators' | |
2 | import { Directive, ElementRef, EventEmitter, Input, OnDestroy, OnInit, Output } from '@angular/core' | |
3 | import { fromEvent, Subscription } from 'rxjs' | |
4 | ||
5 | @Directive({ | |
6 | selector: '[myInfiniteScroller]' | |
7 | }) | |
8 | export class InfiniteScrollerDirective implements OnInit, OnDestroy { | |
9 | @Input() containerHeight: number | |
10 | @Input() pageHeight: number | |
11 | @Input() firstLoadedPage = 1 | |
12 | @Input() percentLimit = 70 | |
13 | @Input() autoInit = false | |
14 | @Input() onItself = false | |
15 | ||
16 | @Output() nearOfBottom = new EventEmitter<void>() | |
17 | @Output() nearOfTop = new EventEmitter<void>() | |
18 | @Output() pageChanged = new EventEmitter<number>() | |
19 | ||
20 | private decimalLimit = 0 | |
21 | private lastCurrentBottom = -1 | |
22 | private lastCurrentTop = 0 | |
23 | private scrollDownSub: Subscription | |
24 | private scrollUpSub: Subscription | |
25 | private pageChangeSub: Subscription | |
26 | private middleScreen: number | |
27 | private container: HTMLElement | |
28 | ||
29 | constructor (private el: ElementRef) { | |
30 | this.decimalLimit = this.percentLimit / 100 | |
31 | } | |
32 | ||
33 | ngOnInit () { | |
34 | if (this.autoInit === true) return this.initialize() | |
35 | } | |
36 | ||
37 | ngOnDestroy () { | |
38 | if (this.scrollDownSub) this.scrollDownSub.unsubscribe() | |
39 | if (this.scrollUpSub) this.scrollUpSub.unsubscribe() | |
40 | if (this.pageChangeSub) this.pageChangeSub.unsubscribe() | |
41 | } | |
42 | ||
43 | initialize () { | |
44 | if (this.onItself) { | |
45 | this.container = this.el.nativeElement | |
46 | } | |
47 | ||
48 | this.middleScreen = window.innerHeight / 2 | |
49 | ||
50 | // Emit the last value | |
51 | const throttleOptions = { leading: true, trailing: true } | |
52 | ||
53 | const scrollObservable = fromEvent(this.container || window, 'scroll') | |
54 | .pipe( | |
55 | startWith(null), | |
56 | throttleTime(200, undefined, throttleOptions), | |
57 | map(() => this.getScrollInfo()), | |
58 | distinctUntilChanged((o1, o2) => o1.current === o2.current), | |
59 | share() | |
60 | ) | |
61 | ||
62 | // Scroll Down | |
63 | this.scrollDownSub = scrollObservable | |
64 | .pipe( | |
65 | // Check we scroll down | |
66 | filter(({ current }) => { | |
67 | const res = this.lastCurrentBottom < current | |
68 | ||
69 | this.lastCurrentBottom = current | |
70 | return res | |
71 | }), | |
72 | filter(({ current, maximumScroll }) => maximumScroll <= 0 || (current / maximumScroll) > this.decimalLimit) | |
73 | ) | |
74 | .subscribe(() => this.nearOfBottom.emit()) | |
75 | ||
76 | // Scroll up | |
77 | this.scrollUpSub = scrollObservable | |
78 | .pipe( | |
79 | // Check we scroll up | |
80 | filter(({ current }) => { | |
81 | const res = this.lastCurrentTop > current | |
82 | ||
83 | this.lastCurrentTop = current | |
84 | return res | |
85 | }), | |
86 | filter(({ current, maximumScroll }) => { | |
87 | return current !== 0 && (1 - (current / maximumScroll)) > this.decimalLimit | |
88 | }) | |
89 | ) | |
90 | .subscribe(() => this.nearOfTop.emit()) | |
91 | ||
92 | // Page change | |
93 | this.pageChangeSub = scrollObservable | |
94 | .pipe( | |
95 | distinct(), | |
96 | map(({ current }) => this.calculateCurrentPage(current)), | |
97 | distinctUntilChanged() | |
98 | ) | |
99 | .subscribe(res => this.pageChanged.emit(res)) | |
100 | } | |
101 | ||
102 | private calculateCurrentPage (current: number) { | |
103 | const scrollY = current + this.middleScreen | |
104 | ||
105 | const page = Math.max(1, Math.ceil(scrollY / this.pageHeight)) | |
106 | ||
107 | // Offset page | |
108 | return page + (this.firstLoadedPage - 1) | |
109 | } | |
110 | ||
111 | private getScrollInfo () { | |
112 | if (this.container) { | |
113 | return { current: this.container.scrollTop, maximumScroll: this.container.scrollHeight } | |
114 | } | |
115 | ||
116 | return { current: window.scrollY, maximumScroll: document.body.clientHeight - window.innerHeight } | |
117 | } | |
118 | } |