@angular/cdk/scrolling#VIRTUAL_SCROLL_STRATEGY TypeScript Examples

The following examples show how to use @angular/cdk/scrolling#VIRTUAL_SCROLL_STRATEGY. You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. You may check out the related API usage on the sidebar.
Example #1
Source File: fixed-size-virtual-scroll.directive.ts    From alauda-ui with MIT License 6 votes vote down vote up 
@Directive({
  // eslint-disable-next-line @angular-eslint/directive-selector
  selector: 'aui-virtual-scroll-viewport[itemSize]',
  providers: [
    {
      provide: VIRTUAL_SCROLL_STRATEGY,
      useFactory: _fixedSizeVirtualScrollStrategyFactory,
      deps: [forwardRef(() => FixedSizeVirtualScrollDirective)],
    },
  ],
})
export class FixedSizeVirtualScrollDirective extends CdkFixedSizeVirtualScroll {}
Example #2
Source File: fixed-size-table-virtual-scroll.directive.ts    From alauda-ui with MIT License 4 votes vote down vote up 
@Directive({
  // eslint-disable-next-line @angular-eslint/directive-selector
  selector: 'aui-virtual-scroll-viewport[fixedSize]',
  exportAs: 'viewPort',
  providers: [
    {
      provide: VIRTUAL_SCROLL_STRATEGY,
      useFactory: _tableVirtualScrollDirectiveStrategyFactory,
      deps: [forwardRef(() => FixedSizeTableVirtualScrollDirective)],
    },
  ],
})
export class FixedSizeTableVirtualScrollDirective<T = unknown>
  implements AfterContentInit, OnChanges, OnDestroy
{
  private readonly onDestroy$ = new Subject();
  private readonly _dataSource$$ = new BehaviorSubject<T[]>([]);

  @Input()
  rowHeight: number = defaults.rowHeight;

  @Input()
  headerHeight: number = defaults.headerHeight;

  @Input()
  buffer: number = defaults.buffer;

  @Input()
  set dataSource(dataSource: T[]) {
    this._dataSource$$.next(dataSource);
    this.scrollStrategy.dataLength = dataSource?.length;
  }

  @ContentChild(TableComponent, { static: false })
  table: TableComponent<any>;

  scrollStrategy = new FixedSizeTableVirtualScrollStrategy();

  private stickyPositions: Map<HTMLElement, number>;

  ngAfterContentInit() {
    this.scrollStrategy.stickyChange
      .pipe(
        filter(() => this.isStickyEnabled()),
        tap(() => {
          if (!this.stickyPositions) {
            this.initStickyPositions();
          }
        }),
        takeUntil(this.onDestroy$),
      )
      .subscribe(stickyOffset => {
        this.setSticky(stickyOffset);
      });
    combineLatest([this.scrollStrategy.renderedRangeStream, this._dataSource$$])
      .pipe(
        map(([{ start, end }, dataSource]) =>
          typeof start !== 'number' || typeof end !== 'number'
            ? dataSource
            : dataSource?.slice(start, end),
        ),
        takeUntil(this.onDestroy$),
      )
      .subscribe(data => {
        this.table.dataSource = data;
      });
  }

  ngOnChanges({ rowHeight, headerHeight, buffer }: SimpleChanges) {
    if (rowHeight || headerHeight || buffer) {
      this.scrollStrategy.setConfig(
        this.rowHeight,
        this.headerHeight,
        this.buffer,
      );
    }
  }

  ngOnDestroy() {
    this.onDestroy$.next(null);
    this.onDestroy$.complete();
  }

  private isStickyEnabled(): boolean {
    return (
      !!this.scrollStrategy.viewport &&
      // @ts-expect-error
      (this.table._headerRowDefs as CdkHeaderRowDef[])
        .map(def => def.sticky)
        .reduce((prev, curr) => prev && curr, true)
    );
  }

  private initStickyPositions() {
    this.stickyPositions = new Map<HTMLElement, number>();
    this.scrollStrategy.viewport.elementRef.nativeElement
      .querySelectorAll(stickyHeaderSelector)
      .forEach(el => {
        const parent = el.parentElement;
        if (!this.stickyPositions.has(parent)) {
          this.stickyPositions.set(parent, parent.offsetTop);
        }
      });
  }

  private setSticky(offset: number) {
    this.scrollStrategy.viewport.elementRef.nativeElement
      .querySelectorAll<HTMLElement>(stickyHeaderSelector)
      .forEach(el => {
        const parent = el.parentElement;
        let baseOffset = 0;
        if (this.stickyPositions.has(parent)) {
          baseOffset = this.stickyPositions.get(parent);
        }
        el.style.top = `${baseOffset - offset}px`;
      });
  }
}