Default sorting in Angular Material - Sort header

问题:

How can I change Angular Material code below, so that data-table is sorted by 'name' column, ascending order by default. Arrow (indicating current sort direction) must be displayed.

This is what I want to achieve:

Original code:

<table matSort (matSortChange)="sortData($event)">
  <tr>
    <th mat-sort-header="name">Dessert (100g)</th>
    <th mat-sort-header="calories">Calories</th>
    <th mat-sort-header="fat">Fat (g)</th>
    <th mat-sort-header="carbs">Carbs (g)</th>
    <th mat-sort-header="protein">Protein (g)</th>
  </tr>

  <tr *ngFor="let dessert of sortedData">
    <td>{{dessert.name}}</td>
    <td>{{dessert.calories}}</td>
    <td>{{dessert.fat}}</td>
    <td>{{dessert.carbs}}</td>
    <td>{{dessert.protein}}</td>
  </tr>
</table>

I was trying something like this, but it doesn't work (no arrow displayed, not sorted)

<table matSort (matSortChange)="sortData($event)" matSortActive="name" matSortStart="asc" matSortDisableClear>

Here's link to Plunker

回答1:

You're mistaking matSortStart for matSortDirection.

Try this:

<table matSort (matSortChange)="sortData($event)" matSortActive="name" matSortDirection="asc" matSortDisableClear>

https://plnkr.co/edit/sg0hC5d8LTjLKhbH9Eug?p=preview

matSortStart can be used to reverse the cycle used when sort (e.g. when the user clicks to sort, it starts at desc instead of asc).

回答2:

You can programmatically sort the table by invoking the sort(Sortable) method of the data source. Assuming you've got a dataSource component property for the data source:

// to put next to the class fields of the component
@ViewChild(MatSort) sort: MatSort

// to put where you want the sort to be programmatically triggered, for example inside ngOnInit
this.sort.sort(({ id: 'name', start: 'asc'}) as MatSortable);
this.dataSource.sort = this.sort;

回答3:

@ViewChild(MatSort) sort: MatSort;

this.dataSource.sort = this.sort;

const sortState: Sort = {active: 'name', direction: 'desc'};
this.sort.active = sortState.active;
this.sort.direction = sortState.direction;
this.sort.sortChange.emit(sortState);

should work. demo

And to show sorting direction arrow, add next css (workaround)

th.mat-header-cell .mat-sort-header-container.mat-sort-header-sorted .mat-sort-header-arrow {
    opacity: 1 !important;
    transform: translateY(0) !important;
}

回答4:

Update for Material (tested with v7.3):

@ViewChild(MatSort) matSort: MatSort;

private someMethod(): void {
  this.matSort.sort({ id: 'columnName', start: 'asc', disableClear: false });
}

This will also update the mat-sort-header's arrow without any workaround

回答5:

Maybe have you tried to call on the init of the page the sort function forced on name and direction?

     ngOnInit() {
    let defSort: Sort = {};
    defSort.direction = 'asc';
    defSort.active = 'name';
    this.sortData(defSort);
  }