fix(selection-list): allow users to jump focus to a particular item by typing (#9026)

Similarly to our other listbox-based components, this allows people to move focus to a particular item by typing the first letters of its label.

Author: crisbeto

src/lib/list/list-option.html

@@ -7,10 +7,10 @@
     [matRippleTrigger]="_getHostElement()"
     [matRippleDisabled]="_isRippleDisabled()"></div>
 
-  <mat-pseudo-checkbox #autocheckbox
+  <mat-pseudo-checkbox
     [state]="selected ? 'checked' : 'unchecked'"
     [disabled]="disabled"></mat-pseudo-checkbox>
 
-  <div class="mat-list-text"><ng-content></ng-content></div>
+  <div class="mat-list-text" #text><ng-content></ng-content></div>
 
 </div>

src/lib/list/selection-list.spec.ts

@@ -1,6 +1,11 @@
 import {DOWN_ARROW, END, ENTER, HOME, SPACE, UP_ARROW} from '@angular/cdk/keycodes';
 import {Platform} from '@angular/cdk/platform';
-import {createKeyboardEvent, dispatchFakeEvent, dispatchKeyboardEvent} from '@angular/cdk/testing';
+import {
+  createKeyboardEvent,
+  dispatchFakeEvent,
+  dispatchEvent,
+  dispatchKeyboardEvent,
+} from '@angular/cdk/testing';
 import {Component, DebugElement} from '@angular/core';
 import {async, ComponentFixture, fakeAsync, inject, TestBed, tick} from '@angular/core/testing';
 import {FormControl, FormsModule, NgModel, ReactiveFormsModule} from '@angular/forms';
@@ -287,6 +292,25 @@ describe('MatSelectionList without forms', () => {
       expect(event.defaultPrevented).toBe(true);
     });
 
+    it('should be able to jump focus down to an item by typing', fakeAsync(() => {
+      const listEl = selectionList.nativeElement;
+      const manager = selectionList.componentInstance._keyManager;
+
+      expect(manager.activeItemIndex).toBe(-1);
+
+      dispatchEvent(listEl, createKeyboardEvent('keydown', 83, undefined, 's'));
+      fixture.detectChanges();
+      tick(200);
+
+      expect(manager.activeItemIndex).toBe(1);
+
+      dispatchEvent(listEl, createKeyboardEvent('keydown', 68, undefined, 'd'));
+      fixture.detectChanges();
+      tick(200);
+
+      expect(manager.activeItemIndex).toBe(3);
+    }));
+
     it('should be able to select all options', () => {
       const list: MatSelectionList = selectionList.componentInstance;
 

src/lib/list/selection-list.ts

@@ -27,6 +27,7 @@ import {
   Optional,
   Output,
   QueryList,
+  ViewChild,
   ViewEncapsulation,
 } from '@angular/core';
 import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
@@ -118,6 +119,9 @@ export class MatListOption extends _MatListOptionMixinBase
 
   @ContentChildren(MatLine) _lines: QueryList<MatLine>;
 
+  /** DOM element containing the item's text. */
+  @ViewChild('text') _text: ElementRef;
+
   /** Whether the label should appear before or after the checkbox. Defaults to 'after' */
   @Input() checkboxPosition: 'before' | 'after' = 'after';
 
@@ -197,6 +201,14 @@ export class MatListOption extends _MatListOptionMixinBase
     this._element.nativeElement.focus();
   }
 
+  /**
+   * Returns the list item's text label. Implemented as a part of the FocusKeyManager.
+   * @docs-private
+   */
+  getLabel() {
+    return this._text ? this._text.nativeElement.textContent : '';
+  }
+
   /** Whether this list item should show a ripple effect when clicked.  */
   _isRippleDisabled() {
     return this.disabled || this.disableRipple || this.selectionList.disableRipple;
@@ -309,7 +321,7 @@ export class MatSelectionList extends _MatSelectionListMixinBase implements Focu
   }
 
   ngAfterContentInit(): void {
-    this._keyManager = new FocusKeyManager<MatListOption>(this.options).withWrap();
+    this._keyManager = new FocusKeyManager<MatListOption>(this.options).withWrap().withTypeAhead();
 
     if (this._tempValues) {
       this._setOptionsFromValues(this._tempValues);