feat(checkbox): expose ripple instance (#9176)

src/lib/checkbox/checkbox.spec.ts

@@ -74,6 +74,10 @@ describe('MatCheckbox', () => {
       expect(inputElement.checked).toBe(false);
     });
 
+    it('should expose the ripple instance', () => {
+      expect(checkboxInstance.ripple).toBeTruthy();
+    });
+
     it('should add and remove indeterminate state', () => {
       expect(checkboxNativeElement.classList).not.toContain('mat-checkbox-checked');
       expect(inputElement.checked).toBe(false);

src/lib/checkbox/checkbox.ts

@@ -177,8 +177,8 @@ export class MatCheckbox extends _MatCheckboxMixinBase implements ControlValueAc
   /** The native `<input type="checkbox"> element */
   @ViewChild('input') _inputElement: ElementRef;
 
-  /** Called when the checkbox is blurred. Needed to properly implement ControlValueAccessor. */
-  @ViewChild(MatRipple) _ripple: MatRipple;
+  /** Reference to the ripple instance of the checkbox. */
+  @ViewChild(MatRipple) ripple: MatRipple;
 
   /** Ripple configuration for the mouse ripples and focus indicators. */
   _rippleConfig: RippleConfig = {centered: true, radius: 25, speedFactor: 1.5};
@@ -341,7 +341,7 @@ export class MatCheckbox extends _MatCheckboxMixinBase implements ControlValueAc
   /** Function is called whenever the focus changes for the input element. */
   private _onInputFocusChange(focusOrigin: FocusOrigin) {
     if (!this._focusRipple && focusOrigin === 'keyboard') {
-      this._focusRipple = this._ripple.launch(0, 0, {persistent: true, ...this._rippleConfig});
+      this._focusRipple = this.ripple.launch(0, 0, {persistent: true, ...this._rippleConfig});
     } else if (!focusOrigin) {
       this._removeFocusRipple();
       this.onTouched();