[Ripple] Add a convenience API for finding the ripple view in the vie…

…w's subviews.

If a ripple view is not found, a new instance of a ripple view is created.

PiperOrigin-RevId: 317610319

components/Ripple/src/MDCRippleView.h

@@ -152,4 +152,19 @@ typedef NS_ENUM(NSInteger, MDCRippleStyle) {
 - (void)beginRippleTouchUpAnimated:(BOOL)animated
                         completion:(nullable MDCRippleCompletionBlock)completion;
 
+/**
+ Enumerates the given view's subviews for an instance of MDCRippleView and returns it if found, or
+ creates and adds a new instance of MDCRippleView if not.
+
+ This method is a convenience method for adding ripple to an arbitrary view without needing to
+ subclass the target view. Use this method in situations where you expect there to be many distinct
+ ripple views in existence for a single ripple touch controller. Example scenarios include:
+
+ - Adding ripple to individual collection view/table view cells
+
+ This method can be used in your MDCRippleTouchController delegate's
+ -rippleTouchController:rippleViewAtTouchLocation: implementation.
+ */
++ (nonnull MDCRippleView *)injectedRippleViewForView:(nonnull UIView *)view;
+
 @end

components/Ripple/src/MDCRippleView.m

@@ -304,6 +304,22 @@ - (void)rippleLayerTouchUpAnimationDidEnd:(MDCRippleLayer *)rippleLayer {
   return nil;
 }
 
+#pragma mark - Convenience API
+
++ (MDCRippleView *)injectedRippleViewForView:(UIView *)view {
+  for (MDCRippleView *subview in view.subviews) {
+    if ([subview isKindOfClass:[MDCRippleView class]]) {
+      return subview;
+    }
+  }
+
+  MDCRippleView *newRippleView = [[MDCRippleView alloc] initWithFrame:view.bounds];
+  newRippleView.autoresizingMask =
+      UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
+  [view addSubview:newRippleView];
+  return newRippleView;
+}
+
 @end
 
 @implementation MDCRipplePendingAnimation

components/Ripple/tests/unit/MDCRippleViewTests.m

@@ -273,4 +273,31 @@ - (void)testTraitCollectionDidChangeBlockCalledWithExpectedParameters {
   XCTAssertEqual(passedTraitCollection, fakeTraitCollection);
 }
 
+- (void)testInjectedRippleViewFindsRippleViewInHierarchy {
+  // Given
+  UIView *parentView = [[UIView alloc] init];
+  MDCRippleView *rippleView = [[MDCRippleView alloc] init];
+  [parentView addSubview:rippleView];
+
+  // When
+  MDCRippleView *injectedRippleView = [MDCRippleView injectedRippleViewForView:parentView];
+
+  // Then
+  XCTAssertEqual(rippleView, injectedRippleView);
+}
+
+- (void)testInjectedRippleViewCreatesRippleViewInstance {
+  // Given
+  UIView *firstLevelView = [[UIView alloc] init];
+  UIView *secondLevelView = [[UIView alloc] init];
+  [firstLevelView addSubview:secondLevelView];
+
+  // When
+  MDCRippleView *injectedRippleView = [MDCRippleView injectedRippleViewForView:firstLevelView];
+
+  // Then
+  XCTAssertNotNil(injectedRippleView);
+  XCTAssertEqualObjects(injectedRippleView.superview, firstLevelView);
+}
+
 @end