There are two separate systems trying to manage touch events on the MDCButton. First, the button itself uses its standard UIControl event infrastructure to trigger ink ripples. Second, an external MDCInkTouchController attaches its own gesture recognizers to do the same thing. This creates a conflict where both systems respond to the same touch, causing two ink animations to be created and displayed simultaneously, which results in incorrect visual feedback.

PiperOrigin-RevId: 770704081

Author: Nobody

components/Ink/src/MDCInkView.m

@@ -43,7 +43,9 @@ @interface MDCInkView () <CALayerDelegate, MDCInkLayerDelegate, MDCLegacyInkLaye
 
 @end
 
-@implementation MDCInkView
+@implementation MDCInkView {
+  BOOL _isActiveInkLayerAnimationRunning;
+}
 
 + (Class)layerClass {
   return [MDCLegacyInkLayer class];
@@ -179,6 +181,13 @@ - (void)startTouchBeganAtPoint:(CGPoint)point
   if (self.usesLegacyInkRipple) {
     [self.inkLayer spreadFromPoint:point completion:completionBlock];
   } else {
+    @synchronized(self) {
+      if (animated && _isActiveInkLayerAnimationRunning) {
+        // Only one ink layer animation can be running at a time.
+        return;
+      }
+      _isActiveInkLayerAnimationRunning = YES;
+    }
     self.startInkRippleCompletionBlock = completionBlock;
     MDCInkLayer *inkLayer = [MDCInkLayer layer];
     inkLayer.inkColor = self.inkColor;
@@ -277,6 +286,14 @@ - (void)inkLayerAnimationDidStart:(MDCInkLayer *)inkLayer {
   }
 }
 
+- (void)inkLayerStartAnimationDidFinish:(MDCInkLayer *)inkLayer {
+  @synchronized(self) {
+    if (self.activeInkLayer == inkLayer && _isActiveInkLayerAnimationRunning) {
+      _isActiveInkLayerAnimationRunning = NO;
+    }
+  }
+}
+
 - (void)inkLayerAnimationDidEnd:(MDCInkLayer *)inkLayer {
   if (self.activeInkLayer == inkLayer && self.endInkRippleCompletionBlock) {
     self.endInkRippleCompletionBlock();

components/Ink/src/private/MDCInkLayer.m

@@ -165,6 +165,9 @@ - (void)startInkAtPoint:(CGPoint)point animated:(BOOL)animated {
     animGroup.removedOnCompletion = NO;
     [CATransaction setCompletionBlock:^{
       self->_startAnimationActive = NO;
+      if ([self.animationDelegate respondsToSelector:@selector(inkLayerStartAnimationDidFinish:)]) {
+        [self.animationDelegate inkLayerStartAnimationDidFinish:self];
+      }
     }];
     [self addAnimation:animGroup forKey:nil];
     [CATransaction commit];

components/Ink/src/private/MDCInkLayerDelegate.h

@@ -38,6 +38,12 @@ NS_SWIFT_UI_ACTOR
  */
 - (void)inkLayerAnimationDidStart:(nonnull MDCInkLayer *)inkLayer;
 
+/**
+ Called when the ink ripple appearing animation: scale up, reposition and fade in animation,
+ finishes.
+ */
+- (void)inkLayerStartAnimationDidFinish:(nonnull MDCInkLayer *)inkLayer;
+
 /**
  Called when the ink ripple animation ends.
 

components/Ink/tests/unit/MDCInkViewTests.m

@@ -164,4 +164,23 @@ - (void)testInkViewLayerDoesntMaskToBoundsWithInkStyleUnbounded {
   XCTAssertFalse(masksToBoundsWhenUnbounded);
 }
 
+- (void)testStartTouchBeganAtPointAddsInkLayerWithAnimationIsIdempotent {
+  // Given
+  MDCInkView *testInkView = [[MDCInkView alloc] init];
+  testInkView.usesLegacyInkRipple = NO;
+
+  // Verifies that only one ink animation layer is added, even with concurrent triggers.
+  // The initial sublayer count is 1 due to the button's default shape-drawing layer.
+  // After adding the ink layer via startTouchBeganAtPoint:, the count must be 2.
+  // This assertion ensures subsequent calls do not erroneously add more layers.
+  [testInkView startTouchBeganAtPoint:CGPointZero animated:YES withCompletion:nil];
+  [testInkView startTouchBeganAtPoint:CGPointZero animated:YES withCompletion:nil];
+
+  XCTAssertEqual(testInkView.layer.sublayers.count, 2);
+
+  // Verifies that the ink layer is removed when cancelAllAnimationsAnimated:NO is called.
+  [testInkView cancelAllAnimationsAnimated:NO];
+  XCTAssertEqual(testInkView.layer.sublayers.count, 1);
+}
+
 @end