[Snackbar] Add ability to set presentation host view on specific mess…

…age.

This allows finer granularity to set specific snackbar messages under certain views.

PiperOrigin-RevId: 309919536

components/Snackbar/examples/SnackbarSimpleExample.m

@@ -35,15 +35,10 @@ - (void)viewDidLoad {
         [[MDCTypographyScheme alloc] initWithDefaults:MDCTypographySchemeDefaultsMaterial201804];
   }
   [self setupExampleViews:@[
-    @"Simple Snackbar",
-    @"Snackbar with Action Button",
-    @"Snackbar with Long Text",
-    @"Attributed Text Example",
-    @"Color Themed Snackbar",
-    @"Customize Font Example",
-    @"De-Customize Example",
-    @"Customized Message Using Block",
-    @"Non Transient Snackbar",
+    @"Simple Snackbar", @"Snackbar with Action Button", @"Snackbar with Long Text",
+    @"Attributed Text Example", @"Color Themed Snackbar", @"Customize Font Example",
+    @"De-Customize Example", @"Customized Message Using Block", @"Non Transient Snackbar",
+    @"Snackbar Presented On Custom View"
   ]];
   self.title = @"Snackbar";
   _legacyMode = YES;
@@ -204,6 +199,14 @@ - (void)showNonTransientSnackbar:(id)sender {
   [MDCSnackbarManager showMessage:message];
 }
 
+- (void)showSimpleSnackbarOnCustomPresentationHostView:(id)sender {
+  MDCSnackbarMessage *message = [[MDCSnackbarMessage alloc] init];
+  message.text = @"Snackbar Message";
+  message.focusOnShow = YES;
+  message.presentationHostViewOverride = self.collectionView;
+  [MDCSnackbarManager showMessage:message];
+}
+
 #pragma mark - UICollectionView
 
 - (void)collectionView:(UICollectionView *)collectionView
@@ -237,6 +240,9 @@ - (void)collectionView:(UICollectionView *)collectionView
     case 8:
       [self showNonTransientSnackbar:nil];
       break;
+    case 9:
+      [self showSimpleSnackbarOnCustomPresentationHostView:nil];
+      break;
     default:
       break;
   }

components/Snackbar/src/MDCSnackbarManager.m

@@ -237,7 +237,7 @@ - (void)displaySnackbarViewForMessage:(MDCSnackbarMessage *)message {
   self.currentSnackbar = snackbarView;
   self.overlayView.accessibilityViewIsModal = snackbarView.accessibilityViewIsModal;
   self.overlayView.hidden = NO;
-  [self activateOverlay:self.overlayView];
+  [self activateOverlay:self.overlayView forMessage:message];
 
   // Once the Snackbar has finished animating on screen, start the automatic dismiss timeout, but
   // only if the user isn't running VoiceOver.
@@ -349,11 +349,13 @@ - (BOOL)isSnackbarTransient:(MDCSnackbarMessageView *)snackbarView {
 
 #pragma mark - Overlay Activation
 
-- (void)activateOverlay:(UIView *)overlay {
+- (void)activateOverlay:(UIView *)overlay forMessage:(MDCSnackbarMessage *)message {
   UIWindow *window = [self bestGuessWindow];
   UIView *targetView = nil;
 
-  if (self.presentationHostView) {
+  if (message.presentationHostViewOverride) {
+    targetView = message.presentationHostViewOverride;
+  } else if (self.presentationHostView) {
     targetView = self.presentationHostView;
   } else if ([window isKindOfClass:[MDCOverlayWindow class]]) {
     // If the application's window is an overlay window, take advantage of it. Otherwise, just add

components/Snackbar/src/MDCSnackbarMessage.h

@@ -198,6 +198,18 @@ extern NSString *__nonnull const MDCSnackbarMessageBoldAttributeName;
  */
 @property(nonatomic) BOOL automaticallyDismisses;
 
+/**
+ MDCSnackbarManager will display the snackbar message in this view.
+
+ Call this method to choose where in the view hierarchy this specific snackbar message will be
+ presented. This method should be called only in cases where the default behavior is unable to find
+ the correct view to place the snackbar message in. Furthermore, please set this property only if
+ this message is a special case and needs to be presented on a view different than the other
+ messages of this specific snackbar manager. Otherwise, please set the presentation host view by
+ using MDCSnackbarManager's @c setPresentationHostView.
+ */
+@property(nonatomic, weak, nullable) UIView *presentationHostViewOverride;
+
 @end
 
 /**

components/Snackbar/src/MDCSnackbarMessage.m

@@ -74,6 +74,7 @@ - (instancetype)copyWithZone:(__unused NSZone *)zone {
   copy.focusOnShow = self.focusOnShow;
   copy.elementToFocusOnDismiss = self.elementToFocusOnDismiss;
   copy.automaticallyDismisses = self.automaticallyDismisses;
+  copy.presentationHostViewOverride = self.presentationHostViewOverride;
 
   // Unfortunately there's not really a concept of 'copying' a block (in the same way you would copy
   // a string, for example). A block's pointer is immutable once it is created and copied to the

components/Snackbar/tests/unit/MDCSnackbarMessageViewTests.m

@@ -547,4 +547,24 @@ - (void)testSnackbarDidDisappearDelegateCalled {
   [self waitForExpectationsWithTimeout:3 handler:nil];
 }
 
+- (void)testSettingPresentationHostViewOverrideDisplaysSnackbarInCorrectView {
+  // Given
+  UIView *customView = [[UIView alloc] init];
+  self.message.presentationHostViewOverride = customView;
+
+  // When
+  [self.manager showMessage:self.message];
+  XCTestExpectation *expectation = [self expectationWithDescription:@"completed"];
+  dispatch_time_t popTime =
+      dispatch_time(DISPATCH_TIME_NOW, (int64_t)((CGFloat)0.1 * NSEC_PER_SEC));
+  dispatch_after(popTime, dispatch_get_main_queue(), ^{
+    [expectation fulfill];
+  });
+  [self waitForExpectationsWithTimeout:3 handler:nil];
+
+  // Then
+  XCTAssertTrue([customView.subviews count] > 0);
+  XCTAssertEqual([customView.subviews.firstObject class], [MDCSnackbarOverlayView class]);
+}
+
 @end