[iOS] Ensure the keyboard bottom inset is zero when keyboard dismiss. (flutter#31982)

Author: luckysmg

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -1180,8 +1180,30 @@ - (void)keyboardWillChangeFrame:(NSNotification*)notification {
 }
 
 - (void)keyboardWillBeHidden:(NSNotification*)notification {
-  // When keyboard hide, the keyboardWillChangeFrame function will be called to update viewport
-  // metrics. So do not call [self updateViewportMetrics] here again.
+  NSDictionary* info = [notification userInfo];
+
+  if (@available(iOS 9, *)) {
+    // Ignore keyboard notifications related to other apps.
+    id isLocal = info[UIKeyboardIsLocalUserInfoKey];
+    if (isLocal && ![isLocal boolValue]) {
+      return;
+    }
+  }
+
+  // Ignore keyboard notifications if engine’s viewController is not current viewController.
+  if ([_engine.get() viewController] != self) {
+    return;
+  }
+
+  if (self.targetViewInsetBottom != 0) {
+    // Ensure the keyboard will be dismissed. Just like the keyboardWillChangeFrame,
+    // keyboardWillBeHidden is also in an animation block in iOS sdk, so we don't need to set the
+    // animation curve. Related issue: https://github.com/flutter/flutter/issues/99951
+    self.targetViewInsetBottom = 0;
+    NSTimeInterval duration =
+        [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
+    [self startKeyBoardAnimation:duration];
+  }
 }
 
 - (void)startKeyBoardAnimation:(NSTimeInterval)duration {

shell/platform/darwin/ios/framework/Source/FlutterViewControllerTest.mm

@@ -125,6 +125,9 @@ @interface FlutterEmbedderKeyResponder (Tests)
 @end
 
 @interface FlutterViewController (Tests)
+
+@property(nonatomic, assign) double targetViewInsetBottom;
+
 - (void)surfaceUpdated:(BOOL)appeared;
 - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences;
 - (void)handlePressEvent:(FlutterUIPressProxy*)press
@@ -135,6 +138,7 @@ - (void)onUserSettingsChanged:(NSNotification*)notification;
 - (void)applicationWillTerminate:(NSNotification*)notification;
 - (void)goToApplicationLifecycle:(nonnull NSString*)state;
 - (void)keyboardWillChangeFrame:(NSNotification*)notification;
+- (void)keyboardWillBeHidden:(NSNotification*)notification;
 - (void)startKeyBoardAnimation:(NSTimeInterval)duration;
 - (void)ensureViewportMetricsIsCorrect;
 - (void)invalidateDisplayLink;
@@ -198,6 +202,30 @@ - (void)testkeyboardWillChangeFrameWillStartKeyboardAnimation {
   [self waitForExpectationsWithTimeout:5.0 handler:nil];
 }
 
+- (void)testEnsureBottomInsetIsZeroWhenKeyboardDismissed {
+  FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
+  [mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];
+  FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:mockEngine
+                                                                                nibName:nil
+                                                                                 bundle:nil];
+
+  FlutterViewController* viewControllerMock = OCMPartialMock(viewController);
+  CGRect keyboardFrame = CGRectMake(0, 0, 0, 0);
+  BOOL isLocal = YES;
+  NSNotification* fakeNotification = [NSNotification
+      notificationWithName:@""
+                    object:nil
+                  userInfo:@{
+                    @"UIKeyboardFrameEndUserInfoKey" : [NSValue valueWithCGRect:keyboardFrame],
+                    @"UIKeyboardAnimationDurationUserInfoKey" : @(0.25),
+                    @"UIKeyboardIsLocalUserInfoKey" : @(isLocal)
+                  }];
+
+  viewControllerMock.targetViewInsetBottom = 10;
+  [viewControllerMock keyboardWillBeHidden:fakeNotification];
+  XCTAssertTrue(viewControllerMock.targetViewInsetBottom == 0);
+}
+
 - (void)testEnsureViewportMetricsWillInvokeAndDisplayLinkWillInvalidateInViewDidDisappear {
   FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
   [mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];