use null aware operators for function invocations (#79049)

dev/integration_tests/flutter_gallery/lib/demo/shrine/category_menu_page.dart

@@ -25,9 +25,7 @@ class CategoryMenuPage extends StatelessWidget {
           GestureDetector(
             onTap: () {
               model.setCategory(category);
-              if (onCategoryTap != null) {
+              onCategoryTap?.call();
-                onCategoryTap!();
-              }
             },
             child: model.selectedCategory == category
               ? Column(

dev/integration_tests/flutter_gallery/lib/demo/transformations/transformations_demo_color_picker.dart

@@ -27,9 +27,7 @@ class ColorPicker extends StatelessWidget {
           color: color,
           selected: color == selectedColor,
           onTap: () {
-            if (onColorSelection != null) {
+            onColorSelection?.call(color);
-              onColorSelection!(color);
-            }
           },
         );
       }).toList(),
@@ -59,9 +57,7 @@ class _ColorPickerSwatch extends StatelessWidget {
       child: RawMaterialButton(
         fillColor: color,
         onPressed: () {
-          if (onTap != null) {
+          onTap?.call();
-            onTap!();
-          }
         },
         child: !selected ? null : const Icon(
           Icons.check,

dev/integration_tests/flutter_gallery/lib/demo/transformations/transformations_demo_gesture_transformable.dart

@@ -392,9 +392,7 @@ class _GestureTransformableState extends State<GestureTransformable> with Ticker
 
   // Handle the start of a gesture of _GestureType.
   void _onScaleStart(ScaleStartDetails details) {
-    if (widget.onScaleStart != null) {
+    widget.onScaleStart?.call(details);
-      widget.onScaleStart!(details);
-    }
 
     if (_controller.isAnimating) {
       _controller.stop();
@@ -417,13 +415,11 @@ class _GestureTransformableState extends State<GestureTransformable> with Ticker
   // Handle an update to an ongoing gesture of _GestureType.
   void _onScaleUpdate(ScaleUpdateDetails details) {
     double scale = _transform.getMaxScaleOnAxis();
-    if (widget.onScaleUpdate != null) {
+    widget.onScaleUpdate?.call(ScaleUpdateDetails(
-      widget.onScaleUpdate!(ScaleUpdateDetails(
+      focalPoint: fromViewport(details.focalPoint, _transform),
-        focalPoint: fromViewport(details.focalPoint, _transform),
+      scale: details.scale,
-        scale: details.scale,
+      rotation: details.rotation,
-        rotation: details.rotation,
+    ));
-      ));
-    }
     final Offset focalPointScene = fromViewport(
       details.focalPoint,
       _transform,
@@ -476,9 +472,7 @@ class _GestureTransformableState extends State<GestureTransformable> with Ticker
 
   // Handle the end of a gesture of _GestureType.
   void _onScaleEnd(ScaleEndDetails details) {
-    if (widget.onScaleEnd != null) {
+    widget.onScaleEnd?.call(details);
-      widget.onScaleEnd!(details);
-    }
     setState(() {
       _scaleStart = null;
       _rotationStart = null;

packages/flutter/lib/src/cupertino/picker.dart

@@ -255,9 +255,7 @@ class _CupertinoPickerState extends State<CupertinoPicker> {
       HapticFeedback.selectionClick();
     }
 
-    if (widget.onSelectedItemChanged != null) {
+    widget.onSelectedItemChanged?.call(index);
-      widget.onSelectedItemChanged!(index);
-    }
   }
 
   /// Draws the selectionOverlay.

packages/flutter/lib/src/cupertino/slider.dart

@@ -475,18 +475,14 @@ class _RenderCupertinoSlider extends RenderConstrainedBox {
 
   void _startInteraction(Offset globalPosition) {
     if (isInteractive) {
-      if (onChangeStart != null) {
+      onChangeStart?.call(_discretizedCurrentDragValue);
-        onChangeStart!(_discretizedCurrentDragValue);
-      }
       _currentDragValue = _value;
       onChanged!(_discretizedCurrentDragValue);
     }
   }
 
   void _endInteraction() {
-    if (onChangeEnd != null) {
+    onChangeEnd?.call(_discretizedCurrentDragValue);
-      onChangeEnd!(_discretizedCurrentDragValue);
-    }
     _currentDragValue = 0.0;
   }
 

packages/flutter/lib/src/cupertino/text_field.dart

@@ -116,8 +116,7 @@ class _CupertinoTextFieldSelectionGestureDetectorBuilder extends TextSelectionGe
     }
     super.onSingleTapUp(details);
     _state._requestKeyboard();
-    if (_state.widget.onTap != null)
+    _state.widget.onTap?.call();
-      _state.widget.onTap!();
   }
 
   @override

packages/flutter/lib/src/foundation/assertions.dart

@@ -1104,9 +1104,7 @@ class FlutterError extends Error with DiagnosticableTreeMixin implements Asserti
   static void reportError(FlutterErrorDetails details) {
     assert(details != null);
     assert(details.exception != null);
-    if (onError != null) {
+    onError?.call(details);
-      onError!(details);
-    }
   }
 }
 

packages/flutter/lib/src/material/bottom_sheet.dart

@@ -193,9 +193,7 @@ class _BottomSheetState extends State<BottomSheet> {
   bool get _dismissUnderway => widget.animationController!.status == AnimationStatus.reverse;
 
   void _handleDragStart(DragStartDetails details) {
-    if (widget.onDragStart != null) {
+    widget.onDragStart?.call(details);
-      widget.onDragStart!(details);
-    }
   }
 
   void _handleDragUpdate(DragUpdateDetails details) {
@@ -226,12 +224,10 @@ class _BottomSheetState extends State<BottomSheet> {
       widget.animationController!.forward();
     }
 
-    if (widget.onDragEnd != null) {
+    widget.onDragEnd?.call(
-      widget.onDragEnd!(
+      details,
-        details,
+      isClosing: isClosing,
-        isClosing: isClosing,
+    );
-      );
-    }
 
     if (isClosing) {
       widget.onClosing();

packages/flutter/lib/src/material/button.dart

@@ -330,9 +330,7 @@ class _RawMaterialButtonState extends State<RawMaterialButton> {
     if (_pressed != value) {
       setState(() {
         _updateState(MaterialState.pressed, value);
-        if (widget.onHighlightChanged != null) {
+        widget.onHighlightChanged?.call(value);
-          widget.onHighlightChanged!(value);
-        }
       });
     }
   }

packages/flutter/lib/src/material/dropdown.dart

@@ -150,9 +150,7 @@ class _DropdownMenuItemButtonState<T> extends State<_DropdownMenuItemButton<T>>
   void _handleOnTap() {
     final DropdownMenuItem<T> dropdownMenuItem = widget.route.items[widget.itemIndex].item!;
 
-    if (dropdownMenuItem.onTap != null) {
+    dropdownMenuItem.onTap?.call();
-      dropdownMenuItem.onTap!();
-    }
 
     Navigator.pop(
       context,
@@ -1270,13 +1268,10 @@ class _DropdownButtonState<T> extends State<DropdownButton<T>> with WidgetsBindi
       _removeDropdownRoute();
       if (!mounted || newValue == null)
         return;
-      if (widget.onChanged != null)
+      widget.onChanged?.call(newValue.result);
-        widget.onChanged!(newValue.result);
     });
 
-    if (widget.onTap != null) {
+    widget.onTap?.call();
-      widget.onTap!();
-    }
   }
 
   // When isDense is true, reduce the height of this button from _kMenuItemHeight to

packages/flutter/lib/src/material/expand_icon.dart

@@ -137,8 +137,7 @@ class _ExpandIconState extends State<ExpandIcon> with SingleTickerProviderStateM
   }
 
   void _handlePressed() {
-    if (widget.onPressed != null)
+    widget.onPressed?.call(widget.isExpanded);
-      widget.onPressed!(widget.isExpanded);
   }
 
   /// Default icon colors and opacities for when [Theme.brightness] is set to

packages/flutter/lib/src/material/expansion_panel.dart

@@ -442,8 +442,7 @@ class _ExpansionPanelListState extends State<ExpansionPanelList> {
   }
 
   void _handlePressed(bool isExpanded, int index) {
-    if (widget.expansionCallback != null)
+    widget.expansionCallback?.call(index, isExpanded);
-      widget.expansionCallback!(index, isExpanded);
 
     if (widget._allowOnlyOnePanelOpen) {
       final ExpansionPanelRadio pressedChild = widget.children[index] as ExpansionPanelRadio;

packages/flutter/lib/src/material/expansion_tile.dart

@@ -241,8 +241,7 @@ class _ExpansionTileState extends State<ExpansionTile> with SingleTickerProvider
       }
       PageStorage.of(context)?.writeState(context, _isExpanded);
     });
-    if (widget.onExpansionChanged != null)
+    widget.onExpansionChanged?.call(_isExpanded);
-      widget.onExpansionChanged!(_isExpanded);
   }
 
   Widget _buildChildren(BuildContext context, Widget? child) {

packages/flutter/lib/src/material/material.dart

@@ -626,8 +626,7 @@ abstract class InkFeature {
       return true;
     }());
     _controller._removeFeature(this);
-    if (onRemoved != null)
+    onRemoved?.call();
-      onRemoved!();
   }
 
   void _paint(Canvas canvas) {

packages/flutter/lib/src/material/popup_menu.dart

@@ -1110,12 +1110,10 @@ class PopupMenuButtonState<T> extends State<PopupMenuButton<T>> {
         if (!mounted)
           return null;
         if (newValue == null) {
-          if (widget.onCanceled != null)
+          widget.onCanceled?.call();
-            widget.onCanceled!();
           return null;
         }
-        if (widget.onSelected != null)
+        widget.onSelected?.call(newValue);
-          widget.onSelected!(newValue);
       });
     }
   }

packages/flutter/lib/src/material/range_slider.dart

@@ -1131,9 +1131,7 @@ class _RenderRangeSlider extends RenderBox with RelayoutWhenSystemFontsChangeMix
       }
       _updateLabelPainter(_lastThumbSelection!);
 
-      if (onChangeStart != null) {
+      onChangeStart?.call(currentValues);
-        onChangeStart!(currentValues);
-      }
 
       onChanged!(_discretizeRangeValues(_newValues));
 
@@ -1202,9 +1200,7 @@ class _RenderRangeSlider extends RenderBox with RelayoutWhenSystemFontsChangeMix
 
     if (_active && _state.mounted && _lastThumbSelection != null) {
       final RangeValues discreteValues = _discretizeRangeValues(_newValues);
-      if (onChangeEnd != null) {
+      onChangeEnd?.call(discreteValues);
-        onChangeEnd!(discreteValues);
-      }
       _active = false;
     }
     _state.overlayController.reverse();
@@ -1710,12 +1706,8 @@ class _RenderValueIndicator extends RenderBox with RelayoutWhenSystemFontsChange
 
   @override
   void paint(PaintingContext context, Offset offset) {
-    if (_state.paintBottomValueIndicator != null) {
+    _state.paintBottomValueIndicator?.call(context, offset);
-      _state.paintBottomValueIndicator!(context, offset);
+    _state.paintTopValueIndicator?.call(context, offset);
-    }
-    if (_state.paintTopValueIndicator != null) {
-      _state.paintTopValueIndicator!(context, offset);
-    }
   }
 
   @override

packages/flutter/lib/src/material/slider.dart

@@ -1230,9 +1230,7 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
       // We supply the *current* value as the start location, so that if we have
       // a tap, it consists of a call to onChangeStart with the previous value and
       // a call to onChangeEnd with the new value.
-      if (onChangeStart != null) {
+      onChangeStart?.call(_discretize(value));
-        onChangeStart!(_discretize(value));
-      }
       _currentDragValue = _getValueFromGlobalPosition(globalPosition);
       onChanged!(_discretize(_currentDragValue));
       _state.overlayController.forward();
@@ -1256,9 +1254,7 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     }
 
     if (_active && _state.mounted) {
-      if (onChangeEnd != null) {
+      onChangeEnd?.call(_discretize(_currentDragValue));
-        onChangeEnd!(_discretize(_currentDragValue));
-      }
       _active = false;
       _currentDragValue = 0.0;
       _state.overlayController.reverse();
@@ -1584,9 +1580,7 @@ class _RenderValueIndicator extends RenderBox with RelayoutWhenSystemFontsChange
 
   @override
   void paint(PaintingContext context, Offset offset) {
-    if (_state.paintValueIndicator != null) {
+    _state.paintValueIndicator?.call(context, offset);
-      _state.paintValueIndicator!(context, offset);
-    }
   }
 
   @override

packages/flutter/lib/src/material/stepper.dart

@@ -648,8 +648,7 @@ class _StepperState extends State<Stepper> with TickerProviderStateMixin {
                     duration: kThemeAnimationDuration,
                   );
 
-                  if (widget.onStepTapped != null)
+                  widget.onStepTapped?.call(i);
-                    widget.onStepTapped!(i);
                 } : null,
                 canRequestFocus: widget.steps[i].state != StepState.disabled,
                 child: _buildVerticalHeader(i),
@@ -666,8 +665,7 @@ class _StepperState extends State<Stepper> with TickerProviderStateMixin {
       for (int i = 0; i < widget.steps.length; i += 1) ...<Widget>[
         InkResponse(
           onTap: widget.steps[i].state != StepState.disabled ? () {
-            if (widget.onStepTapped != null)
+            widget.onStepTapped?.call(i);
-              widget.onStepTapped!(i);
           } : null,
           canRequestFocus: widget.steps[i].state != StepState.disabled,
           child: Row(

packages/flutter/lib/src/material/tabs.dart

@@ -1123,9 +1123,7 @@ class _TabBarState extends State<TabBar> {
   void _handleTap(int index) {
     assert(index >= 0 && index < widget.tabs.length);
     _controller!.animateTo(index);
-    if (widget.onTap != null) {
+    widget.onTap?.call(index);
-      widget.onTap!(index);
-    }
   }
 
   Widget _buildStyledTab(Widget child, bool selected, Animation<double> animation) {

packages/flutter/lib/src/material/text_field.dart

@@ -114,8 +114,7 @@ class _TextFieldSelectionGestureDetectorBuilder extends TextSelectionGestureDete
       }
     }
     _state._requestKeyboard();
-    if (_state.widget.onTap != null)
+    _state.widget.onTap?.call();
-      _state.widget.onTap!();
   }
 
   @override

packages/flutter/lib/src/material/time_picker.dart

@@ -1074,9 +1074,7 @@ class _DialState extends State<_Dial> with SingleTickerProviderStateMixin {
     _center = null;
     _animateTo(_getThetaForTime(widget.selectedTime));
     if (widget.mode == _TimePickerMode.hour) {
-      if (widget.onHourSelected != null) {
+      widget.onHourSelected?.call();
-        widget.onHourSelected!();
-      }
     }
   }
 
@@ -1092,9 +1090,7 @@ class _DialState extends State<_Dial> with SingleTickerProviderStateMixin {
       } else {
         _announceToAccessibility(context, localizations.formatDecimal(newTime.hourOfPeriod));
       }
-      if (widget.onHourSelected != null) {
+      widget.onHourSelected?.call();
-        widget.onHourSelected!();
-      }
     } else {
       _announceToAccessibility(context, localizations.formatDecimal(newTime.minute));
     }

packages/flutter/lib/src/painting/decoration_image.dart

@@ -534,9 +534,7 @@ void paintImage({
       if (existingSizeInfo == null || existingSizeInfo.displaySizeInBytes < sizeInfo.displaySizeInBytes) {
         _pendingImageSizeInfo[sizeInfo.source!] = sizeInfo;
       }
-      if (debugOnPaintImage != null) {
+      debugOnPaintImage?.call(sizeInfo);
-        debugOnPaintImage!(sizeInfo);
-      }
       SchedulerBinding.instance!.addPostFrameCallback((Duration timeStamp) {
         _lastFrameImageSizeInfo = _pendingImageSizeInfo.values.toSet();
         if (_pendingImageSizeInfo.isEmpty) {

packages/flutter/lib/src/rendering/editable.dart

@@ -598,9 +598,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     if (nextSelection == selection && cause != SelectionChangedCause.keyboard && !focusingEmpty) {
       return;
     }
-    if (onSelectionChanged != null) {
+    onSelectionChanged?.call(nextSelection, this, cause);
-      onSelectionChanged!(nextSelection, this, cause);
-    }
   }
 
   static final Set<LogicalKeyboardKey> _movementKeys = <LogicalKeyboardKey>{

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -4760,103 +4760,83 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
   }
 
   void _performTap() {
-    if (onTap != null)
+    onTap?.call();
-      onTap!();
   }
 
   void _performLongPress() {
-    if (onLongPress != null)
+    onLongPress?.call();
-      onLongPress!();
   }
 
   void _performDismiss() {
-    if (onDismiss != null)
+    onDismiss?.call();
-      onDismiss!();
   }
 
   void _performScrollLeft() {
-    if (onScrollLeft != null)
+    onScrollLeft?.call();
-      onScrollLeft!();
   }
 
   void _performScrollRight() {
-    if (onScrollRight != null)
+    onScrollRight?.call();
-      onScrollRight!();
   }
 
   void _performScrollUp() {
-    if (onScrollUp != null)
+    onScrollUp?.call();
-      onScrollUp!();
   }
 
   void _performScrollDown() {
-    if (onScrollDown != null)
+    onScrollDown?.call();
-      onScrollDown!();
   }
 
   void _performIncrease() {
-    if (onIncrease != null)
+    onIncrease?.call();
-      onIncrease!();
   }
 
   void _performDecrease() {
-    if (onDecrease != null)
+    onDecrease?.call();
-      onDecrease!();
   }
 
   void _performCopy() {
-    if (onCopy != null)
+    onCopy?.call();
-      onCopy!();
   }
 
   void _performCut() {
-    if (onCut != null)
+    onCut?.call();
-      onCut!();
   }
 
   void _performPaste() {
-    if (onPaste != null)
+    onPaste?.call();
-      onPaste!();
   }
 
   void _performMoveCursorForwardByCharacter(bool extendSelection) {
-    if (onMoveCursorForwardByCharacter != null)
+    onMoveCursorForwardByCharacter?.call(extendSelection);
-      onMoveCursorForwardByCharacter!(extendSelection);
   }
 
   void _performMoveCursorBackwardByCharacter(bool extendSelection) {
-    if (onMoveCursorBackwardByCharacter != null)
+    onMoveCursorBackwardByCharacter?.call(extendSelection);
-      onMoveCursorBackwardByCharacter!(extendSelection);
   }
 
   void _performMoveCursorForwardByWord(bool extendSelection) {
-    if (onMoveCursorForwardByWord != null)
+    onMoveCursorForwardByWord?.call(extendSelection);
-      onMoveCursorForwardByWord!(extendSelection);
   }
 
   void _performMoveCursorBackwardByWord(bool extendSelection) {
-    if (onMoveCursorBackwardByWord != null)
+    onMoveCursorBackwardByWord?.call(extendSelection);
-      onMoveCursorBackwardByWord!(extendSelection);
   }
 
   void _performSetSelection(TextSelection selection) {
-    if (onSetSelection != null)
+    onSetSelection?.call(selection);
-      onSetSelection!(selection);
   }
 
   void _performSetText(String text) {
-    if (onSetText != null)
+    onSetText?.call(text);
-      onSetText!(text);
   }
 
   void _performDidGainAccessibilityFocus() {
-    if (onDidGainAccessibilityFocus != null)
+    onDidGainAccessibilityFocus?.call();
-      onDidGainAccessibilityFocus!();
   }
 
   void _performDidLoseAccessibilityFocus() {
-    if (onDidLoseAccessibilityFocus != null)
+    onDidLoseAccessibilityFocus?.call();
-      onDidLoseAccessibilityFocus!();
   }
 }
 

packages/flutter/lib/src/widgets/basic.dart

@@ -6178,8 +6178,7 @@ class WidgetToRenderBoxAdapter extends LeafRenderObjectWidget {
 
   @override
   void updateRenderObject(BuildContext context, RenderBox renderObject) {
-    if (onBuild != null)
+    onBuild?.call();
-      onBuild!();
   }
 }
 

packages/flutter/lib/src/widgets/dismissible.dart

@@ -543,13 +543,9 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
 
   void _handleResizeProgressChanged() {
     if (_resizeController!.isCompleted) {
-      if (widget.onDismissed != null) {
+      widget.onDismissed?.call(_dismissDirection);
-        final DismissDirection direction = _dismissDirection;
-        widget.onDismissed!(direction);
-      }
     } else {
-      if (widget.onResize != null)
+      widget.onResize?.call();
-        widget.onResize!();
     }
   }
 

packages/flutter/lib/src/widgets/drag_target.dart

@@ -576,8 +576,7 @@ class _DraggableState<T extends Object> extends State<Draggable<T>> {
           widget.onDraggableCanceled!(velocity, offset);
       },
     );
-    if (widget.onDragStarted != null)
+    widget.onDragStarted?.call();
-      widget.onDragStarted!();
     return avatar;
   }
 
@@ -754,8 +753,7 @@ class _DragTargetState<T extends Object> extends State<DragTarget<T>> {
       _candidateAvatars.remove(avatar);
       _rejectedAvatars.remove(avatar);
     });
-    if (widget.onLeave != null)
+    widget.onLeave?.call(avatar.data as T?);
-      widget.onLeave!(avatar.data as T?);
   }
 
   void didDrop(_DragAvatar<Object> avatar) {
@@ -765,17 +763,14 @@ class _DragTargetState<T extends Object> extends State<DragTarget<T>> {
     setState(() {
       _candidateAvatars.remove(avatar);
     });
-    if (widget.onAccept != null)
+    widget.onAccept?.call(avatar.data! as T);
-      widget.onAccept!(avatar.data! as T);
+    widget.onAcceptWithDetails?.call(DragTargetDetails<T>(data: avatar.data! as T, offset: avatar._lastOffset!));
-    if (widget.onAcceptWithDetails != null)
-      widget.onAcceptWithDetails!(DragTargetDetails<T>(data: avatar.data! as T, offset: avatar._lastOffset!));
   }
 
   void didMove(_DragAvatar<Object> avatar) {
     if (!mounted)
       return;
-    if (widget.onMove != null)
+    widget.onMove?.call(DragTargetDetails<T>(data: avatar.data! as T, offset: avatar._lastOffset!));
-      widget.onMove!(DragTargetDetails<T>(data: avatar.data! as T, offset: avatar._lastOffset!));
   }
 
   @override
@@ -937,8 +932,7 @@ class _DragAvatar<T extends Object> extends Drag {
     _entry!.remove();
     _entry = null;
     // TODO(ianh): consider passing _entry as well so the client can perform an animation.
-    if (onDragEnd != null)
+    onDragEnd?.call(velocity ?? Velocity.zero, _lastOffset!, wasAccepted);
-      onDragEnd!(velocity ?? Velocity.zero, _lastOffset!, wasAccepted);
   }
 
   Widget _build(BuildContext context) {

packages/flutter/lib/src/widgets/focus_scope.dart

@@ -670,9 +670,7 @@ class _FocusState extends State<Focus> {
     final bool hasPrimaryFocus = focusNode.hasPrimaryFocus;
     final bool canRequestFocus = focusNode.canRequestFocus;
     final bool descendantsAreFocusable = focusNode.descendantsAreFocusable;
-    if (widget.onFocusChange != null) {
+    widget.onFocusChange?.call(focusNode.hasFocus);
-      widget.onFocusChange!(focusNode.hasFocus);
-    }
     if (_hasPrimaryFocus != hasPrimaryFocus) {
       setState(() {
         _hasPrimaryFocus = hasPrimaryFocus;

packages/flutter/lib/src/widgets/form.dart

@@ -167,9 +167,7 @@ class FormState extends State<Form> {
   // Called when a form field has changed. This will cause all form fields
   // to rebuild, useful if form fields have interdependencies.
   void _fieldDidChange() {
-    if (widget.onChanged != null)
+    widget.onChanged?.call();
-      widget.onChanged!();
-
 
     _hasInteractedByUser = _fields
         .any((FormFieldState<dynamic> field) => field._hasInteractedByUser);
@@ -435,8 +433,7 @@ class FormFieldState<T> extends State<FormField<T>> {
 
   /// Calls the [FormField]'s onSaved method with the current value.
   void save() {
-    if (widget.onSaved != null)
+    widget.onSaved?.call(value);
-      widget.onSaved!(value);
   }
 
   /// Resets the field to its initial value.

packages/flutter/lib/src/widgets/framework.dart

@@ -4241,9 +4241,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
     if (_lifecycleState != _ElementLifecycle.active || !_dirty)
       return;
     assert(() {
-      if (debugOnRebuildDirtyWidget != null) {
+      debugOnRebuildDirtyWidget?.call(this, _debugBuiltOnce);
-        debugOnRebuildDirtyWidget!(this, _debugBuiltOnce);
-      }
       if (debugPrintRebuildDirtyWidgets) {
         if (!_debugBuiltOnce) {
           debugPrint('Building $this');

packages/flutter/lib/src/widgets/gesture_detector.dart

@@ -1332,12 +1332,9 @@ class _DefaultSemanticsGestureDelegate extends SemanticsGestureDelegate {
 
     return () {
       assert(tap != null);
-      if (tap.onTapDown != null)
+      tap.onTapDown?.call(TapDownDetails());
-        tap.onTapDown!(TapDownDetails());
+      tap.onTapUp?.call(TapUpDetails(kind: PointerDeviceKind.unknown));
-      if (tap.onTapUp != null)
+      tap.onTap?.call();
-        tap.onTapUp!(TapUpDetails(kind: PointerDeviceKind.unknown));
-      if (tap.onTap != null)
-        tap.onTap!();
     };
   }
 
@@ -1347,14 +1344,10 @@ class _DefaultSemanticsGestureDelegate extends SemanticsGestureDelegate {
       return null;
 
     return () {
-      if (longPress.onLongPressStart != null)
+      longPress.onLongPressStart?.call(const LongPressStartDetails());
-        longPress.onLongPressStart!(const LongPressStartDetails());
+      longPress.onLongPress?.call();
-      if (longPress.onLongPress != null)
+      longPress.onLongPressEnd?.call(const LongPressEndDetails());
-        longPress.onLongPress!();
+      longPress.onLongPressUp?.call();
-      if (longPress.onLongPressEnd != null)
-        longPress.onLongPressEnd!(const LongPressEndDetails());
-      if (longPress.onLongPressUp != null)
-        longPress.onLongPressUp!();
     };
   }
 
@@ -1365,27 +1358,19 @@ class _DefaultSemanticsGestureDelegate extends SemanticsGestureDelegate {
     final GestureDragUpdateCallback? horizontalHandler = horizontal == null ?
       null :
       (DragUpdateDetails details) {
-        if (horizontal.onDown != null)
+        horizontal.onDown?.call(DragDownDetails());
-          horizontal.onDown!(DragDownDetails());
+        horizontal.onStart?.call(DragStartDetails());
-        if (horizontal.onStart != null)
+        horizontal.onUpdate?.call(details);
-          horizontal.onStart!(DragStartDetails());
+        horizontal.onEnd?.call(DragEndDetails(primaryVelocity: 0.0));
-        if (horizontal.onUpdate != null)
-          horizontal.onUpdate!(details);
-        if (horizontal.onEnd != null)
-          horizontal.onEnd!(DragEndDetails(primaryVelocity: 0.0));
       };
 
     final GestureDragUpdateCallback? panHandler = pan == null ?
       null :
       (DragUpdateDetails details) {
-        if (pan.onDown != null)
+        pan.onDown?.call(DragDownDetails());
-          pan.onDown!(DragDownDetails());
+        pan.onStart?.call(DragStartDetails());
-        if (pan.onStart != null)
+        pan.onUpdate?.call(details);
-          pan.onStart!(DragStartDetails());
+        pan.onEnd?.call(DragEndDetails());
-        if (pan.onUpdate != null)
-          pan.onUpdate!(details);
-        if (pan.onEnd != null)
-          pan.onEnd!(DragEndDetails());
       };
 
     if (horizontalHandler == null && panHandler == null)
@@ -1405,27 +1390,19 @@ class _DefaultSemanticsGestureDelegate extends SemanticsGestureDelegate {
     final GestureDragUpdateCallback? verticalHandler = vertical == null ?
       null :
       (DragUpdateDetails details) {
-        if (vertical.onDown != null)
+        vertical.onDown?.call(DragDownDetails());
-          vertical.onDown!(DragDownDetails());
+        vertical.onStart?.call(DragStartDetails());
-        if (vertical.onStart != null)
+        vertical.onUpdate?.call(details);
-          vertical.onStart!(DragStartDetails());
+        vertical.onEnd?.call(DragEndDetails(primaryVelocity: 0.0));
-        if (vertical.onUpdate != null)
-          vertical.onUpdate!(details);
-        if (vertical.onEnd != null)
-          vertical.onEnd!(DragEndDetails(primaryVelocity: 0.0));
       };
 
     final GestureDragUpdateCallback? panHandler = pan == null ?
       null :
       (DragUpdateDetails details) {
-        if (pan.onDown != null)
+        pan.onDown?.call(DragDownDetails());
-          pan.onDown!(DragDownDetails());
+        pan.onStart?.call(DragStartDetails());
-        if (pan.onStart != null)
+        pan.onUpdate?.call(details);
-          pan.onStart!(DragStartDetails());
+        pan.onEnd?.call(DragEndDetails());
-        if (pan.onUpdate != null)
-          pan.onUpdate!(details);
-        if (pan.onEnd != null)
-          pan.onEnd!(DragEndDetails());
       };
 
     if (verticalHandler == null && panHandler == null)

packages/flutter/lib/src/widgets/implicit_animations.dart

@@ -370,8 +370,7 @@ abstract class ImplicitlyAnimatedWidgetState<T extends ImplicitlyAnimatedWidget>
     _controller.addStatusListener((AnimationStatus status) {
       switch (status) {
         case AnimationStatus.completed:
-          if (widget.onEnd != null)
+          widget.onEnd?.call();
-            widget.onEnd!();
           break;
         case AnimationStatus.dismissed:
         case AnimationStatus.forward:

packages/flutter/lib/src/widgets/modal_barrier.dart

@@ -228,8 +228,7 @@ class _AnyTapGestureRecognizer extends BaseTapGestureRecognizer {
   @protected
   @override
   void handleTapUp({PointerDownEvent? down, PointerUpEvent? up}) {
-    if (onAnyTapUp != null)
+    onAnyTapUp?.call();
-      onAnyTapUp!();
   }
 
   @protected

packages/flutter/lib/src/widgets/navigator.dart

@@ -5968,9 +5968,7 @@ class RestorableRouteFuture<T> extends RestorableProperty<String?> {
       _route?.restorationScopeId.removeListener(notifyListeners);
       _route = null;
       notifyListeners();
-      if (onComplete != null) {
+      onComplete?.call(result as T);
-        onComplete!(result as T);
-      }
     });
   }
 

packages/flutter/lib/src/widgets/platform_view.dart

@@ -638,9 +638,7 @@ class _UiKitViewState extends State<UiKitView> {
       controller.dispose();
       return;
     }
-    if (widget.onPlatformViewCreated != null) {
+    widget.onPlatformViewCreated?.call(id);
-      widget.onPlatformViewCreated!(id);
-    }
     setState(() { _controller = controller; });
   }
 }

packages/flutter/lib/src/widgets/raw_keyboard_listener.dart

@@ -121,8 +121,7 @@ class _RawKeyboardListenerState extends State<RawKeyboardListener> {
   }
 
   void _handleRawKeyEvent(RawKeyEvent event) {
-    if (widget.onKey != null)
+    widget.onKey?.call(event);
-      widget.onKey!(event);
   }
 
   @override

packages/flutter/lib/src/widgets/routes.dart

@@ -445,8 +445,7 @@ class LocalHistoryEntry {
   }
 
   void _notifyRemoved() {
-    if (onRemove != null)
+    onRemove?.call();
-      onRemove!();
   }
 }
 

packages/flutter/lib/src/widgets/scroll_activity.dart

@@ -214,8 +214,7 @@ class HoldScrollActivity extends ScrollActivity implements ScrollHoldController
 
   @override
   void dispose() {
-    if (onHoldCanceled != null)
+    onHoldCanceled?.call();
-      onHoldCanceled!();
     super.dispose();
   }
 }
@@ -406,8 +405,7 @@ class ScrollDragController implements Drag {
   @mustCallSuper
   void dispose() {
     _lastDetails = null;
-    if (onDragCanceled != null)
+    onDragCanceled?.call();
-      onDragCanceled!();
   }
 
   /// The most recently observed [DragStartDetails], [DragUpdateDetails], or

packages/flutter/lib/src/widgets/text_selection.dart

@@ -782,8 +782,7 @@ class _TextSelectionHandleOverlayState
   }
 
   void _handleTap() {
-    if (widget.onSelectionHandleTapped != null)
+    widget.onSelectionHandleTapped?.call();
-      widget.onSelectionHandleTapped!();
   }
 
   @override
@@ -1386,9 +1385,7 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
   // The down handler is force-run on success of a single tap and optimistically
   // run before a long press success.
   void _handleTapDown(TapDownDetails details) {
-    if (widget.onTapDown != null) {
+    widget.onTapDown?.call(details);
-      widget.onTapDown!(details);
-    }
     // This isn't detected as a double tap gesture in the gesture recognizer
     // because it's 2 single taps, each of which may do different things depending
     // on whether it's a single tap, the first tap of a double tap, the second
@@ -1396,9 +1393,7 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
     if (_doubleTapTimer != null && _isWithinDoubleTapTolerance(details.globalPosition)) {
       // If there was already a previous tap, the second down hold/tap is a
       // double tap down.
-      if (widget.onDoubleTapDown != null) {
+      widget.onDoubleTapDown?.call(details);
-        widget.onDoubleTapDown!(details);
-      }
 
       _doubleTapTimer!.cancel();
       _doubleTapTimeout();
@@ -1408,9 +1403,7 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
 
   void _handleTapUp(TapUpDetails details) {
     if (!_isDoubleTap) {
-      if (widget.onSingleTapUp != null) {
+      widget.onSingleTapUp?.call(details);
-        widget.onSingleTapUp!(details);
-      }
       _lastTapOffset = details.globalPosition;
       _doubleTapTimer = Timer(kDoubleTapTimeout, _doubleTapTimeout);
     }
@@ -1418,9 +1411,7 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
   }
 
   void _handleTapCancel() {
-    if (widget.onSingleTapCancel != null) {
+    widget.onSingleTapCancel?.call();
-      widget.onSingleTapCancel!();
-    }
   }
 
   DragStartDetails? _lastDragStartDetails;
@@ -1430,9 +1421,7 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
   void _handleDragStart(DragStartDetails details) {
     assert(_lastDragStartDetails == null);
     _lastDragStartDetails = details;
-    if (widget.onDragSelectionStart != null) {
+    widget.onDragSelectionStart?.call(details);
-      widget.onDragSelectionStart!(details);
-    }
   }
 
   void _handleDragUpdate(DragUpdateDetails details) {
@@ -1450,9 +1439,7 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
   void _handleDragUpdateThrottled() {
     assert(_lastDragStartDetails != null);
     assert(_lastDragUpdateDetails != null);
-    if (widget.onDragSelectionUpdate != null) {
+    widget.onDragSelectionUpdate?.call(_lastDragStartDetails!, _lastDragUpdateDetails!);
-      widget.onDragSelectionUpdate!(_lastDragStartDetails!, _lastDragUpdateDetails!);
-    }
     _dragUpdateThrottleTimer = null;
     _lastDragUpdateDetails = null;
   }
@@ -1465,9 +1452,7 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
       _dragUpdateThrottleTimer!.cancel();
       _handleDragUpdateThrottled();
     }
-    if (widget.onDragSelectionEnd != null) {
+    widget.onDragSelectionEnd?.call(details);
-      widget.onDragSelectionEnd!(details);
-    }
     _dragUpdateThrottleTimer = null;
     _lastDragStartDetails = null;
     _lastDragUpdateDetails = null;
@@ -1476,13 +1461,11 @@ class _TextSelectionGestureDetectorState extends State<TextSelectionGestureDetec
   void _forcePressStarted(ForcePressDetails details) {
     _doubleTapTimer?.cancel();
     _doubleTapTimer = null;
-    if (widget.onForcePressStart != null)
+    widget.onForcePressStart?.call(details);
-      widget.onForcePressStart!(details);
   }
 
   void _forcePressEnded(ForcePressDetails details) {
-    if (widget.onForcePressEnd != null)
+    widget.onForcePressEnd?.call(details);
-      widget.onForcePressEnd!(details);
   }
 
   void _handleLongPressStart(LongPressStartDetails details) {

packages/flutter/test/gestures/team_test.dart

@@ -130,9 +130,7 @@ class PassiveGestureRecognizer extends OneSequenceGestureRecognizer {
 
   @override
   void acceptGesture(int pointer) {
-    if (onGestureAccepted != null) {
+    onGestureAccepted?.call();
-      onGestureAccepted!();
-    }
   }
 
   @override

packages/flutter/test/rendering/mouse_tracker_test_utils.dart

@@ -89,8 +89,7 @@ class TestAnnotationTarget with Diagnosticable implements MouseTrackerAnnotation
   @override
   void handleEvent(PointerEvent event, HitTestEntry entry) {
     if (event is PointerHoverEvent)
-      if (onHover != null)
+      onHover?.call(event);
-        onHover!(event);
   }
 }
 

packages/flutter/test/widgets/image_filter_quality_test.dart

@@ -111,9 +111,7 @@ class _TestImageStreamCompleter extends ImageStreamCompleter {
   }) {
     final List<ImageStreamListener> localListeners = listeners.toList();
     for (final ImageStreamListener listener in localListeners) {
-      if (listener.onError != null) {
+      listener.onError?.call(exception, stackTrace);
-        listener.onError!(exception, stackTrace);
-      }
     }
   }
 }

packages/flutter/test/widgets/image_test.dart

@@ -2026,9 +2026,7 @@ class _TestImageStreamCompleter extends ImageStreamCompleter {
   }) {
     final List<ImageStreamListener> localListeners = listeners.toList();
     for (final ImageStreamListener listener in localListeners) {
-      if (listener.onError != null) {
+      listener.onError?.call(exception, stackTrace);
-        listener.onError!(exception, stackTrace);
-      }
     }
   }
 }

packages/flutter/test/widgets/independent_widget_layout_test.dart

@@ -86,8 +86,7 @@ class Counter {
 class Trigger {
   VoidCallback? callback;
   void fire() {
-    if (callback != null)
+    callback?.call();
-      callback!();
   }
 }
 

packages/flutter/test/widgets/mouse_region_test.dart

@@ -29,21 +29,13 @@ class HoverClient extends StatefulWidget {
 
 class HoverClientState extends State<HoverClient> {
   void _onExit(PointerExitEvent details) {
-    if (widget.onExit != null) {
+    widget.onExit?.call();
-      widget.onExit!();
+    widget.onHover?.call(false);
-    }
-    if (widget.onHover != null) {
-      widget.onHover!(false);
-    }
   }
 
   void _onEnter(PointerEnterEvent details) {
-    if (widget.onEnter != null) {
+    widget.onEnter?.call();
-      widget.onEnter!();
+    widget.onHover?.call(true);
-    }
-    if (widget.onHover != null) {
-      widget.onHover!(true);
-    }
   }
 
   @override

packages/flutter/test/widgets/navigator_test.dart

@@ -3587,22 +3587,19 @@ class RouteAnnouncementSpy extends Route<void> {
   @override
   void didChangeNext(Route<dynamic>? nextRoute) {
     super.didChangeNext(nextRoute);
-    if (onDidChangeNext != null)
+    onDidChangeNext?.call(nextRoute);
-      onDidChangeNext!(nextRoute);
   }
 
   @override
   void didChangePrevious(Route<dynamic>? previousRoute) {
     super.didChangePrevious(previousRoute);
-    if (onDidChangePrevious != null)
+    onDidChangePrevious?.call(previousRoute);
-      onDidChangePrevious!(previousRoute);
   }
 
   @override
   void didPopNext(Route<dynamic> nextRoute) {
     super.didPopNext(nextRoute);
-    if (onDidPopNext != null)
+    onDidPopNext?.call(nextRoute);
-      onDidPopNext!(nextRoute);
   }
 }
 
@@ -3728,9 +3725,7 @@ class HeroControllerSpy extends HeroController {
   OnObservation? onPushed;
   @override
   void didPush(Route<dynamic>? route, Route<dynamic>? previousRoute) {
-    if (onPushed != null) {
+    onPushed?.call(route, previousRoute);
-      onPushed!(route, previousRoute);
-    }
   }
 }
 

packages/flutter/test/widgets/observer_tester.dart

@@ -16,33 +16,26 @@ class TestObserver extends NavigatorObserver {
 
   @override
   void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
-    if (onPushed != null) {
+    onPushed?.call(route, previousRoute);
-      onPushed!(route, previousRoute);
-    }
   }
 
   @override
   void didPop(Route<dynamic> route, Route<dynamic>? previousRoute) {
-    if (onPopped != null) {
+    onPopped?.call(route, previousRoute);
-      onPopped!(route, previousRoute);
-    }
   }
 
   @override
   void didRemove(Route<dynamic> route, Route<dynamic>? previousRoute) {
-    if (onRemoved != null)
+    onRemoved?.call(route, previousRoute);
-      onRemoved!(route, previousRoute);
   }
 
   @override
   void didReplace({ Route<dynamic>? oldRoute, Route<dynamic>? newRoute }) {
-    if (onReplaced != null)
+    onReplaced?.call(newRoute, oldRoute);
-      onReplaced!(newRoute, oldRoute);
   }
 
   @override
   void didStartUserGesture(Route<dynamic> route, Route<dynamic>? previousRoute) {
-    if (onStartUserGesture != null)
+    onStartUserGesture?.call(route, previousRoute);
-      onStartUserGesture!(route, previousRoute);
   }
 }

packages/flutter_test/lib/src/test_text_input.dart

@@ -102,8 +102,7 @@ class TestTextInput {
       case 'TextInput.clearClient':
         _client = 0;
         _isVisible = false;
-        if (onCleared != null)
+        onCleared?.call();
-          onCleared!();
         break;
       case 'TextInput.setEditingState':
         editingState = methodCall.arguments as Map<String, dynamic>;