Revert "`InputDecorator`: Switch hint to Opacity instead of AnimatedOpacity" (#107406)

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

@@ -2157,8 +2157,10 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
     final TextBaseline textBaseline = labelStyle.textBaseline!;
 
     final TextStyle hintStyle = _getInlineHintStyle(themeData);
-    final Widget? hint = decoration!.hintText == null ? null : Opacity(
+    final Widget? hint = decoration!.hintText == null ? null : AnimatedOpacity(
       opacity: (isEmpty && !_hasInlineLabel) ? 1.0 : 0.0,
+      duration: _kTransitionDuration,
+      curve: _kTransitionCurve,
       alwaysIncludeSemantics: true,
       child: Text(
         decoration!.hintText!,

packages/flutter/test/material/input_date_picker_form_field_test.dart

@@ -61,12 +61,13 @@ void main() {
   }
 
   double textOpacity(WidgetTester tester, String textValue) {
-    return tester.widget<Opacity>(
+    final FadeTransition opacityWidget = tester.widget<FadeTransition>(
       find.ancestor(
         of: find.text(textValue),
-        matching: find.byType(Opacity),
+        matching: find.byType(FadeTransition),
       ).first,
-    ).opacity;
+    );
+    return opacityWidget.opacity.value;
   }
 
   group('InputDatePickerFormField', () {

packages/flutter/test/material/input_decorator_test.dart

@@ -144,15 +144,6 @@ double getOpacity(WidgetTester tester, String textValue) {
   return opacityWidget.opacity.value;
 }
 
-double getStaticOpacity(WidgetTester tester, String textValue) {
-  return tester.widget<Opacity>(
-    find.ancestor(
-      of: find.text(textValue),
-      matching: find.byType(Opacity),
-    ).first,
-  ).opacity;
-}
-
 void main() {
   testWidgets('InputDecorator input/label text layout', (WidgetTester tester) async {
     // The label appears above the input text
@@ -972,7 +963,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('text')).dy, 44.0);
     expect(tester.getTopLeft(find.text('label')).dy, 20.0);
     expect(tester.getBottomLeft(find.text('label')).dy, 36.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderBottom(tester), 56.0);
     expect(getBorderWeight(tester), 1.0);
 
@@ -988,6 +979,17 @@ void main() {
       ),
     );
 
+    // The hint's opacity animates from 0.0 to 1.0.
+    // The animation's duration is 200ms.
+    {
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity50ms = getOpacity(tester, 'hint');
+      expect(hintOpacity50ms, inExclusiveRange(0.0, 1.0));
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity100ms = getOpacity(tester, 'hint');
+      expect(hintOpacity100ms, inExclusiveRange(hintOpacity50ms, 1.0));
+    }
+
     await tester.pumpAndSettle();
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 56.0));
     expect(tester.getTopLeft(find.text('text')).dy, 28.0);
@@ -996,7 +998,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('label')).dy, 24.0);
     expect(tester.getTopLeft(find.text('hint')).dy, 28.0);
     expect(tester.getBottomLeft(find.text('hint')).dy, 44.0);
-    expect(getStaticOpacity(tester, 'hint'), 1.0);
+    expect(getOpacity(tester, 'hint'), 1.0);
     expect(getBorderBottom(tester), 56.0);
     expect(getBorderWeight(tester), 2.0);
 
@@ -1010,6 +1012,17 @@ void main() {
       ),
     );
 
+    // The hint's opacity animates from 1.0 to 0.0.
+    // The animation's duration is 200ms.
+    {
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity50ms = getOpacity(tester, 'hint');
+      expect(hintOpacity50ms, inExclusiveRange(0.0, 1.0));
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity100ms = getOpacity(tester, 'hint');
+      expect(hintOpacity100ms, inExclusiveRange(0.0, hintOpacity50ms));
+    }
+
     await tester.pumpAndSettle();
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 56.0));
     expect(tester.getTopLeft(find.text('text')).dy, 28.0);
@@ -1018,7 +1031,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('label')).dy, 24.0);
     expect(tester.getTopLeft(find.text('hint')).dy, 28.0);
     expect(tester.getBottomLeft(find.text('hint')).dy, 44.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderBottom(tester), 56.0);
     expect(getBorderWeight(tester), 2.0);
   });
@@ -1058,7 +1071,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('text')).dy, 40.0);
     expect(tester.getTopLeft(find.text('label')).dy, 16.0);
     expect(tester.getBottomLeft(find.text('label')).dy, 32.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderBottom(tester), 48.0);
     expect(getBorderWeight(tester), 1.0);
 
@@ -1080,7 +1093,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('text')).dy, 40.0);
     expect(tester.getTopLeft(find.text('label')).dy, 8.0);
     expect(tester.getBottomLeft(find.text('label')).dy, 20.0);
-    expect(getStaticOpacity(tester, 'hint'), 1.0);
+    expect(getOpacity(tester, 'hint'), 1.0);
     expect(getBorderBottom(tester), 48.0);
     expect(getBorderWeight(tester), 2.0);
   });
@@ -1855,7 +1868,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('text')).dy, 40.0);
     expect(tester.getTopLeft(find.text('label')).dy, 16.0);
     expect(tester.getBottomLeft(find.text('label')).dy, 32.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderBottom(tester), 48.0);
     expect(getBorderWeight(tester), 1.0);
 
@@ -1872,6 +1885,17 @@ void main() {
       ),
     );
 
+    // The hint's opacity animates from 0.0 to 1.0.
+    // The animation's duration is 200ms.
+    {
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity50ms = getOpacity(tester, 'hint');
+      expect(hintOpacity50ms, inExclusiveRange(0.0, 1.0));
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity100ms = getOpacity(tester, 'hint');
+      expect(hintOpacity100ms, inExclusiveRange(hintOpacity50ms, 1.0));
+    }
+
     await tester.pumpAndSettle();
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 48.0));
     expect(tester.getTopLeft(find.text('text')).dy, 24.0);
@@ -1880,7 +1904,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('label')).dy, 24.0);
     expect(tester.getTopLeft(find.text('hint')).dy, 24.0);
     expect(tester.getBottomLeft(find.text('hint')).dy, 40.0);
-    expect(getStaticOpacity(tester, 'hint'), 1.0);
+    expect(getOpacity(tester, 'hint'), 1.0);
     expect(getBorderBottom(tester), 48.0);
     expect(getBorderWeight(tester), 2.0);
 
@@ -1895,6 +1919,17 @@ void main() {
       ),
     );
 
+    // The hint's opacity animates from 1.0 to 0.0.
+    // The animation's duration is 200ms.
+    {
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity50ms = getOpacity(tester, 'hint');
+      expect(hintOpacity50ms, inExclusiveRange(0.0, 1.0));
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity100ms = getOpacity(tester, 'hint');
+      expect(hintOpacity100ms, inExclusiveRange(0.0, hintOpacity50ms));
+    }
+
     await tester.pumpAndSettle();
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 48.0));
     expect(tester.getTopLeft(find.text('text')).dy, 24.0);
@@ -1903,7 +1938,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('label')).dy, 24.0);
     expect(tester.getTopLeft(find.text('hint')).dy, 24.0);
     expect(tester.getBottomLeft(find.text('hint')).dy, 40.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderBottom(tester), 48.0);
     expect(getBorderWeight(tester), 2.0);
   });
@@ -1927,7 +1962,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('text')).dy, 48.0);
     expect(tester.getTopLeft(find.text('label')).dy, 24.0);
     expect(tester.getBottomLeft(find.text('label')).dy, 40.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderBottom(tester), 64.0);
     expect(getBorderWeight(tester), 1.0);
 
@@ -1944,6 +1979,17 @@ void main() {
       ),
     );
 
+    // The hint's opacity animates from 0.0 to 1.0.
+    // The animation's duration is 200ms.
+    {
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity50ms = getOpacity(tester, 'hint');
+      expect(hintOpacity50ms, inExclusiveRange(0.0, 1.0));
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity100ms = getOpacity(tester, 'hint');
+      expect(hintOpacity100ms, inExclusiveRange(hintOpacity50ms, 1.0));
+    }
+
     await tester.pumpAndSettle();
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 64.0));
     expect(tester.getTopLeft(find.text('text')).dy, 32.0);
@@ -1952,7 +1998,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('label')).dy, 24.0);
     expect(tester.getTopLeft(find.text('hint')).dy, 32.0);
     expect(tester.getBottomLeft(find.text('hint')).dy, 48.0);
-    expect(getStaticOpacity(tester, 'hint'), 1.0);
+    expect(getOpacity(tester, 'hint'), 1.0);
     expect(getBorderBottom(tester), 64.0);
     expect(getBorderWeight(tester), 2.0);
 
@@ -1967,6 +2013,17 @@ void main() {
       ),
     );
 
+    // The hint's opacity animates from 1.0 to 0.0.
+    // The animation's duration is 200ms.
+    {
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity50ms = getOpacity(tester, 'hint');
+      expect(hintOpacity50ms, inExclusiveRange(0.0, 1.0));
+      await tester.pump(const Duration(milliseconds: 50));
+      final double hintOpacity100ms = getOpacity(tester, 'hint');
+      expect(hintOpacity100ms, inExclusiveRange(0.0, hintOpacity50ms));
+    }
+
     await tester.pumpAndSettle();
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 64.0));
     expect(tester.getTopLeft(find.text('text')).dy, 32.0);
@@ -1975,7 +2032,7 @@ void main() {
     expect(tester.getBottomLeft(find.text('label')).dy, 24.0);
     expect(tester.getTopLeft(find.text('hint')).dy, 32.0);
     expect(tester.getBottomLeft(find.text('hint')).dy, 48.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderBottom(tester), 64.0);
     expect(getBorderWeight(tester), 2.0);
   });
@@ -3213,7 +3270,7 @@ void main() {
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 18.0));
     expect(tester.getSize(find.text('text')).height, 16.0);
     expect(tester.getTopLeft(find.text('text')).dy, 1.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderWeight(tester), 1.0);
 
     await tester.pumpWidget(
@@ -3236,7 +3293,7 @@ void main() {
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 16.0));
     expect(tester.getSize(find.text('text')).height, 16.0);
     expect(tester.getTopLeft(find.text('text')).dy, 0.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderWeight(tester), 1.0);
 
     await tester.pumpWidget(
@@ -3258,7 +3315,7 @@ void main() {
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, kMinInteractiveDimension));
     expect(tester.getSize(find.text('text')).height, 16.0);
     expect(tester.getTopLeft(find.text('text')).dy, 16.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderWeight(tester), 0.0);
   });
 
@@ -3280,7 +3337,7 @@ void main() {
     expect(tester.getSize(find.byType(InputDecorator)), const Size(800.0, 16.0));
     expect(tester.getSize(find.text('text')).height, 16.0);
     expect(tester.getTopLeft(find.text('text')).dy, 0.0);
-    expect(getStaticOpacity(tester, 'hint'), 0.0);
+    expect(getOpacity(tester, 'hint'), 0.0);
     expect(getBorderWeight(tester), 0.0);
 
     // The hint should appear
@@ -5026,7 +5083,7 @@ void main() {
     );
     await tester.pumpAndSettle();
 
-    expect(getStaticOpacity(tester, 'hint'), 1.0);
+    expect(getOpacity(tester, 'hint'), 1.0);
   });
 
   testWidgets('InputDecorator floating label width scales when focused', (WidgetTester tester) async {

packages/flutter/test/material/text_field_test.dart

@@ -131,15 +131,6 @@ double getOpacity(WidgetTester tester, Finder finder) {
   ).opacity.value;
 }
 
-double getStaticOpacity(WidgetTester tester, Finder finder) {
-  return tester.widget<Opacity>(
-    find.ancestor(
-      of: finder,
-      matching: find.byType(Opacity),
-    ).first,
-  ).opacity;
-}
-
 class TestFormatter extends TextInputFormatter {
   TestFormatter(this.onFormatEditUpdate);
   FormatEditUpdateCallback onFormatEditUpdate;
@@ -3681,7 +3672,7 @@ void main() {
     // Neither the prefix or the suffix should initially be visible, only the hint.
     expect(getOpacity(tester, find.text('Prefix')), 0.0);
     expect(getOpacity(tester, find.text('Suffix')), 0.0);
-    expect(getStaticOpacity(tester, find.text('Hint')), 1.0);
+    expect(getOpacity(tester, find.text('Hint')), 1.0);
 
     await tester.tap(find.byKey(secondKey));
     await tester.pumpAndSettle();
@@ -3689,7 +3680,7 @@ void main() {
     // Focus the Input. The hint, prefix, and suffix should appear
     expect(getOpacity(tester, find.text('Prefix')), 1.0);
     expect(getOpacity(tester, find.text('Suffix')), 1.0);
-    expect(getStaticOpacity(tester, find.text('Hint')), 1.0);
+    expect(getOpacity(tester, find.text('Hint')), 1.0);
 
     // Enter some text, and the hint should disappear and the prefix and suffix
     // should continue to be visible
@@ -3698,7 +3689,7 @@ void main() {
 
     expect(getOpacity(tester, find.text('Prefix')), 1.0);
     expect(getOpacity(tester, find.text('Suffix')), 1.0);
-    expect(getStaticOpacity(tester, find.text('Hint')), 0.0);
+    expect(getOpacity(tester, find.text('Hint')), 0.0);
 
     // Check and make sure that the right styles were applied.
     final Text prefixText = tester.widget(find.text('Prefix'));