chagne the elevation from int to double (#82340)

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

@@ -55,7 +55,7 @@ class _DropdownMenuPainter extends CustomPainter {
        super(repaint: resize);
 
   final Color? color;
-  final int? elevation;
+  final double? elevation;
   final int? selectedIndex;
   final Animation<double> resize;
   final ValueGetter<double> getSelectedItemOffset;
@@ -425,7 +425,7 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
   final EdgeInsetsGeometry padding;
   final Rect buttonRect;
   final int selectedIndex;
-  final int elevation;
+  final double elevation;
   final CapturedThemes capturedThemes;
   final TextStyle style;
   final double? itemHeight;
@@ -568,7 +568,7 @@ class _DropdownRoutePage<T> extends StatelessWidget {
   final EdgeInsetsGeometry padding;
   final Rect buttonRect;
   final int selectedIndex;
-  final int elevation;
+  final double elevation;
   final CapturedThemes capturedThemes;
   final TextStyle? style;
   final Color? dropdownColor;
@@ -997,12 +997,8 @@ class DropdownButton<T> extends StatefulWidget {
   final DropdownButtonBuilder? selectedItemBuilder;
 
   /// The z-coordinate at which to place the menu when open.
-  ///
-  /// The following elevations have defined shadows: 1, 2, 3, 4, 6, 8, 9, 12,
-  /// 16, and 24. See [kElevationToShadow].
-  ///
   /// Defaults to 8, the appropriate elevation for dropdown buttons.
-  final int elevation;
+  final double elevation;
 
   /// The text style to use for text in the dropdown button and the dropdown
   /// menu that appears when you tap the button.
@@ -1540,7 +1536,7 @@ class DropdownButtonFormField<T> extends FormField<T> {
     Widget? disabledHint,
     this.onChanged,
     VoidCallback? onTap,
-    int elevation = 8,
+    double elevation = 8,
     TextStyle? style,
     Widget? icon,
     Color? iconDisabledColor,

packages/flutter/test/material/dropdown_form_field_test.dart

@@ -27,7 +27,7 @@ Finder _iconRichText(Key iconKey) {
 Widget buildFormFrame({
   Key? buttonKey,
   AutovalidateMode autovalidateMode = AutovalidateMode.disabled,
-  int elevation = 8,
+  double elevation = 8,
   String? value = 'two',
   ValueChanged<String?>? onChanged,
   VoidCallback? onTap,
@@ -125,7 +125,7 @@ class TestApp extends StatefulWidget {
   State<TestApp> createState() => _TestAppState();
 }
 
-void verifyPaintedShadow(Finder customPaint, int elevation) {
+void verifyPaintedShadow(Finder customPaint, double elevation) {
   const Rect originalRectangle = Rect.fromLTRB(0.0, 0.0, 800, 208.0);
 
   final List<BoxShadow> boxShadows = List<BoxShadow>.generate(3, (int index) => kElevationToShadow[elevation]![index]);

packages/flutter/test/material/dropdown_test.dart

@@ -237,7 +237,7 @@ void checkSelectedItemTextGeometry(WidgetTester tester, String value) {
   expect(box0.size, equals(box1.size));
 }
 
-void verifyPaintedShadow(Finder customPaint, int elevation) {
+void verifyPaintedShadow(Finder customPaint, double elevation) {
   const Rect originalRectangle = Rect.fromLTRB(0.0, 0.0, 800, 208.0);
 
   final List<BoxShadow> boxShadows = List<BoxShadow>.generate(3, (int index) => kElevationToShadow[elevation]![index]);