feat: Programmatically expand/collapse ExpansionTile

packages/flet/lib/src/controls/cupertino_sliding_segmented_button.dart

@@ -19,14 +19,13 @@ class CupertinoSlidingSegmentedButtonControl extends StatelessWidget {
     debugPrint("CupertinoSlidingSegmentedButtonControl build: ${control.id}");
 
     var controls = control.buildWidgets("controls");
-
     if (controls.length < 2) {
       return const ErrorControl(
           "CupertinoSlidingSegmentedButton must have at minimum two visible controls");
     }
 
     var button = CupertinoSlidingSegmentedControl(
-      groupValue: control.getInt("selected_index"),
+      groupValue: control.getInt("selected_index", 0)!,
       proportionalWidth: control.getBool("proportional_width", false)!,
       backgroundColor: control.getColor(
           "bgcolor", context, CupertinoColors.tertiarySystemFill)!,
@@ -36,15 +35,13 @@ class CupertinoSlidingSegmentedButtonControl extends StatelessWidget {
           "thumb_color",
           context,
           const CupertinoDynamicColor.withBrightness(
-            color: Color(0xFFFFFFFF),
-            darkColor: Color(0xFF636366),
-          ))!,
+              color: Color(0xFFFFFFFF), darkColor: Color(0xFF636366)))!,
       children: controls.asMap().map((i, c) => MapEntry(i, c)),
       onValueChanged: (int? index) {
         if (!control.disabled) {
-          control
-              .updateProperties({"selected_index": index ?? 0}, notify: true);
-          control.triggerEvent("change", index ?? 0);
+          index = index ?? 0;
+          control.updateProperties({"selected_index": index}, notify: true);
+          control.triggerEvent("change", index);
         }
       },
     );

packages/flet/lib/src/controls/expansion_tile.dart

@@ -1,4 +1,6 @@
+import 'package:flet/src/utils/animations.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
 
 import '../extensions/control.dart';
 import '../models/control.dart';
@@ -11,97 +13,114 @@ import '../utils/numbers.dart';
 import '../utils/theme.dart';
 import '../widgets/error.dart';
 import 'base_controls.dart';
-import 'control_widget.dart';
 
-class ExpansionTileControl extends StatelessWidget {
+class ExpansionTileControl extends StatefulWidget {
   final Control control;
 
-  const ExpansionTileControl({
-    super.key,
-    required this.control,
-  });
+  const ExpansionTileControl({super.key, required this.control});
 
   @override
-  Widget build(BuildContext context) {
-    debugPrint("ExpansionTile build: ${control.id}");
+  State<ExpansionTileControl> createState() => _ExpansionTileControlState();
+}
+
+class _ExpansionTileControlState extends State<ExpansionTileControl> {
+  late final ExpansibleController _controller;
+  bool _expanded = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = ExpansibleController();
+    _expanded = widget.control.getBool("expanded", false)!;
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
 
-    var controls = control
-        .children("controls")
-        .map((child) => ControlWidget(control: child, key: ValueKey(child.id)))
-        .toList();
+  // Schedules an update to the controller after the current frame.
+  // This ensures the expansion/collapse animation is triggered safely.
+  void _scheduleControllerUpdate(bool expanded) {
+    SchedulerBinding.instance.addPostFrameCallback((_) {
+      if (!mounted) return; // Prevents updates if the widget is disposed.
 
-    var leading = control.buildIconOrWidget("leading");
-    var title = control.buildTextOrWidget("title");
-    var subtitle = control.buildTextOrWidget("subtitle");
-    var trailing = control.buildIconOrWidget("trailing");
+      if (expanded) {
+        _controller.expand();
+      } else {
+        _controller.collapse();
+      }
+    });
+  }
 
+  @override
+  Widget build(BuildContext context) {
+    debugPrint("ExpansionTile build: ${widget.control.id}");
+
+    final title = widget.control.buildTextOrWidget("title");
     if (title == null) {
       return const ErrorControl(
           "ExpansionTile.title must be provided and visible");
     }
 
-    bool maintainState = control.getBool("maintain_state", false)!;
-    bool initiallyExpanded = control.getBool("initially_expanded", false)!;
-
-    var iconColor = control.getColor("icon_color", context);
-    var textColor = control.getColor("text_color", context);
-    var bgColor = control.getColor("bgcolor", context);
-    var collapsedBgColor = control.getColor("collapsed_bgcolor", context);
-    var collapsedIconColor = control.getColor("collapsed_icon_color", context);
-    var collapsedTextColor = control.getColor("collapsed_text_color", context);
-
-    var affinity = control.getListTileControlAffinity(
-        "affinity", ListTileControlAffinity.platform)!;
-    var clipBehavior = parseClip(control.getString("clip_behavior"));
+    var expanded = widget.control.getBool("expanded", false)!;
+    if (_expanded != expanded) {
+      _expanded = expanded;
+      _scheduleControllerUpdate(expanded);
+    }
 
-    var expandedCrossAxisAlignment = control.getCrossAxisAlignment(
+    var expandedCrossAxisAlignment = widget.control.getCrossAxisAlignment(
         "expanded_cross_axis_alignment", CrossAxisAlignment.center)!;
-
     if (expandedCrossAxisAlignment == CrossAxisAlignment.baseline) {
       return const ErrorControl(
-          'CrossAxisAlignment.baseline is not supported since the expanded '
+          'CrossAxisAlignment.BASELINE is not supported since the expanded '
           'controls are aligned in a column, not a row. '
           'Try aligning the controls differently.');
     }
 
-    Function(bool)? onChange = !control.disabled
-        ? (expanded) {
-            control.triggerEvent("change", expanded);
-          }
-        : null;
-
-    Widget tile = ExpansionTile(
-      controlAffinity: affinity,
-      childrenPadding: control.getPadding("controls_padding"),
-      tilePadding: control.getEdgeInsets("tile_padding"),
-      expandedAlignment: control.getAlignment("expanded_alignment"),
-      expandedCrossAxisAlignment:
-          control.getCrossAxisAlignment("expanded_cross_axis_alignment"),
-      backgroundColor: bgColor,
-      iconColor: iconColor,
-      textColor: textColor,
-      collapsedBackgroundColor: collapsedBgColor,
-      collapsedIconColor: collapsedIconColor,
-      collapsedTextColor: collapsedTextColor,
-      maintainState: maintainState,
-      initiallyExpanded: initiallyExpanded,
-      clipBehavior: clipBehavior,
-      shape: control.getShape("shape", Theme.of(context)),
-      collapsedShape: control.getShape("collapsed_shape", Theme.of(context)),
-      onExpansionChanged: onChange,
-      visualDensity: control.getVisualDensity("visual_density"),
-      enableFeedback: control.getBool("enable_feedback"),
-      showTrailingIcon: control.getBool("show_trailing_icon", true)!,
-      enabled: !control.disabled,
-      minTileHeight: control.getDouble("min_tile_height"),
-      dense: control.getBool("dense"),
-      leading: leading,
+    final tile = ExpansionTile(
+      controller: _controller,
+      controlAffinity: widget.control.getListTileControlAffinity("affinity"),
+      childrenPadding: widget.control.getPadding("controls_padding"),
+      tilePadding: widget.control.getEdgeInsets("tile_padding"),
+      expandedAlignment: widget.control.getAlignment("expanded_alignment"),
+      expandedCrossAxisAlignment: expandedCrossAxisAlignment,
+      backgroundColor: widget.control.getColor("bgcolor", context),
+      iconColor: widget.control.getColor("icon_color", context),
+      textColor: widget.control.getColor("text_color", context),
+      collapsedBackgroundColor:
+          widget.control.getColor("collapsed_bgcolor", context),
+      collapsedIconColor:
+          widget.control.getColor("collapsed_icon_color", context),
+      collapsedTextColor:
+          widget.control.getColor("collapsed_text_color", context),
+      maintainState: widget.control.getBool("maintain_state", false)!,
+      initiallyExpanded: expanded,
+      clipBehavior: widget.control.getClipBehavior("clip_behavior"),
+      shape: widget.control.getShape("shape", Theme.of(context)),
+      collapsedShape:
+          widget.control.getShape("collapsed_shape", Theme.of(context)),
+      onExpansionChanged: (bool expanded) {
+        _expanded = expanded;
+        widget.control.updateProperties({"expanded": expanded});
+        widget.control.triggerEvent("change", expanded);
+      },
+      visualDensity: widget.control.getVisualDensity("visual_density"),
+      enableFeedback: widget.control.getBool("enable_feedback"),
+      showTrailingIcon: widget.control.getBool("show_trailing_icon", true)!,
+      enabled: !widget.control.disabled,
+      minTileHeight: widget.control.getDouble("min_tile_height"),
+      dense: widget.control.getBool("dense"),
+      expansionAnimationStyle:
+          widget.control.getAnimationStyle("animation_style"),
+      leading: widget.control.buildIconOrWidget("leading"),
       title: title,
-      subtitle: subtitle,
-      trailing: trailing,
-      children: controls,
+      subtitle: widget.control.buildTextOrWidget("subtitle"),
+      trailing: widget.control.buildIconOrWidget("trailing"),
+      children: widget.control.buildWidgets("controls"),
     );
 
-    return LayoutControl(control: control, child: tile);
+    return LayoutControl(control: widget.control, child: tile);
   }
 }

packages/flet/lib/src/utils/theme.dart

@@ -8,6 +8,7 @@ import '../flet_backend.dart';
 import '../models/control.dart';
 import '../utils/transforms.dart';
 import 'alignment.dart';
+import 'animations.dart';
 import 'borders.dart';
 import 'box.dart';
 import 'buttons.dart';
@@ -850,6 +851,9 @@ ListTileThemeData? parseListTileTheme(
         parseTextStyle(value["leading_and_trailing_text_style"], theme),
     mouseCursor: parseWidgetStateMouseCursor(value["mouse_cursor"]),
     minTileHeight: parseDouble(value["min_height"]),
+    controlAffinity: parseListTileControlAffinity(value["affinity"]),
+    style: parseListTileStyle(value["style"]),
+    titleAlignment: parseListTileTitleAlignment(value["title_alignment"]),
   );
 }
 
@@ -894,6 +898,10 @@ ExpansionTileThemeData? parseExpansionTileTheme(
     tilePadding: parsePadding(value["tile_padding"]),
     expandedAlignment: parseAlignment(value["expanded_alignment"]),
     childrenPadding: parsePadding(value["controls_padding"]),
+    shape: parseShape(value["shape"], theme),
+    collapsedShape: parseShape(value["collapsed_shape"], theme),
+    expansionAnimationStyle:
+        parseAnimationStyle(value["expansion_animation_style"]),
   );
 }
 

sdk/python/examples/controls/expansion_tile/custom_animations.py

@@ -0,0 +1,44 @@
+import flet as ft
+
+
+def main(page: ft.Page):
+    page.horizontal_alignment = ft.CrossAxisAlignment.CENTER
+    page.spacing = 20
+
+    def switch_animation(e: ft.Event[ft.CupertinoSlidingSegmentedButton]):
+        if e.control.selected_index == 0:
+            tile.animation_style = None
+        elif e.control.selected_index == 1:
+            tile.animation_style = ft.AnimationStyle(
+                curve=ft.AnimationCurve.BOUNCE_OUT,
+                duration=ft.Duration(seconds=5),
+            )
+        else:
+            tile.animation_style = ft.AnimationStyle.no_animation()
+
+    page.add(
+        ft.CupertinoSlidingSegmentedButton(
+            selected_index=0,
+            thumb_color=ft.Colors.BLUE_400,
+            on_change=switch_animation,
+            controls=[
+                ft.Text("Default animation"),
+                ft.Text("Custom animation"),
+                ft.Text("No animation"),
+            ],
+        ),
+        tile := ft.ExpansionTile(
+            expanded=True,
+            title=ft.Text(
+                "Expand/Collapse me while being attentive to the animations!"
+            ),
+            controls=[
+                ft.ListTile(title=ft.Text("Sub-item 1")),
+                ft.ListTile(title=ft.Text("Sub-item 2")),
+                ft.ListTile(title=ft.Text("Sub-item 3")),
+            ],
+        ),
+    )
+
+
+ft.run(main)

sdk/python/examples/controls/expansion_tile/programmatic_expansion.py

@@ -0,0 +1,34 @@
+import flet as ft
+
+
+def main(page: ft.Page):
+    page.spacing = 20
+
+    def expand_tile(e: ft.Event[ft.FilledButton]):
+        tile.expanded = True
+
+    def collapse_tile(e: ft.Event[ft.OutlinedButton]):
+        tile.expanded = False
+
+    page.add(
+        ft.Row(
+            alignment=ft.MainAxisAlignment.CENTER,
+            controls=[
+                ft.FilledButton("Expand Tile", on_click=expand_tile),
+                ft.OutlinedButton("Collapse Tile", on_click=collapse_tile),
+            ],
+        ),
+        tile := ft.ExpansionTile(
+            title=ft.Text("I am the title of this tile.", weight=ft.FontWeight.BOLD),
+            subtitle=ft.Text("This is the subtitle."),
+            affinity=ft.TileAffinity.LEADING,
+            controls=[ft.Text("👻", size=80)],
+            expanded=True,
+            on_change=lambda e: print(
+                f"Tile was {'expanded' if e.data else 'collapsed'}"
+            ),
+        ),
+    )
+
+
+ft.run(main)

sdk/python/packages/flet/docs/controls/expansiontile.md

@@ -19,6 +19,17 @@ example_media: ../examples/controls/expansion_tile/media
 
 {{ image(example_media + "/basic.png", alt="basic", width="80%") }}
 
+## Programmatic expansion/collapse
+
+```python
+--8<-- "{{ examples }}/programmatic_expansion.py"
+```
+
+## Custom animations
+
+```python
+--8<-- "{{ examples }}/custom_animations.py"
+```
 
 ### Theme mode toggle
 

sdk/python/packages/flet/src/flet/controls/animation.py

@@ -86,6 +86,16 @@ def copy(
 
 @dataclass
 class AnimationStyle:
+    """
+    Used to override the default parameters of an animation.
+
+    Note:
+        If [`duration`][(c).] and [`reverse_duration`][(c).] are set to
+        [`Duration()`][flet.Duration], the corresponding animation will be disabled.
+        See [`no_animation()`][(c).no_animation] method for a convenient way to create
+        such an instance.
+    """
+
     duration: Optional[DurationValue] = None
     """
     The duration of the animation.
@@ -106,6 +116,16 @@ class AnimationStyle:
     The curve to use for the reverse animation.
     """
 
+    @staticmethod
+    def no_animation() -> "AnimationStyle":
+        """
+        Creates an instance of `AnimationStyle` with no animation.
+        """
+        return AnimationStyle(
+            duration=Duration(),
+            reverse_duration=Duration(),
+        )
+
     def copy(
         self,
         *,