Implement message_list

flutter/lib/components/bottom_fab/fab_bottom_app_bar.dart

@@ -0,0 +1,107 @@
+import 'package:flutter/material.dart';
+
+class FABBottomAppBarItem {
+  FABBottomAppBarItem({required this.iconData, required this.text});
+  IconData iconData;
+  String text;
+}
+
+class FABBottomAppBar extends StatelessWidget {
+  FABBottomAppBar({
+    super.key,
+    required this.items,
+    this.centerItemText,
+    this.height = 60.0,
+    this.iconSize = 24.0,
+    this.backgroundColor,
+    this.color,
+    this.selectedColor,
+    this.notchedShape,
+    this.onTabSelected,
+    this.selectedIndex = 0,
+  }) {
+    assert(items.length == 2 || items.length == 4);
+  }
+
+  final List<FABBottomAppBarItem> items;
+  final String? centerItemText;
+  final double height;
+  final double iconSize;
+  final Color? backgroundColor;
+  final Color? color;
+  final Color? selectedColor;
+  final NotchedShape? notchedShape;
+  final ValueChanged<int>? onTabSelected;
+  final int selectedIndex;
+
+  @override
+  Widget build(BuildContext context) {
+    List<Widget> items = List.generate(this.items.length, (int index) {
+      return _buildTabItem(
+        item: this.items[index],
+        index: index,
+        onPressed: _updateIndex,
+      );
+    });
+    items.insert(items.length >> 1, _buildMiddleTabItem());
+
+    return BottomAppBar(
+      shape: notchedShape,
+      color: backgroundColor,
+      child: Row(
+        mainAxisSize: MainAxisSize.max,
+        mainAxisAlignment: MainAxisAlignment.spaceAround,
+        children: items,
+      ),
+    );
+  }
+
+  Widget _buildMiddleTabItem() {
+    return Expanded(
+      child: SizedBox(
+        height: height,
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            SizedBox(height: iconSize),
+            Text(
+              centerItemText ?? '',
+              style: TextStyle(color: color),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildTabItem({required FABBottomAppBarItem item, required int index, required ValueChanged<int> onPressed}) {
+    Color color = (selectedIndex == index ? selectedColor : this.color) ?? Colors.black;
+    return Expanded(
+      child: SizedBox(
+        height: height,
+        child: Material(
+          type: MaterialType.transparency,
+          child: InkWell(
+            onTap: () => onPressed(index),
+            child: Column(
+              mainAxisSize: MainAxisSize.min,
+              mainAxisAlignment: MainAxisAlignment.center,
+              children: <Widget>[
+                Icon(item.iconData, color: color, size: iconSize),
+                Text(
+                  item.text,
+                  style: TextStyle(color: color),
+                )
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  void _updateIndex(int index) {
+    if (onTabSelected != null) onTabSelected!(index);
+  }
+}