Toast 组件统一与消息堆叠显示

/// Toast 消息队列管理
class _ToastManager {
  static final List<OverlayEntry> _entries = [];
  static const Duration _defaultDuration = Duration(seconds: 3);
  static const double _spacing = 8.0;
  static const double _bottomPadding = 80.0;
 
  /// 显示 Toast
  static void show(BuildContext context, String message, {
    Duration? duration,
    Color? backgroundColor,
    Color? textColor,
  }) {
    final overlay = Overlay.of(context);
    
    // 创建 Toast 条目
    late OverlayEntry entry;
    entry = OverlayEntry(
      builder: (context) => _ToastWidget(
        message: message,
        backgroundColor: backgroundColor,
        textColor: textColor,
        onDismiss: () => _removeEntry(entry),
        index: _entries.length,
      ),
    );
    
    // 添加到队列
    _entries.add(entry);
    overlay.insert(entry);
    
    // 更新其他 Toast 位置
    _updatePositions();
    
    // 定时移除
    Future.delayed(duration ?? _defaultDuration, () {
      if (_entries.contains(entry)) {
        _removeEntry(entry);
      }
    });
  }
  
  /// 更新所有 Toast 的位置
  static void _updatePositions() {
    for (int i = 0; i < _entries.length; i++) {
      _entries[i].markNeedsBuild();
    }
  }
  
  /// 移除 Toast
  static void _removeEntry(OverlayEntry entry) {
    entry.remove();
    _entries.remove(entry);
    _updatePositions();
  }
}
 
/// Toast 组件
class _ToastWidget extends StatefulWidget {
  final String message;
  final Color? backgroundColor;
  final Color? textColor;
  final VoidCallback onDismiss;
  final int index;
  
  // ...
}
 
class _ToastWidgetState extends State<_ToastWidget>
    with SingleTickerProviderStateMixin {
  late AnimationController _controller;
  late Animation<double> _fadeAnimation;
  late Animation<Offset> _slideAnimation;
  
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(milliseconds: 300),
      vsync: this,
    );
    
    _fadeAnimation = Tween<double>(begin: 0.0, end: 1.0)
        .animate(_controller);
    _slideAnimation = Tween<Offset>(
      begin: const Offset(0, 1),
      end: Offset.zero,
    ).animate(_controller);
    
    _controller.forward();
  }
  
  @override
  Widget build(BuildContext context) {
    // 计算底部位置（堆叠显示）
    final bottom = _ToastManager._bottomPadding + 
        widget.index * (_toastHeight + _ToastManager._spacing);
    
    return Positioned(
      left: 16,
      right: 16,
      bottom: bottom,
      child: SlideTransition(
        position: _slideAnimation,
        child: FadeTransition(
          opacity: _fadeAnimation,
          child: Material(
            elevation: 6,
            borderRadius: BorderRadius.circular(8),
            color: widget.backgroundColor ?? Colors.black87,
            child: Padding(
              padding: const EdgeInsets.symmetric(
                horizontal: 16,
                vertical: 12,
              ),
              child: Text(
                widget.message,
                style: TextStyle(
                  color: widget.textColor ?? Colors.white,
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}
 
/// 全局便捷方法
void showAppToast(BuildContext context, String message) {
  _ToastManager.show(context, message);
}