mathtool2/lib/tools/function_plotter.dart

// tools/function_plotter.dart
import 'package:flutter/material.dart';
import 'package:math_expressions/math_expressions.dart';
import 'package:fl_chart/fl_chart.dart';

class FunctionPlotterPage extends StatefulWidget {
  @override
  _FunctionPlotterPageState createState() => _FunctionPlotterPageState();
}

class _FunctionPlotterPageState extends State<FunctionPlotterPage> {
  final List<TextEditingController> _functionControllers = [
    TextEditingController(text: 'x^2'),
  ];
  final TextEditingController _xMinController = TextEditingController(text: '-5');
  final TextEditingController _xMaxController = TextEditingController(text: '5');
  final TextEditingController _yMinController = TextEditingController(text: '-10');
  final TextEditingController _yMaxController = TextEditingController(text: '10');
  
  List<Color> _functionColors = [
    Colors.blue,
    Colors.red,
    Colors.green,
    Colors.orange,
    Colors.purple,
  ];
  
  List<String> _functionErrors = [];

  @override
  void dispose() {
    for (var controller in _functionControllers) {
      controller.dispose();
    }
    _xMinController.dispose();
    _xMaxController.dispose();
    _yMinController.dispose();
    _yMaxController.dispose();
    super.dispose();
  }

  void _addFunction() {
    if (_functionControllers.length < 5) {
      setState(() {
        _functionControllers.add(TextEditingController());
      });
    }
  }

  void _removeFunction(int index) {
    if (_functionControllers.length > 1) {
      setState(() {
        _functionControllers.removeAt(index);
        if (_functionErrors.length > index) {
          _functionErrors.removeAt(index);
        }
      });
    }
  }

  List<FlSpot> _evaluateFunction(String function, double xMin, double xMax, int functionIndex) {
    List<FlSpot> points = [];
    
    try {
      Parser p = Parser();
      Expression exp = p.parse(function);
      ContextModel cm = ContextModel();
      
      int numberOfPoints = 200;
      double step = (xMax - xMin) / numberOfPoints;
      
      for (int i = 0; i <= numberOfPoints; i++) {
        double xValue = xMin + i * step;
        
        try {
          cm.bindVariable(Variable('x'), Number(xValue));
          double yValue = exp.evaluate(EvaluationType.REAL, cm);
          
          if (yValue.isFinite && yValue.abs() < 1e10) {
            points.add(FlSpot(xValue, yValue));
          } else {
            points.add(FlSpot.nullSpot);
          }
        } catch (e) {
          points.add(FlSpot.nullSpot);
        }
      }
    } catch (e) {
      if (_functionErrors.length <= functionIndex) {
        _functionErrors.addAll(List.filled(functionIndex - _functionErrors.length + 1, ''));
      }
      _functionErrors[functionIndex] = '函数解析错误: ${e.toString()}';
    }
    
    return points;
  }

  void _plotFunctions() {
    setState(() {
      _functionErrors.clear();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('函数图像绘制', style: TextStyle(color: Colors.black)),
        backgroundColor: Colors.white,
        elevation: 1,
        actions: [
          IconButton(
            icon: Icon(Icons.refresh),
            onPressed: _plotFunctions,
            tooltip: '重新绘制',
          ),
        ],
      ),
      body: SingleChildScrollView( // 添加外层滚动
        child: Padding(
          padding: EdgeInsets.all(16),
          child: Column(
            children: [
              // 函数输入区域 - 移除固定高度约束
              _buildFunctionInputs(),
              
              SizedBox(height: 16), // 添加间距
              
              // 绘图区域 - 设置固定高度
              Container(
                height: MediaQuery.of(context).size.height * 0.5, // 使用屏幕高度的一半
                child: _buildPlotArea(),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildFunctionInputs() {
    return Card(
      elevation: 4,
      child: Padding(
        padding: EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              '函数表达式 (使用 x 作为变量)',
              style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 10),
            Text(
              '支持: +, -, *, /, ^, sin, cos, tan, ln, sqrt, e',
              style: TextStyle(fontSize: 12, color: Colors.grey),
            ),
            SizedBox(height: 10),
            
            // 坐标范围设置 - 在小屏幕上改为垂直布局
            LayoutBuilder(
              builder: (context, constraints) {
                if (constraints.maxWidth < 600) {
                  // 小屏幕垂直布局
                  return Column(
                    children: [
                      _buildRangeTextField(_xMinController, 'x最小值'),
                      SizedBox(height: 10),
                      _buildRangeTextField(_xMaxController, 'x最大值'),
                      SizedBox(height: 10),
                      _buildRangeTextField(_yMinController, 'y最小值'),
                      SizedBox(height: 10),
                      _buildRangeTextField(_yMaxController, 'y最大值'),
                    ],
                  );
                } else {
                  // 大屏幕水平布局
                  return Row(
                    children: [
                      Expanded(child: _buildRangeTextField(_xMinController, 'x最小值')),
                      SizedBox(width: 10),
                      Expanded(child: _buildRangeTextField(_xMaxController, 'x最大值')),
                      SizedBox(width: 10),
                      Expanded(child: _buildRangeTextField(_yMinController, 'y最小值')),
                      SizedBox(width: 10),
                      Expanded(child: _buildRangeTextField(_yMaxController, 'y最大值')),
                    ],
                  );
                }
              },
            ),
            SizedBox(height: 10),
            
            // 函数输入列表 - 设置最大高度并允许滚动
            Container(
              constraints: BoxConstraints(
                maxHeight: 200, // 限制最大高度
              ),
              child: ListView.builder(
                shrinkWrap: true,
                itemCount: _functionControllers.length,
                itemBuilder: (context, index) {
                  return Padding(
                    padding: EdgeInsets.symmetric(vertical: 5),
                    child: Row(
                      children: [
                        Container(
                          width: 20,
                          height: 20,
                          decoration: BoxDecoration(
                            color: _functionColors[index],
                            shape: BoxShape.circle,
                          ),
                        ),
                        SizedBox(width: 10),
                        Expanded(
                          child: TextField(
                            controller: _functionControllers[index],
                            decoration: InputDecoration(
                              hintText: '例如: x^2, sin(x), ln(x)',
                              border: OutlineInputBorder(),
                              errorText: _functionErrors.length > index ? _functionErrors[index] : null,
                            ),
                            onChanged: (value) => _plotFunctions(),
                          ),
                        ),
                        SizedBox(width: 10),
                        if (_functionControllers.length > 1)
                          IconButton(
                            icon: Icon(Icons.remove, color: Colors.red),
                            onPressed: () => _removeFunction(index),
                          ),
                      ],
                    ),
                  );
                },
              ),
            ),
            
            SizedBox(height: 10),
            
            // 添加函数按钮
            if (_functionControllers.length < 5)
              Center(
                child: ElevatedButton.icon(
                  onPressed: () {
                    _addFunction();
                    _plotFunctions();
                  },
                  icon: Icon(Icons.add),
                  label: Text('添加函数'),
                  style: ElevatedButton.styleFrom(
                    backgroundColor: Colors.blue,
                    foregroundColor: Colors.white,
                  ),
                ),
              ),
          ],
        ),
      ),
    );
  }

  // 辅助方法：构建范围输入框
  Widget _buildRangeTextField(TextEditingController controller, String label) {
    return TextField(
      controller: controller,
      decoration: InputDecoration(
        labelText: label,
        border: OutlineInputBorder(),
        contentPadding: EdgeInsets.symmetric(horizontal: 12, vertical: 8),
      ),
      keyboardType: TextInputType.numberWithOptions(signed: true, decimal: true),
      onChanged: (value) => _plotFunctions(),
    );
  }

  Widget _buildPlotArea() {
    return Card(
      elevation: 4,
      child: Padding(
        padding: EdgeInsets.all(16),
        child: Column(
          children: [
            Text(
              '函数图像',
              style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 10),
            Expanded(
              child: _buildPlot(),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildPlot() {
    double xMin, xMax, yMin, yMax;
    
    try {
      xMin = double.parse(_xMinController.text);
      xMax = double.parse(_xMaxController.text);
      yMin = double.parse(_yMinController.text);
      yMax = double.parse(_yMaxController.text);
    } catch (e) {
      return Center(
        child: Text('请输入有效的坐标范围', style: TextStyle(color: Colors.red)),
      );
    }
    
    if (xMin >= xMax || yMin >= yMax) {
      return Center(
        child: Text('最小值必须小于最大值', style: TextStyle(color: Colors.red)),
      );
    }
    
    List<LineChartBarData> lineBars = [];
    
    for (int i = 0; i < _functionControllers.length; i++) {
      String function = _functionControllers[i].text.trim();
      if (function.isEmpty) continue;
      
      List<FlSpot> spots = _evaluateFunction(function, xMin, xMax, i);
      
      if (spots.isNotEmpty) {
        lineBars.add(
          LineChartBarData(
            spots: spots,
            isCurved: true,
            color: _functionColors[i],
            barWidth: 2,
            isStrokeCapRound: true,
            dotData: FlDotData(show: false),
            belowBarData: BarAreaData(show: false),
          ),
        );
      }
    }
    
    if (lineBars.isEmpty) {
      return Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Icon(Icons.functions, size: 50, color: Colors.grey),
            SizedBox(height: 10),
            Text('暂无函数图像可显示', style: TextStyle(color: Colors.grey)),
            Text('请输入有效的函数表达式', style: TextStyle(color: Colors.grey, fontSize: 12)),
          ],
        ),
      );
    }
    
    return LineChart(
      LineChartData(
        clipData: FlClipData.all(),
        gridData: FlGridData(
          show: true,
          drawVerticalLine: true,
          drawHorizontalLine: true,
          getDrawingHorizontalLine: (value) {
            return FlLine(
              color: Colors.grey.withOpacity(0.3),
              strokeWidth: 1,
            );
          },
          getDrawingVerticalLine: (value) {
            return FlLine(
              color: Colors.grey.withOpacity(0.3),
              strokeWidth: 1,
            );
          },
        ),
        titlesData: FlTitlesData(
          show: true,
          bottomTitles: AxisTitles(
            sideTitles: SideTitles(
              showTitles: true,
              reservedSize: 30,
              interval: _calculateInterval(xMin, xMax),
              getTitlesWidget: (value, meta) {
                return Text(
                  value.toStringAsFixed(1),
                  style: TextStyle(fontSize: 10, color: Colors.black),
                );
              },
            ),
          ),
          leftTitles: AxisTitles(
            sideTitles: SideTitles(
              showTitles: true,
              reservedSize: 40,
              interval: _calculateInterval(yMin, yMax),
              getTitlesWidget: (value, meta) {
                return Text(
                  value.toStringAsFixed(1),
                  style: TextStyle(fontSize: 10, color: Colors.black),
                );
              },
            ),
          ),
          rightTitles: AxisTitles(sideTitles: SideTitles(showTitles: false)),
          topTitles: AxisTitles(sideTitles: SideTitles(showTitles: false)),
        ),
        borderData: FlBorderData(
          show: true,
          border: Border.all(color: Colors.black, width: 2),
        ),
        minX: xMin,
        maxX: xMax,
        minY: yMin,
        maxY: yMax,
        lineBarsData: lineBars,
        lineTouchData: LineTouchData(enabled: false),
        extraLinesData: ExtraLinesData(
          horizontalLines: [
            HorizontalLine(
              y: 0,
              color: Colors.black,
              strokeWidth: 1,
            ),
          ],
          verticalLines: [
            VerticalLine(
              x: 0,
              color: Colors.black,
              strokeWidth: 1,
            ),
          ],
        ),
      ),
    );
  }

  double _calculateInterval(double min, double max) {
    double range = max - min;
    if (range <= 0) return 1.0;
    
    if (range <= 2) return 0.5;
    if (range <= 5) return 1.0;
    if (range <= 10) return 2.0;
    if (range <= 20) return 5.0;
    if (range <= 50) return 10.0;
    if (range <= 100) return 20.0;
    return 50.0;
  }
}