flutter 设置字体大小，适应各种屏幕

起因， 目的:

来源就是客户需求。 从个人角度来说，我讨厌 flutter, 和 java 一样， 都是 臃肿，繁琐，死板.

1. 过程:

根据用户的屏幕尺寸，把子元素大小， 字体的大小，都设置为百分比，无需插件。

2. 有个报错: 无法打开包括文件: “atlstr.h”: No such file…

• 我先换成 Chrome 浏览器运行。成功。
• 然后，把代码复制到另一个新项目，运行，成功。
• 所以，原因是，客户提供的配置环境与我电脑上的环境不匹配， 而不是代码有问题！ 也不是我的环境有问题。

3. 代码: tree_1.dart

import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(home: MyApp())); // Wrap MyApp with MaterialApp
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class NodeTemplate {
  int id = 0;
  int value = 0;
  bool solid = false;
  Color color = Colors.grey;

  NodeTemplate();
}

// --------------------  从这里开始 ！！！！ ----------------------------
class _MyAppState extends State<MyApp> {
  // This list holds the color of each box, initially all are grey.
  int nodeValue = 100;
  List<Color> boxColors = List<Color>.filled(15, Colors.grey);
  List<NodeTemplate> treeNodes =
      List<NodeTemplate>.generate(15, (_) => NodeTemplate());

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Draggable Blue Box'),
      ),

      body: Column(
        children: [
          // Binary tree structure
          Expanded(
            child: Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  // Level 1 - 1 box 11111111111111111111111111111111111111111111111111111111
                  Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      buildDragTarget(0),
                    ],
                  ),
                  SizedBox(height: 16.0), // For spacing between levels

                  // Level 2 - 2 boxes 22222222222222222222222222222222222222222222222222222222
                  Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      buildDragTarget(1),
                      SizedBox(width: 100),
                      buildDragTarget(2),
                    ],
                  ),
                  SizedBox(height: 16.0), // For spacing between levels

                  // Level 3 - 4 boxes 333333333333333333333333333333333333333333333333333333
                  Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      buildDragTarget(3),
                      SizedBox(width: 50),
                      buildDragTarget(4),
                      SizedBox(width: 50),
                      buildDragTarget(5),
                      SizedBox(width: 50),
                      buildDragTarget(6),
                    ],
                  ),
                  SizedBox(height: 16.0), // For spacing between levels

                  // Level 4 - 8 boxes 44444444444444444444444444444444444444444444444444
                  Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: [
                      buildDragTarget(7),
                      buildDragTarget(8),
                      buildDragTarget(9),
                      buildDragTarget(10),
                      buildDragTarget(11),
                      buildDragTarget(12),
                      buildDragTarget(13),
                      buildDragTarget(14),
                    ],
                  ),
                ],
              ),
            ),
          ),

          // Draggable blue box at the bottom
          Draggable<int>(
            data: nodeValue,
            feedback: Container(
              width: 50.0,
              height: 50.0,
              color: Colors.blue.withOpacity(0.7),
              child: Center(child: Text(nodeValue.toString())),
            ),
            childWhenDragging: Container(
              width: 50.0,
              height: 50.0,
              color: Colors.blue.withOpacity(0.3),
            ),
            child: Container(
              width: 50.0,
              height: 50.0,
              color: Colors.blue,
              child: Center(child: Text(nodeValue.toString())),
            ),
          ),
          SizedBox(height: 30),
        ],
      ),

      // Use the built-in floatingActionButton property
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          _showInputDialog(context); // Show the dialog to enter value
        },
        backgroundColor: Colors.blue,
        child: Icon(Icons.add),
      ),
    );
  }

  void _showInputDialog(BuildContext context) {
    TextEditingController controller = TextEditingController();

    showDialog(
      context: context,
      builder: (context) {
        return AlertDialog(
          title: Text('Enter value for the Node'),
          content: TextField(
            controller: controller,
            keyboardType: TextInputType.number,
            decoration: InputDecoration(hintText: "Enter value"),
          ),
          actions: [
            TextButton(
              onPressed: () {
                setState(() {
                  nodeValue = int.tryParse(controller.text) ??
                      0; // Parse input or default to 0
                });
                Navigator.of(context).pop(); // Close the dialog
              },
              child: Text('Submit'),
            ),
          ],
        );
      },
    );
  }

  // Function to build a DragTarget for the grey boxes
  Widget buildDragTarget(int index) {
    return GestureDetector(
      onLongPress: () {
        setState(() {
          treeNodes[index].id = index;
          treeNodes[index].value = 0;
          treeNodes[index].color = Colors.grey;
          treeNodes[index].solid = false;
        });
      },
      child: DragTarget<int>(
        onAccept: (data) {
          setState(() {
            treeNodes[index].color =
                Colors.blue; // Change color when blue box is dropped
            treeNodes[index].value = data;
            treeNodes[index].solid = true;
          });
        },
        builder: (context, candidateData, rejectedData) {
          // 获取屏幕的宽度和高度
          double screenWidth = MediaQuery.of(context).size.width;
          double screenHeight = MediaQuery.of(context).size.height;

          // 根据屏幕大小调整宽度和高度，可以设置为屏幕宽度的百分比
          double containerWidth = screenWidth * 0.08; // 比如宽度占屏幕宽度的 10%
          double containerHeight = screenHeight * 0.1; // 比如高度占屏幕高度的 10%

          // 动态调整 字体大小
          double fontSize = 500 * 0.05; // 根据屏幕宽度动态调整字体大小

          return Container(
            width: containerWidth, //50.0, 80.0
            height: containerHeight, //100.0,
            margin: EdgeInsets.symmetric(horizontal: 4.0),
            decoration: BoxDecoration(
              color: treeNodes[index].color, // Dynamic color based on state
              shape: BoxShape.circle, // Makes the container a circle
            ),
            //color: treeNodes[index].color, // Dynamic color based on state
            child: Center(
              child: Text(
                treeNodes[index].value.toString(),
                // style: TextStyle(fontSize: 10),
                style: TextStyle(fontSize: fontSize),
              ),
            ),
          );
        },
      ),
    );
  }
}

效果图

个人接单，留学生辅导，python, R语言，私聊.

老哥，支持一下啊。