计算相对路径

Use the relative() function in the path Pub package to calculate relative paths. This function calculates the relative path from the current directory by default. To calculate the relative path from another path, specify that path using the from argument.

import 'dart:io' show Directory;
import 'package:path/path.dart' as path;

main() {
  // The path from the current directory to the system temp directory.
  print(path.relative(Directory.systemTemp.path));

  // You can work with relative paths.
  var path1 = 'docs/book.html';
  var path2 = 'articles/list';
  print(path.relative(path1, from: path2)); // Prints '../../docs/book.html'.
  print(path.relative(path2, from: path1)); // Prints '../../articles/list'.

  // Or you can work with absolute paths.
  var samples = 'http://www.dartlang.org/samples';
  var docs = 'http://www.dartlang.org/docs';
  print(path.relative(samples, from: docs)); // Prints '../samples'.
}