Flutter – How to place a Spacer between two TextSpan widgets?

Currently, there is no direct way of doing it, but it can be achieved by using some tricks. One such approach I could think of is using your TextSpan widget with text ‘yyyy’ twice along with Stack widget, to achieve what you need. The reason for using it twice is that the first YYYY widget will always be invisible but will occupy the same width as the second YYYY and it will always keep a space at the end of the RichText. It’s more difficult for me to explain in words, instead the code will be more helpful.
You can also find the following code at dart pad

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: const Text("Flutter App"),
      ),
      body: Stack(
        children: [
          Row(
            mainAxisSize: MainAxisSize.max,
            children: [
              Expanded(
                child: RichText(
                    overflow: TextOverflow.visible,
                    text: const TextSpan(
                      children: [
                        TextSpan(
                            text: "xxxxx xxxx xx x xxx xxxxx xxx  xxxx xxxx xxx",
                            style: TextStyle(
                              color: Colors.black,
                              fontSize: 24,
                            )),
                        TextSpan(
                          text: "yyyy",
                          style: TextStyle(
                            color: Colors.transparent,
                            fontSize: 24,
                          ),
                        ),
                      ],
                    )),
              ),
            ],
          ),
          Positioned(
            bottom: 0,
              right: 0,
              child: RichText(text: const TextSpan(
            text: "yyyy",
                style: TextStyle(
                  color: Colors.black,
                  fontSize: 24,
                ),
          ),))
        ],
      ),
    );
  }
}

Here is the screenshot