小编Moh*_*sri的帖子

升级到 flutter 3.0.0 后，运行应用程序时开始出现问题，

（该应用程序可以运行，但终端中出现错误（警告））。

这似乎是一个绑定问题。

错误（警告）说：\n警告：null 感知操作 \'!\' 的操作数具有类型 \'WidgetsBinding\'，其中排除 null。

: Warning: Operand of null-aware operation \'!\' has type \'WidgetsBinding\' which excludes null.\n../\xe2\x80\xa6/src/keyboard_visibility.dart:21\n- \'WidgetsBinding\' is from \'package:flutter/src/widgets/binding.dart\' (\'../../../fvm/versions/3.0.0/packages/flutter/lib/src/widgets/binding.dart\').\npackage:flutter/\xe2\x80\xa6/widgets/binding.dart:1\n    WidgetsBinding.instance!.addObserver(this);\n\n                   ^\n: Warning: Operand of null-aware operation \'!\' has type \'WidgetsBinding\' which excludes null.\n../\xe2\x80\xa6/src/keyboard_visibility.dart:37\n- \'WidgetsBinding\' is from \'package:flutter/src/widgets/binding.dart\' (\'../../../fvm/versions/3.0.0/packages/flutter/lib/src/widgets/binding.dart\').\npackage:flutter/\xe2\x80\xa6/widgets/binding.dart:1\n    WidgetsBinding.instance!.removeObserver(this);\n                   ^\n: Warning: Operand of null-aware operation \'!\' has type \'WidgetsBinding\' which excludes null.\n../\xe2\x80\xa6/src/bot_toast_init.dart:15\n- \'WidgetsBinding\' is from \'package:flutter/src/widgets/binding.dart\' (\'../../../fvm/versions/3.0.0/packages/flutter/lib/src/widgets/binding.dart\').\npackage:flutter/\xe2\x80\xa6/widgets/binding.dart:1\n    WidgetsBinding.instance!.addObserver(this);\n                   ^\n: Warning: Operand of null-aware operation \'!\' …

我正在尝试使用 API 与 PHP 后端进行通信，但无法到达响应正文。

我从邮递员那里得到了基本代码。这是身体反应的数据：

我需要到达消息，并在 UI 中显示错误，问题是response.stream它的类型是 Bytesreem，我无法将其转换为 Map

我的代码：

  Future<void> _authenticateUp(String email, String password,
      String passwordconfirmation, String username, String name,
      {String phonenumber}) async {

    var headers = {
      'Content-Type': 'application/json',
      'X-Requested-With': 'XMLHttpRequest'
    };

    var request = http.MultipartRequest('POST', Uri.parse('$siteUrl/register'));

    request.fields.addAll({
      'email': email,
      'password': password,
      'password_confirmation': passwordconfirmation,
      'username': username,
      'name': name,
      'phone_number': phonenumber
    });

    request.headers.addAll(headers);
    http.StreamedResponse response = await request.send();

    try {
      if (response.statusCode == 200) {
        await response.stream.bytesToString().then((value) {
          print(value);
        });
      } else {
        // here …