Handling TypeErrorImpl: Unexpected Null Value When Tapping Profile Icon in Flutter

Question

I encountered a TypeErrorImpl exception with the message "Unexpected null value" when I clicked on the "Profile" icon in my Flutter application. Below is the detailed error log from the console:

══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════ The following TypeErrorImpl was thrown while handling a gesture: Unexpected null value. When the exception was thrown, this was the stack: C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/internal/js_dev_runtime/private/ddc_runtime/errors.dart 266:49 throw C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 561:63 nullCheck packages/pomodoro/apilar_codigo/stacked_all.dart 117:49
packages/flutter/src/material/ink_well.dart 1096:21
handleTap packages/flutter/src/gestures/recognizer.dart 253:24
invokeCallback C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 367:37 _checkAndCall C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 372:39 dcall Handler: "onTap" Recognizer:
TapGestureRecognizer#fc203

Here's the snippet of my Flutter code where the error occurs:

GestureDetector(
  behavior: HitTestBehavior.translucent,
  onTapDown: (details) {
    tapOffset = details.globalPosition;
  },
  child: IconButton(
    onPressed: () {
      showMenu(
        position: RelativeRect.fromLTRB(
          tapOffset!.dx - 150, // assuming popUp width
          64,
          tapOffset?.dx ?? 0,
          0,
        ),
        constraints: const BoxConstraints(maxWidth: 600),
        context: context,
        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(10)),
        items: [...], // PopupMenuItem widgets
      );
    },
    icon: Tooltip(
      message: 'Profile',
      child: Semantics(
        label: 'Pomodoro timer More',
        child: const Icon(
          Icons.account_circle_outlined,
          color: Color(0xff3B3B3B),
          size: 24,
        ),
      ),
    ),
  ),
),

I suspect the issue might be related to null safety, as the error points to a null value being unexpectedly passed somewhere in my code. However, I'm not sure which part of the code is causing this error or how to properly address it.

Has anyone faced a similar issue, or does anyone have suggestions on how to resolve this null safety error in Flutter?

Any help or insights would be greatly appreciated. Thank you!

Answer 1

You're using null check (!) in the tapOffset. Looks like in that moment, tapOffset is null. You could use ? operator instead of !, and define a default value (just like you do if in the line below)

                                position: RelativeRect.fromLTRB(
                                  tapOffset!.dx -
                                      150, // here is the problem
                                  64,
                                  tapOffset?.dx ?? 0,
                                  0,
                                ),