hard pull down sometimes causes: 'dart:ui/text.dart': Failed assertion: line 1372: '<optimized out>': is not true.

[remoteportal]

(Thank you for writing this! I spent half a day last week trying to pull it off (pun intended) and didn't make any progress--was happy to find yours...)

How to reproduce:

• hit the FAB 30x
• pull down list and tap text field to move focus there
• pull down list
• pull up list
• pull down list again, and this sometimes happens on real Android phone running from Android Studio on Windows 7:

on this line:

         revealableBuilder: (BuildContext context, RevealableToggler opener,
              RevealableToggler closer, BoxConstraints constraints) {
            return Row(
              key: Key('scrollable-row'),
              children: <Widget>[
                SizedBox(width: 10),
                Flexible(
                  child: TextFormField(     <--- HERE

I Google this issue to debug it but I don't understand it:
flutter/flutter#45526

════════ (23) Exception caught by rendering library ════════════════════════════════════════════════
'dart:ui/text.dart': Failed assertion: line 1372: '<optimized out>': is not true.
The relevant error-causing widget was: 
  TextFormField file:///E:/readonly/flutter_pull_to_reveal/example/lib/main.dart:103:26
The following RenderObject was being processed when the exception was fired: RenderEditable#ebb63
  parentData: <none> (can use size)
  constraints: BoxConstraints(w=286.7, h=0.0)
  size: Size(286.7, 0.0)
  cursorColor: Color(0x004285f4)
  showCursor: ValueNotifier<bool>#003c4(true)
  maxLines: 1
  minLines: null
  selectionColor: Color(0xff90caf9)
  textScaleFactor: 1.0
  locale: en_US
  selection: TextSelection(baseOffset: 0, extentOffset: 0, affinity: null, isDirectional: false)
  offset: ScrollPositionWithSingleContext#22845(offset: 0.0, range: 0.0..0.0, viewport: 286.7, ScrollableState, ClampingScrollPhysics, IdleScrollActivity#62f15, ScrollDirection.idle)
  text: TextSpan
    debugLabel: (englishLike subhead 2014).merge(blackMountainView subhead)
    inherit: false
    color: Color(0xdd000000)
    family: Roboto
    size: 16.0
    weight: 400
    baseline: alphabetic
    decoration: TextDecoration.none
    ""
RenderObject: RenderEditable#ebb63
  parentData: <none> (can use size)
  constraints: BoxConstraints(w=286.7, h=0.0)
  size: Size(286.7, 0.0)
  cursorColor: Color(0x004285f4)
  showCursor: ValueNotifier<bool>#003c4(true)
  maxLines: 1
  minLines: null
  selectionColor: Color(0xff90caf9)
  textScaleFactor: 1.0
  locale: en_US
  selection: TextSelection(baseOffset: 0, extentOffset: 0, affinity: null, isDirectional: false)
  offset: ScrollPositionWithSingleContext#22845(offset: 0.0, range: 0.0..0.0, viewport: 286.7, ScrollableState, ClampingScrollPhysics, IdleScrollActivity#62f15, ScrollDirection.idle)
  text: TextSpan
    debugLabel: (englishLike subhead 2014).merge(blackMountainView subhead)
    inherit: false
    color: Color(0xdd000000)
    family: Roboto
    size: 16.0
    weight: 400
    baseline: alphabetic
    decoration: TextDecoration.none
    ""
════════════════════════════════════════════════════════════════════════════════════════════════════

════════ (24) Exception caught by rendering library ════════════════════════════════════════════════
'dart:ui/text.dart': Failed assertion: line 1372: '<optimized out>': is not true.
The relevant error-causing widget was: 
  TextFormField file:///E:/readonly/flutter_pull_to_reveal/example/lib/main.dart:103:26
The following RenderObject was being processed when the exception was fired: RenderEditable#ebb63 relayoutBoundary=up23
  parentData: <none> (can use size)
  constraints: BoxConstraints(w=286.7, 0.0<=h<=26.0)
  size: Size(286.7, 19.0)
  cursorColor: Color(0x004285f4)
  showCursor: ValueNotifier<bool>#003c4(true)
  maxLines: 1
  minLines: null
  selectionColor: Color(0xff90caf9)
  textScaleFactor: 1.0
  locale: en_US
  selection: TextSelection(baseOffset: 0, extentOffset: 0, affinity: null, isDirectional: false)
  offset: ScrollPositionWithSingleContext#22845(offset: 0.0, range: 0.0..0.0, viewport: 286.7, ScrollableState, ClampingScrollPhysics, IdleScrollActivity#62f15, ScrollDirection.idle)
  text: TextSpan
    debugLabel: (englishLike subhead 2014).merge(blackMountainView subhead)
    inherit: false
    color: Color(0xdd000000)
    family: Roboto
    size: 16.0
    weight: 400
    baseline: alphabetic
    decoration: TextDecoration.none
    ""
RenderObject: RenderEditable#ebb63 relayoutBoundary=up23
  parentData: <none> (can use size)
  constraints: BoxConstraints(w=286.7, 0.0<=h<=26.0)
  size: Size(286.7, 19.0)
  cursorColor: Color(0x004285f4)
  showCursor: ValueNotifier<bool>#003c4(true)
  maxLines: 1
  minLines: null
  selectionColor: Color(0xff90caf9)
  textScaleFactor: 1.0
  locale: en_US
  selection: TextSelection(baseOffset: 0, extentOffset: 0, affinity: null, isDirectional: false)
  offset: ScrollPositionWithSingleContext#22845(offset: 0.0, range: 0.0..0.0, viewport: 286.7, ScrollableState, ClampingScrollPhysics, IdleScrollActivity#62f15, ScrollDirection.idle)
  text: TextSpan
    debugLabel: (englishLike subhead 2014).merge(blackMountainView subhead)
    inherit: false
    color: Color(0xdd000000)
    family: Roboto
    size: 16.0
    weight: 400
    baseline: alphabetic
    decoration: TextDecoration.none
    ""
════════════════════════════════════════════════════════════════════════════════════════════════════

flutter -v:

[√] Flutter (Channel stable, v1.12.13+hotfix.5, on Microsoft Windows [Version 6.1.7601], locale en-US)
    • Flutter version 1.12.13+hotfix.5 at E:\Src\flutter
    • Framework revision 27321ebbad (5 weeks ago), 2019-12-10 18:15:01 -0800
    • Engine revision 2994f7e1e6
    • Dart version 2.7.0

[√] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at C:\Users\pete\AppData\Local\Android\sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-29, build-tools 29.0.2
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b03)
    • All Android licenses accepted.

[√] Android Studio (version 3.5)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin version 42.1.1
    • Dart plugin version 191.8593
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b03)

[√] Connected device (1 available)
    • Mi 9T • 844fb80a • android-arm64 • Android 9 (API 28)

• No issues found!

[craiglabenz]

I've seen this before myself and have never been able to isolate the problem. Does the issue create visible problems for you, or does it only lead to annoying warnings in the debug console?