Unable to run flutter_markdown example

[jimmyshiau]

Steps to Reproduce

Run flutter run -v with flutter_markdown example (Nexus 7 (2013) Android 4.4.4)
https://github.com/flutter/flutter/blob/master/packages/flutter_markdown/example/demo.dart

It will show error

Flutter Doctor

[✓] Flutter (on Mac OS, channel unknown)
• Flutter at /usr/local/flutter/flutter
• Framework revision 8a82332 (17 hours ago), 2016-09-29 08:59:43
• Engine revision 3551e7a
• Tools Dart version 1.20.0-dev.5.0

[✓] Android toolchain - develop for Android devices (Android SDK 24.0.2)
• Android SDK at /Users/jimmy/Library/Android/sdk
• Platform android-24, build-tools 24.0.2
• Java(TM) SE Runtime Environment (build 1.8.0_45-b14)

[✓] iOS toolchain - develop for iOS devices (Xcode 8.0)
• XCode at /Applications/Xcode.app/Contents/Developer
• Xcode 8.0, Build version 8A218a

[✓] Atom - a lightweight development environment for Flutter
• flutter plugin version 0.2.5
• dartlang plugin version 0.6.39

[✓] Connected devices
• Nexus 7 • 0874da9c • android-arm

Logs and Crash Reports

  29 ms • I/flutter : ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
   2 ms • I/flutter : The following assertion was thrown building RawGestureDetector([GlobalKey 587447520]; state:
   0 ms • I/flutter : RawGestureDetectorState(127753856; gestures: vertical drag; behavior: opaque)):
   0 ms • I/flutter : inheritFromWidgetOfExactType(Theme) was called before _MarkdownBodyRawState.initState() completed.
   0 ms • I/flutter : When an inherited widget changes, for example if the value of Theme.of() changes, its dependent
   0 ms • I/flutter : widgets are rebuilt. If the dependent widget's reference to the inherited widget is in a constructor
   0 ms • I/flutter : or an initState() method, then the rebuilt dependent widget will not reflect the changes in the
   0 ms • I/flutter : inherited widget.
   0 ms • I/flutter : Typically references to to inherited widgets should occur in widget build() methods. Alternatively,
   4 ms • I/flutter : initialization based on inherited widgets can be placed in the dependenciesChanged method, which is
2295 ms • I/flutter : called after initState and whenever the dependencies change thereafter.
  70 ms • I/flutter : When the exception was thrown, this was the stack:
   0 ms • I/flutter : #0      StatefulElement.inheritFromWidgetOfExactType.<anonymous closure> (package:flutter/src/widgets/framework.dart:2827:9)
   0 ms • I/flutter : #2      StatefulElement.inheritFromWidgetOfExactType (package:flutter/src/widgets/framework.dart:2825:12)
   0 ms • I/flutter : #3      Theme.of (package:flutter/src/material/theme.dart:43:27)
   0 ms • I/flutter : #4      MarkdownBody.createDefaultStyle (package:flutter_markdown/src/markdown.dart:90:53)
   0 ms • I/flutter : #5      _MarkdownBodyRawState._buildMarkdownCache (package:flutter_markdown/src/markdown_raw.dart:156:69)
   2 ms • I/flutter : #6      _MarkdownBodyRawState.initState (package:flutter_markdown/src/markdown_raw.dart:135:5)
   0 ms • I/flutter : #7      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:2761:14)
   0 ms • I/flutter : #8      ComponentElement.mount (package:flutter/src/widgets/framework.dart:2647:5)
   0 ms • I/flutter : #9      Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
   0 ms • I/flutter : #10     Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
   0 ms • I/flutter : #11     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)
   0 ms • I/flutter : #12     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
   0 ms • I/flutter : #13     Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
   0 ms • I/flutter : #14     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)
   0 ms • I/flutter : #15     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
   0 ms • I/flutter : #16     Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
   0 ms • I/flutter : #17     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)

[abarth]

Thanks for the report! We added this assert to catch bugs and it looks like the markdown example has an instance of this bug.

/cc @Hixie

[Hixie]

also cc @HansMuller who added this assert.

My guess is that to fix this we just have to move the call to _buildMarkdownCache from initState to dependenciesChanged in this file:
https://github.com/flutter/flutter/blob/master/packages/flutter_markdown/lib/src/markdown_raw.dart

[HansMuller]

See also: #6166

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.