AppBar customization for iOS and Android back button

[canberkozcelik]

Steps to Reproduce

I'm trying to decide for AppBar to show/hide back button for iOS or android
Inside AppScreenState's build method I'm returning home;

    Widget home = new Scaffold(
      appBar: new AppBar(
        title: new Container(
          margin: const EdgeInsets.symmetric(
              vertical: 1.0, horizontal: 1.0),
          child: new Row(
            children: <Widget>[
              Navigator.canPop(context) && defaultTargetPlatform == TargetPlatform.iOS ? new IconButton(
                  icon: new Icon(Icons.arrow_back_ios), onPressed: () {
                Navigator.pop(context);
              }) : null,
              new Text("Flutter App"),
            ],
          ),
        ),
      ),

Logs

flutter run log output:

Syncing files to device iPhone X...                       
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
'package:flutter/src/widgets/framework.dart': Failed assertion: line 1612 pos 14:

Either the assertion indicates an error in the framework itself, or we should provide substantially
more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
https://github.com/flutter/flutter/issues/new

When the exception was thrown, this was the stack:

🔥  To hot reload your app on the fly, press "r". To restart the app entirely, press "R".
An Observatory debugger and profiler on iPhone X is available at: http://127.0.0.1:8100/
For a more detailed help message, press "h". To quit, press "q".
════════════════════════════════════════════════════════════════════════════════════════════════════

Flutter Doctor

flutter doctor output:

[✓] Flutter (on Mac OS X 10.13.2 17C88, locale en-TR, channel alpha)
    • Flutter at /Users/canberkozcelik/Documents/Development/flutter
    • Framework revision 8f65fec5f5 (6 weeks ago), 2017-12-12 09:50:14 -0800
    • Engine revision edaecdc8b8
    • Tools Dart version 1.25.0-dev.11.0
    • Engine Dart version 2.0.0-edge.d8ae797298c3a6cf8dc9f4558707bd2672224d3e

[✓] Android toolchain - develop for Android devices (Android SDK 27.0.1)
    • Android SDK at /Users/canberkozcelik/Library/Android/sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-27, build-tools 27.0.1
    • ANDROID_HOME = /Users/canberkozcelik/Library/Android/sdk
    • Java binary at: /Applications/Android Studio 3.0/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)

[✓] iOS toolchain - develop for iOS devices (Xcode 9.2)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 9.2, Build version 9C40b
    • ios-deploy 1.9.2
    • CocoaPods version 1.3.1

[✓] Android Studio (version 3.0)
    • Android Studio at /Applications/Android Studio 3.0/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio 2.3.3/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] Connected devices
    • iPhone X • FFF1E041-754E-4C4A-8529-7B52FA72E5EA • ios • iOS 11.2 (simulator)

[rmtmckenzie]

You're getting an error because you're assigning 'null' as element in a row, which is not allowed per the documentation. If you're new to flutter, when you get an issue like this (especially since it's an assertion) it's worth looking at the framework code as the assertions are generally fairly self-explanatory.

Also - if you're going to paste code in to github, try to make sure it gets formatted properly as it's a lot easier to tell what's going on. See https://guides.github.com/features/mastering-markdown/

[Hixie]

@rmtmckenzie is correct, though I'm concerned about the error message being blank. Is that really the message that you saw? No message and no stack?

[zoechi]

@Hixie shouldn't this issue have been closed by now because of the "waiting for customer response" label?

[no-response]

Without additional information, we are unfortunately not sure how to resolve this issue. We are therefore reluctantly going to close this bug for now. Please don't hesitate to comment on the bug if you have any more information for us; we will reopen it right away!
Thanks for your contribution.
cc @Hixie

[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.