In CupertinoNavigationBar how do i show a button besides back button in leading?

Question

I tried something like this:

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      navigationBar: CupertinoNavigationBar(
        middle: Text(widget.title),
      ),
      child: Center(
        child: Container(
          child: CupertinoButton.filled(
            child: const Text('Push screen'),
            onPressed: () {
              CupertinoNavigationBar navBar = CupertinoNavigationBar(
                leading: Row(children: <Widget>[
                  const CupertinoNavigationBarBackButton(),
                  CupertinoButton(
                    child: const Text('Button 2'),
                    padding: EdgeInsets.zero,
                    onPressed: () {},
                  ),
                ]),
              );
              Navigator.push(context, CupertinoPageRoute<CupertinoPageScaffold>(
                builder: (_) => CupertinoPageScaffold(
                  navigationBar: navBar,
                  child: Center(child: const Text('Content')),
                )
              ));
            },
          ),
        ),
      ),
    );
  }

And when tapping the button, it fails with

I/flutter (30855): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (30855): The following NoSuchMethodError was thrown building CupertinoNavigationBarBackButton(dirty):
I/flutter (30855): The getter 'canPop' was called on null.
I/flutter (30855): Receiver: null
I/flutter (30855): Tried calling: canPop

The reason is that this code in CupertinoNavigationBarBackButton returns null

final ModalRoute<dynamic> currentRoute = ModalRoute.of(context);

I wonder why that's the case? Is it because when I push the button, context still hasn't gotten the route yet?

What's the correct way to manually add a back button?

Thanks in advance.

Volker Andres · Answer 1 · 2020-07-16T21:35:31.517

Here is a very simple snippet of code. I hope it helps you:

class DemoView extends StatelessWidget {
  @override
  Widget build(BuildContext context) {

    return CupertinoPageScaffold(
      navigationBar: CupertinoNavigationBar(
        leading: GestureDetector(
          onTap: () {
            debugPrint('Back button tapped');
          },
          child: Row(
            children: <Widget>[
              Icon(CupertinoIcons.left_chevron),
              Text(
                'Back',
                style: TextStyle(
                  color: CupertinoColors.activeBlue,
                ),
              ),
            ],
          ),
        ),
        middle: Text('Demo'),
        trailing: GestureDetector(
          onTap: () {
            debugPrint('add icon tapped');
          },
          child: Icon(
            CupertinoIcons.add,
            color: CupertinoColors.black,
          ),
        ),
      ),
      child: Center(
        child: Text(
          'Content',
          style: TextStyle(fontSize: 36.0),
        ),
      ),
    );
  }
}

There is a mistake at debugPrint('add icon tapped')); you have to remove one parenthesis at the end — Emre Akcan, Jul 16 '20 at 20:42

score 1 · Answer 2 · edited Dec 14 '19 at 12:00

Which is the correct way to add manually back button?

I use code like this:

@override
Widget build(BuildContext context) {
  return CupertinoPageScaffold(
    navigationBar: CupertinoNavigationBar(
      middle: Text(widget.title),
      leading: CupertinoNavigationBarBackButton(
        onPressed: () => Navigator.of(context).pop(),
      ),
      child: _myAppBody() // return widget
    ),
  );
}

In CupertinoNavigationBar how do i show a button besides back button in leading?

2 Answers2