[BUG] Can't override back button functionality because of persistent_bottom_nav_bar

[utkarshshendge]

• Issue Description: We can't call onWillPop for the children pages of PersistentBottomNavBar. And because of this we are not able to override back button functionality inside the app.

• Issue Severity: Medium

• Observed Behaviour: Not able to control the behaviour of back button

• Expected Behaviour: We should be able to call onWillPop function so we can control the behaviour of back button.

• Steps to reproduce issue: Implementing WillPopScope for the chideren pages of PersistentBottomNavBar
  ( Children pages are : NewsFeed, Groups,Events, Organizations, ProfilePage, ) won't call onWillPop .

• Snapshots/Videos:

• I implemented a different BottomNavigation bar and everything worked fine in that,But brings changes to UI.
  Here is the video for it.
  https://user-images.githubusercontent.com/57677520/111951124-3aa83200-8b09-11eb-91a9-30010e4e50e8.mp4

• Video of PersistentBottomNavBar that we are using.
  https://user-images.githubusercontent.com/57677520/111951196-56abd380-8b09-11eb-9cf2-ad1a7672ec4b.mp4

• Does this issue need immediate attention? No

• Are you willing to work on this issue: Yes

• Other information: Personally ,I don't see much value in using PersistentBottomNavBar. Apps like Instagram,WhatsApp
  do not persist the navigation bar pages .Also the UI doesn't Look good with PersistentBottomNavBar.
  I found out that there is already an issue regarding this behaviour of PersistentBottomNavBar , can be found
  here.
  Since UI refactoring is for GSoC , I don't know if its the right time to work on this.
  We can wait for the maintainer of PersistentBottomNavBar but it will take few days (Github activity of maintainer is less).

Since this is something which is related to both UI, inner-functionality of app, I'd appreciate hearing your opinion on this
@Sagar2366 Sir , @DeltaHarbinger Sir.

[shauravshikhar]

if @utkarshshendge u want any help plz let me know i will try to help u

[utkarshshendge]

if @utkarshshendge u want any help plz let me know i will try to help u

Sure @shikharsaurav , Thanks!!

[CyberWake]

Do we really need this on like the changes I observed not need changing the nav bar we just need to change the page pushing method arguments.

newsfeed.dart
To

pushNewScreenWithRouteSettings(context,
              screen: AddPost(), settings: RouteSettings(),withNavBar:false);

From

pushNewScreenWithRouteSettings(context,
              screen: AddPost(), settings: RouteSettings());

events.dart
To

pushNewScreen(
            context,
            withNavBar: false,
            screen: AddEvent(),
          );

From

pushNewScreen(
            context,
            withNavBar: true,
            screen: AddEvent(),
          );

Basically we just need to add the parameter withNavBar: false whenever a page is push from any tab and add also add handleAndroidBackButtonPress: true argument in the PersistentTabView this would help you get all the desired functionality.

[utkarshshendge]

I will try to do the same in next PR.
I checked the docs of PersistentTabView the issue is fixed in new version.
Thanks @CyberWake !!

[utkarshshendge]

PR #523 fixes this issue as well.
Maintainer of persistent_bottom_nav_bar has fixed the issue regrading Willpop scope.
Closing this issue.