I am using IndexedStack for BottomNavigationBar to prevent pages initial every time I change tab.
However, it seems that there is another problem about pages initailization. I find all pages will initial at the time. Is that true?
If so, how can I solve it?
Oh, I have already solved this problem. Just using PageView instead of IndexedStack. If you don't wanna rebuild page every time you tab into. Let pages' state with AutomaticKeepAliveClientMixin, and IDE will make you know what to do to work.
Related
I'm working on a custom calendar package but I'm having some performance difficulties while doing that.
My calendar layout is built from PageViews and each pageview contains a Gridview and each GridView contains 42 children representing the days of the month. Like this:-
Issue -
The problem is with scrolling the pageview. When I scroll to the new PageView the new PageView gets build and it builds its GridView and GridView builds its Children. All these tasks while scrolling leads to jank in scrolling animation.
Note: Scrolling to previous PageViews is smooth because I'm using AutomaticKeepAlives in PageView which stops PageView from rebuilding constantly on scroll.
DartPad -
The example DartPad for the above calendar can be found here - https://dartpad.dev/?id=762d835c5b9acadd785ee9269294c1e6
Now, what I'm looking for are the ways through which I can improve its performance.
Maybe I can somehow reuse the components for GridView children's dates by manually caching them by storing them as fields somewhere. But I don't know if that would work as these date styles have non-constant properties like the trailing one has different colors and the general one has a different one.
Maybe I can somehow preload pageviews in advance? I don't know if that would work when swiping fast.
Also, if it matters, currently I'm using Riverpod in my package for managing the calendar state.
So, if there is any way to improve the performance then please help me with that.
Current dirty solutions I found to this problem are:-
Setting viewportFraction: 0.99 in PageController of PageView. (It will help as it preloads the previous page and forward page). Suggested here #504337877.
Or use this preload_page_view package. Suggested here #636388237.
Currently, flutter doesn't support pre caching the PageView pages in advance but there are several issues about it on Github like this - #31191 , #45632 , and a closed pull request #42107 due to IOS related issue.
I failed to reuse the same widget in multiple places without rebuilding them.
And even if I succeed with the above I might fail to reuse states of child widgets of PageView as changing Pages means the whole child of PageView to be rebuilt as the index is new. So I cannot cache child widgets until I can reuse states in PageView.builder and GridView.Builder. A similar case for ListView is described in #49126.
If I'm wrong about the reusing same widget at multiple places then please correct me with a working small example as I'm more than happy to learn more. You can use this DartPad as starting point. The task is to bring the rebuild of customContainer from 42 to 1.
Not accepted as an answer as there could be more great answers to this in the future.
I have a problem with my Here Maps Navigation. I can start the navigation on my flutter app but every time I open another page on the app and come back to the navigation page, it restarts the navigation. It tries to get the current location again, takes a lot of time to do that, and shows the default "invalid" map page. I want the navigation to save it's current state even if I change the view to another page on my app and come back to navigating. Is there a way to do this? Am I missing something here?
I finally found a way to solve it by saving the state of my Flutter pages. I used the PageView widget for the main.dart's scaffold body and AutomaticKeepAliveClientMixin on the pages I wanted to save the states of. You can check this YouTube video for how to implement this: https://www.youtube.com/watch?v=fGe45NikVqE
I have a PageView with a large amount of pages in my app. Each of the pages is very complex with a PageView and its own pages.
I'm new to Flutter and my first hunch is that it needs optimization. So within the build() function of the outmost PageView I check the index and only make full page for current, previous and the next page(I guess swipe animation needs current page and the page next to it built ahead). For other pages I just give it an empty Container().
Is this necessary and the right thing to do? I felt this is an obvious optimization that the Flutter should do, but I can't find any related discussion online. Any suggestions are appreciated!
Flutter's PageView is lazily calling itemBuilder you provided. For an index it's called only when the page is really needed and you don't need to do anything more. But for further improvements you can make your view hierarchy simpler and prevent unnecessary build method calls. Here you can read more about Performance best practices.
No, it's not. ListView, GridView, and widgets alike are already optimized to build and render only what is needed in the moment. You get a hint of that in the PageView.builder description :
Creates a scrollable list that works page by page using widgets that
are created on demand
I think the difference between a regular PageView and a PageView.builder is that PageView initializes all children at startup, while PageView.builder are initialized lazily.
I'm making an app with a BottomNavigationBar with 5 different screens, each of them has a web view. The problem is that everytime I come back to a screen that was previously loaded, it reloads. I have tried using AutomaticKeepAliveClient from copy pasting this code but I doesn't seem to work. I'm new with Flutter so be precise please, thank you.
AutomaticKeepAliveClient is mainly used for keeping a child alive in lazily rendered list views. In your case whenever you switch tabs your current page get disposed and new page materializes on top of it, that means each time when you switch tab a new page is created including all it's widgets.
So if you want to keep your previously loaded web views alive, you have to go with either PageView widget or use Stack widget to load your pages programmatically while the user clicks on a tab.
This is a detailed example about implementing your requirement using PageView widget . you can also find an example with Stack widget under that question.
In my app, the navigation bar works fine between the tabs, but when I go inside of each item in my list, I want the navigation bar to be there too.
What I did is that I made it a separate widget, and called in the bottomNavigationBar inside the Scaffold of the pages, but the problem is that I am changing the state of the navigation bar in my main page only, so the state doesn't get distributed across all pages in my app.
How do I make the body of the page change in an app where there is not only one body, but many?
Thanks!
Since there is not code over here in your post and I don't know what you have done so far so I can only advise you to go through this post.
I know you might have already seen this, but still, try to follow and this will really help.
Thanks....!!!!!!
https://medium.com/#lucassaltoncardinali/keeping-state-with-the-bottom-navigation-bar-in-flutter-69e4168878e1