If we implement any chart ( whether it be a Linechart or Barchart from chart_flutter ) and in behaviours we have added charts.PanAndZoomBehavior(), pan and zoom behaviour is working fine when it is added in a screen without a scrollview
Here is the scenario Widget hierarchy as
SingleChildScrollView -> charts.LineChart
In gesture arena only SingleChildScrollView gesture is winning, Pan and zoom Behaviour is not working google/charts google/charts#677
This article is helpful https://medium.com/koahealth/combining-multiple-gesturedetectors-in-flutter-26d899d008b2
Does any one know what can be a better approach for this
I believe that is because you need to wrap the Chart Widget that is inside some other widget that has physics (property) in it.. The charts itself doesn't have any physics defined. It's managed using states model references.. I had this problem a long time ago too.. Here's my recommendation (with very amateurish knowledge on flutter):
First, I would wrap my charts within a card widget.
Second, I would avoid using SingleChildScrollView. Unless you are absolutely certain what widget you are building under that parent and they each have Intrinsic sizes defined within the child widgets. I would highly recommend using CustomScrollView -> And add a simple SliverChildBuilderDelegate. That lazily builds your charts (now wrapped in a card/container/column.. anything you chose).. That way you don't have to worry about sizes and scrolling. And any children that you add gets lazily built when they scroll into viewport..
Related
Looking at the Flutter Hero Transition, it appears to move the tagged Widgets to an Overlay class that exists in all Navigator Widgets but sits above the main content in the stack.
If this is correct, it allows the Hero to widgets to still respond to the Route scope and its animators but exist above the actual route content. How is this actually done efficiently? Surely this involves taking an entire Widget and storing it in a state for the duration of the animation. That Widget still has to respond to intrinsic responses from its original position such as slivers responding to active scroll actions.
Recreating this could be done with state management but I wondered how the standard hero actually does this. It seems like Widgets are effectively duplicated and then conditionally rendered on the screen defaulting to the overlay during the route animation and swapping out the original widget with an Offstage or similar. Is this how it is done?
The reason for trying to understand it is the need to replicate this behaviour in situations where Navigator is not an effective use case for a transition taking place internally on a page. I built an accordion style navigator but still want a hero transition to take place on the AppBar / NavigationBar. I know that this could be done with Navigator but it doesn't suit the use case. I could also predefine the AppBar content for each internal navigator state of the accordion but that is a lot of additional code.
Problem summary
I'm building simple animation in which, simply, a panel expands to the right on a onTap event. The layout can be summarized as follows:
The panel has many tiles. Each tile has its own:
leading icon
title text
trailing icon
Each tile, when expanded, shows the three widgets above
Each tile, when shrinked, just shows the leading icon
The panel is scrollable to hold many icons such as these
At the end of the panel there's a simple icon which, when tapped, triggers the "expand" or "shrink" animation
The animation is built with an AnimatedContainer on the panel and a SizeTransition on the single tiles (via one single controller on the parent class)
The problem is simple: when the tiles shrink, their inner text overflows in the row.
Sample code
I just made this reproducible example on DartPad.
The obvious solution isn't helping me out
The most obvious solution is to simply wrap the Text inside a Flexible Widget: this advised by Flutter's docs and it makes sense, but unluckily it completely breaks my Layout.
Flexible introduces a flex factor that in this context is 100% unwanted.
I want my leading icons to be always at the end of the row, so my Spacer widget should "prevail" there.
I can't just play with flex factors there, as it would unintendedly hide text depending on its value.
Another code smell
Another thing I really don't like is the fact that I have to build a controller on the parent class, but I'm not actually using it on the parent class (I'm just exploiting it so I can give it to the children).
I'm new to animations in Flutter so I'm kinda confused on how I should orchestrate the whole thing here.
Any help will be appreciated / upvoted / accepted. Thank you!
As far as I understood you in a right way you just need set sizes for Row inside of SizeTransition instead of Container sizes
Here is your modified sample https://dartpad.dev/?id=a2408d29a1e8c6ce7a1cef8f21e7491d
I'd try an OverflowBox or a FittedBox (wrapping your text), depending on the result you want to achieve.
Consider the case that I have 3 adjacent list view with each list view having a sized widget of some height. Each list view has around 24 child items. I'm trying to scale the widget using onScaleUpdate in GestureDetector.
onScaleUpdate I want to change the height of each child item of all the 3 listviews.
Is rebuilding all child better or should I rebuild the whole widget?
As #Yeasin Sheikh pointed out, using ListView.builder is good because it builds only the needed children (the ones inside the screen and just a few ones outside as precaution). And as to actually answering your question, I'm no Flutter expert, but using ListView.builder I don't think it makes that much difference, Flutter is intelligent enough to solve this by itself.
When we want to achieve a button, we can choose raisedButton in flutter lib, also can a Container with onTap() function. So what's the difference between the two and which one should we choose in different situation?
Container function doesnot have onTap option, but you can achieve it by wrapping it in Guesture detector or Inkwell. There are no changes in the backend. But Raised button gives you the elevation, and animation on tap. You can also do it in the container, but it requires you to manually do it.
If you want a simple button quickly use RaisedButton.
If you want a more complex one, use Container or mixture of Containers, RaisedButton etc.
I am gonna offer something different... A tale of a treasure that is known to have answers to many questions, use cases and sometimes even examples. The name of this treasure is: official documentation. ;)
RaisedButton
A raised button is based on a Material widget whose Material.elevation increases when the button is pressed. Use raised buttons to add dimension to otherwise mostly flat layouts, e.g. in long busy lists of content, or in wide spaces. Avoid using raised buttons on already-raised content such as dialogs or cards.
Container
A convenience widget that combines common painting, positioning, and
sizing widgets.
GestureDetector
A widget that detects gestures. Attempts to recognize gestures that
correspond to its non-null callbacks. If this widget has a child, it
defers to that child for its sizing behavior. If it does not have a
child, it grows to fit the parent instead. By default a
GestureDetector with an invisible child ignores touches; this behavior
can be controlled with behavior. GestureDetector also listens for
accessibility events and maps them to the callbacks. To ignore
accessibility events, set excludeFromSemantics to true. See
flutter.dev/gestures/ for additional information. Material design
applications typically react to touches with ink splash effects. The
InkWell class implements this effect and can be used in place of a
GestureDetector for handling taps.
InkWell
A rectangular area of a Material that responds to touch. For a variant
of this widget that does not clip splashes, see InkResponse... The
InkWell widget must have a Material widget as an ancestor. The
Material widget is where the ink reactions are actually painted. This
matches the material design premise wherein the Material is what is
actually reacting to touches by spreading ink.
Well, technically you are right, they can both react to a click event. But a RaisedButton will have all the styles specific to the target platform taken care of for you (it inherits from MaterialButton).
note that it's the same in html: you can use a regular div with a click handler or use a button tag. The button will have a few styles already taken care of for you...
I want users to scroll between pages in PageView, but I don't want to show them an animation when they try to scroll before first and after last page. I can switch between colorful animation, black animation and no scrolling, but I could not find any possibility to disable the animation at all.
If there is no such possibility, how can I change the color of that animation or make it transparent at least?
Based on your screenshot, I can say that you are using BouncingScrollPhysics for your PageView. This behavior is commonly used by iOS devices. Nonetheless, I have also reviewed the entire source code you have provided here.
What went wrong
You have added PageView without accompanying it with a Scaffold or Material widget at the top level that's why the background behind the children of the PageView is color black.
https://dartpad.dev/c709e410d0a68248ac5b387b3bc6af93
From the documentation:
Scaffold implements the basic material design visual layout structure.
Without this widget, you'll notice that your app may occupy the entire screen of your device, including the notification bar, because it (PageView) does not know where is the status bar is located in the screen.
What you can do
I noticed that all of the children added inside the PageView has individual Scaffold and AppBar, it's not really necessary to nest scaffolds and you may want to use TabBarView instead of PageView, and let the parent widget handle the AppBar changes via TabController.
But if you think it'll cost you too much effort to refactor, feel free to review the following options that require minimal changes which will suit your needs:
Option 1. You can wrap your widget inside a Scaffold widget.
https://dartpad.dev/4620ff91444353f5e000d2063594bd96
Option 2. Given that nesting Scaffold widgets is not a good practice, you can just use the plain Material widget to wrap your PageView with children wrapped with Scaffold widget.
https://dartpad.dev/43f8730e5592ce1f96193fc01f08a29c
These solutions will change the background color of the PageView from black to white.
Option 3. If you really want to get rid of the animation, the easiest way to hack it is changing your scroll physics:
physics: ClampingScrollPhysics(),
However, this still has a glowing or ripple effect when you try to swipe at the end of the screen.
To further get rid of this effect, I'll share with you these SO answers:
How to remove scroll glow? (works for Android)
How to remove overscroll on ios? (works for iOS)
Further reading
https://api.flutter.dev/flutter/widgets/ScrollPhysics-class.html
https://medium.com/flutter-community/custom-scroll-physics-in-flutter-3224dd9e9b41