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Description:

fluid bottom nav bar

Fluid Navigation Bar #

Many thanks to gskinner for "The vignettes" showcase presented at Flutter Interact '19 :
They created an awesome creative experience and most of the code in this package comes from
their realisation. I was really impressed by their huge work but the code, even if it was open-sourced,
was not usable as it. So I did some refactoring for maintainability, I extracted some
fields to be able to adapt and skin the widget according to our design and decided to share it.
Enjoy

Basic Usage #
FluidNavBar is simply a bottom navigation bar but with a very cool and fluid effect while
animating the transition between an active button to another one.
The example below shows you the minimal code to use the widget.
@override
Widget build(context) {
return MaterialApp(
home: Scaffold(
backgroundColor: Color(0xFF75B7E1),
extendBody: true,
body: _theBody,
bottomNavigationBar: FluidNavBar( // (1)
icons: [ // (2)
FluidNavBarIcon(svgPath: "assets/home.svg"), // (3)
FluidNavBarIcon(svgPath: "assets/bookmark.svg"),
],
onChange: _handleNavigationChange, // (4)
),
),
);
}
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(1) Create an instance of FluidNavBar
(2) Set the icons, of type FluidNavBarIcon, to display in the navigation bar
(3) FluidNavBarIcon supports SVG asset or IconData
(4) Set the callback to react when the user tap an icon (the callback parameter contains the icon's index)

When defining FluidNavBarIcon you can provide an SVG asset or an IconData. Use the field svgPath for an SVG or
the field icon for an IconData.
Example:
FluidNavBar(
icons: [
FluidNavBarIcon(
svgPath: "assets/home.svg",
backgroundColor: Color(0xFF4285F4),
extras: {"label": "home"}),
FluidNavBarIcon(
icon: Icons.bookmark_border,
backgroundColor: Color(0xFFEC4134),
extras: {"label": "bookmark"}),
],
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Note: For backward compatibility (previous to v1.2.0) you can still use the field iconPath to set
the SVG asset to use (this is the same behaviour of svgPath). But this field has been deprecated and will
be removed in a future version.
How To Style #
FluidNavBar comes with a default set of styles which are directly inherited from the gskinner showcase.
You can override different properties to adapt the fluid navigation bar to your current design:

the bar background color (Colors.white by default)
the icon background color (the same color as the bar background color by default)
the icon foreground color when it's selected (Colors.black by default)
the icon foreground color when it's unselected (Colors.grey by default)

Global Styles #
The easiest way is to define one or more properties in a FluidNavBatStyle and set this instance
in the style property of the FluidNavBar:
FluidNavBar(
icons: [
FluidNavBarIcon(svgPath: "assets/home.svg"),
FluidNavBarIcon(svgPath: "assets/bookmark.svg"),
],
onChange: _handleNavigationChange,
style: FluidNavBarStyle(
barBackgroundColor: Color(0xFFFB5C66),
iconBackgroundColor: Colors.white,
iconSelectedForegroundColor: Color(0xFFFB5C66),
iconUnselectedForegroundColor: Colors.black
),
)
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is displayed as:

Properties:

Property
Description

barBackgroundColor
Set the background color of the bar

iconBackgroundColor
Set the background color for all icons

iconSelectedForegroundColor
Set the foreground color for the selected icon

iconUnselectedForegroundColor
Set the background color for all unselected icons

Local Styles #
You can also define some specific styles per icon, by using optional parameters of FluidNavBarIcon:
FluidNavBar(
icons: [
FluidNavBarIcon(svgPath: "assets/home.svg", backgroundColor: Color(0xFF4285F4)),
FluidNavBarIcon(svgPath: "assets/bookmark.svg", backgroundColor: Color(0xFFEC4134)),
FluidNavBarIcon(svgPath: "assets/partner.svg", backgroundColor: Color(0xFFFCBA02)),
FluidNavBarIcon(svgPath: "assets/conference.svg", backgroundColor: Color(0xFF34A950)),
],
onChange: _handleNavigationChange,
style: FluidNavBarStyle(
iconUnselectedForegroundColor: Colors.white
)
),
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is displayed as

Note: In this example I used also a global style for the foreground color of unselected icons, as I don't want
to set the same color for all icons
Properties:

Property
Description

backgroundColor
Set the background color of the icon

selectedForegroundColor
Set the foreground color for a selected icon

unselectedForegroundColor
Set the foreground color for all unselected icons

Styles Priorities #
You can define global styles, local styles, both or no style at all!
To define the proper style to apply it tries, for each style, to resolve its value in the following order:
1- local style
2- global style
3- default value
when a value is resolved then it applies it to the widget.
For example if you set the global style iconBackgroundColor to Colors.red and you also
set the local style backgroundColor to Colors.green for an icon, then it will use the green color
as the local style will be resolved before the global one.
Other options #
There are also few options, you can play with. They are global options and accessible throw FluidNaBar fields.

Property
Description

animationFactor
Set the factor to boost or slowdown animation. The default value is 1.0. If you use a value < 1 then the animation will be faster, if you use a value > 1 the animation will be slower

scaleFactor
Define the factor used by the animation to zoom the selected icon. The default value is 1.2. If the value is > 1 then it is a zoom-in, if you use a value < 1 then it is zoom-out

defaultIndex
Set to change selected item on start of the application. By default set to 0.

For an animationFactor of 2.0 (slower) and a scaleFactor of 2.0 (a zoom-in bigger than the default one), the result is:

Contributions #
Feel free to create an issue if you find a bug or if you need new features. Of course PRs are welcome!
If you want to contact me on Twitter: @etaix
Contributors #
Many thanks to these contributors:

Umair M
Dmitriy Govorov
Christos Tsortanidis
Dorbmon