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flutter_wisetronic/lib/widgets/general/sliding_up_panel.dart
2021-08-31 13:28:33 -04:00

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Dart

/*
Name: Akshath Jain
Date: 3/18/2019 - 4/2/2020
Purpose: Defines the sliding_up_panel widget
Copyright: © 2020, Akshath Jain. All rights reserved.
Licensing: More information can be found here: https://github.com/akshathjain/sliding_up_panel/blob/master/LICENSE
*/
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'dart:math';
import 'package:flutter/physics.dart';
enum SlideDirection{
UP,
DOWN,
}
enum PanelState{
OPEN,
CLOSED
}
class SlidingUpPanel extends StatefulWidget {
/// The Widget that slides into view. When the
/// panel is collapsed and if [collapsed] is null,
/// then top portion of this Widget will be displayed;
/// otherwise, [collapsed] will be displayed overtop
/// of this Widget. If [panel] and [panelBuilder] are both non-null,
/// [panel] will be used.
final Widget panel;
/// WARNING: This feature is still in beta and is subject to change without
/// notice. Stability is not gauranteed. Provides a [ScrollController] and
/// [ScrollPhysics] to attach to a scrollable object in the panel that links
/// the panel position with the scroll position. Useful for implementing an
/// infinite scroll behavior. If [panel] and [panelBuilder] are both non-null,
/// [panel] will be used.
final Widget Function(ScrollController sc) panelBuilder;
/// The Widget displayed overtop the [panel] when collapsed.
/// This fades out as the panel is opened.
final Widget collapsed;
/// The Widget that lies underneath the sliding panel.
/// This Widget automatically sizes itself
/// to fill the screen.
final Widget body;
/// Optional persistent widget that floats above the [panel] and attaches
/// to the top of the [panel]. Content at the top of the panel will be covered
/// by this widget. Add padding to the bottom of the `panel` to
/// avoid coverage.
final Widget header;
/// Optional persistent widget that floats above the [panel] and
/// attaches to the bottom of the [panel]. Content at the bottom of the panel
/// will be covered by this widget. Add padding to the bottom of the `panel`
/// to avoid coverage.
final Widget footer;
/// The height of the sliding panel when fully collapsed.
final double minHeight;
/// The height of the sliding panel when fully open.
final double maxHeight;
/// A point between [minHeight] and [maxHeight] that the panel snaps to
/// while animating. A fast swipe on the panel will disregard this point
/// and go directly to the open/close position. This value is represented as a
/// percentage of the total animation distance ([maxHeight] - [minHeight]),
/// so it must be between 0.0 and 1.0, exclusive.
final double snapPoint;
/// A border to draw around the sliding panel sheet.
final Border border;
/// If non-null, the corners of the sliding panel sheet are rounded by this [BorderRadiusGeometry].
final BorderRadiusGeometry borderRadius;
/// A list of shadows cast behind the sliding panel sheet.
final List<BoxShadow> boxShadow;
/// The color to fill the background of the sliding panel sheet.
final Color color;
/// The amount to inset the children of the sliding panel sheet.
final EdgeInsetsGeometry padding;
/// Empty space surrounding the sliding panel sheet.
final EdgeInsetsGeometry margin;
/// Set to false to not to render the sheet the [panel] sits upon.
/// This means that only the [body], [collapsed], and the [panel]
/// Widgets will be rendered.
/// Set this to false if you want to achieve a floating effect or
/// want more customization over how the sliding panel
/// looks like.
final bool renderPanelSheet;
/// Set to false to disable the panel from snapping open or closed.
final bool panelSnapping;
/// If non-null, this can be used to control the state of the panel.
final PanelController controller;
/// If non-null, shows a darkening shadow over the [body] as the panel slides open.
final bool backdropEnabled;
/// Shows a darkening shadow of this [Color] over the [body] as the panel slides open.
final Color backdropColor;
/// The opacity of the backdrop when the panel is fully open.
/// This value can range from 0.0 to 1.0 where 0.0 is completely transparent
/// and 1.0 is completely opaque.
final double backdropOpacity;
/// Flag that indicates whether or not tapping the
/// backdrop closes the panel. Defaults to true.
final bool backdropTapClosesPanel;
/// If non-null, this callback
/// is called as the panel slides around with the
/// current position of the panel. The position is a double
/// between 0.0 and 1.0 where 0.0 is fully collapsed and 1.0 is fully open.
final void Function(double position) onPanelSlide;
/// If non-null, this callback is called when the
/// panel is fully opened
final VoidCallback onPanelOpened;
/// If non-null, this callback is called when the panel
/// is fully collapsed.
final VoidCallback onPanelClosed;
/// If non-null and true, the SlidingUpPanel exhibits a
/// parallax effect as the panel slides up. Essentially,
/// the body slides up as the panel slides up.
final bool parallaxEnabled;
/// Allows for specifying the extent of the parallax effect in terms
/// of the percentage the panel has slid up/down. Recommended values are
/// within 0.0 and 1.0 where 0.0 is no parallax and 1.0 mimics a
/// one-to-one scrolling effect. Defaults to a 10% parallax.
final double parallaxOffset;
/// Allows toggling of the draggability of the SlidingUpPanel.
/// Set this to false to prevent the user from being able to drag
/// the panel up and down. Defaults to true.
final bool isDraggable;
/// Either SlideDirection.UP or SlideDirection.DOWN. Indicates which way
/// the panel should slide. Defaults to UP. If set to DOWN, the panel attaches
/// itself to the top of the screen and is fully opened when the user swipes
/// down on the panel.
final SlideDirection slideDirection;
/// The default state of the panel; either PanelState.OPEN or PanelState.CLOSED.
/// This value defaults to PanelState.CLOSED which indicates that the panel is
/// in the closed position and must be opened. PanelState.OPEN indicates that
/// by default the Panel is open and must be swiped closed by the user.
final PanelState defaultPanelState;
SlidingUpPanel({
Key key,
this.panel,
this.panelBuilder,
this.body,
this.collapsed,
this.minHeight = 100.0,
this.maxHeight = 500.0,
this.snapPoint,
this.border,
this.borderRadius,
this.boxShadow = const <BoxShadow>[
BoxShadow(
blurRadius: 8.0,
color: Color.fromRGBO(0, 0, 0, 0.25),
)
],
this.color = Colors.white,
this.padding,
this.margin,
this.renderPanelSheet = true,
this.panelSnapping = true,
this.controller,
this.backdropEnabled = false,
this.backdropColor = Colors.black,
this.backdropOpacity = 0.5,
this.backdropTapClosesPanel = true,
this.onPanelSlide,
this.onPanelOpened,
this.onPanelClosed,
this.parallaxEnabled = false,
this.parallaxOffset = 0.1,
this.isDraggable = true,
this.slideDirection = SlideDirection.UP,
this.defaultPanelState = PanelState.CLOSED,
this.header,
this.footer
}) : assert(panel != null || panelBuilder != null),
assert(0 <= backdropOpacity && backdropOpacity <= 1.0),
assert (snapPoint == null || 0 < snapPoint && snapPoint < 1.0),
super(key: key);
@override
_SlidingUpPanelState createState() => _SlidingUpPanelState();
}
class _SlidingUpPanelState extends State<SlidingUpPanel> with SingleTickerProviderStateMixin{
AnimationController _ac;
ScrollController _sc;
bool _scrollingEnabled = false;
VelocityTracker _vt = new VelocityTracker();
bool _isPanelVisible = true;
@override
void initState(){
super.initState();
_ac = new AnimationController(
vsync: this,
duration: const Duration(milliseconds: 300),
value: widget.defaultPanelState == PanelState.CLOSED ? 0.0 : 1.0 //set the default panel state (i.e. set initial value of _ac)
)..addListener((){
if(widget.onPanelSlide != null) widget.onPanelSlide(_ac.value);
if(widget.onPanelOpened != null && _ac.value == 1.0) widget.onPanelOpened();
if(widget.onPanelClosed != null && _ac.value == 0.0) widget.onPanelClosed();
});
// prevent the panel content from being scrolled only if the widget is
// draggable and panel scrolling is enabled
_sc = new ScrollController();
_sc.addListener((){
if(widget.isDraggable && !_scrollingEnabled)
_sc.jumpTo(0);
});
widget.controller?._addState(this);
}
@override
Widget build(BuildContext context) {
return Stack(
alignment: widget.slideDirection == SlideDirection.UP ? Alignment.bottomCenter : Alignment.topCenter,
children: <Widget>[
//make the back widget take up the entire back side
widget.body != null ? AnimatedBuilder(
animation: _ac,
builder: (context, child){
return Positioned(
top: widget.parallaxEnabled ? _getParallax() : 0.0,
child: child,
);
},
child: Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: widget.body,
),
) : Container(),
//the backdrop to overlay on the body
!widget.backdropEnabled ? Container() : GestureDetector(
onVerticalDragEnd: widget.backdropTapClosesPanel ? (DragEndDetails dets){
// only trigger a close if the drag is towards panel close position
if((widget.slideDirection == SlideDirection.UP ? 1 : -1) * dets.velocity.pixelsPerSecond.dy > 0)
_close();
} : null,
onTap: widget.backdropTapClosesPanel ? () => _close() : null,
child: AnimatedBuilder(
animation: _ac,
builder: (context, _) {
return Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
//set color to null so that touch events pass through
//to the body when the panel is closed, otherwise,
//if a color exists, then touch events won't go through
color: _ac.value == 0.0 ? null : widget.backdropColor.withOpacity(widget.backdropOpacity * _ac.value),
);
}
),
),
//the actual sliding part
!_isPanelVisible ? Container() : _gestureHandler(
child: AnimatedBuilder(
animation: _ac,
builder: (context, child) {
return Container(
height: _ac.value * (widget.maxHeight - widget.minHeight) + widget.minHeight,
margin: widget.margin,
padding: widget.padding,
decoration: widget.renderPanelSheet ? BoxDecoration(
border: widget.border,
borderRadius: widget.borderRadius,
boxShadow: widget.boxShadow,
color: widget.color,
) : null,
child: child,
);
},
child: Stack(
overflow: Overflow.visible,
children: <Widget>[
//open panel
Positioned(
top: widget.slideDirection == SlideDirection.UP ? 0.0 : null,
bottom: widget.slideDirection == SlideDirection.DOWN ? 0.0 : null,
width: MediaQuery.of(context).size.width -
(widget.margin != null ? widget.margin.horizontal : 0) -
(widget.padding != null ? widget.padding.horizontal : 0),
child: Container(
height: widget.maxHeight,
child: widget.panel != null
? widget.panel
: widget.panelBuilder(_sc),
),
),
// header
widget.header != null ? Positioned(
top: widget.slideDirection == SlideDirection.UP ? 0.0 : null,
bottom: widget.slideDirection == SlideDirection.DOWN ? 0.0 : null,
child: widget.header,
) : Container(),
// footer
widget.footer != null ? Positioned(
top: widget.slideDirection == SlideDirection.UP ? null : 0.0,
bottom: widget.slideDirection == SlideDirection.DOWN ? null : 0.0,
child: widget.footer
) : Container(),
// collapsed panel
Positioned(
top: widget.slideDirection == SlideDirection.UP ? 0.0 : null,
bottom: widget.slideDirection == SlideDirection.DOWN ? 0.0 : null,
width: MediaQuery.of(context).size.width -
(widget.margin != null ? widget.margin.horizontal : 0) -
(widget.padding != null ? widget.padding.horizontal : 0),
child: Container(
height: widget.minHeight,
child: widget.collapsed == null ? Container() : FadeTransition(
opacity: Tween(begin: 1.0, end: 0.0).animate(_ac),
// if the panel is open ignore pointers (touch events) on the collapsed
// child so that way touch events go through to whatever is underneath
child: IgnorePointer(
ignoring: _isPanelOpen,
child: widget.collapsed
),
),
),
),
],
),
),
),
],
);
}
@override
void dispose(){
_ac.dispose();
super.dispose();
}
double _getParallax(){
if(widget.slideDirection == SlideDirection.UP)
return -_ac.value * (widget.maxHeight - widget.minHeight) * widget.parallaxOffset;
else
return _ac.value * (widget.maxHeight - widget.minHeight) * widget.parallaxOffset;
}
// returns a gesture detector if panel is used
// and a listener if panelBuilder is used.
// this is because the listener is designed only for use with linking the scrolling of
// panels and using it for panels that don't want to linked scrolling yields odd results
Widget _gestureHandler({Widget child}){
if (!widget.isDraggable) return child;
if (widget.panel != null){
return GestureDetector(
onVerticalDragUpdate: (DragUpdateDetails dets) => _onGestureSlide(dets.delta.dy),
onVerticalDragEnd: (DragEndDetails dets) => _onGestureEnd(dets.velocity),
child: child,
);
}
return Listener(
onPointerDown: (PointerDownEvent p) => _vt.addPosition(p.timeStamp, p.position),
onPointerMove: (PointerMoveEvent p){
_vt.addPosition(p.timeStamp, p.position); // add current position for velocity tracking
_onGestureSlide(p.delta.dy);
},
onPointerUp: (PointerUpEvent p) => _onGestureEnd(_vt.getVelocity()),
child: child,
);
}
// handles the sliding gesture
void _onGestureSlide(double dy){
// only slide the panel if scrolling is not enabled
if(!_scrollingEnabled){
if(widget.slideDirection == SlideDirection.UP)
_ac.value -= dy / (widget.maxHeight - widget.minHeight);
else
_ac.value += dy / (widget.maxHeight - widget.minHeight);
}
// if the panel is open and the user hasn't scrolled, we need to determine
// whether to enable scrolling if the user swipes up, or disable closing and
// begin to close the panel if the user swipes down
if(_isPanelOpen && _sc.hasClients && _sc.offset <= 0){
setState(() {
if(dy < 0){
_scrollingEnabled = true;
}else{
_scrollingEnabled = false;
}
});
}
}
// handles when user stops sliding
void _onGestureEnd(Velocity v){
double minFlingVelocity = 365.0;
double kSnap = 8;
//let the current animation finish before starting a new one
if(_ac.isAnimating) return;
// if scrolling is allowed and the panel is open, we don't want to close
// the panel if they swipe up on the scrollable
if(_isPanelOpen && _scrollingEnabled) return;
//check if the velocity is sufficient to constitute fling to end
double visualVelocity = -v.pixelsPerSecond.dy / (widget.maxHeight - widget.minHeight);
// reverse visual velocity to account for slide direction
if(widget.slideDirection == SlideDirection.DOWN)
visualVelocity = -visualVelocity;
// get minimum distances to figure out where the panel is at
double d2Close = _ac.value;
double d2Open = 1 - _ac.value;
double d2Snap = ((widget.snapPoint ?? 3) -_ac.value).abs(); // large value if null results in not every being the min
double minDistance = min(d2Close, min(d2Snap, d2Open));
// check if velocity is sufficient for a fling
if(v.pixelsPerSecond.dy.abs() >= minFlingVelocity){
// snapPoint exists
if(widget.panelSnapping && widget.snapPoint != null){
if(v.pixelsPerSecond.dy.abs() >= kSnap*minFlingVelocity || minDistance == d2Snap)
_ac.fling(velocity: visualVelocity);
else
_flingPanelToPosition(widget.snapPoint, visualVelocity);
// no snap point exists
}else if(widget.panelSnapping){
_ac.fling(velocity: visualVelocity);
// panel snapping disabled
}else{
_ac.animateTo(
_ac.value + visualVelocity * 0.16,
duration: Duration(milliseconds: 410),
curve: Curves.decelerate,
);
}
return;
}
// check if the controller is already halfway there
if (widget.panelSnapping) {
if(minDistance == d2Close){
_close();
}else if(minDistance == d2Snap){
_flingPanelToPosition(widget.snapPoint, visualVelocity);
}else{
_open();
}
}
}
void _flingPanelToPosition(double targetPos, double velocity){
final Simulation simulation = SpringSimulation(
SpringDescription.withDampingRatio(
mass: 1.0,
stiffness: 500.0,
ratio: 1.0,
),
_ac.value,
targetPos,
velocity
);
_ac.animateWith(simulation);
}
//---------------------------------
//PanelController related functions
//---------------------------------
//close the panel
Future<void> _close(){
return _ac.fling(velocity: -1.0);
}
//open the panel
Future<void> _open(){
return _ac.fling(velocity: 1.0);
}
//hide the panel (completely offscreen)
Future<void> _hide(){
return _ac.fling(velocity: -1.0).then((x){
setState(() {
_isPanelVisible = false;
});
});
}
//show the panel (in collapsed mode)
Future<void> _show(){
return _ac.fling(velocity: -1.0).then((x){
setState(() {
_isPanelVisible = true;
});
});
}
//animate the panel position to value - must
//be between 0.0 and 1.0
Future<void> _animatePanelToPosition(double value, {Duration duration, Curve curve = Curves.linear}){
assert(0.0 <= value && value <= 1.0);
return _ac.animateTo(value, duration: duration, curve: curve);
}
//animate the panel position to the snap point
//REQUIRES that widget.snapPoint != null
Future<void> _animatePanelToSnapPoint({Duration duration, Curve curve = Curves.linear}){
assert(widget.snapPoint != null);
return _ac.animateTo(widget.snapPoint, duration: duration, curve: curve);
}
//set the panel position to value - must
//be between 0.0 and 1.0
set _panelPosition(double value){
assert(0.0 <= value && value <= 1.0);
_ac.value = value;
}
//get the current panel position
//returns the % offset from collapsed state
//as a decimal between 0.0 and 1.0
double get _panelPosition => _ac.value;
//returns whether or not
//the panel is still animating
bool get _isPanelAnimating => _ac.isAnimating;
//returns whether or not the
//panel is open
bool get _isPanelOpen => _ac.value == 1.0;
//returns whether or not the
//panel is closed
bool get _isPanelClosed => _ac.value == 0.0;
//returns whether or not the
//panel is shown/hidden
bool get _isPanelShown => _isPanelVisible;
}
class PanelController{
_SlidingUpPanelState _panelState;
void _addState(_SlidingUpPanelState panelState){
this._panelState = panelState;
}
/// Determine if the panelController is attached to an instance
/// of the SlidingUpPanel (this property must return true before any other
/// functions can be used)
bool get isAttached => _panelState != null;
/// Closes the sliding panel to its collapsed state (i.e. to the minHeight)
Future<void> close(){
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._close();
}
/// Opens the sliding panel fully
/// (i.e. to the maxHeight)
Future<void> open(){
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._open();
}
/// Hides the sliding panel (i.e. is invisible)
Future<void> hide(){
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._hide();
}
/// Shows the sliding panel in its collapsed state
/// (i.e. "un-hide" the sliding panel)
Future<void> show(){
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._show();
}
/// Animates the panel position to the value.
/// The value must between 0.0 and 1.0
/// where 0.0 is fully collapsed and 1.0 is completely open.
/// (optional) duration specifies the time for the animation to complete
/// (optional) curve specifies the easing behavior of the animation.
Future<void> animatePanelToPosition(double value, {Duration duration, Curve curve = Curves.linear}){
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
assert(0.0 <= value && value <= 1.0);
return _panelState._animatePanelToPosition(value, duration: duration, curve: curve);
}
/// Animates the panel position to the snap point
/// Requires that the SlidingUpPanel snapPoint property is not null
/// (optional) duration specifies the time for the animation to complete
/// (optional) curve specifies the easing behavior of the animation.
Future<void> animatePanelToSnapPoint({Duration duration, Curve curve = Curves.linear}){
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
assert(_panelState.widget.snapPoint != null, "SlidingUpPanel snapPoint property must not be null");
return _panelState._animatePanelToSnapPoint(duration: duration, curve: curve);
}
/// Sets the panel position (without animation).
/// The value must between 0.0 and 1.0
/// where 0.0 is fully collapsed and 1.0 is completely open.
set panelPosition(double value){
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
assert(0.0 <= value && value <= 1.0);
_panelState._panelPosition = value;
}
/// Gets the current panel position.
/// Returns the % offset from collapsed state
/// to the open state
/// as a decimal between 0.0 and 1.0
/// where 0.0 is fully collapsed and
/// 1.0 is full open.
double get panelPosition{
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._panelPosition;
}
/// Returns whether or not the panel is
/// currently animating.
bool get isPanelAnimating{
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._isPanelAnimating;
}
/// Returns whether or not the
/// panel is open.
bool get isPanelOpen{
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._isPanelOpen;
}
/// Returns whether or not the
/// panel is closed.
bool get isPanelClosed{
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._isPanelClosed;
}
/// Returns whether or not the
/// panel is shown/hidden.
bool get isPanelShown{
assert(isAttached, "PanelController must be attached to a SlidingUpPanel");
return _panelState._isPanelShown;
}
}