get_transition_mixin.dart
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import 'dart:math';
import 'dart:ui';
import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import '../../../get.dart';
import '../root/get_root.dart';
const double _kBackGestureWidth = 20.0;
const double _kMinFlingVelocity = 1; // Screen widths per second.
// An eyeballed value for the maximum time it takes for a page to animate
// forward if the user releases a page mid swipe.
const int _kMaxMidSwipePageForwardAnimationTime = 800; // Milliseconds.
// The maximum time for a page to get reset to it's original position if the
// user releases a page mid swipe.
const int _kMaxPageBackAnimationTime = 300; // Milliseconds.
class GetBackGestureDetector<T> extends StatefulWidget {
const GetBackGestureDetector({
super.key,
required this.limitedSwipe,
required this.gestureWidth,
required this.initialOffset,
required this.popGestureEnable,
required this.onStartPopGesture,
required this.child,
});
final bool limitedSwipe;
final double gestureWidth;
final double initialOffset;
final Widget child;
final ValueGetter<bool> popGestureEnable;
final ValueGetter<GetBackGestureController<T>> onStartPopGesture;
@override
GetBackGestureDetectorState<T> createState() =>
GetBackGestureDetectorState<T>();
}
class GetBackGestureDetectorState<T> extends State<GetBackGestureDetector<T>> {
GetBackGestureController<T>? _backGestureController;
void _handleDragStart(DragStartDetails details) {
assert(mounted);
assert(_backGestureController == null);
_backGestureController = widget.onStartPopGesture();
}
void _handleDragUpdate(DragUpdateDetails details) {
assert(mounted);
assert(_backGestureController != null);
_backGestureController!.dragUpdate(
_convertToLogical(details.primaryDelta! / context.size!.width),
);
}
void _handleDragEnd(DragEndDetails details) {
assert(mounted);
assert(_backGestureController != null);
_backGestureController!.dragEnd(_convertToLogical(
details.velocity.pixelsPerSecond.dx / context.size!.width,
));
_backGestureController = null;
}
void _handleDragCancel() {
assert(mounted);
// This can be called even if start is not called, paired with the "down"
// event that we don't consider here.
_backGestureController?.dragEnd(0);
_backGestureController = null;
}
double _convertToLogical(double value) {
switch (Directionality.of(context)) {
case TextDirection.rtl:
return -value;
case TextDirection.ltr:
return value;
}
}
@override
Widget build(BuildContext context) {
assert(debugCheckHasDirectionality(context));
final gestureDetector = RawGestureDetector(
behavior: HitTestBehavior.translucent,
gestures: {
_DirectionalityDragGestureRecognizer:
GestureRecognizerFactoryWithHandlers<
_DirectionalityDragGestureRecognizer>(
() {
final directionality = Directionality.of(context);
return _DirectionalityDragGestureRecognizer(
debugOwner: this,
isRTL: directionality == TextDirection.rtl,
isLTR: directionality == TextDirection.ltr,
hasbackGestureController: () => _backGestureController != null,
popGestureEnable: widget.popGestureEnable,
);
},
(directionalityDragGesture) => directionalityDragGesture
..onStart = _handleDragStart
..onUpdate = _handleDragUpdate
..onEnd = _handleDragEnd
..onCancel = _handleDragCancel,
)
},
);
return Stack(
fit: StackFit.passthrough,
children: [
widget.child,
if (widget.limitedSwipe)
PositionedDirectional(
start: widget.initialOffset,
width: _dragAreaWidth(context),
top: 0,
bottom: 0,
child: gestureDetector,
)
else
Positioned.fill(child: gestureDetector),
],
);
}
double _dragAreaWidth(BuildContext context) {
// For devices with notches, the drag area needs to be larger on the side
// that has the notch.
final dragAreaWidth = Directionality.of(context) == TextDirection.ltr
? context.mediaQuery.padding.left
: context.mediaQuery.padding.right;
return max(dragAreaWidth, widget.gestureWidth);
}
}
class GetBackGestureController<T> {
GetBackGestureController({
required this.navigator,
required this.controller,
}) {
navigator.didStartUserGesture();
}
final AnimationController controller;
final NavigatorState navigator;
/// The drag gesture has changed by [delta]. The total range of the
/// drag should be 0.0 to 1.0.
void dragUpdate(double delta) {
controller.value -= delta;
}
/// The drag gesture has ended with a horizontal motion of [velocity] as a
/// fraction of screen width per second.
void dragEnd(double velocity) {
// Fling in the appropriate direction.
// AnimationController.fling is guaranteed to
// take at least one frame.
//
// This curve has been determined through rigorously eyeballing native iOS
// animations.
const Curve animationCurve = Curves.fastLinearToSlowEaseIn;
final bool animateForward;
// If the user releases the page before mid screen with sufficient velocity,
// or after mid screen, we should animate the page out. Otherwise, the page
// should be animated back in.
if (velocity.abs() >= _kMinFlingVelocity) {
animateForward = velocity <= 0;
} else {
animateForward = controller.value > 0.5;
}
if (animateForward) {
// The closer the panel is to dismissing, the shorter the animation is.
// We want to cap the animation time, but we want to use a linear curve
// to determine it.
final droppedPageForwardAnimationTime = min(
lerpDouble(_kMaxMidSwipePageForwardAnimationTime, 0, controller.value)!
.floor(),
_kMaxPageBackAnimationTime,
);
controller.animateTo(1.0,
duration: Duration(milliseconds: droppedPageForwardAnimationTime),
curve: animationCurve);
} else {
// This route is destined to pop at this point. Reuse navigator's pop.
Get.back();
// The popping may have finished inline if already at the
// target destination.
if (controller.isAnimating) {
// Otherwise, use a custom popping animation duration and curve.
final droppedPageBackAnimationTime = lerpDouble(
0, _kMaxMidSwipePageForwardAnimationTime, controller.value)!
.floor();
controller.animateBack(0.0,
duration: Duration(milliseconds: droppedPageBackAnimationTime),
curve: animationCurve);
}
}
if (controller.isAnimating) {
// Keep the userGestureInProgress in true state so we don't change the
// curve of the page transition mid-flight since CupertinoPageTransition
// depends on userGestureInProgress.
late AnimationStatusListener animationStatusCallback;
animationStatusCallback = (status) {
navigator.didStopUserGesture();
controller.removeStatusListener(animationStatusCallback);
};
controller.addStatusListener(animationStatusCallback);
} else {
navigator.didStopUserGesture();
}
}
}
mixin GetPageRouteTransitionMixin<T> on PageRoute<T> {
ValueNotifier<String?>? _previousTitle;
@override
Color? get barrierColor => null;
@override
String? get barrierLabel => null;
double Function(BuildContext context)? get gestureWidth;
/// True if an iOS-style back swipe pop gesture is currently
/// underway for this route.
///
/// See also:
///
/// * [isPopGestureInProgress], which returns true if a Cupertino pop gesture
/// is currently underway for specific route.
/// * [popGestureEnabled], which returns true if a user-triggered pop gesture
/// would be allowed.
//bool get popGestureInProgress => isPopGestureInProgress(this);
/// The title string of the previous [CupertinoPageRoute].
///
/// The [ValueListenable]'s value is readable after the route is installed
/// onto a [Navigator]. The [ValueListenable] will also notify its listeners
/// if the value changes (such as by replacing the previous route).
///
/// The [ValueListenable] itself will be null before the route is installed.
/// Its content value will be null if the previous route has no title or
/// is not a [CupertinoPageRoute].
///
/// See also:
///
/// * [ValueListenableBuilder], which can be used to listen and rebuild
/// widgets based on a ValueListenable.
ValueListenable<String?> get previousTitle {
assert(
_previousTitle != null,
'''
Cannot read the previousTitle for a route that has not yet been installed''',
);
return _previousTitle!;
}
bool get showCupertinoParallax;
/// {@template flutter.cupertino.CupertinoRouteTransitionMixin.title}
/// A title string for this route.
///
/// Used to auto-populate [CupertinoNavigationBar] and
/// [CupertinoSliverNavigationBar]'s `middle`/`largeTitle` widgets when
/// one is not manually supplied.
/// {@endtemplate}
String? get title;
@override
// A relatively rigorous eyeball estimation.
Duration get transitionDuration;
@override
Duration get reverseTransitionDuration;
/// Builds the primary contents of the route.
@protected
Widget buildContent(BuildContext context);
@override
Widget buildPage(BuildContext context, Animation<double> animation,
Animation<double> secondaryAnimation) {
final child = buildContent(context);
final Widget result = Semantics(
scopesRoute: true,
explicitChildNodes: true,
child: child,
);
return result;
}
@override
Widget buildTransitions(BuildContext context, Animation<double> animation,
Animation<double> secondaryAnimation, Widget child) {
return buildPageTransitions<T>(
this, context, animation, secondaryAnimation, child);
}
@override
bool canTransitionTo(TransitionRoute<dynamic> nextRoute) {
// Don't perform outgoing animation if the next route is a
// fullscreen dialog.
return (nextRoute is GetPageRouteTransitionMixin &&
!nextRoute.fullscreenDialog &&
nextRoute.showCupertinoParallax) ||
(nextRoute is CupertinoRouteTransitionMixin &&
!nextRoute.fullscreenDialog);
}
@override
void didChangePrevious(Route<dynamic>? previousRoute) {
final previousTitleString = previousRoute is CupertinoRouteTransitionMixin
? previousRoute.title
: null;
if (_previousTitle == null) {
_previousTitle = ValueNotifier<String?>(previousTitleString);
} else {
_previousTitle!.value = previousTitleString;
}
super.didChangePrevious(previousRoute);
}
static bool canSwipe(GetPageRoute route) =>
route.popGesture ?? Get.defaultPopGesture;
/// Returns a [CupertinoFullscreenDialogTransition] if [route] is a full
/// screen dialog, otherwise a [CupertinoPageTransition] is returned.
///
/// Used by [CupertinoPageRoute.buildTransitions].
///
/// This method can be applied to any [PageRoute], not just
/// [CupertinoPageRoute]. It's typically used to provide a Cupertino style
/// horizontal transition for material widgets when the target platform
/// is [TargetPlatform.iOS].
///
/// See also:
///
/// * [CupertinoPageTransitionsBuilder], which uses this method to define a
/// [PageTransitionsBuilder] for the [PageTransitionsTheme].
static Widget buildPageTransitions<T>(
PageRoute<T> rawRoute,
BuildContext context,
Animation<double> animation,
Animation<double> secondaryAnimation,
Widget child, {
bool limitedSwipe = false,
double initialOffset = 0,
}) {
// Check if the route has an animation that's currently participating
// in a back swipe gesture.
//
// In the middle of a back gesture drag, let the transition be linear to
// match finger motions.
final route = rawRoute as GetPageRoute<T>;
final linearTransition = route.popGestureInProgress;
final finalCurve = route.curve ?? Get.defaultTransitionCurve;
final hasCurve = route.curve != null;
if (route.fullscreenDialog && route.transition == null) {
return CupertinoFullscreenDialogTransition(
primaryRouteAnimation: hasCurve
? CurvedAnimation(parent: animation, curve: finalCurve)
: animation,
secondaryRouteAnimation: secondaryAnimation,
linearTransition: linearTransition,
child: child,
);
} else {
if (route.customTransition != null) {
return route.customTransition!.buildTransition(
context,
finalCurve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
),
);
}
/// Apply the curve by default...
final iosAnimation = animation;
animation = CurvedAnimation(parent: animation, curve: finalCurve);
switch (route.transition ?? Get.defaultTransition) {
case Transition.leftToRight:
return SlideLeftTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.downToUp:
return SlideDownTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.upToDown:
return SlideTopTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.noTransition:
return GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
);
case Transition.rightToLeft:
return SlideRightTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.zoom:
return ZoomInTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.fadeIn:
return FadeInTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.rightToLeftWithFade:
return RightToLeftFadeTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.leftToRightWithFade:
return LeftToRightFadeTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.cupertino:
return CupertinoPageTransition(
primaryRouteAnimation: animation,
secondaryRouteAnimation: secondaryAnimation,
linearTransition: linearTransition,
child: GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.size:
return SizeTransitions().buildTransitions(
context,
route.curve!,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.fade:
return const FadeUpwardsPageTransitionsBuilder().buildTransitions(
route,
context,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.topLevel:
return const ZoomPageTransitionsBuilder().buildTransitions(
route,
context,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.native:
return const PageTransitionsTheme().buildTransitions(
route,
context,
iosAnimation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
case Transition.circularReveal:
return CircularRevealTransition().buildTransitions(
context,
route.curve,
route.alignment,
animation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(_isPopGestureEnabled(route, canSwipe(route), context));
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
default:
final customTransition = GetRoot.of(context).config.customTransition;
if (customTransition != null) {
return customTransition.buildTransition(context, route.curve,
route.alignment, animation, secondaryAnimation, child);
}
PageTransitionsTheme pageTransitionsTheme =
Theme.of(context).pageTransitionsTheme;
return pageTransitionsTheme.buildTransitions(
route,
context,
iosAnimation,
secondaryAnimation,
GetBackGestureDetector<T>(
popGestureEnable: () =>
_isPopGestureEnabled(route, canSwipe(route), context),
onStartPopGesture: () {
assert(
_isPopGestureEnabled(route, canSwipe(route), context),
);
return _startPopGesture(route);
},
limitedSwipe: limitedSwipe,
gestureWidth:
route.gestureWidth?.call(context) ?? _kBackGestureWidth,
initialOffset: initialOffset,
child: child,
));
}
}
}
// Called by GetBackGestureDetector when a pop ("back") drag start
// gesture is detected. The returned controller handles all of the subsequent
// drag events.
/// True if an iOS-style back swipe pop gesture is currently
/// underway for [route].
///
/// This just check the route's [NavigatorState.userGestureInProgress].
///
/// See also:
///
/// * [popGestureEnabled], which returns true if a user-triggered pop gesture
/// would be allowed.
static bool isPopGestureInProgress(BuildContext context) {
final route = ModalRoute.of(context)!;
return route.navigator!.userGestureInProgress;
}
static bool _isPopGestureEnabled<T>(
PageRoute<T> route, bool canSwipe, BuildContext context) {
// If there's nothing to go back to, then obviously we don't support
// the back gesture.
if (route.isFirst) return false;
// If the route wouldn't actually pop if we popped it, then the gesture
// would be really confusing (or would skip internal routes),
// so disallow it.
if (route.willHandlePopInternally) return false;
// support [PopScope]
if (route.popDisposition == RoutePopDisposition.doNotPop) return false;
// Fullscreen dialogs aren't dismissible by back swipe.
if (route.fullscreenDialog) return false;
// If we're in an animation already, we cannot be manually swiped.
if (route.animation!.status != AnimationStatus.completed) return false;
// If we're being popped into, we also cannot be swiped until the pop above
// it completes. This translates to our secondary animation being
// dismissed.
if (route.secondaryAnimation!.status != AnimationStatus.dismissed) {
return false;
}
// If we're in a gesture already, we cannot start another.
if (GetPageRouteTransitionMixin.isPopGestureInProgress(context)) {
return false;
}
// Don't perfome swipe if canSwipe be false
if (!canSwipe) return false;
// Looks like a back gesture would be welcome!
return true;
}
static GetBackGestureController<T> _startPopGesture<T>(
PageRoute<T> route,
) {
return GetBackGestureController<T>(
navigator: route.navigator!,
controller: route.controller!, // protected access
);
}
}
class _DirectionalityDragGestureRecognizer
extends HorizontalDragGestureRecognizer {
final ValueGetter<bool> popGestureEnable;
final ValueGetter<bool> hasbackGestureController;
final bool isRTL;
final bool isLTR;
_DirectionalityDragGestureRecognizer({
required this.isRTL,
required this.isLTR,
required this.popGestureEnable,
required this.hasbackGestureController,
super.debugOwner,
});
@override
void handleEvent(PointerEvent event) {
final dx = event.delta.dx;
if (hasbackGestureController() ||
popGestureEnable() && (isRTL && dx < 0 || isLTR && dx > 0 || dx == 0)) {
super.handleEvent(event);
} else {
stopTrackingPointer(event.pointer);
}
}
}