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Cleanup how we manage scrollOffset in Scrollable

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- Introduce _setScrollOffset as a backend for the animations so that scrollTo
   can stop animations.

 - Create a single function that stops both kinds of scroll animations.

 - Refactor how we update the bounds for bounded scroll behaviors so that we
   update the bounds and compute the new scroll offset at the same time.
This commit is contained in:
Adam Barth 2015-08-21 16:03:09 -07:00
parent 010589be9e
commit d3eaff2765
3 changed files with 71 additions and 75 deletions
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41
packages/flutter/lib/animation/scroll_behavior.dart
View File

@ -17,32 +17,33 @@ abstract class ScrollBehavior {
class BoundedBehavior extends ScrollBehavior {
BoundedBehavior({ double contentsSize: 0.0, double containerSize: 0.0 })
: _contentsSize = contentsSize,
_containerSize = containerSize;
: _contentsExtents = contentsSize,
_containerExtents = containerSize;
double _contentsSize;
double get contentsSize => _contentsSize;
void set contentsSize (double value) {
if (_contentsSize != value) {
_contentsSize = value;
// TODO(ianh) now what? what if we have a simulation ongoing?
}
}
double _contentsExtents;
double get contentsExtents => _contentsExtents;
double _containerSize;
double get containerSize => _containerSize;
void set containerSize (double value) {
if (_containerSize != value) {
_containerSize = value;
// TODO(ianh) now what? what if we have a simulation ongoing?
}
double _containerExtents;
double get containerExtents => _containerExtents;
/// Returns the new scrollOffset.
double updateExtents({
double contentsExtents,
double containerExtents,
double scrollOffset: 0.0
}) {
if (contentsExtents != null)
_contentsExtents = contentsExtents;
if (containerExtents != null)
_containerExtents = containerExtents;
return scrollOffset.clamp(minScrollOffset, maxScrollOffset);
}
final double minScrollOffset = 0.0;
double get maxScrollOffset => math.max(0.0, _contentsSize - _containerSize);
double get maxScrollOffset => math.max(0.0, _contentsExtents - _containerExtents);
double applyCurve(double scrollOffset, double scrollDelta) {
return (scrollOffset + scrollDelta).clamp(0.0, maxScrollOffset);
return (scrollOffset + scrollDelta).clamp(minScrollOffset, maxScrollOffset);
}
}
@ -80,7 +81,7 @@ class OverscrollBehavior extends BoundedBehavior {
}
class OverscrollWhenScrollableBehavior extends OverscrollBehavior {
bool get isScrollable => contentsSize > containerSize;
bool get isScrollable => contentsExtents > containerExtents;
Simulation release(double position, double velocity) {
if (isScrollable || position < minScrollOffset || position > maxScrollOffset)

98
packages/flutter/lib/widgets/scrollable.dart
View File

@ -22,7 +22,6 @@ import 'package:sky/widgets/scrollable.dart';
export 'package:sky/widgets/mixed_viewport.dart' show MixedViewportLayoutState;
// The GestureEvent velocity properties are pixels/second, config min,max limits are pixels/ms
const double _kMillisecondsPerSecond = 1000.0;
const double _kMinFlingVelocity = -config.kMaxFlingVelocity * _kMillisecondsPerSecond;
@ -48,11 +47,11 @@ abstract class Scrollable extends StatefulComponent {
ValueAnimation<double> _toOffsetAnimation; // Started by scrollTo()
void initState() {
_toEndAnimation = new AnimatedSimulation(_tickScrollOffset);
_toEndAnimation = new AnimatedSimulation(_setScrollOffset);
_toOffsetAnimation = new ValueAnimation<double>()
..addListener(() {
AnimatedValue<double> offset = _toOffsetAnimation.variable;
scrollTo(offset.value);
_setScrollOffset(offset.value);
});
}
@ -93,8 +92,7 @@ abstract class Scrollable extends StatefulComponent {
}
Future _startToOffsetAnimation(double newScrollOffset, Duration duration, Curve curve) {
_stopToEndAnimation();
_stopToOffsetAnimation();
_stopAnimations();
_toOffsetAnimation
..variable = new AnimatedValue<double>(scrollOffset,
end: newScrollOffset,
@ -105,47 +103,46 @@ abstract class Scrollable extends StatefulComponent {
return _toOffsetAnimation.play();
}
void _stopToOffsetAnimation() {
void _stopAnimations() {
if (_toOffsetAnimation.isAnimating)
_toOffsetAnimation.stop();
if (_toEndAnimation.isAnimating)
_toEndAnimation.stop();
}
void _startToEndAnimation({ double velocity: 0.0 }) {
_stopToEndAnimation();
_stopToOffsetAnimation();
_stopAnimations();
Simulation simulation = scrollBehavior.release(scrollOffset, velocity);
if (simulation != null)
_toEndAnimation.start(simulation);
}
void _stopToEndAnimation() {
_toEndAnimation.stop();
void didUnmount() {
_stopAnimations();
super.didUnmount();
}
void didUnmount() {
_stopToEndAnimation();
_stopToOffsetAnimation();
super.didUnmount();
void _setScrollOffset(double newScrollOffset) {
if (_scrollOffset == newScrollOffset)
return;
setState(() {
_scrollOffset = newScrollOffset;
});
if (_listeners.length > 0)
_notifyListeners();
}
Future scrollTo(double newScrollOffset, { Duration duration, Curve curve: ease }) {
if (newScrollOffset == _scrollOffset)
return new Future.value();
Future result;
if (duration == null) {
setState(() {
_scrollOffset = newScrollOffset;
});
result = new Future.value();
} else {
result = _startToOffsetAnimation(newScrollOffset, duration, curve);
_stopAnimations();
_setScrollOffset(newScrollOffset);
return new Future.value();
}
if (_listeners.length > 0)
_notifyListeners();
return result;
return _startToOffsetAnimation(newScrollOffset, duration, curve);
}
Future scrollBy(double scrollDelta, { Duration duration, Curve curve }) {
@ -157,10 +154,6 @@ abstract class Scrollable extends StatefulComponent {
_startToEndAnimation();
}
void _tickScrollOffset(double value) {
scrollTo(value);
}
// Return the event's velocity in pixels/second.
double _eventVelocity(sky.GestureEvent event) {
double velocity = scrollDirection == ScrollDirection.horizontal
@ -170,8 +163,7 @@ abstract class Scrollable extends StatefulComponent {
}
EventDisposition _handlePointerDown(_) {
_stopToEndAnimation();
_stopToOffsetAnimation();
_stopAnimations();
return EventDisposition.processed;
}
@ -293,10 +285,10 @@ class ScrollableViewport extends Scrollable {
_updateScrollBehaviour();
}
void _updateScrollBehaviour() {
scrollBehavior.contentsSize = _childSize;
scrollBehavior.containerSize = _viewportSize;
if (scrollOffset > scrollBehavior.maxScrollOffset)
settleScrollOffset();
scrollTo(scrollBehavior.updateExtents(
contentsExtents: _childSize,
containerExtents: _viewportSize,
scrollOffset: scrollOffset));
}
Widget buildContent() {
@ -375,6 +367,11 @@ abstract class ScrollableWidgetList extends Scrollable {
itemExtent = source.itemExtent;
super.syncFields(source); // update scrollDirection
if (itemCount != _previousItemCount) {
scrollBehaviorUpdateNeeded = true;
_previousItemCount = itemCount;
}
if (scrollBehaviorUpdateNeeded)
_updateScrollBehavior();
}
@ -416,17 +413,14 @@ abstract class ScrollableWidgetList extends Scrollable {
}
void _updateScrollBehavior() {
scrollBehavior.containerSize = _containerExtent;
double contentsExtent = itemExtent * itemCount;
if (padding != null)
contentsExtent += _leadingPadding + _trailingPadding;
scrollBehavior.contentsSize = contentsExtent;
}
void _updateScrollOffset() {
if (scrollOffset > scrollBehavior.maxScrollOffset)
settleScrollOffset();
scrollTo(scrollBehavior.updateExtents(
contentsExtents: contentsExtent,
containerExtents: _containerExtent,
scrollOffset: scrollOffset));
}
Offset _toOffset(double value) {
@ -439,7 +433,6 @@ abstract class ScrollableWidgetList extends Scrollable {
if (itemCount != _previousItemCount) {
_previousItemCount = itemCount;
_updateScrollBehavior();
_updateScrollOffset();
}
double paddedScrollOffset = scrollOffset;
@ -643,18 +636,19 @@ class ScrollableMixedWidgetList extends Scrollable {
OverscrollBehavior get scrollBehavior => super.scrollBehavior;
void _handleSizeChanged(Size newSize) {
scrollBehavior.containerSize = newSize.height;
scrollBy(scrollBehavior.updateExtents(
containerExtents: newSize.height,
scrollOffset: scrollOffset
));
}
void _handleLayoutChanged() {
if (layoutState.didReachLastChild) {
scrollBehavior.contentsSize = layoutState.contentsSize;
if (_contentsChanged && scrollOffset > scrollBehavior.maxScrollOffset) {
_contentsChanged = false;
settleScrollOffset();
}
} else {
scrollBehavior.contentsSize = double.INFINITY;
double newScrollOffset = scrollBehavior.updateExtents(
contentsExtents: layoutState.didReachLastChild ? layoutState.contentsSize : double.INFINITY,
scrollOffset: scrollOffset);
if (_contentsChanged) {
_contentsChanged = false;
scrollTo(newScrollOffset);
}
}

7
packages/flutter/lib/widgets/tabs.dart
View File

@ -460,7 +460,7 @@ class TabBar extends Scrollable {
}
double _centeredTabScrollOffset(int tabIndex) {
double viewportWidth = scrollBehavior.containerSize;
double viewportWidth = scrollBehavior.containerExtents;
return (_tabRect(tabIndex).left + _tabWidths[tabIndex] / 2.0 - viewportWidth / 2.0)
.clamp(scrollBehavior.minScrollOffset, scrollBehavior.maxScrollOffset);
}
@ -495,8 +495,9 @@ class TabBar extends Scrollable {
setState(() {
_tabBarSize = tabBarSize;
_tabWidths = tabWidths;
scrollBehavior.containerSize = _tabBarSize.width;
scrollBehavior.contentsSize = _tabWidths.reduce((sum, width) => sum + width);
scrollBehavior.updateExtents(
containerExtents: _tabBarSize.width,
contentsExtents: _tabWidths.reduce((sum, width) => sum + width));
});
}